Fishery, growth, and mortality of threatened Asian Sunfish, Horabagrus brachysoma (Gu¨nther 1864) in five rivers of Western Ghats hotspot, India

Fishery, growth, and mortality of threatened Asian Sunfish, Horabagrus brachysoma (Gu¨nther 1864) in five rivers of Western Ghats hotspot, India | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Fishery, growth, and mortality of threatened Asian Sunfish, Horabagrus brachysoma (Gu¨nther 1864) in five rivers of Western Ghats hotspot, India Chelapurath Radhakrishnan Renjithkumar, Kuttanelloor Roshni This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4585679/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Community-based data monitoring (CBM) systems in small-scale inland fisheries provide insights into the catch patterns of diverse fish species over extended periods. In this study, a participatory approach was employed to ascertain the fishery, demography, and exploitation patterns of Asian Sun fish catfish, Horabagrus brachysoma , across five river systems within the Western Ghats biodiversity hotspot of India. H. brachysoma (Gu¨nther 1864) is a commercially important food fish that is heavily exploited from rivers of Kerala state, India and is listed as ‘Vulnerable’ on the IUCN red list. The monthly catches of this species from various landing centres across the Western Ghats' rivers varied between 303 kg to 631 kg annually. These fish typically measured between 11.00 and 41.10 cm in Total Length (TL) and weighed between 26.00 g to 470.00 g in Total Weight (TW). Using the annual length frequency data provided by local fishers, the estimated growth parameters of H. brachysoma are estimated as; asymptotic length (( L ∞ ) between 316.05 and 421.05 mm, growth coefficient ( K ) between 0.58 and 1.10 yr − 1 from different rivers. The total mortality ( Z ) was calculated to range between1.25 yr − 1 and 2.91 yr − 1 while the fishing mortality ( F) was estimated between 0.62 yr − 1 and 2.09 yr − 1 . The fishing mortality rate of H. brachysoma in the Periyar River, at 2.09 yr⁻¹, appears to be one of the highest recorded for this species. This rate suggests a potentially indiscriminate level of exploitation by local fishers in this area. The calculated exploitation rate ( E ) ranging from 0.49 to 0.72 yr⁻¹ exceeds the anticipated optimum exploitation levels (0.5). This suggests that the populations of H. brachysoma in the river systems of the Western Ghats are experiencing overexploitation. This approach includes measures such as implementing fishing closures during spawning seasons, imposing restrictions on mesh sizes, non-fishing zones and establishing quota systems for local fishermen. These strategies collectively aim to promote sustainable practices and preserve the population of H. brachysoma . Yellow catfish Western Ghats Vulnerable Fishery mortality environmental variables conservation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Only 10% of the world’s exploited fish stocks are assessed (FAO 2010), and many unassessed stocks are generally ‘uncertain risk’ category (Costello et al. 2012 ). These unassessed stocks often sustain artisanal and subsistence inland fisheries, offering employment opportunities for rural communities (Smith et al. 2005 ; Lynch et al. 2016 ). Inland fish and fisheries play a pivotal role in food security by offering local and cost-effective sources of protein, essential fatty acids, oils, and micronutrients to hundreds of millions of people worldwide, especially in developing nations (Funge-Smith and Bennett 2019 ). This type of fishing is typically characterized by small-scale, household-based, and subsistence practices, where the majority of the catch is consumed within the local community rather than being exported to other regions (Youn et al. 2014 ). In developing countries, inland fisheries serve as a crucial source of food security and income, supporting the livelihoods of over 60 million people (Cooke et al. 2016 ). Global inland fisheries encounter a multitude of risks that significantly impact the well-being of millions of people worldwide (Smith et al. 2005 ). Collecting precise data on inland fisheries production poses challenges due to the dispersed nature of most inland fisheries activities, often leading to underreporting or no reporting at all to government agencies (Allan et al. 2005 ). Despite the important contributions, inland fish and fisheries generally remain economically and socially undervalued and biologically underappreciated because accurate information about these small scale highly dispersed fisheries is inherently difficult to acquire (Youn et al. 2014 ). The Western Ghats, a part of the Western Ghats-Sri Lanka biodiversity hotspot, comprises a mountain range stretching over 1600 km along the west coast of peninsular India, encompassing an area spanning 180,000 km 2 (Myers et al. 2000 ). It is one of 34 worldwide biodiversity hotspots with high endemicity, as well as one of four in the Indian subcontinent (Divya et al. 2021 ). Despite covering less than 6% of India's surface area, the WG has approximately 30% of the country's biodiversity, with a significant number of endemic and vulnerable species (CEPF 2016 ). This mountain range is classified into four phytogeographic subregions: northern WG (River Tapi to Goa), central WG (River Kali to Coorg), Nilgiris, and southern WG (Anamalai, Palani, and Cardamom hills) (Subramanyam and Nayar 1974 ). The streams and rivers that originate and pass through the WG freshwater ecoregion in the Southern Indian state of Kerala are home of 300 species of freshwater fish, 70% of which are endemic and one-third are threatened (Dahanukar and Raghavan 2013 ). Freshwater fishes are directly linked to the livelihood of local communities in the Southern WG, serving as a source of food and revenue generating (Raghavan et al. 2011 ). This rising demand has resulted in indiscriminate exploitation of endemic and threatened fishes at unsustainable levels via small-scale and open-access fisheries, as well as a variety of complex anthropogenic pressures such as pollution, habitat destruction, and diseases, which can cause rapid declines in native fish populations. (Raghavan et al. 2011 ). Managing the overexploitation of freshwater fish species is important for both food security and minimizing biodiversity loss (Tickner et al. 2020 ). This may be done by the management of exploitation (reduction of bycatch, minimizing fishing effort and size limits regulation), management of fish habitat (river flow regulation and management of aquatic vegetation) and the use of fisheries enhancements (river ranching and use of artificial reefs) (Arlinghaus et al. 2016 ; Lorenzen et al. 2016 ). Fish stock assessment models assist fishery managers in understanding the dynamics of fish stocks and how fish populations respond to external stressors such as commercial fishing and predation (Hilborn et al. 2020 ; Sun et al. 2020 ). Appropriate data for length-based stock evaluations can be collected through sampling at commercial fish landings hubs or through fisheries-cruise surveys, with no need for total removals from a target stock (Shephard et al. 2021 ). However, in inland habitats where local knowledge of fishers is essential, researchers and fisheries managers may find it difficult to obtain and validate data for stock assessment (Valbo-Jørgensen and Poulsen 2000). Community-based data monitoring (CBM) systems offer an alternate approach in such small-scale and artisanal fisheries, which are playing an increasingly important role in sustaining local food supply and food security (Humber et al. 2017 ; Oviedo and Bursztyn 2017 ; Lam et al. 2019 ; Lowitt et al. 2020 ). Local communities frequently monitor fish catch patterns in their fishing practises throughout the year, and this knowledge can be captured as quantitative indicators (Thompson 2018; Shephard et al. 2021 ). The Asian Sun catfish or the yellow catfish, Horabagrus brachysoma (Gu¨nther 1864) belongs to the family Horabagridae and is an important food fish exploited by traditional fishers from rivers, lakes, backwaters, and associated inland canal systems in the Western Ghats region of Kerala, Karnataka, and Maharashtra (Raghavan et al 2016 ). During the monsoon floodplain fishing, H. brachysoma is a prominent catfish species in the Central Kerala Rivers. (Shaji and Laladhas 2013 ). The landing of the species from Kerala state rivers ranges from 3.67 t to 17.1 t (Renjithkumar et al. 2011 , 2016 ) whereas annual landings in Vembanad Lake ranged between 2 and 439 t (Bindu 2006 ; Sreeraj et al. 2007 ; Kurup et al. 1995 ). Overall, the fishery for H. brachysoma appears to be unsustainable in many rivers of the Western Ghats due to overexploitation of stock and habitat destruction (Raghavan et al. 2016 ), and the IUCN has classed the species as 'Vulnerable' due to an overall population drop (Raghavan and Ali 2013 ). Management of the fishery of yellow catfish is hindered due to the lack of successful fisheries management programmes in Kerala’s WG waters, where the largest share of exploitation takes place (Prasad et al. 2012 ). Previously, Prasad et al. ( 2012 ) reported H. brachysoma population characteristics from a single river system in Southern India. Despite this, there are no reliable estimates of the yellow cat fish's fishery, growth, mortality, and exploitation in its native ranges in the Western Ghats. The current study examines the fishery, growth, and exploitation status of vulnerable H. brachysoma exploited from different river systems (Pampa, Achenkovil, Muvattupuzha, Periyar, and Chalakudy Rivers) in the Southern Western Ghats of India in connection to environmental variables. Materials and Methods Study area The study was carried out in the major fish landing centres of Periyar (244 km), Chalakudy (146 km), Pampa (176 km), Muvattupuzha (121 km), and Achenkovil (128 km) Rivers, which are located in the central region of Kerala state. The five fish landing sites were selected based on the high occurrence of H. brachysoma in the daily catches of local fishers. Bhoothanthankettu, Periyar (10°08’12.75” N; 76°39’51.27” E); Pulikakadavu, Chalakudy (10°14’28.53” N; 76°19’50.27” E); Mulakulam, Muvatupuzha (09°51’15.00” N; 76°29’19.12” E); Prayikkara, Achenkovil (09°15’44.04” N; 76°32’28.72” E) and Edatuva, Pampa (09°21’53.29” N; 76°28’35.05” E) (Fig. 1 ) were the landing centres selected for the study. River Periyar, the longest of Kerala's 44 perennial rivers, is regarded as the state's lifeline, home to 77 fish species (Radhakrishnan 2006 ). The Chalakudy River has a varied fish fauna of 98 species, several of which are endangered or threatened (Raghavan et al. 2008 a). The fish fauna of the Chalakudy River is threatened by habitat destruction, overfishing, water pollution, and fish species invasion (Raghavan et al. 2008 b). Muvattupuzha River is the one of the important rivers in Ernakulam district of Kerala contains 36 fish species and Horabagrus brachysoma contributed 3.67 t yearly to the fish landing (Renjithkumar et al. 2016 ). The Achenkovil River flows through two Western Ghats hill ranges: Kottavasal and Devarmalai, covering 1484 km 2 and home to 52 fish species (Swapna 2009 ). Pampa River, which runs through Kuttanad (low-lying agricultural fields) in central Kerala, contributed 17.11 t of H. brachysomain fishery (Renjithkumar et al. 2011 ). Data collection Data on the fishery for H. brachysoma were collected from local fishermen monthly from April 2020 to March 2021 from five rivers. Hook and line and gill nets were the main fishing gears using for catching yellow cat fish. Gill nets ranged in length from 75 to 150 metres, with mesh sizes ranging from 30 to 60 mm are normally used for fishing. The catch (kg) from the haul of gill nets and hook & lines were recorded. Daily landings from each type of gears were computed following Kurup et al. ( 1993 ); W = (w/n) X N, where W = total weight of fish, w = total weight of fish from gear sampled, n = number of gears sampled, N = total number of similar gears operated. Monthly catch was estimated by multiplying daily catch with total number of fishing days in a month (25 fishing days). The annual exploited quantity was calculated by summarising the landings of 12 months. Samples of H. brachysoma for demographics were collected from the catches of small-scale fishermen at fish landing centres along five rivers in the Southern Western Ghats from April 2020 to March 2021. Total length (TL) was measured to the nearest 0.01 mm using a digital sliding calliper, and total body weight (BW) was measured to the nearest 0.01 g using an electronic weighted scale. For the demography of H. brachysoma , 1938 specimens from different river systems were used: Periyar (n = 383), Chalakudy (n = 407), Pampa (n = 448), Muvatupuzha (n = 351), and Achenkovil (n = 349). The length frequency data were classified into 25 mm class intervals. Growth, mortality and exploitation The growth pattern, mortality, and exploitation of H. brachysoma were estimated using the length frequency distribution. ELEFAN-1 (Electronic Length Frequency Analysis) module of FAO-ICLARM Stock Assessment Tools II (FiSAT-II) software was used to estimate the von Bertalanffy growth parameters; asymptotic length ( L∞ ) and growth coefficient ( K ). (Gayanilo et al. 2005 ). The von Bertalanffy growth formula (VBGF) was fitted using L t = L ∞ [1- exp –K ( t−t 0 ) ], where L t is the growth at time t, L ∞ is the asymptotic length, K is the growth coefficient, t is the age of fish and t 0 is the age the fish at which the organism will have zero length. The potential longevity (t max - 3/K ) and growth performance index, φ = Log 10 ( K ) + 2 + Log 10 ( L∞ ) were calculated using the empirical equations of Pauly ( 1984 ). Total mortality ( Z ) was estimated from the length-converted catch curve approach (Pauly 1984 ) and natural mortality ( M ) was determined using the empirical formula of Pauly ( 1980 ): In M = 0.0152–0.279 In ( L ∞ ) + 0.6543 In ( K ) + 0.4634 In ( T ), where, L ∞ is the asymptotic length in mm, K is the growth constant in year –1 and T is the annual mean temperature (26–30 ◦ C). Fishing mortality ( F ) was calculated using the formula F = Z-M . Present level of exploitation rate ( E ) was estimated by the formula E = F/Z given by Gulland ( 1970 ). Length at first capture ( L c or L 50 ) was calculated from length converted catch curves (Pauly 1984 ). Recruitment pattern was determined by reconstructing the recruitment pulses from a time series of length-frequency data (Gayanilo et al. 2005 ). The relative yield per recruit ( Y/R ) and relative biomass per recruit ( B/R ) analysis were estimated using knife selected method given by Beverton and Holt (1966), which help to understand whether populations are overexploited, E max (exploitation rate with maximum yield) and E 50 (exploitation that retains 50% of the biomass). Results Fishery Gill nets, cast nets, seine nets, and hook and lines were the most common fishing gears used in the different river systems. Among them, gill nets and hook and lines are the main gears used for catching H. brachysoma. Depending on the net size, about 3–6 gill nets and 1–2 hook and lines are actively engaged in yellow cat fishing in each landing centre of the rivers. Fishing occurred throughout the week except on Sunday, the traditional rest day for fishermen in the state Kerala, resulting around 25–26 fishing days per month. The annual exploited fishery of H. brachysoma from the rivers was estimated to be 2.01 t. High landing was observed in Pampa River (631 kg) and low landing in Muvattupuzha (303 kg) (Fig. 2 ). Length frequency of exploited fishery The frequency distribution of length groups showed considerable variation in the length range of H. brachysoma exploited from various rivers of Western Ghats region (Fig. 3 ). The length range of H. brachysoma populations in Chalakudy and Muvatupuzha Rivers are much smaller than other rivers. In Chalakudy and Muvatupuzha Rivers the maximum length of fishes was recorded in the size class 330 mm and 308 mm respectively. The highest length of H. brachysoma in Pampa was 406 mm, while the maximum lengths in Achenkovil and Periyar River were 384 mm and 350 mm, respectively. Although only 29% of the exploited H. brachysoma in the River Pampa were 50% in the Rivers Chalakudy and Muvatupuzha. Growth, mortality and exploitation parameters Restructured form of the length frequency data of exploited H. brachysoma populations from five river presented as output of ELEFAN I shows that the growth curves for different populations differ considerably (Fig. 4 ). The asymptotic length ( L∞ ) ranged from 316.05 mm in Achenkovil to 421.05 mm in Pampa, while the growth coefficient ( K ) ranged from 0.58 year − 1 in Chalakudy to 1.10 year − 1 in Muvatupuzha (Table 1 and Fig. 5 ). Potential longevity of H. brachysoma was the highest (5.17) in Chalakudy and lowest in lowest (3.3) in Muvatupuzha (Table 1 ). Fishing mortality ( F ) was highest in Periyar (2.09 year − 1 ) and lowest in Achenkovil (0.62 year − 1 ), whereas natural mortality ( M ) was lowest in Pampa (0.62 year − 1 ) and highest in Muvatupuzha (0.99 year − 1 ) Rivers (Table 2 ). Table 1 Growth parameters of Horabagrus brachysoma from different rivers on the Western Ghats Rivers Asymptotic length ( L∞ , mm) Growth coefficient ( K ) year –1 Growth performance index ( φ ) Longevity ( 3/K ) years Chalakudy 342.30 0.580 4.29 5.17 Periyar 368.55 0.890 4.52 3.70 Muvattupuzha 316.05 1.100 4.45 3.30 Pampa 421.05 0.590 4.40 5.08 Achenkovil 394.8 0.600 4.37 5.00 Table 2 Mortality rates (year − 1 ) and exploitation level of Horabagrus brachysoma from different rivers on the Western Ghats River Total mortality rate ( Z ) Natural mortality rate ( M) Fishing mortality rate ( F ) Exploitation rate ( E ) Chalakudy 2.08 0.63 1.45 0.70 Periyar 2.91 0.82 2.09 0.72 Muvattupuzha 2.07 0.99 1.08 0.52 Pampa 1.30 0.62 0.68 0.53 Achenkovil 1.25 0.63 0.62 0.49 Yellow catfish exploitation level ( E ) in the Chalakudy, Periyar, Muvatupuzha and Pampa were higher (0.7, 0.72, 0.52 and 0.53) than the expected optimal exploitation level ( E 50 , ), indicating that these populations are overexploited. When compared to the Muvatupuzha and Pampa Rivers, populations of H. brachysosma in the Chalakudy and Periyar Rivers had higher levels of exploitation and fishing mortality. The size at first capture ( Lc ) calculated from the probability of capture was 197.86 mm − 288.22mm (Table 3 ). Lc was 78% of L ∞ in Rivers Chalakudy and Periyar, but it was it was 61– 63.5% of L ∞ in the Muvatupuzha, Pampa and Achenkovil. The harvest of smaller individuals suggests that specimens are being caught even before they reach sexual maturity, which contributes to future recruitments. Virtual population analysis (VPA) revealed that the species experienced considerable natural mortality in Achenkovil and Pampa Rivers at a young age, but the fishing mostly targeted comparatively larger sized individuals in Chalakudy, Periyar, and Muvatupuzha Rivers. (Fig. 6 ). Exploitation levels estimated using relative yield per recruit ( Y’/R ) and relative biomass per recruit ( B’/R ) analysis using knife-edge selection were found to range between 0.398–0.442 ( E 50 ) and 0.794-1.00 ( E max ) respectively in various river system (Fig. 7 ). The current level of exploitation was found in between 62% and 87% of the maximum exploitation ( E max ) from the five river systems. Table 3 Length of first capture ( L c), E 10 , E 50 and E max of Horabagrus brachysoma from different rivers on the Western Ghats River Length at first capture ( Lc) mm E 10 E 50 E ma x Chalakudy 268.42 1.00 0.442 1.00 Periyar 288.22 0.753 0.406 0.834 Muvattupuzha 197.86 0.718 0.399 0.802 Pampa 267.63 0.707 0.403 0.821 Achenkovil 242.16 0.707 0.398 0.794 Discussion Freshwater fisheries are intricately linked to the livelihoods of local dwelling communities living around rivers and reservoirs of Western Ghats region of India because it provide a source of food and livelihood for local community (Rajeev et al. 2011; Prasad et al. 2012 ). Freshwater fisheries in this region are under increasing pressure as a result of the “open-access” nature of the fisheries, the use of destructive fishing gears, overfishing of resources and poor enforcement of rules and regulations (Raghavan et al. 2011 ). Horabagrus brachysoma is an important food fish exploited from Western Ghats rivers by traditional fishers using various fishing methods such as gill nets, cast nets, drag nets, stake-nets, and hook-and-lines (Bindu 2006 ; Sreeraj et al. 2007 ; Renjithkumar et al. 2011 , 2016 ). The unregulated and unmanaged nature of the fishery is seen as a significant threat to the species (Raghavan and Ali 2013 ). Roughly 100 kilograms of mature H. brachysoma are captured within a week during the monsoon floodplain fishery ( Oothapiditham in the local language) using traditional fishing traps, gill nets, and electric fishing methods (Shaji and Laladhas 2013 ). The fishery of H. brachysoma in many rivers of Western Ghats seems unsustainable due to excessive fishing effort with over fishing such as growth fishing (capturing individuals before they reach a size significant enough to contribute to the spawning stock) and recruitment fishing (exploiting the spawning stock itself) (Prasad et al. 2012 ; Raghavan et al. 2016 ). The conservation of endemic and vulnerable fish populations exploited by small-scale fisheries is a major social and biological concern worldwide (Mace and Reynolds 2001 ). Only a few research have looked at the growth and exploitation aspects of freshwater species harvested from the Western Ghats (Prasad et al. 2012 ; Raghavan et al. 2011 ; Renjithkumar et al. 2020 ; Shanmughan et al. 2021). The population's natural growth rate is significantly influenced by the age or size when individuals reach at fist maturity (Vandermeer and Goldberg 2003). The size at first maturity for the H. brachysoma is known to be 175 mm and 188 mm TL in males, and 168 mm and 185 mm TL in females (Bindu et al. 2012 ; Chandran and Prasad 2014 ). According to the length–frequency analysis, high proportions of yellow catfish are caught in small scale fisheries before reaching sexual maturity. Collecting small fish before they mature leads to a slow recovery of exploited populations and reduces the fish capture and profit (Myers and Mertz 1998 ; Isaac and Ruffino 1996 ). Despite the fact that H. brachysoma can grow to a maximum length of 420 cm (Bindu and Padmakumar 2019 ), such large size individuals were not reported in the current investigation. The largest exploited stock reported in the present study was 410 mm. There have been few studies on the demography of H. brachysoma with the exception of Prasad et al ( 2012 ) in the Periyar River, therefore the comparison between geographic populations becomes difficult. The growth coefficient ( K ) for the H. brachysoma population in the five rivers (0.58 year − 1 - 1.100 year − 1 ) was lower than in Periyar River population (4.60 year − 1 ) from Southern Western Ghats of India (Prasad et al. 2012 ). These observed differences in the H. brachysoma growth parameters from different rivers could be attributed to stock variances, ecological conditions of the habitat, feeding habits, and environmental parameters. The high growth coefficient ( K ) and low longevity were recorded in Periyar and Muvatupuzha Rivers when compared to Chalakudy, Pampa and Achenkovil Rivers. It indicated that Periyar and Muvatupuzha Rivers yellow catfish populations acquired asymptotic length ( L∞ ) quickly which agree with Pauly and Munro ( 1984 ), that species having shorter life have higher ‘ K ’ values and reach their L ∞ within one or three years of life history. Estimates of growth performance index ( φ ) recorded in this study (4.29 to 4.52) were lower (4.99) than those observed for Periyar River (Prasad et al. 2012 ). The decrease in the size of a fish population can be attributed to by two factors: natural death ( M ) (disease, predation, pollution etc.) and fishing pressure ( F ). The fishing mortality rate of H. brachysoma was higher than the natural mortality rate in four rivers (Periyar, Muvatupuzha, Chalakudy and Pampa) indicating a rather significant fishing pressure on the species. The mortality rate of species is crucial for developing exploitation strategies to harvest and manage the fishery resources optimally. A ratio of more than 1.0 between total mortality and growth coefficient ( Z/K ) suggests a mortality dominated population, whereas a ratio of less than 1.0 indicates a growth dominated population (Etim et al. 1999 ). Yellow catfish populations in all five rivers studied were dominated by mortality ( Z/K = 1.88–3.58). This is an alarming condition in which overfishing gradually reduce recruitment, resulting in severe population losses in the near future (Rajeev et al. 2018). Fishing mortality ( F ) should be almost equal to natural mortality ( M ) in an ideally exploited stock, resulting in an exploitation rate ( E ) of 0.5 year − 1 (Gulland 1970 ). The exploitation rates ( E ) of yellow catfish in four rivers (Chalakudy, Pampa, Periyar, and Muvatupuzha) are greater than 0.5, whereas the exploitation level in the Achenkovil River nearly equals to E 0.5 , indicating uncertain future for native yellow cat fish population if management attention is not taken. The lengths at first capture (Lc) of H. brachysoma in all rivers were greater than their mean sizes at first maturity, indicating the possibility of no growth overfishing. Conservation management measures The current study is likely the first study on community-based data monitoring systems in small-scale inland fisheries in Western Ghats of India and it shows that yellow catfish are under heavy exploitation pressure and native populations are vulnerable to collapse in the absence of immediate management interventions. Controlling the overall harvest of yellow catfish could be the most significant management method for conserving the H. brachysoma population, however reducing fishing effort in an artisanal subsistence fishery like India is nearly difficult. As a result, management interventions for the protection of H. brachysoma in Western Ghats rivers should be based on a combination of technical measures such as restrictions on fishing gear and mesh size limits, closed seasons, non-fishing zones, and the introduction of catch quotas. There is currently no upper size limit for landing H. brachysoma in Western Ghats rivers. Implementing an upper size limit stimulate stock recovery and improve the sustainability of its fishery. The length at first maturity of H. brachysoma was estimated to be 175–188 mm in males, and 168–185 mm in females. A minimum catch size limit of 200 mm can be enforced in the rivers to prevent recruitment overfishing. Allowing them to attain this size ensures they have the opportunity to spawn at least once, aiding in the conservation of the species. In addition to setting size limits, restrictions on net mesh size should be implemented. Currently, the fishers use gill nets with mesh sizes ranging from 20 and 60 mm, resulting in the capture of small-sized juvenile fishes before they reach maturity. Gill nets should have a minimum mesh size of 40–80 mm to prevent the capture of immature juveniles. Restriction on the limits on mesh size or size of the fish to enforce is challenge for developing management measures for small-scale subsistence fisheries in Western Ghats Rivers. Yellow catfishes are spawn in South west monsoon months (June-September) in Kerala state, implementing a four-month closed season for collection is essential. In cooperation with local fishermen, a temporary shutdown of the fishery during the spawning season (closed season) should be developed. This measure aims to safeguard the spawning stock and support the enhancement of recruitment levels. Catch quotas for each fishing fleet will be developed in consultation with local fishermen, scientists, and fisheries managers for each river. The Department of Fisheries should prohibit indiscriminate exploitation of catfish during flood plain fisheries in central Kerala rivers and suggest a fine of Rs. 25000 rupees and imprisonment for up to three months. Strict monitoring and implementation of legislation can aid in the reduction of mature catfish harvest from natural waters. Finally engaging local communities in conservation efforts through education about the importance of the species and the preservation of their habitats. Declarations Conflicts of Interest The authors declare that they have no conflict of interest. Data availability statement The data that support the findings of this study are available from the corresponding author upon reasonable request. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript Ethical approval This is an observational study. The Cochin University of Science and Technology (CUSAT) Research Ethics Committee has confirmed that no ethical approval is required. Acknowledgements The authors are thankful to local fishers for collection of fish samples. 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Ambio 45:753–764. https ://doi.org/10.1007/s13280-016-0787-4 Costello C, Ovando D, Hilborn R, Gaines SD, Deschenes O, Lester SE (2012) Status and solutions for the world’s unassessed fisheries. Science 338(6106):7–520. https://doi.org/10.1126/ science.1223389 Dahanukar N, Raghavan R (2013). Freshwater fishes of Western Ghats: Checklist v 1.0 August 2013. MIN - Newsletter of IUCN SSC/WI Freshwater Fish Specialist Group - South Asia and the Freshwater Fish Conservation Network of South Asia (FFCNSA) 1: 6–16 Divya B, Ramesh BR, Karanth KP (2021) Contrasting patterns of phylogenetic diversity across climatic zones of Western Ghats: A biodiversity hotspot in peninsular India. J Syst Evol 59(2):240-250. https://doi.org/10.1111/jse.12663 Etim L, Lebo PE, King RP (1999) The dynamics of an exploited population of a siluroid catfish ( Schilbe intermedius Ruppell, 1832) in the Cross River, Nigeria. 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(2017) Assessing the small-scale Shark fishery of Madagascar through community-based monitoring and knowledge. Fish Res 186: 131–143 Isaac VJ, Ruffino ML (1996) Population dynamics of tambaqui, Colossoma macropomum Cuvier, in the lower Amazon, Brazil. Fish Manag Ecol 3:315–333. Kurup BM, Sebastian MJ, Sankaran TM, Rabindranath P (1993) Exploited Fishery Resources of the Vembanad Lake, Status of Residents and Migrants. Fish Technol (Special issue: Society of Fishery Technologists, India), 44-49 Kurup BM, Sebastian MJ, Sankaran TM, Rabindranath P (1995) Exploited fishery resources of Vembanad lake 4: estimates of marketable surplus of production. J Mar Biol Assoc Ind 37:1–10 Lam S, Dodd W, Skinner K, Papadopoulos A, Zivot, C, Ford J. et al. (2019) Community-based monitoring of indigenous food security in a changing climate: Global trends and future directions. Environ Res Lett 14(7): 073002. Lorenzen, K, Cowx IG, Entsua-Mensah REM, Lester NP, Koehn JD, Randall, R.G. et al. (2016) Stock assessment in inland fisheries: A foundation for sustainable use and conservation. Rev Fish Biol Fish 26(3):405–440. Lowitt K, Levkoe CZ, Spring A, Turlo C, Williams PL, Bird, S et al (2020) Empowering small-scale, community-based fisheries through a food systems framework. Mar Policy 120:104-150 Lynch AJ, Cooke SJ, Deines AM, Bower SD, Bunnell DB, Cowx IG et al (2016) The social, economic, and environmental importance of inland fish and fisheries. Environ. Rev 24(2):115–121. https://doi.org/10.1139/er-2015-0064 Mace GM, Reynolds JD (2001) Exploitation as a conservation issue In: Reynolds JD, Mace, GM, Redford KH, Robinson JG, Conservation of Exploited Species. Cambridge University Press, Cambridge, pp 4-15 Myers N, Mittermeier RA, Mittermeier CG, Da Fonseca GA, Kent J (2000) Biodiversity hotspots for conservation priorities. Nature 403(6772):853 Myers RA, Mertz G (1998) The limits of exploitation: A precautionary approach. Ecol Appl 8: 165–169 Oviedo AFP, Bursztyn M (2017) Community-based monitoring of small-scale fisheries with digital devices in Brazilian Amazon. Fish Manag Ecol 24(4):320–329 Pauly D (1980) On the interrelationships between natural mortality, growth parameters, and mean environmental temperature in 175 fish stocks. J de Conseil, Conseil Intt Pour L’Expl de la Mer 39:175–192. Pauly D (1984) Fish population dynamics in tropical waters: A manual for use with programmable calculators. ICLARM Stud Rev 8:325. Pauly D, Munro JL (1984) Once more on the comparison of growth in fish and invertebrates. Fishbyte, The WorldFish Center 2(1):1-21 Payne AL, Temple SA (1996) River and Floodplain Fisheries in the Ganges River. Final Report. DFID Fisheries Management Sciences Programme R 5485, London, MRAG Ltd, 177 pp. Prasad G, Ali A, Harikrishnan M, Raghavan R (2012) Population dynamics of an endemic and threatened Yellow Catfish, Horabagrus brachysoma (Gunther) from Periyar River, Southern Western Ghats, India. J Thre Taxa 4:2333–2342. Radhakrishnan KV (2006) Systematics, germplasm evaluation and patterns of distribution and abundance of freshwater fishes of Kerala, Ph. D. thesis submitted to Cochin University of Science and Technology, 305 pp. Raghavan R, Ali A (2013) Horabagrus brachysoma . The IUCN red list of threatened species. Version 2015.1. www. iucnredlist.org. Raghavan R, Prasad G, Ali A, Pereira B (2008) Fish fauna of River Chalakudy part of Western Ghats biodiversity hotspot (South India): patterns of distribution, threats and conservation needs. Biodivers Conserv 17:3119–3131 Raghavan R, Prasad G, Ali A, Pereira B (2008b) Exotic fish species in a global biodiversity hotspot: observations from river Chalakudy, part of Western Ghats, Kerala, India. Biol Invasions 10:37–40 Raghavan R, Ali A, Dahanukar N, Rosser A (2011) Is the Deccan Mahseer, Tor khudree (Sykes) fishery in the Western Ghats Hotspot sustainable? A participatory approach to assessment. Fish Res 110:29–38. https://doi.org/10.1016/j.fishr es.2011.03.008 Raghavan R, Philip S, Ali A, Katwate U, Dahanukar N (2016) Fishery, biology, aquaculture and conservation of the threatened Asian Sun catfish. Rev Fish Biol Fisheries 26:169–180 Raghavan R, Ramprasanth MR, Ali A, Dahanukar N (2018) Population dynamics of an endemic cyprinid ( Hypselobarbus kurali): Insights from an exploited reservoir fishery in the Western Ghats of India. Lakes Reser Res Manag 23(3):250-255. https://doi.org/10.1111/lre.12233 Renjithkumar CR, Harikrishnan M, Kurup BM (2011) Exploited fisheries resources of the Pampa River, Kerala, India. Ind J Fish 58(3):13–22 Renjithkumar CR, Roshni K, Kurup BM (2016) Exploited Fishery Resources of Muvattupuzha River, Kerala, India. Fishery Technology 53: 177–182 Renjithkumar CR, Roshni K, Harikrishnan M, Kurup BM (2020) Population dynamics of Hypselobarbus thomassi (Day 1874), an endemic cyprinid fish from a tropical reservoir of Southern Western Ghats, India. Lakes Reser Res Manag 25 (4):388-393. https://doi. org/10.1111/lre.12343. Shaji CP, Laladhas KP (2013) Monsoon flood plain fishery and traditional fishing methods in Thrissur District, Kerala. Ind J Tradit Knowl 12(1):102–108 Shanmughan A, Dahanukar N, Harrison A, Pinder AC, Ranjeet K, Raghavan R (2022) Demographics and exploitation of two Near Threatened freshwater eels, Anguilla bengalensis and Anguilla bicolor , in small-scale subsistence fisheries and implications for conservation. Aquat Conserv Mar Freshw 32(2):269-281. https://doi.org/10.1002/aqc.3765. Shephard S, Ryan D, O'Reilly P, Roche W (2021) Using local ecological knowledge to inform semi-quantitative fishery surveillance indicators: an example in marine recreational angling. ICES J Mar Sci 78(10):3805–3816. Smith LED, Khoa SN, Lorenzen K (2005) Livelihood functions of inland fisheries: Policy implications in developing countries. Water Policy 7(4):359–383. http://wp.iwaponline.com/content/7/4/359 Sreeraj N, Raghavan R, Prasad G (2007) Some aspects of the fishery of the threatened Yellow Catfish, Horabagrus brachysoma from Vembanad Lake and a note on their landings in Vaikom, Kerala, India. Zoos Print J 22(4):2665–2666 Subramanyam K, Nayar MP (1974) Vegetation and phytogeography of the Western Ghats. In: Mani MS (ed) Ecology and Biogeography in India, Vol. 23 Monographiae Biologicae, Dr W Junk Publishers. pp 178–196. Sun M, Li Y, Zhang C, Xu B, Ren Y, Chen Y (2020) Management of data-limited fisheries: identifying informative data to achieve sustainable fisheries. N Am J Fish Manag 40(3):733–751. Swapna S (2009) Fish Diversity in Achenkovil River, Kerala, India. J Bombay Nat Hist 106: 104–106 Tickner D, Opperman JJ, Abell R, Acreman M, Arthington AH, Bunn SE et al. (2020) Bending the curve of global freshwater biodiversity loss: an emergency recovery plan. Biosci 70(4):330–342. Welcomme RL, Valbo-Jorgensen J, Halls AS (2014) Inland fisheries evolution and management: case studies from four continents. FAO Fisheries and Aquaculture Technical Paper 579. Youn S, Taylor, J., Lynch WW, Cowx AJ, Beard I G, Jr Bartley D, Wu F (2014) Inland capture fishery contributions to global food security and threats to their future. Glob Food Sec 3:142–148. https ://doi.org/10.1016/j.gfs.2014.09.005 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4585679","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":320713796,"identity":"4812dda7-123d-4b27-b085-a824c60f7e9c","order_by":0,"name":"Chelapurath Radhakrishnan Renjithkumar","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABGklEQVRIiWNgGAWjYJACgwSGAwwSYOYPtvp+EJ1QQEhLAlQLYw8f48wGkBYDQvbAtDCwyTFuOAA2Brdi8/beAwUPf9xhkJyRnfi5gseM2fj86sQPDwwY5PnFDmDVInPmXALQYc8YpCVyN0uesUhjM7vxdrME0GGGM2cnYNUiIZFjANRymEFOIneDZAPPMR6zG2c3gLQkGNzGoUX+DVzL5p8NbP8ljGec3fwDrxYJHogWoMO2STawsRkY8Pduw28LD8hhaYd5JHvebrNs7GFLkLjBu80iwUACt1/Yz5gZ/rA5LCdxPHfzzYYfbAn8/Wc33/xRYSPPL41dCxCwgeKAB8kUsEoJXMpBgPkBKp//AD7Vo2AUjIJRMAIBAFvKXnWpnzEPAAAAAElFTkSuQmCC","orcid":"","institution":"St Albert’s College (Autonomous)","correspondingAuthor":true,"prefix":"","firstName":"Chelapurath","middleName":"Radhakrishnan","lastName":"Renjithkumar","suffix":""},{"id":320713797,"identity":"eeb45d53-176b-4018-bce1-d889f5c6b9ff","order_by":1,"name":"Kuttanelloor Roshni","email":"","orcid":"","institution":"Cochin University of Science and Technology (CUSAT)","correspondingAuthor":false,"prefix":"","firstName":"Kuttanelloor","middleName":"","lastName":"Roshni","suffix":""}],"badges":[],"createdAt":"2024-06-15 08:51:04","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-4585679/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4585679/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":59463514,"identity":"33163d28-336e-4482-a76b-50522fe7e83a","added_by":"auto","created_at":"2024-07-02 05:55:06","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":179544,"visible":true,"origin":"","legend":"\u003cp\u003eMap showing the landing centre of different rivers of Western Ghats were \u003cem\u003eH. brachysoma\u003c/em\u003e collected\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4585679/v1/c7e0c663bc5303841e76f952.png"},{"id":59463917,"identity":"4fea18af-9189-41d1-b473-a9d7bb450870","added_by":"auto","created_at":"2024-07-02 06:03:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":16546,"visible":true,"origin":"","legend":"\u003cp\u003eMonthly variations in the landing of \u003cem\u003eH. brachysoma\u003c/em\u003e from different river systems of Western Ghats\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4585679/v1/906bb724d13f6e24a2f20c81.png"},{"id":59463516,"identity":"3d99360f-a1a1-484e-ae85-a3033c4ceded","added_by":"auto","created_at":"2024-07-02 05:55:06","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":497766,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of length frequencies of \u003cem\u003eH. brachysoma\u003c/em\u003e across five rivers in the Western Ghats (a) Chalakudy (b) Periyar (c) Muvatupuzha (d) Pampa (e) Achenkovil\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4585679/v1/e57524b5e72589429d51d0bd.png"},{"id":59463517,"identity":"d921b5c5-a568-4241-b91f-4a4f6439664c","added_by":"auto","created_at":"2024-07-02 05:55:06","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":902337,"visible":true,"origin":"","legend":"\u003cp\u003evon-Bertalanffy growth curves for \u003cem\u003eH. brachysoma\u003c/em\u003e from different rivers on the Western Ghats (a) Chalakudy (b) Periyar (c) Muvatupuzha (d) Pampa (e) Achenkovil\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4585679/v1/68492fd478017b1249f93b49.png"},{"id":59463918,"identity":"89a3410d-5936-4674-9c07-7eafd9715764","added_by":"auto","created_at":"2024-07-02 06:03:06","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":475208,"visible":true,"origin":"","legend":"\u003cp\u003eLength converted catch curve for the estimation of mortality of \u003cem\u003eH. brachysoma\u003c/em\u003e from different rivers on the Western Ghats (a) Chalakudy (b) Periyar (c) Muvatupuzha (d) Pampa (e) Achenkovil\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4585679/v1/cadb8a86fdefbb70c5595129.png"},{"id":59463518,"identity":"76261b33-152b-46b7-8beb-efe03680e840","added_by":"auto","created_at":"2024-07-02 05:55:06","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1494809,"visible":true,"origin":"","legend":"\u003cp\u003eLength-structured virtual population analysis (VPA) of \u003cem\u003eH. brachysoma\u003c/em\u003e from different rivers on the Western Ghats (a) Chalakudy (b) Periyar (c) Muvatupuzha (d) Pampa (e) Achenkovil\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4585679/v1/75cd8625e37a3fd254941492.png"},{"id":59463519,"identity":"e62006d5-945e-4c42-b35c-4902f3685dee","added_by":"auto","created_at":"2024-07-02 05:55:06","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":959352,"visible":true,"origin":"","legend":"\u003cp\u003eRelative yield per recruit (\u003cem\u003eY’/R\u003c/em\u003e) and relative biomass per recruit (\u003cem\u003eB’/R\u003c/em\u003e) plots of\u003cem\u003e H. brachysoma\u003c/em\u003e from different rivers on the Western Ghats (a) Chalakudy (b) Periyar (c) Muvatupuzha (d) Pampa (e) Achenkovil\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4585679/v1/bbfc7172914b48fe8dfc3cd4.png"},{"id":61464991,"identity":"ee1067fe-1f2d-405e-b331-d01e6f16795d","added_by":"auto","created_at":"2024-07-31 05:35:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6744814,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4585679/v1/c0cecc92-07af-45a0-b51c-9fd1e0132e7a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Fishery, growth, and mortality of threatened Asian Sunfish, Horabagrus brachysoma (Gu¨nther 1864) in five rivers of Western Ghats hotspot, India","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOnly 10% of the world\u0026rsquo;s exploited fish stocks are assessed (FAO 2010), and many unassessed stocks are generally \u0026lsquo;uncertain risk\u0026rsquo; category (Costello et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). These unassessed stocks often sustain artisanal and subsistence inland fisheries, offering employment opportunities for rural communities (Smith et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Lynch et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Inland fish and fisheries play a pivotal role in food security by offering local and cost-effective sources of protein, essential fatty acids, oils, and micronutrients to hundreds of millions of people worldwide, especially in developing nations (Funge-Smith and Bennett \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). This type of fishing is typically characterized by small-scale, household-based, and subsistence practices, where the majority of the catch is consumed within the local community rather than being exported to other regions (Youn et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). In developing countries, inland fisheries serve as a crucial source of food security and income, supporting the livelihoods of over 60\u0026nbsp;million people (Cooke et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Global inland fisheries encounter a multitude of risks that significantly impact the well-being of millions of people worldwide (Smith et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Collecting precise data on inland fisheries production poses challenges due to the dispersed nature of most inland fisheries activities, often leading to underreporting or no reporting at all to government agencies (Allan et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Despite the important contributions, inland fish and fisheries generally remain economically and socially undervalued and biologically underappreciated because accurate information about these small scale highly dispersed fisheries is inherently difficult to acquire (Youn et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe Western Ghats, a part of the Western Ghats-Sri Lanka biodiversity hotspot, comprises a mountain range stretching over 1600 km along the west coast of peninsular India, encompassing an area spanning 180,000 km\u003csup\u003e2\u003c/sup\u003e (Myers et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). It is one of 34 worldwide biodiversity hotspots with high endemicity, as well as one of four in the Indian subcontinent (Divya et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Despite covering less than 6% of India's surface area, the WG has approximately 30% of the country's biodiversity, with a significant number of endemic and vulnerable species (CEPF \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). This mountain range is classified into four phytogeographic subregions: northern WG (River Tapi to Goa), central WG (River Kali to Coorg), Nilgiris, and southern WG (Anamalai, Palani, and Cardamom hills) (Subramanyam and Nayar \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e1974\u003c/span\u003e). The streams and rivers that originate and pass through the WG freshwater ecoregion in the Southern Indian state of Kerala are home of 300 species of freshwater fish, 70% of which are endemic and one-third are threatened (Dahanukar and Raghavan \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Freshwater fishes are directly linked to the livelihood of local communities in the Southern WG, serving as a source of food and revenue generating (Raghavan et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). This rising demand has resulted in indiscriminate exploitation of endemic and threatened fishes at unsustainable levels via small-scale and open-access fisheries, as well as a variety of complex anthropogenic pressures such as pollution, habitat destruction, and diseases, which can cause rapid declines in native fish populations. (Raghavan et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eManaging the overexploitation of freshwater fish species is important for both food security and minimizing biodiversity loss (Tickner et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). This may be done by the management of exploitation (reduction of bycatch, minimizing fishing effort and size limits regulation), management of fish habitat (river flow regulation and management of aquatic vegetation) and the use of fisheries enhancements (river ranching and use of artificial reefs) (Arlinghaus et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Lorenzen et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Fish stock assessment models assist fishery managers in understanding the dynamics of fish stocks and how fish populations respond to external stressors such as commercial fishing and predation (Hilborn et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Sun et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Appropriate data for length-based stock evaluations can be collected through sampling at commercial fish landings hubs or through fisheries-cruise surveys, with no need for total removals from a target stock (Shephard et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). However, in inland habitats where local knowledge of fishers is essential, researchers and fisheries managers may find it difficult to obtain and validate data for stock assessment (Valbo-J\u0026oslash;rgensen and Poulsen 2000). Community-based data monitoring (CBM) systems offer an alternate approach in such small-scale and artisanal fisheries, which are playing an increasingly important role in sustaining local food supply and food security (Humber et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Oviedo and Bursztyn \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Lam et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Lowitt et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Local communities frequently monitor fish catch patterns in their fishing practises throughout the year, and this knowledge can be captured as quantitative indicators (Thompson 2018; Shephard et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe Asian Sun catfish or the yellow catfish, \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e (Gu\u0026uml;nther 1864) belongs to the family Horabagridae and is an important food fish exploited by traditional fishers from rivers, lakes, backwaters, and associated inland canal systems in the Western Ghats region of Kerala, Karnataka, and Maharashtra (Raghavan et al \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). During the monsoon floodplain fishing, \u003cem\u003eH. brachysoma\u003c/em\u003e is a prominent catfish species in the Central Kerala Rivers. (Shaji and Laladhas \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The landing of the species from Kerala state rivers ranges from 3.67 t to 17.1 t (Renjithkumar et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2011\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) whereas annual landings in Vembanad Lake ranged between 2 and 439 t (Bindu \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Sreeraj et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Kurup et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). Overall, the fishery for \u003cem\u003eH. brachysoma\u003c/em\u003e appears to be unsustainable in many rivers of the Western Ghats due to overexploitation of stock and habitat destruction (Raghavan et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), and the IUCN has classed the species as 'Vulnerable' due to an overall population drop (Raghavan and Ali \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Management of the fishery of yellow catfish is hindered due to the lack of successful fisheries management programmes in Kerala\u0026rsquo;s WG waters, where the largest share of exploitation takes place (Prasad et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Previously, Prasad et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) reported \u003cem\u003eH. brachysoma\u003c/em\u003e population characteristics from a single river system in Southern India. Despite this, there are no reliable estimates of the yellow cat fish's fishery, growth, mortality, and exploitation in its native ranges in the Western Ghats. The current study examines the fishery, growth, and exploitation status of vulnerable \u003cem\u003eH. brachysoma\u003c/em\u003e exploited from different river systems (Pampa, Achenkovil, Muvattupuzha, Periyar, and Chalakudy Rivers) in the Southern Western Ghats of India in connection to environmental variables.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy area\u003c/h2\u003e \u003cp\u003eThe study was carried out in the major fish landing centres of Periyar (244 km), Chalakudy (146 km), Pampa (176 km), Muvattupuzha (121 km), and Achenkovil (128 km) Rivers, which are located in the central region of Kerala state. The five fish landing sites were selected based on the high occurrence of \u003cem\u003eH. brachysoma\u003c/em\u003e in the daily catches of local fishers. Bhoothanthankettu, Periyar (10\u0026deg;08\u0026rsquo;12.75\u0026rdquo; N; 76\u0026deg;39\u0026rsquo;51.27\u0026rdquo; E); Pulikakadavu, Chalakudy (10\u0026deg;14\u0026rsquo;28.53\u0026rdquo; N; 76\u0026deg;19\u0026rsquo;50.27\u0026rdquo; E); Mulakulam, Muvatupuzha (09\u0026deg;51\u0026rsquo;15.00\u0026rdquo; N; 76\u0026deg;29\u0026rsquo;19.12\u0026rdquo; E); Prayikkara, Achenkovil (09\u0026deg;15\u0026rsquo;44.04\u0026rdquo; N; 76\u0026deg;32\u0026rsquo;28.72\u0026rdquo; E) and Edatuva, Pampa (09\u0026deg;21\u0026rsquo;53.29\u0026rdquo; N; 76\u0026deg;28\u0026rsquo;35.05\u0026rdquo; E) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) were the landing centres selected for the study. River Periyar, the longest of Kerala's 44 perennial rivers, is regarded as the state's lifeline, home to 77 fish species (Radhakrishnan \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). The Chalakudy River has a varied fish fauna of 98 species, several of which are endangered or threatened (Raghavan et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2008\u003c/span\u003e a). The fish fauna of the Chalakudy River is threatened by habitat destruction, overfishing, water pollution, and fish species invasion (Raghavan et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2008\u003c/span\u003e b). Muvattupuzha River is the one of the important rivers in Ernakulam district of Kerala contains 36 fish species and \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e contributed 3.67 t yearly to the fish landing (Renjithkumar et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The Achenkovil River flows through two Western Ghats hill ranges: Kottavasal and Devarmalai, covering 1484 km\u003csup\u003e2\u003c/sup\u003e and home to 52 fish species (Swapna \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Pampa River, which runs through Kuttanad (low-lying agricultural fields) in central Kerala, contributed 17.11 t of \u003cem\u003eH. brachysomain\u003c/em\u003e fishery (Renjithkumar et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eData collection\u003c/h2\u003e \u003cp\u003eData on the fishery for \u003cem\u003eH. brachysoma\u003c/em\u003e were collected from local fishermen monthly from April 2020 to March 2021 from five rivers. Hook and line and gill nets were the main fishing gears using for catching yellow cat fish. Gill nets ranged in length from 75 to 150 metres, with mesh sizes ranging from 30 to 60 mm are normally used for fishing. The catch (kg) from the haul of gill nets and hook \u0026amp; lines were recorded. Daily landings from each type of gears were computed following Kurup et al. (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1993\u003c/span\u003e); W = (w/n) X N, where W\u0026thinsp;=\u0026thinsp;total weight of fish, w\u0026thinsp;=\u0026thinsp;total weight of fish from gear sampled, n\u0026thinsp;=\u0026thinsp;number of gears sampled, N\u0026thinsp;=\u0026thinsp;total number of similar gears operated. Monthly catch was estimated by multiplying daily catch with total number of fishing days in a month (25 fishing days). The annual exploited quantity was calculated by summarising the landings of 12 months.\u003c/p\u003e \u003cp\u003eSamples of \u003cem\u003eH. brachysoma\u003c/em\u003e for demographics were collected from the catches of small-scale fishermen at fish landing centres along five rivers in the Southern Western Ghats from April 2020 to March 2021. Total length (TL) was measured to the nearest 0.01 mm using a digital sliding calliper, and total body weight (BW) was measured to the nearest 0.01 g using an electronic weighted scale. For the demography of \u003cem\u003eH. brachysoma\u003c/em\u003e, 1938 specimens from different river systems were used: Periyar (n\u0026thinsp;=\u0026thinsp;383), Chalakudy (n\u0026thinsp;=\u0026thinsp;407), Pampa (n\u0026thinsp;=\u0026thinsp;448), Muvatupuzha (n\u0026thinsp;=\u0026thinsp;351), and Achenkovil (n\u0026thinsp;=\u0026thinsp;349). The length frequency data were classified into 25 mm class intervals.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003eGrowth, mortality and exploitation\u003c/h2\u003e \u003cp\u003eThe growth pattern, mortality, and exploitation of \u003cem\u003eH. brachysoma\u003c/em\u003e were estimated using the length frequency distribution. ELEFAN-1 (Electronic Length Frequency Analysis) module of FAO-ICLARM Stock Assessment Tools II (FiSAT-II) software was used to estimate the von Bertalanffy growth parameters; asymptotic length (\u003cem\u003eL\u0026infin;\u003c/em\u003e) and growth coefficient (\u003cem\u003eK\u003c/em\u003e). (Gayanilo et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). The von Bertalanffy growth formula (VBGF) was fitted using \u003cem\u003eL\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e =\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026infin;\u003c/em\u003e\u003c/sub\u003e [1- exp \u003csup\u003e\u0026ndash;K (\u003cem\u003et\u0026minus;t\u003c/em\u003e\u003c/sup\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e)\u003c/sup\u003e], where \u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e is the growth at time t, \u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u0026infin;\u003c/sub\u003e is the asymptotic length, \u003cem\u003eK\u003c/em\u003e is the growth coefficient, \u003cem\u003et\u003c/em\u003e is the age of fish and \u003cem\u003et\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e is the age the fish at which the organism will have zero length. The potential longevity (t\u003csub\u003emax\u003c/sub\u003e- \u003cem\u003e3/K\u003c/em\u003e) and growth performance index, \u003cem\u003eφ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;Log 10 (\u003cem\u003eK\u003c/em\u003e)\u0026thinsp;+\u0026thinsp;2\u0026thinsp;+\u0026thinsp;Log 10 (\u003cem\u003eL\u0026infin;\u003c/em\u003e) were calculated using the empirical equations of Pauly (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). Total mortality (\u003cem\u003eZ\u003c/em\u003e) was estimated from the length-converted catch curve approach (Pauly \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1984\u003c/span\u003e) and natural mortality (\u003cem\u003eM\u003c/em\u003e) was determined using the empirical formula of Pauly (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1980\u003c/span\u003e): In \u003cem\u003eM\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0152\u0026ndash;0.279 In (\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026infin;\u003c/em\u003e\u003c/sub\u003e)\u0026thinsp;+\u0026thinsp;0.6543 In (\u003cem\u003eK\u003c/em\u003e)\u0026thinsp;+\u0026thinsp;0.4634 In (\u003cem\u003eT\u003c/em\u003e), where, \u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026infin;\u003c/em\u003e\u003c/sub\u003e is the asymptotic length in mm, \u003cem\u003eK\u003c/em\u003e is the growth constant in year\u003csup\u003e\u0026ndash;1\u003c/sup\u003e and \u003cem\u003eT\u003c/em\u003e is the annual mean temperature (26\u0026ndash;30\u003csup\u003e◦\u003c/sup\u003eC). Fishing mortality (\u003cem\u003eF\u003c/em\u003e) was calculated using the formula \u003cem\u003eF\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u003cem\u003eZ-M\u003c/em\u003e. Present level of exploitation rate (\u003cem\u003eE\u003c/em\u003e) was estimated by the formula \u003cem\u003eE\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u003cem\u003eF/Z\u003c/em\u003e given by Gulland (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1970\u003c/span\u003e). Length at first capture (\u003cem\u003eL\u003c/em\u003ec or \u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003e50\u003c/em\u003e\u003c/sub\u003e) was calculated from length converted catch curves (Pauly \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). Recruitment pattern was determined by reconstructing the recruitment pulses from a time series of length-frequency data (Gayanilo et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). The relative yield per recruit (\u003cem\u003eY/R\u003c/em\u003e) and relative biomass per recruit (\u003cem\u003eB/R\u003c/em\u003e) analysis were estimated using knife selected method given by Beverton and Holt (1966), which help to understand whether populations are overexploited, \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e (exploitation rate with maximum yield) and \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e50\u003c/em\u003e\u003c/sub\u003e (exploitation that retains 50% of the biomass).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eFishery\u003c/h2\u003e \u003cp\u003eGill nets, cast nets, seine nets, and hook and lines were the most common fishing gears used in the different river systems. Among them, gill nets and hook and lines are the main gears used for catching \u003cem\u003eH. brachysoma.\u003c/em\u003e Depending on the net size, about 3\u0026ndash;6 gill nets and 1\u0026ndash;2 hook and lines are actively engaged in yellow cat fishing in each landing centre of the rivers. Fishing occurred throughout the week except on Sunday, the traditional rest day for fishermen in the state Kerala, resulting around 25\u0026ndash;26 fishing days per month. The annual exploited fishery of \u003cem\u003eH. brachysoma\u003c/em\u003e from the rivers was estimated to be 2.01 t. High landing was observed in Pampa River (631 kg) and low landing in Muvattupuzha (303 kg) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eLength frequency of exploited fishery\u003c/h2\u003e \u003cp\u003eThe frequency distribution of length groups showed considerable variation in the length range of \u003cem\u003eH. brachysoma\u003c/em\u003e exploited from various rivers of Western Ghats region (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The length range of \u003cem\u003eH. brachysoma\u003c/em\u003e populations in Chalakudy and Muvatupuzha Rivers are much smaller than other rivers. In Chalakudy and Muvatupuzha Rivers the maximum length of fishes was recorded in the size class 330 mm and 308 mm respectively. The highest length of \u003cem\u003eH. brachysoma\u003c/em\u003e in Pampa was 406 mm, while the maximum lengths in Achenkovil and Periyar River were 384 mm and 350 mm, respectively. Although only 29% of the exploited \u003cem\u003eH. brachysoma\u003c/em\u003e in the River Pampa were \u0026lt;\u0026thinsp;200 mm TL, the proportions increased to 31% in the River Achenkovil, 42% in the River Periyar, and \u0026gt;\u0026thinsp;50% in the Rivers Chalakudy and Muvatupuzha.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003eGrowth, mortality and exploitation parameters\u003c/h2\u003e \u003cp\u003eRestructured form of the length frequency data of exploited \u003cem\u003eH. brachysoma\u003c/em\u003e populations from five river presented as output of ELEFAN I shows that the growth curves for different populations differ considerably (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The asymptotic length (\u003cem\u003eL\u0026infin;\u003c/em\u003e) ranged from 316.05 mm in Achenkovil to 421.05 mm in Pampa, while the growth coefficient (\u003cem\u003eK\u003c/em\u003e) ranged from 0.58 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in Chalakudy to 1.10 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in Muvatupuzha (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Potential longevity of \u003cem\u003eH. brachysoma\u003c/em\u003e was the highest (5.17) in Chalakudy and lowest in lowest (3.3) in Muvatupuzha (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Fishing mortality (\u003cem\u003eF\u003c/em\u003e) was highest in Periyar (2.09 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and lowest in Achenkovil (0.62 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), whereas natural mortality (\u003cem\u003eM\u003c/em\u003e) was lowest in Pampa (0.62 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and highest in Muvatupuzha (0.99 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) Rivers (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eGrowth parameters of \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e from different rivers on the Western Ghats\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRivers\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAsymptotic length (\u003cem\u003eL\u0026infin;\u003c/em\u003e, mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGrowth coefficient (\u003cem\u003eK\u003c/em\u003e) year\u003csup\u003e\u0026ndash;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGrowth performance index (\u003cem\u003eφ\u003c/em\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLongevity (\u003cem\u003e3/K\u003c/em\u003e) years\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChalakudy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e342.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.580\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeriyar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e368.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.890\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.70\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMuvattupuzha\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e316.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePampa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e421.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.590\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAchenkovil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e394.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMortality rates (year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and exploitation level of \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e from different rivers on the Western Ghats\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRiver\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal mortality rate (\u003cem\u003eZ\u003c/em\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNatural mortality rate (\u003cem\u003eM)\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFishing mortality rate (\u003cem\u003eF\u003c/em\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eExploitation rate (\u003cem\u003eE\u003c/em\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChalakudy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.70\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeriyar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.72\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMuvattupuzha\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePampa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAchenkovil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eYellow catfish exploitation level (\u003cem\u003eE\u003c/em\u003e) in the Chalakudy, Periyar, Muvatupuzha and Pampa were higher (0.7, 0.72, 0.52 and 0.53) than the expected optimal exploitation level (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e50\u003c/em\u003e,\u003c/sub\u003e), indicating that these populations are overexploited. When compared to the Muvatupuzha and Pampa Rivers, populations of \u003cem\u003eH. brachysosma\u003c/em\u003e in the Chalakudy and Periyar Rivers had higher levels of exploitation and fishing mortality. The size at first capture (\u003cem\u003eLc\u003c/em\u003e) calculated from the probability of capture was 197.86 mm \u0026minus;\u0026thinsp;288.22mm (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). \u003cem\u003eLc\u003c/em\u003e was 78% of \u003cem\u003eL\u0026thinsp;\u0026infin;\u003c/em\u003e\u0026thinsp;in Rivers Chalakudy and Periyar, but it was it was 61\u0026ndash; 63.5% of \u003cem\u003eL\u0026thinsp;\u0026infin;\u003c/em\u003e\u0026thinsp;in the Muvatupuzha, Pampa and Achenkovil. The harvest of smaller individuals suggests that specimens are being caught even before they reach sexual maturity, which contributes to future recruitments. Virtual population analysis (VPA) revealed that the species experienced considerable natural mortality in Achenkovil and Pampa Rivers at a young age, but the fishing mostly targeted comparatively larger sized individuals in Chalakudy, Periyar, and Muvatupuzha Rivers. (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Exploitation levels estimated using relative yield per recruit (\u003cem\u003eY\u0026rsquo;/R\u003c/em\u003e) and relative biomass per recruit (\u003cem\u003eB\u0026rsquo;/R\u003c/em\u003e) analysis using knife-edge selection were found to range between 0.398\u0026ndash;0.442 (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e50\u003c/em\u003e\u003c/sub\u003e) and 0.794-1.00 (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e) respectively in various river system (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The current level of exploitation was found in between 62% and 87% of the maximum exploitation (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e)\u003c/em\u003e from the five river systems.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLength of first capture (\u003cem\u003eL\u003c/em\u003ec), \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e10\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e50\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e of \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e from different rivers on the Western Ghats\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRiver\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLength at first capture (\u003cem\u003eLc)\u003c/em\u003e mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e10\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e50\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003ema\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChalakudy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e268.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.442\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeriyar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e288.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.753\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.406\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.834\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMuvattupuzha\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e197.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.718\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.399\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.802\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePampa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e267.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.707\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.403\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.821\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAchenkovil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e242.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.707\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.398\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.794\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eFreshwater fisheries are intricately linked to the livelihoods of local dwelling communities living around rivers and reservoirs of Western Ghats region of India because it provide a source of food and livelihood for local community (Rajeev et al. 2011; Prasad et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Freshwater fisheries in this region are under increasing pressure as a result of the \u0026ldquo;open-access\u0026rdquo; nature of the fisheries, the use of destructive fishing gears, overfishing of resources and poor enforcement of rules and regulations (Raghavan et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e is an important food fish exploited from Western Ghats rivers by traditional fishers using various fishing methods such as gill nets, cast nets, drag nets, stake-nets, and hook-and-lines (Bindu \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Sreeraj et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Renjithkumar et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2011\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The unregulated and unmanaged nature of the fishery is seen as a significant threat to the species (Raghavan and Ali \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Roughly 100 kilograms of mature \u003cem\u003eH. brachysoma\u003c/em\u003e are captured within a week during the monsoon floodplain fishery (\u003cem\u003eOothapiditham\u003c/em\u003e in the local language) using traditional fishing traps, gill nets, and electric fishing methods (Shaji and Laladhas \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The fishery of \u003cem\u003eH. brachysoma\u003c/em\u003e in many rivers of Western Ghats seems unsustainable due to excessive fishing effort with over fishing such as growth fishing (capturing individuals before they reach a size significant enough to contribute to the spawning stock) and recruitment fishing (exploiting the spawning stock itself) (Prasad et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Raghavan et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe conservation of endemic and vulnerable fish populations exploited by small-scale fisheries is a major social and biological concern worldwide (Mace and Reynolds \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Only a few research have looked at the growth and exploitation aspects of freshwater species harvested from the Western Ghats (Prasad et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Raghavan et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Renjithkumar et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Shanmughan et al. 2021). The population's natural growth rate is significantly influenced by the age or size when individuals reach at fist maturity (Vandermeer and Goldberg 2003). The size at first maturity for the \u003cem\u003eH. brachysoma\u003c/em\u003e is known to be 175 mm and 188 mm TL in males, and 168 mm and 185 mm TL in females (Bindu et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Chandran and Prasad \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). According to the length\u0026ndash;frequency analysis, high proportions of yellow catfish are caught in small scale fisheries before reaching sexual maturity. Collecting small fish before they mature leads to a slow recovery of exploited populations and reduces the fish capture and profit (Myers and Mertz \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Isaac and Ruffino \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1996\u003c/span\u003e). Despite the fact that \u003cem\u003eH. brachysoma\u003c/em\u003e can grow to a maximum length of 420 cm (Bindu and Padmakumar \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), such large size individuals were not reported in the current investigation. The largest exploited stock reported in the present study was 410 mm.\u003c/p\u003e \u003cp\u003eThere have been few studies on the demography of \u003cem\u003eH. brachysoma\u003c/em\u003e with the exception of Prasad et al (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) in the Periyar River, therefore the comparison between geographic populations becomes difficult. The growth coefficient (\u003cem\u003eK\u003c/em\u003e) for the \u003cem\u003eH. brachysoma\u003c/em\u003e population in the five rivers (0.58 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e- 1.100 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) was lower than in Periyar River population (4.60 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) from Southern Western Ghats of India (Prasad et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). These observed differences in the \u003cem\u003eH. brachysoma\u003c/em\u003e growth parameters from different rivers could be attributed to stock variances, ecological conditions of the habitat, feeding habits, and environmental parameters. The high growth coefficient (\u003cem\u003eK\u003c/em\u003e) and low longevity were recorded in Periyar and Muvatupuzha Rivers when compared to Chalakudy, Pampa and Achenkovil Rivers. It indicated that Periyar and Muvatupuzha Rivers yellow catfish populations acquired asymptotic length (\u003cem\u003eL\u0026infin;\u003c/em\u003e) quickly which agree with Pauly and Munro (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1984\u003c/span\u003e), that species having shorter life have higher \u0026lsquo;\u003cem\u003eK\u003c/em\u003e\u0026rsquo; values and reach their \u003cem\u003eL\u0026thinsp;\u0026infin;\u003c/em\u003e\u0026thinsp;within one or three years of life history. Estimates of growth performance index (\u003cem\u003eφ\u003c/em\u003e ) recorded in this study (4.29 to 4.52) were lower (4.99) than those observed for Periyar River (Prasad et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe decrease in the size of a fish population can be attributed to by two factors: natural death (\u003cem\u003eM\u003c/em\u003e) (disease, predation, pollution etc.) and fishing pressure (\u003cem\u003eF\u003c/em\u003e). The fishing mortality rate of \u003cem\u003eH. brachysoma\u003c/em\u003e was higher than the natural mortality rate in four rivers (Periyar, Muvatupuzha, Chalakudy and Pampa) indicating a rather significant fishing pressure on the species. The mortality rate of species is crucial for developing exploitation strategies to harvest and manage the fishery resources optimally. A ratio of more than 1.0 between total mortality and growth coefficient (\u003cem\u003eZ/K\u003c/em\u003e) suggests a mortality dominated population, whereas a ratio of less than 1.0 indicates a growth dominated population (Etim et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). Yellow catfish populations in all five rivers studied were dominated by mortality (\u003cem\u003eZ/K\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.88\u0026ndash;3.58). This is an alarming condition in which overfishing gradually reduce recruitment, resulting in severe population losses in the near future (Rajeev et al. 2018). Fishing mortality (\u003cem\u003eF\u003c/em\u003e) should be almost equal to natural mortality (\u003cem\u003eM\u003c/em\u003e) in an ideally exploited stock, resulting in an exploitation rate (\u003cem\u003eE\u003c/em\u003e) of 0.5 year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Gulland \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1970\u003c/span\u003e). The exploitation rates (\u003cem\u003eE\u003c/em\u003e) of yellow catfish in four rivers (Chalakudy, Pampa, Periyar, and Muvatupuzha) are greater than 0.5, whereas the exploitation level in the Achenkovil River nearly equals to \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e0.5\u003c/em\u003e\u003c/sub\u003e, indicating uncertain future for native yellow cat fish population if management attention is not taken. The lengths at first capture (Lc) of \u003cem\u003eH. brachysoma\u003c/em\u003e in all rivers were greater than their mean sizes at first maturity, indicating the possibility of no growth overfishing.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eConservation management measures\u003c/h2\u003e \u003cp\u003eThe current study is likely the first study on community-based data monitoring systems in small-scale inland fisheries in Western Ghats of India and it shows that yellow catfish are under heavy exploitation pressure and native populations are vulnerable to collapse in the absence of immediate management interventions. Controlling the overall harvest of yellow catfish could be the most significant management method for conserving the \u003cem\u003eH. brachysoma\u003c/em\u003e population, however reducing fishing effort in an artisanal subsistence fishery like India is nearly difficult. As a result, management interventions for the protection of \u003cem\u003eH. brachysoma\u003c/em\u003e in Western Ghats rivers should be based on a combination of technical measures such as restrictions on fishing gear and mesh size limits, closed seasons, non-fishing zones, and the introduction of catch quotas.\u003c/p\u003e \u003cp\u003eThere is currently no upper size limit for landing \u003cem\u003eH. brachysoma\u003c/em\u003e in Western Ghats rivers. Implementing an upper size limit stimulate stock recovery and improve the sustainability of its fishery. The length at first maturity of \u003cem\u003eH. brachysoma\u003c/em\u003e was estimated to be 175\u0026ndash;188 mm in males, and 168\u0026ndash;185 mm in females. A minimum catch size limit of 200 mm can be enforced in the rivers to prevent recruitment overfishing. Allowing them to attain this size ensures they have the opportunity to spawn at least once, aiding in the conservation of the species. In addition to setting size limits, restrictions on net mesh size should be implemented. Currently, the fishers use gill nets with mesh sizes ranging from 20 and 60 mm, resulting in the capture of small-sized juvenile fishes before they reach maturity. Gill nets should have a minimum mesh size of 40\u0026ndash;80 mm to prevent the capture of immature juveniles. Restriction on the limits on mesh size or size of the fish to enforce is challenge for developing management measures for small-scale subsistence fisheries in Western Ghats Rivers. Yellow catfishes are spawn in South west monsoon months (June-September) in Kerala state, implementing a four-month closed season for collection is essential. In cooperation with local fishermen, a temporary shutdown of the fishery during the spawning season (closed season) should be developed. This measure aims to safeguard the spawning stock and support the enhancement of recruitment levels. Catch quotas for each fishing fleet will be developed in consultation with local fishermen, scientists, and fisheries managers for each river. The Department of Fisheries should prohibit indiscriminate exploitation of catfish during flood plain fisheries in central Kerala rivers and suggest a fine of Rs. 25000 rupees and imprisonment for up to three months. Strict monitoring and implementation of legislation can aid in the reduction of mature catfish harvest from natural waters. Finally engaging local communities in conservation efforts through education about the importance of the species and the preservation of their habitats.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cem\u003eConflicts of Interest\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eData availability statement\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eDeclaration of competing interest\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFunding\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eEthical approval\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis is an observational study. The Cochin University of Science and Technology (CUSAT) Research Ethics Committee has confirmed that no ethical approval is required.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAcknowledgements\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are thankful to local fishers for collection of fish samples.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAllan JD, Abell R, Hogan Z, Revenga C, Taylor BW, Welcomme RL, Winemiller K (2005) Overfishing of Inland Waters. Bio Science 55(12):1041\u0026ndash;1051.doi:10.1641/0006 3568(2005)055[1041:OOIW]2.0.CO;2.\u003c/li\u003e\n\u003cli\u003eArlinghaus R, Lorenzen K, Johnson BM, Cooke SJ, Cowx IG (2016) Management of freshwater fisheries: addressing habitat, people and fishes. 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Rev Fish Biol Fish\u003cem\u003e \u003c/em\u003e26(3):405\u0026ndash;440.\u003c/li\u003e\n\u003cli\u003eLowitt K, Levkoe CZ, Spring A, Turlo C, Williams PL, Bird, S et al (2020) Empowering small-scale, community-based fisheries through a food systems framework. Mar Policy 120:104-150\u003c/li\u003e\n\u003cli\u003eLynch AJ, Cooke SJ, Deines AM, Bower SD, Bunnell DB, Cowx IG et al (2016) The social, economic, and environmental importance of inland fish and fisheries. Environ. Rev 24(2):115\u0026ndash;121. https://doi.org/10.1139/er-2015-0064\u003c/li\u003e\n\u003cli\u003eMace GM, Reynolds JD (2001) Exploitation as a conservation issue In: Reynolds JD, Mace, GM, Redford KH, Robinson JG, Conservation of Exploited Species. Cambridge University Press, Cambridge, pp 4-15\u003c/li\u003e\n\u003cli\u003eMyers N, Mittermeier RA, Mittermeier CG, Da Fonseca GA, Kent J (2000) Biodiversity hotspots for conservation priorities. Nature 403(6772):853\u003c/li\u003e\n\u003cli\u003eMyers RA, Mertz G (1998) The limits of exploitation: A precautionary approach. Ecol Appl 8: 165\u0026ndash;169\u003c/li\u003e\n\u003cli\u003eOviedo AFP, Bursztyn M (2017) Community-based monitoring of small-scale fisheries with digital devices in Brazilian Amazon. Fish Manag Ecol 24(4):320\u0026ndash;329\u003c/li\u003e\n\u003cli\u003ePauly D (1980) On the interrelationships between natural mortality, growth parameters, and mean environmental temperature in 175 fish stocks. J de Conseil, Conseil Intt Pour L\u0026rsquo;Expl de la Mer 39:175\u0026ndash;192.\u003c/li\u003e\n\u003cli\u003ePauly D (1984) Fish population dynamics in tropical waters: A manual for use with programmable calculators. ICLARM Stud Rev 8:325.\u003c/li\u003e\n\u003cli\u003ePauly D, Munro JL (1984) Once more on the comparison of growth in fish and invertebrates. Fishbyte, The WorldFish Center 2(1):1-21\u003c/li\u003e\n\u003cli\u003ePayne AL, Temple SA (1996) River and Floodplain Fisheries in the Ganges River. Final Report. DFID Fisheries Management Sciences Programme R 5485, London, MRAG Ltd, 177 pp.\u003c/li\u003e\n\u003cli\u003ePrasad G, Ali A, Harikrishnan M, Raghavan R (2012) Population dynamics of an endemic and threatened Yellow Catfish, \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e (Gunther) from Periyar River, Southern Western Ghats, India. J Thre Taxa 4:2333\u0026ndash;2342.\u003c/li\u003e\n\u003cli\u003eRadhakrishnan KV (2006) Systematics, germplasm evaluation and patterns of distribution and abundance of freshwater fishes of Kerala,\u003cem\u003e \u003c/em\u003ePh. D. thesis submitted to Cochin\u003cem\u003e \u003c/em\u003eUniversity of Science and Technology, 305 pp.\u003c/li\u003e\n\u003cli\u003eRaghavan R, Ali A (2013) \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e. The IUCN red list of threatened species. Version 2015.1. www. iucnredlist.org.\u003c/li\u003e\n\u003cli\u003eRaghavan R, Prasad G, Ali A, Pereira B (2008) Fish fauna of River Chalakudy part of Western Ghats biodiversity hotspot (South India): patterns of distribution, threats and conservation needs. Biodivers Conserv 17:3119\u0026ndash;3131\u003c/li\u003e\n\u003cli\u003eRaghavan R, Prasad G, Ali A, Pereira B (2008b) Exotic fish species in a global biodiversity hotspot: observations from river Chalakudy, part of Western Ghats, Kerala, India. Biol Invasions 10:37\u0026ndash;40\u003c/li\u003e\n\u003cli\u003eRaghavan R, Ali A, Dahanukar N, Rosser A (2011) Is the Deccan Mahseer, \u003cem\u003eTor khudree \u003c/em\u003e(Sykes) fishery in the Western Ghats Hotspot sustainable? A participatory approach to assessment. 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Ind J Fish 58(3):13\u0026ndash;22\u003c/li\u003e\n\u003cli\u003eRenjithkumar CR, Roshni K, Kurup BM (2016) Exploited Fishery Resources of Muvattupuzha River, Kerala, India. \u003cem\u003eFishery Technology\u003c/em\u003e 53: 177\u0026ndash;182\u003c/li\u003e\n\u003cli\u003eRenjithkumar CR, Roshni K, Harikrishnan M, Kurup BM (2020) Population dynamics of \u003cem\u003eHypselobarbus thomassi \u003c/em\u003e(Day 1874), an endemic cyprinid fish from a tropical reservoir of Southern Western Ghats, India. Lakes Reser Res Manag \u003cem\u003e25\u003c/em\u003e(4):388-393. https://doi. org/10.1111/lre.12343.\u003c/li\u003e\n\u003cli\u003eShaji CP, Laladhas KP (2013) Monsoon flood plain fishery and traditional fishing methods in Thrissur District, Kerala. Ind J Tradit Knowl 12(1):102\u0026ndash;108\u003c/li\u003e\n\u003cli\u003eShanmughan A, Dahanukar N, Harrison A, Pinder AC, Ranjeet K, Raghavan R (2022) Demographics and exploitation of two Near Threatened freshwater eels, \u003cem\u003eAnguilla bengalensis\u003c/em\u003e and \u003cem\u003eAnguilla bicolor\u003c/em\u003e, in small-scale subsistence fisheries and implications for conservation. Aquat Conserv Mar Freshw 32(2):269-281. https://doi.org/10.1002/aqc.3765.\u003c/li\u003e\n\u003cli\u003eShephard S, Ryan D, O\u0026apos;Reilly P, Roche W (2021) Using local ecological knowledge to inform semi-quantitative fishery surveillance indicators: an example in marine recreational angling. ICES J Mar Sci\u003cem\u003e \u003c/em\u003e78(10):3805\u0026ndash;3816.\u003c/li\u003e\n\u003cli\u003eSmith LED, Khoa SN, Lorenzen K (2005) Livelihood functions of inland fisheries: Policy implications in developing countries. Water Policy 7(4):359\u0026ndash;383. http://wp.iwaponline.com/content/7/4/359\u003c/li\u003e\n\u003cli\u003eSreeraj N, Raghavan R, Prasad G (2007) Some aspects of the fishery of the threatened Yellow Catfish, \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e from Vembanad Lake and a note on their landings in Vaikom, Kerala, India. Zoos Print J 22(4):2665\u0026ndash;2666\u003c/li\u003e\n\u003cli\u003eSubramanyam K, Nayar MP (1974) Vegetation and phytogeography of the Western Ghats. In: Mani MS (ed) Ecology and Biogeography in India, Vol. 23 Monographiae Biologicae, Dr W Junk Publishers. pp 178\u0026ndash;196.\u003c/li\u003e\n\u003cli\u003eSun M, Li Y, Zhang C, Xu B, Ren Y, Chen Y (2020) Management of data-limited fisheries: identifying informative data to achieve sustainable fisheries. N Am J Fish Manag 40(3):733\u0026ndash;751.\u003c/li\u003e\n\u003cli\u003eSwapna S (2009) Fish Diversity in Achenkovil River, Kerala, India. J Bombay Nat Hist 106: 104\u0026ndash;106\u003c/li\u003e\n\u003cli\u003eTickner D, Opperman JJ, Abell R, Acreman M, Arthington AH, Bunn SE et al. (2020) Bending the curve of global freshwater biodiversity loss: an emergency recovery plan. Biosci 70(4):330\u0026ndash;342. \u003c/li\u003e\n\u003cli\u003eWelcomme RL, Valbo-Jorgensen J, Halls AS (2014) Inland fisheries evolution and management: case studies from four continents. FAO Fisheries and Aquaculture Technical Paper 579.\u003c/li\u003e\n\u003cli\u003eYoun S, Taylor, J., Lynch WW, Cowx AJ, Beard I G, Jr Bartley D, Wu F (2014) Inland capture fishery contributions to global food security and threats to their future. Glob Food Sec 3:142\u0026ndash;148. https ://doi.org/10.1016/j.gfs.2014.09.005\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Yellow catfish, Western Ghats, Vulnerable, Fishery, mortality, environmental variables, conservation","lastPublishedDoi":"10.21203/rs.3.rs-4585679/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4585679/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCommunity-based data monitoring (CBM) systems in small-scale inland fisheries provide insights into the catch patterns of diverse fish species over extended periods. In this study, a participatory approach was employed to ascertain the fishery, demography, and exploitation patterns of Asian Sun fish catfish, \u003cem\u003eHorabagrus brachysoma\u003c/em\u003e, across five river systems within the Western Ghats biodiversity hotspot of India. \u003cem\u003eH. brachysoma\u003c/em\u003e (Gu\u0026uml;nther 1864) is a commercially important food fish that is heavily exploited from rivers of Kerala state, India and is listed as \u0026lsquo;Vulnerable\u0026rsquo; on the IUCN red list. The monthly catches of this species from various landing centres across the Western Ghats' rivers varied between 303 kg to 631 kg annually. These fish typically measured between 11.00 and 41.10 cm in Total Length (TL) and weighed between 26.00 g to 470.00 g in Total Weight (TW). Using the annual length frequency data provided by local fishers, the estimated growth parameters of \u003cem\u003eH. brachysoma\u003c/em\u003e are estimated as; asymptotic length ((\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026infin;\u003c/em\u003e\u003c/sub\u003e) between 316.05 and 421.05 mm, growth coefficient (\u003cem\u003eK\u003c/em\u003e) between 0.58 and 1.10 yr\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e from different rivers. The total mortality (\u003cem\u003eZ\u003c/em\u003e) was calculated to range between1.25 yr\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2.91 yr\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e while the fishing mortality (\u003cem\u003eF)\u003c/em\u003e was estimated between 0.62 yr\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2.09 yr\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The fishing mortality rate of \u003cem\u003eH. brachysoma\u003c/em\u003e in the Periyar River, at 2.09 yr⁻\u0026sup1;, appears to be one of the highest recorded for this species. This rate suggests a potentially indiscriminate level of exploitation by local fishers in this area. The calculated exploitation rate (\u003cem\u003eE\u003c/em\u003e) ranging from 0.49 to 0.72 yr⁻\u0026sup1; exceeds the anticipated optimum exploitation levels (0.5). This suggests that the populations of \u003cem\u003eH. brachysoma\u003c/em\u003e in the river systems of the Western Ghats are experiencing overexploitation. This approach includes measures such as implementing fishing closures during spawning seasons, imposing restrictions on mesh sizes, non-fishing zones and establishing quota systems for local fishermen. These strategies collectively aim to promote sustainable practices and preserve the population of \u003cem\u003eH. brachysoma\u003c/em\u003e.\u003c/p\u003e","manuscriptTitle":"Fishery, growth, and mortality of threatened Asian Sunfish, Horabagrus brachysoma (Gu¨nther 1864) in five rivers of Western Ghats hotspot, India","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-02 05:55:01","doi":"10.21203/rs.3.rs-4585679/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8c4b7526-45d6-4eba-a070-976a416ff1f5","owner":[],"postedDate":"July 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-07-31T05:27:33+00:00","versionOfRecord":[],"versionCreatedAt":"2024-07-02 05:55:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4585679","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4585679","identity":"rs-4585679","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}