Reproductive bionomics of Spotted Scat, Scatophagus argus (Linnaeus, 1766) off South-east coast of India

Reproductive bionomics of Spotted Scat, Scatophagus argus (Linnaeus, 1766) off South-east coast of 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 Reproductive bionomics of Spotted Scat, Scatophagus argus (Linnaeus, 1766) off South-east coast of India Prapaporn Whaiprib, Selvakumar Narasimman, Dhanasekar Krishnamoorthy, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9166242/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract The study emphasizes reproductive biomomics, population structure and length-weight relationship of spotted scat, Scatophagus argus , off Indian waters. Sampling from Ennore, Muttukadu, and Mandapam along the South-east coast of India registered their occurrence during the south-west monsoon (June to August) and north-east monsoon (October to December) with peaks during July and November. There exists a biased sex ratio towards females in the spotted scat population. Reproductivity performance was assessed based on the gonad-somatic index, which aptly correlated with peak spawning season. This led to a description of six stages of ovarian and testicular development. Histological studies further revealed five stages of oocyte and four stages of sperm maturation. Morphometric analysis indicated that the total length (TL) of the fish in the samples ranged from 9.2 cm to 18.3 cm in females and 12.0 cm to 17.6 cm in males. Length-weight equations of w = 0.0337 L 2.998 and w = 0.055 L 2.804 were derived for females and males, respectively. The relationship showed that the exponent “b” value was below 3, with a negative allometric equation documenting compressed body shape. This study provides baseline data on the population structure, length-weight relationship, sexual maturity, and spawning periodicity of Scatophagus argus in Indian waters. Allometric Population structure Gonadosomatic index Reproductive activity Spotted scat Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction South-east coast of India has a varied diversity of fish with many coastal, estuarine, and creek systems. Scatophagus argus is a euryhaline teleost, widely distributed throughout the nearshore waters of the Indo-West Pacific Ocean from southern India and Sri Lanka to southern Japan and Tahiti (Wongchinawit and Paphavasit, 2009 ; Gandhi et al., 2014 ). Spotted scat occurs in freshwater, brackish water, and marine habitats of the Indo-Pacific, South and South-East Asia, the Malay Archipelago, the Philippines and Australia (Barry, 1988 ). Mandal et al. ( 2020 ) have stated that S. argus is an ornamental fish species in the South-east which is economically important. It has been valued as an aquarium fish around the world due to its colourful appearance, hardiness, slow growth, and calm behaviour (Barry, 1988 ; Amarasinghe et al., 2002 ; Kailasam and Thirunavukkarasu, 2011 ; Sivan and Radhakrishnan, 2011 ; Gupta, 2016 ). This fish is commonly known as “spotted scat” due to the presence of numerous black spots on its body (Barry and Fast, 1992 ). In Philippines and Thailand, high-priced food fish are regarded as high quality (Barry, 1988 ; Sawusdee, 2010 ). This is in high demand in the global market due to its distinctive taste and nutritional quality, including high protein content and meat quality (Anney, 1988 ; Gisha, 2007 ; Biswas et al., 2016 ). Although this fish is important as a food fish in other parts of the world, it is not well popularized as a food fish in India. S. argus can adapt itself to many variables such as temperature, salinity, dissolved oxygen, tidal action, river runoff, turbulence and turbidity, thus it is a species of high aquaculture demand too (Barry and Fast 1992 ; Su et al., 2019 ). It has been listed in the “least concern” category of the IUCN red list of threatened species (IUCN 2021) as the population of this fish in the wild has fallen due to a combination of over-exploitation, habitat destruction, climate changes and so on. Thus, conservation of the species is important, and so is ensuring the population under captive conditions. This fish was chosen by many researchers for artificial reproduction in many countries around the world (Cai et al., 2010 ). Gonado somatic index (GSI), along with fecundity and gonadal histology, are the most essential parameters to determine the spawning cycle of any fish. The GSI allows us to predict the exact time of breeding and breeding frequency of fish species (Ghaffari et al., 2011 ; Shafi, 2012 ; Jan et al., 2014 ). In aquaculture, managing the spawning of fish in a population will become difficult if there is an inappropriate prediction of the maturity stage (Costa, 2009 ). The details of sperm and oocyte development can be authenticated by histological validation of different maturation stages (Mendonça et al., 2006 ). Furthermore, breeding season, gonadal maturity and spawning can also be determined by histology, which may lead to successful artificial propagation (Chakraborty et al., 2007 ; Hasan et al., 2018 ). The sex ratio of fish provides accurate information on the domination of sex in a population of fish (Adebiyi, 2013 ). Arocha et al. ( 2010 ) have studied the importance of sex ratio in determining female fecundity. This enabled him to distinguish the population behaviour and fecundity along with the seasonal differences in sexes and the growth rate (Gogoi and Goswaini, 2014). There may be significant variation in the sex ratio between species, and it differs at different periods in the same population, but in most cases, it is close to one, i.e., 1 male:1 female (Zin et al., 2011 ). Spotted scat spawns throughout the year, with a peak in April - October in Nakhon Si Thammarat, Thailand (Sritakon and Songkaew, 2011 ). The fish is also known to exhibit multiple spawnings during its reproductive period. Generally, the sex ratio is biased toward female dominance (Barry and Fast, 1992 ; Gandhi, 1998 ; Cai et al., 2010 ). Regarding sexual dimorphism, generally females of S. argus are larger and heavier than males of the same length group (Jency et al., 2008 ; Gandhi et al., 2014 ). Furthermore, morphometric observation on the length and weight relationship of fish is useful to determine condition indices and to equate life history and morphology of populations belonging to different regions (Petrakis and Stergiou, 1995 ; Richter et al., 2000 ; Moutopoulos and Stergiou, 2002 ). Studies on the length - weight equation of spotted scat have been made in South-east Asia (Philippines, Thailand, and Malaysia) and India as well (Barry and Fast, 1992 ; Sritakon and Songkaew, 2011 ; Sawusdee, 2010 ; Gandhi et al., 2013 ; Hashim et al., 2017 ). Therefore, the present study aimed to acquire information on the distribution as well as reproductive bionomics of Scatophagus argus to augment its aquaculture potential. 2. Material and Methods Fish samples of S. argus were obtained from fishermen of the Ennore, Muttukadu and Mandapam coastal areas from November 2016 to February 2018. Fishes were brought to the laboratory in the ice box. Morphometric measurements such as total length, standard length and weight of the fish were made as per standard procedure (Barry and Fast, 1992 ; Sawusdee, 2010 ; Sritakon and Songkaew, 2011 ; Gandhi et al., 2013 ; Hashim et al., 2017 ). Fish samples, thus collected, were analyzed for population structure, sex-ratio, and length - weight relationships. The stages of maturity of male and female fish were analyzed based on the size and texture of gonads (Murua et al., 2003 ; Farrell et al., 2012 ; Milton et al., 2018 ). The gonadosomatic index (GSI) of the fish was calculated. 2.1 Histology Gonads of both sexes in S. argus at different size groups were dissected out and fixed in a 4% neutral buffered formaldehyde solution. The samples were dehydrated through a graded alcohol series and embedded in paraffin wax. Sections of 5–6 µm thickness were taken and stained with hematoxylin and eosin. Photomicrographs were taken at various magnifications using a Leica DM 2500 (Germany) microscope. 3. Results 3.1 Diversity and morphological characteristics A survey of S. argus in fish landings indicated its distribution throughout the year in the coastal regions of Ennore, Muttukadu, and Mandapam. However, the size range of fish varied significantly in all sampling sites. The sex of the fish is distinguished by observing their head shape. In females, the head profile ascends at a constant slope, but males have a concave curvature in the head above the eyes. The spotted scat has a quadrangular and strongly compressed body; the body colour is uniformly greenish-silvery or coffee-brown. The mouth is small, not protrusible, and the teeth are small in several rows. The whole body is covered with ctenoid scales and round brown spots (Fig. 1 ). 3.2 Reproductive performance and length-weight relationship The gonadosomatic index (GSI) of female S. argus is aptly related to the gonadal maturity of the fish (Fig. 2 ). The monthly GSI value in females ranged from 3 to 13%. The highest mean of GSI was registered in July (13 ± 0.01%) and November 2017 (11 ± 0.003%), indicating their peak spawning seasons. Males and females were found to mature at around 12.0 -12.5 cm total length (TL). In females, the weight of the fish ranged from 30 g to 800 g and the length was 15.3 cm with a range from 9.20 cm to 30 cm. The weight of males ranged from 55 g to 480 g and the length of 14.97 cm and the length ranged from 12 cm to 21.5 cm. The male and female sex ratio collected from Ennore and Muttukadu registered 1:2.4 (Fig. 3 ). The sex ratio was biased towards females up to 1:17 as recorded along the Mandapam coast as well. Furthermore, the length (L) and weight (W) relationship showed W = 0.0337 L 2.998 (R 2 = 0.9399, n = 46) and W = 0.055 L 2.804 (R 2 = 0.7465, n = 19) for female and male, respectively (Figs. 4 – 5 ). The growth of S. argus is “allometric” meaning that the increase in weight is not proportional to length. 3.3 Ovarian development Based on the colour, texture and size of the ovary, six different developmental stages were recorded (Figs. 6 A-F). These stages include virgin, developing virgin, immature, maturing, mature and ripe ovary. Each stage was characterized by the colour and size of the ovary as well as the nature of oocytes in the ovary. Virgin has small ovaries without visible oocytes. The ovarian wall is thin and identification of the onset of maturity is often difficult. In the developing virgin stage, the ovaries are small and at this stage, oocytes are in the primary growth phase. In the immature stage, the ovary is of medium size, occupying 5% of the body cavity, but is visible with opaque oocytes. At a maturing stage, ovaries occupy 10% of the body cavity; oocytes are seen as opaque and yellow. The mature stage represents larger ovaries occupying 25% of the body cavity. At a ripe stage, oocytes swell; ovaries become yellow and occupy more than 50% of the body cavity. In this stage, oocytes are seen as yellow with apparent blood capillaries. Sections through the ovary at different stages of maturity show five stages of oocyte maturation that include primary oocytes, previtellogenic oocytes, cortical alveolus, vitellogenic and mature oocytes (Figs. 7 A-D). The characteristic features include oocyte size, the presence of a follicular layer, the number of nucleoli and the distribution of ooplasmic inclusions. The primary oocyte is small and measures around 33 to 40 µm in diameter. Previtellogenic oocytes are characterized by chromatin material inside the nucleus of the oocytes. The nucleolus is small, and oocytes measure from 50 to 67 µm in diameter. The cortical alveolus stage includes oocytes around 83 to 133 µm in diameter and characterized by the appearance of cortical alveoli marks (yolk vesicles). The vitellogenic stage represents oocytes with a size range from 134 to 320 µm in diameter and accumulation of yolk material, such as yolk granules and oil droplets. The mature stage represents oocytes in the size range of 185 to 400 µm in diameter with nucleus break-up and the ooplasm full of yolk bodies. 3.4 Testicular development Based on the morphology, colour and texture of the testis, six stages of testicular development are observed (Figs. 8 A-F). These stages include virgin, developing virgin, immature, maturing, mature and ripe testis. Virgin testes are generally tiny, translucent filaments that look like small tubes. At the developing virgin stage, the testis is characterized by a yellowish colour. Semen is not seen in the sperm duct even when squeezed. The immature testis is medium-sized and milt is seen in the sperm duct at this stage. Testes attain near full size but do not appear swollen. Maturing testis increases in size and is larger than the immature stage, and appears swollen. Sperm can be stripped and are visible when cut. Mature testis increase in size with full sperm that can be stripped around 100–200 µl per fish. Ripe testes are larger and swollen fully with sperm and can be stripped of more than 200 µl per fish. A histological study performed on the testis registered four stages of sperm maturation. These stages include spermatogonia, spermatocytes, spermatid and spermatozoa (Figs. 9 A-D). Spermatogonia are commonly found in groups or nests, but they sometimes occur solitary. Spermatocytes include primary and secondary spermatocytes that can be distinguished from each other with accuracy and are seen as the most actively dividing cells of the testis. Spermatids are small and tend to move towards the center of the seminiferous tubule. In the spermatozoa stage, spermatozoa occur within the lumen of the lobule. The fully formed mature spermatozoan is essentially comprised of a prominent head and flagellum (Fig. 8 ). 4. Discussion The present study documents the distribution of S. argus collected in Ennore, Muttukadu and Mandapam from South-east coast of India from November 2016 to February 2018. Distribution of this fish has been reported in other parts of the world (Wongchinawit and Paphavasit, 2009 ; Gandhi et al., 2014 ; Amarasinghe et al., 2002 ; Sawusdee, 2010 ; Gandhi et al., 2013 ). The peak spawning season of S. argus was evident with gonadal maturity during July and November (2017). Gandhi et al. 2014 also reported the spawning of spotted scat twice in a season, during the south-west monsoon (June to August) and north-east monsoon (October to December) with peaks during July and November at the Mandapam coastal region. In South-China coastal waters, the spawning of this fish was during April - August and the peak spawning occurred during May and July. In Philippines, the initiation of spawning was from June to July and from April to October, with the spawning peak in August (Barry and Fast, 1992 ; Cai et al., 2010 ). Gonadal maturity of S. argus registered 13% (GSI) in Indian waters, which is comparable to 14.7% (GSI) in Chinese waters (Cai et al., 2010 ). The monthly GSI value in females registered a maximum during July and November 2017. Gandhi et al. 2014 also reported the first peak of GSI in females in July, which decreased in September and increased again in November. In this study, male and female S. argus were found to mature first at a total length between 12.50 and 12.55 cm, with an average weight of 121. 94 g and 140.71 g, respectively. According to Barry. (1988) , the smallest male found with oozing milt was around 11.5 cm in length and 83.5 g in weight. This may be a reasonable estimate of the size at first maturity in male scat. Females were determined to be sexually mature by plotting their gonad weight as a function of standard length. The increase in gonad weights for fish longer than a total length of 14 cm and heavier than approximately 150 g indicates the size at which females reach first sexual maturity. Sritakon and Songkaew. (2011) reported the average length at first maturity of females was around 11.60 cm. The minimum age of reproduction for both males and females of S. argus is achieved within the age of first year (Cai et al., 2010 ). Regarding the sex ratio, it was biased toward females in Indian waters and fish collected from Ennore and Muttukadu registered at 1:2.4 and 1:17 along the Mandapam coast. An evaluation of the sex ratio in S. argus showed that females were dominant in the population. Similar observations of female dominance in S. argus were also reported in other waters (Gandhi et al., 2014 ; Barry and Fast, 1992 ; Cai et al., 2010 ; Jency et al., 2008 ). Morphometric measurements about the length and weight of S. argus relatively showed a negative growth (b < 3) pattern, indicating that the fish becomes more slender as length increases. A similar growth pattern in S. argus was recorded in Thailand, India, Malaysia and Philippines waters (Barry and Fast, 1992 ; Sawusdee, 2010 ; Gandhi et al., 2013 ; Hashim et al., 2017 ). The growth of S. argus is “allometric” i.e., the increase in weight is non-proportion to the length (W = 0.0562TL 2.7021 , R 2 = 0.93) ( Sawusdee, 2010 ). Similarly, Gandhi et al. ( 2013 ) reported relationships between the total length and weight of each sex separately (Male W = 0.005373 L 2.842 R 2 = 0.97, Female W = 0.002152 L 2.479 R 2 = 0.98). Regression equation revealed that the values of b = 2.842 and 2.479 are significantly different from 3, indicating that the LWR of this species departs significantly from isometry. The ‘b’ values of spotted scat were quite similar to those observed by Barry and Fast. 1992 for the same species in the southern coastal waters of Panay Island, Philippines. The value of ‘b’ may range between 2.5 and 3.5 (Shafiei et al., 2010). The slopes (b) of the regressions were less than 3 for both sexes, hence growth in the individual sex was found to be negative allometric which might be due to the deep, strongly laterally compressed body of spotted scat. S. argus collected from the fish collection center at Gelang Patah, Johor Malaysian coastal also showed a similar allometric negative (b < 3) indicating that the weight increment was lesser than the length increment (Hashim et al., 2017 ). In the majority of teleost fishes, five to eight stages of oocyte maturation have been reported (Murua et al., 2003 ; Farrell et al., 2012 ; Milton et al., 2018 ; Shafiei et al., 2010; Abu El-Nasr, 2016 ). This study has documented ovarian development with six stages of oocyte maturation similar to many teleost fishes (Murua et al., 2003 ; Shafiei et al., 2010; Milton et al., 2018 ). In male spotted scat four stages of testicular development were registered (Abu El-Nasr, 2016 ). Thus, this study provides baseline data on the reproductive performance and length-weight relationship of S. argus , which would be helpful for the aquaculture potential of this species. Declarations Financial interests The authors have no relevant financial or non-financial interests to disclose. Conflict of Interest Statement The authors declare there is no conflict of interest. CRediT author contribution statement Prapaporn Whaiprib: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing - original draft. Narasimman Selvakumar: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing - original draft, Writing - review & editing. Krishnamoorthy Dhanasekar: Writing - review & editing. Natesan Munuswamy: Investigation, Supervision, Writing - review & editing. Funding No funding was received to assist with the preparation of this manuscript. Author Contribution Prapaporn Whaiprib: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing - original draft.Narasimman Selvakumar: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing - original draft, Writing - review & editing.Krishnamoorthy Dhanasekar: Writing - review & editing.Natesan Munuswamy: Investigation, Supervision, Writing - review & editing. Acknowledgements Financial assistance to Dr. Prapaporn Whaiprib from Indian Council for Cultural Relations (ICCR), Ministry of External Affairs, Government of India, for Ph.D programme is gratefully acknowledged. Thanks are due to Council of Scientific and Industrial Research (CSIR) Government of India, New Delhi under CSIR-Emeritus scientist scheme (21(1069)/19/ EMR-II) and Dr. D. S. Kothari Post-Doctoral Fellowship by the University Grants Commission, New Delhi (F.4 − 2/2006(BSR)/BL/18–19/0545). References Abu El-Nasr TM (2016) Evaluation the quality of the oil waste histological changes in the ovaries of the whipfin fish, Gerres filamentosus (Cuvier, 1829) during the reproductive cycle in the Hurdhada Red Sea. Egypt. AENSI J., Adv. Environ. Biol. 10(4), 160–173 Adebiyi FA (2013) The sex ratio, gonadosomatic index, stages of gonadal development and fecundity of sompat grunt, Pomadasys jubelini (Cuvier, 1830). Pakistan J Zool 45(1):41–46 Amarasinghe US, Amarasinghe MD, Nissanka C (2002) Investigation of the Negombo estuary (Sri Lanka) brush park fishery, with an emphasis on community-based management. Fisheries Manag Eco 9(1):41–56. https://doi.org/10.1046/j.1365-2400.2002.00250.x Anney MK, Antony A (1988) Studies On Some Aspects Of Biology Of Two Estuarine Fishes Megalops Cyprinoides And Scatophagus Argus . Ph.D. thesis, Cochin University of Science And Technology, India Arocha F, Marcano. L, Silva. J (2010) Sex ratio at size of sailfish ( Istiophorus albicans ) from the Venezuelan fishery off the Caribbean Sea and adjacent areas. Collective Volume Sci Papers ICCAT 65(5):1633–1640 Barry TP (1988) Natural history of the spotted scat ( Scatophagus argus ). Spawning induction and pond culture of the spotted scat ( Scatophagus argus Linnaeus) in the Philippines. 4–31 Barry TP, Fast AW (1992) Biology of the spotted scat ( Scatophagus argus ) in the Philippines. Asian Fish Sci 5:163–179 Biswas G, Sundaray JK, Bhattacharyya SB, Kailasam M, Prem K, Krishna S, Ghoshal TK (2016) Evaluation of growth performance and survival of wild collected spotted scat, Scatophagus argus (Linnaeus, 1766) during rearing of fry to marketable size juveniles for aquarium trade at varied stocking densities. J Indian Soc Coastal agric Res 34:120–126 Cai ZP, Wang Y, Hu JW, Zhang JB, Lin YG (2010) Reproductive biology of Scatophagus argus and artificial induction of spawning. J Trop Oceanogr 29(5):180–185 Chakraborty BK, Mirza ZA, Miah MI, Habib MAB, Chakraborty A (2007) Reproductive cycle of the endangered sarpunti, Puntius sarana (Hamilton, 1822) in Bangladesh. Asian Fish Sci 20:145–164. https://doi.org/10.33997/j.afs.2007.20.2.002 Costa AM (2009) Macroscopic vs microscopic identification of the maturity stages of female horse mackerel. ICES Mar Sci 66:509–516 Farrell ED, Hüssy K, Coad JO, Clausen LW, Clarke MW (2012) Oocyte development and maturity classification of boarfish ( Capros aper ) in the Northeast Atlantic. ICES Mar Sci 69(4):498–507. https://10.1093/icesjms/fss037 Gandhi V (1998) Studies on the ecology and biology of butterfish Scatophagus argus in Mandapam coastal region. Ph.D. thesis, Madurai Kamaraj University, India Gandhi. V, Venkatesan V, Zacharia PU (2013) Biometry analysis, length-weight relationship and sexual dimorphism of the Spotted Scat, Scatophagus argus (Linnaeus, 1766) (Perciformes: Scatophagidae) from Gulf of Mannar, southeast coast of India. J. Mar. biol. Ass. India. 55 (1), 12–16. https://10.6024/jmbai.2013.55.1.01743-02 Gandhi V, Venkatesan V, Ramamoorthy N (2014) Reproductive biology of the spotted scat Scatophagus argus (Linnaeus, 1766) from Mandapam waters, south-east coast of India. Indian J Fish 61(4):55–59 Ghaffari H, Ardalan AA, Sahafi HH, Babaei MM, Abdollahi R (2011) Annual changes in gonadosomatic index (GSI), hepatosomatic index (HIS) and condition factor (K) of Largescale tonguesole Cynoglossus arel (Bloch & Schneider, 1801) in the coastal waters of Bandar Abbas, Persian Gulf. Aust j basic appl sci 5(9):1640–1646 Gisha S (2007) Studies on Venom of the fish Scatophagus argus from Cochin estuary-a biochemical approach, Ph.D. thesis, Cochin University of Science and Technology, India Gogoi R, Goswami. UC (2014) Length-Weight relationship and sex ratio of fresh water fish Amblypharyngodon mola (HAM-BUCH) from Assam. Int J Fish Aquat 1(4):68–71 Gupta S (2016) An overview on morphology, biology, and culture of spotted scat Scatophagus argus (Linnaeus 1766). Rev fish Sci aquac 24(2):203212. https://10.1080/23308249.2015.1119800 Hasan T, Hossain MF, Mamun M, Alam MJ, Salam MA, Rafiquzzaman SM (2018) Reproductive biology of Puntius sophore in Bangladesh. Fishes 3(2):22 Hashim M, Abidin Z, Das DA, Mazlan SK, A.G (2017) Length-weight relationship, condition factor and TROPH of Scatophagus argus in Malaysian coastal waters. AACL Bioflux 10(2):297–307 Jan M, Jan U, Shah GM (2014) Studies on fecundity and gonadosomatic index of Schizothorax plagiostomus (Cypriniformes: Cyprinidae). J Threat Taxa 6(1):5375–5379 Jency P, Honey S, Inasu ND, Joshi CO (2008) Sexual Dimorphism in spotted scat Scatophagus argus (Linnaeus). J Bombay Nat His Soc 105(3):349–351 Kailasam M, Thirunavukkarasu AR (2011) Mass scale propagation of spotted scat. ICAR News 17(3):4 Mandal B, Kailasam M, Bera A, Sukumaran K, Hussain T, Makesh M, Thiagarajan G, Vijayan KK (2020) Gonadal recrudescence and annual reproductive hormone pattern of captive female spotted scats ( Scatophagus argus ). Anim Reprod Sci 213:106273. https://doi.org/10.1016/j.anireprosci.2020.106273 Mendonça A, Isidro E, Menezes G, Rui Pinho M, Melo O, Estácio S (2006) New contribution to the reproductive features of bluemouth Helicolenus dactylopterus dactylopterus from northeast Atlantic ( Azores Archipelago ). Scientia Mar 70:679–688. https://doi.org/10.3989/scimar.2006.70n4679 Milton J, Bhat AA, Haniffa MA, Hussain SA, Rather IA, Al-Anazi KM, Hailan WA, Farah MA (2018) Ovarian development and histological observations of threatened dwarf snakehead fish, Channa gachua . Saudi J Biol Sci 1822(1):149–153. https://10.1016/j.sjbs.2017.03.011 Epub 2017 Mar 16 Hamilton Moutopoulos DK, Stergiou KI (2002) Length–weight and length–length relationships of fish species from the Aegean Sea (Greece). J Appl Ichthyol 18(3):200–203. https://10.1046/j.1439-0426.2002.00281.x Murua H, Kraus G, Saborido-Rey F, Witthames PR, Thorsen A, Junquera S (2003) Procedures to estimate fecundity of marine fish species from field samples in relation to reproductive strategy. J Northwest Atlan Fis Sci 33:33–54. https://doi.org/10.2960/J.v33.a3 Petrakis G, Stergiou KI (1995) Weight-length relationships for 33 fish species in Greek waters. Fish Res 21(3–4):465–469. https://doi.org/10.1016/0165-7836(94)00294-7 Richter H, Luckstadt C, Focken U, Becker K (2000) An improved procedure to assess fish condition on the basis of length-weight relationships. Archiv Fis Mar Researc 48(3):255–264 Sawusdee A (2010) Population dynamics of the Spotted Scat Scatophagus argus (Linnaeus, 1766) in Pak Panang Bay, Nakhon Si Thammarat, Thailand. Walailak J Sci Tech 7(1):23–31. https://doi.org/10.2004/wjst.v7i1.49 Shafiei Sabet S, Imanpour MR, Aminian Fatideh B, Gorgin S (2010) Histological study of ovarian development and sexual maturity of kutum (Rutilus frisii kutum Kamenskii, 1901). World Appl Sci J 8(11):1343–1350 Shafi S (2012) Study of fecundity and gonadosomatic index of Carassius carassius (Linneaus, 1758- introduced) from Dal lake Kashmir. J Biology Agric Healthc 2(3):68–75 Sivan G, Radhakrishnan CK (2011) Food, feeding habits and biochemical composition of Scatophagus argus . Turk. J Fish Aquat Sci 11(4):603–608. https://doi.org/10.4194/1303-2712-v11_4_14 Sritakon T, Songkaew N (2011) Biology of Spotted Scat, Scatophagus argus (Linnaeus, 1766) in Nakhon Si Thammarat Bay. Southern Marine Fisheries Research and Development Center (Songkhla) Su M, Duan Z, Shi H, Zhang J (2019) The effects of salinity on reproductive development and egg and larvae survival in the spotted scat Scatophagus argus under controlled conditions. Aqua Res 50(7):1782–1794. https://doi.org/10.1111/are.14056 Wongchinawit S, Paphavasit N (2009) Ontogenetic niche shift in the spotted scat, Scatophagus argus , in pak phanang estuary, Nakhon Si Thammarat Province, Thailand. Trop Nat His 9(2):143–169 Zin T, Than AA, Naing TT (2011) Fecundity (F), gonadosomatic index (GSI), hepatosomatic index (HSI), condition factor (K) and length-weight relationship (LWR) in Channa orientalis Bloch & Schneider, 1801. Universities Res J 4(2):47–62 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 14 May, 2026 Reviews received at journal 04 May, 2026 Reviewers agreed at journal 20 Apr, 2026 Reviewers agreed at journal 13 Apr, 2026 Reviewers invited by journal 26 Mar, 2026 Editor assigned by journal 26 Mar, 2026 Submission checks completed at journal 25 Mar, 2026 First submitted to journal 19 Mar, 2026 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-9166242","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":612797519,"identity":"b4d87041-e4cb-4efb-a8aa-2084ffcc0b7e","order_by":0,"name":"Prapaporn Whaiprib","email":"","orcid":"","institution":"University of Madras","correspondingAuthor":false,"prefix":"","firstName":"Prapaporn","middleName":"","lastName":"Whaiprib","suffix":""},{"id":612797520,"identity":"298693ac-24fc-426c-aa8f-49c7644b2db7","order_by":1,"name":"Selvakumar Narasimman","email":"","orcid":"","institution":"University of Madras","correspondingAuthor":false,"prefix":"","firstName":"Selvakumar","middleName":"","lastName":"Narasimman","suffix":""},{"id":612797521,"identity":"c231facb-cc7c-4b81-b138-b5623c2efb87","order_by":2,"name":"Dhanasekar Krishnamoorthy","email":"","orcid":"","institution":"University of Madras","correspondingAuthor":false,"prefix":"","firstName":"Dhanasekar","middleName":"","lastName":"Krishnamoorthy","suffix":""},{"id":612797522,"identity":"a6e3b22b-0898-47c8-95e8-21647f44cc96","order_by":3,"name":"Munuswamy Natesan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1ElEQVRIiWNgGAWjYJADxgcMDAdI08JsQLIWNgmitOjOyD0m+bPNLtrgdndaNU/NHTl+BuaHj27g0WJ2Iy9NmrctOXfDnbPbbvMce2Ys2cBmbJyDV0uOmTTjNubcDTdygVrYDiduOMDDJk1Ii+TPbfVgLcU8/4jUIsG77TBYCzNvGzFazrwxtub9dzx35o3czZJz+w4bSzYT8svxHMObP85U5/bdyN344c23w3L87M0PH+PTAgcKBxgYmHhALGZilIOAfAMwxfwgVvUoGAWjYBSMKAAAu09UA4DEZ7AAAAAASUVORK5CYII=","orcid":"","institution":"University of Madras","correspondingAuthor":true,"prefix":"","firstName":"Munuswamy","middleName":"","lastName":"Natesan","suffix":""}],"badges":[],"createdAt":"2026-03-19 07:24:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9166242/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9166242/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106402198,"identity":"ea433bc6-3ce4-4bfe-aa04-f8f4e505f013","added_by":"auto","created_at":"2026-04-08 09:11:25","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":4026324,"visible":true,"origin":"","legend":"\u003cp\u003eMale and female \u003cem\u003eScatophagus argus\u003c/em\u003e, illustrating sexual dimorphism.\u003c/p\u003e","description":"","filename":"Fig.1.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/dbeff39287f35b7aa0f01f4d.png"},{"id":105952776,"identity":"2d646b83-e392-4532-b6b0-ec05040eace0","added_by":"auto","created_at":"2026-04-01 19:05:42","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1796263,"visible":true,"origin":"","legend":"\u003cp\u003eGonadosomatic index (GSI) of female \u003cem\u003eS. argus \u003c/em\u003ewere collected\u003cem\u003e \u003c/em\u003efrom the South-east coast of India.\u003c/p\u003e","description":"","filename":"Fig.2.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/b64f0f22980765fddc7db75f.png"},{"id":106093567,"identity":"3993608a-97c8-4d20-b2e2-53446e25ceca","added_by":"auto","created_at":"2026-04-03 11:38:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2856014,"visible":true,"origin":"","legend":"\u003cp\u003eFrequency of occurrence of male and female spotted scat (November 2016 - February 2018).\u003c/p\u003e","description":"","filename":"Fig.3.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/63cdf07f37f2c1977600f502.png"},{"id":105952779,"identity":"65ae63f6-d660-43ce-a353-0195c5a84eb9","added_by":"auto","created_at":"2026-04-01 19:05:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2345759,"visible":true,"origin":"","legend":"\u003cp\u003eLength - weight relationship of female \u003cem\u003eS. argus.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"Fig.4.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/7c10684c408c5411bb99c683.png"},{"id":106093375,"identity":"1339e231-d0f1-4735-878b-bfc0799e8710","added_by":"auto","created_at":"2026-04-03 11:37:02","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2052284,"visible":true,"origin":"","legend":"\u003cp\u003eLength - weight relationship of male \u003cem\u003eS. argus\u003c/em\u003e.\u003c/p\u003e","description":"","filename":"Fig.5.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/d5d926f8cf7e436dc8e057a7.png"},{"id":105952780,"identity":"5170c195-74af-48c3-8865-2124dcdc0ccd","added_by":"auto","created_at":"2026-04-01 19:05:42","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA- F.\u003c/strong\u003e Photographs showing different stages of ovarian development in \u003cem\u003eS. argus\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eA. virgin, B. developing virgin, C. immature, D. maturing, E. mature and F. ripe stages of ovarian development.\u003c/p\u003e\n\u003cp\u003eNote the morphology of the ovary at different stages of development.\u003c/p\u003e","description":"","filename":"placeholderimageCopy2.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/460bf31afb95aa93499158bb.png"},{"id":106093568,"identity":"4c796393-2369-4b59-aafb-978cd1558aab","added_by":"auto","created_at":"2026-04-03 11:38:07","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA-D: \u003c/strong\u003ePhotomicrographs of sections through the ovary of \u003cem\u003eS. argus \u003c/em\u003eshowing various stages of oocyte maturation.\u003c/p\u003e\n\u003cp\u003eA. Immature ovary showing Primary oocyte (PMO) with germinal vesicle (GV) and Previtellogenic oocyte (PVO) with accumulation of yolk granules (YG)\u003c/p\u003e\n\u003cp\u003eB. Cortical alveolus (CA) stage showing the oocyte filled with oil droplets (OD) and yolk granules (YG)\u003c/p\u003e\n\u003cp\u003eC. Vitellogenic oocyte (VO) maturing oocyte with germinal vesicle (GV), oil droplets (OD) and yolk granule (YG)\u003c/p\u003e\n\u003cp\u003eD. Mature oocyte (M) with the ooplasm filled with oil droplets (OD) and yolk granules (YG). Note (ZR = Zona radiate, NU = Nucleoli\u003c/p\u003e","description":"","filename":"placeholderimageCopy.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/935c77f0a1744a6fe4e5039c.png"},{"id":105952782,"identity":"4fed848c-9ca1-43bd-9e99-5e37cbe78587","added_by":"auto","created_at":"2026-04-01 19:05:42","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA- F:\u003c/strong\u003e Macroscopic observation of testis at different stages of testicular development.\u003c/p\u003e\n\u003cp\u003eA. virgin, B. developing virgin, C. immature, D. maturing, E. mature and F. ripe of testis development\u003c/p\u003e\n\u003cp\u003eNote the variation in size, shape, texture and colour of the testis during development. (For details refer to text)\u003c/p\u003e","description":"","filename":"placeholderimage.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/4a10eea1e4899eb16a76d1f6.png"},{"id":106093901,"identity":"1ac75851-ad1a-4f19-be07-2ff37be1fb9f","added_by":"auto","created_at":"2026-04-03 11:39:55","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA-D: \u003c/strong\u003ePhotomicrographs of sections through the testis of \u003cem\u003eS. argus \u003c/em\u003eshowing various stages of sperm maturation\u003c/p\u003e\n\u003cp\u003eA\u003cem\u003e.\u003c/em\u003e Cross section through testis shows prominent spermatogonia (SG), spermatocyte (SC) embedded within connective tissue (ct)\u003c/p\u003e\n\u003cp\u003eB. Section through the testis showing mass of spermatids (St)\u003c/p\u003e\n\u003cp\u003eC \u0026amp; D. Section through the testis showing mature spermatozoa (SZ) inside the lumen (L) of Seminiferous Tubule (ST).\u003c/p\u003e","description":"","filename":"placeholderimage.png","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/4b10335e3efe3a0c14380205.png"},{"id":106405534,"identity":"5410f533-d449-4b6b-9afc-0d65131c3d0d","added_by":"auto","created_at":"2026-04-08 09:27:11","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":12895082,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9166242/v1/81b13137-a8da-413d-845b-843a6ea5f1b2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Reproductive bionomics of Spotted Scat, Scatophagus argus (Linnaeus, 1766) off South-east coast of India","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eSouth-east coast of India has a varied diversity of fish with many coastal, estuarine, and creek systems. \u003cem\u003eScatophagus argus\u003c/em\u003e is a euryhaline teleost, widely distributed throughout the nearshore waters of the Indo-West Pacific Ocean from southern India and Sri Lanka to southern Japan and Tahiti (Wongchinawit and Paphavasit, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Gandhi et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Spotted scat occurs in freshwater, brackish water, and marine habitats of the Indo-Pacific, South and South-East Asia, the Malay Archipelago, the Philippines and Australia (Barry, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1988\u003c/span\u003e). Mandal et al. (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) have stated that \u003cem\u003eS. argus\u003c/em\u003e is an ornamental fish species in the South-east which is economically important. It has been valued as an aquarium fish around the world due to its colourful appearance, hardiness, slow growth, and calm behaviour (Barry, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Amarasinghe et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Kailasam and Thirunavukkarasu, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Sivan and Radhakrishnan, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Gupta, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). This fish is commonly known as \u0026ldquo;spotted scat\u0026rdquo; due to the presence of numerous black spots on its body (Barry and Fast, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). In Philippines and Thailand, high-priced food fish are regarded as high quality (Barry, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Sawusdee, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). This is in high demand in the global market due to its distinctive taste and nutritional quality, including high protein content and meat quality (Anney, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Gisha, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Biswas et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Although this fish is important as a food fish in other parts of the world, it is not well popularized as a food fish in India.\u003c/p\u003e \u003cp\u003e \u003cem\u003eS. argus\u003c/em\u003e can adapt itself to many variables such as temperature, salinity, dissolved oxygen, tidal action, river runoff, turbulence and turbidity, thus it is a species of high aquaculture demand too (Barry and Fast \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Su et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). It has been listed in the \u0026ldquo;least concern\u0026rdquo; category of the IUCN red list of threatened species (IUCN 2021) as the population of this fish in the wild has fallen due to a combination of over-exploitation, habitat destruction, climate changes and so on. Thus, conservation of the species is important, and so is ensuring the population under captive conditions. This fish was chosen by many researchers for artificial reproduction in many countries around the world (Cai et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Gonado somatic index (GSI), along with fecundity and gonadal histology, are the most essential parameters to determine the spawning cycle of any fish. The GSI allows us to predict the exact time of breeding and breeding frequency of fish species (Ghaffari et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Shafi, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Jan et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). In aquaculture, managing the spawning of fish in a population will become difficult if there is an inappropriate prediction of the maturity stage (Costa, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). The details of sperm and oocyte development can be authenticated by histological validation of different maturation stages (Mendon\u0026ccedil;a et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Furthermore, breeding season, gonadal maturity and spawning can also be determined by histology, which may lead to successful artificial propagation (Chakraborty et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Hasan et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe sex ratio of fish provides accurate information on the domination of sex in a population of fish (Adebiyi, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Arocha et al. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) have studied the importance of sex ratio in determining female fecundity. This enabled him to distinguish the population behaviour and fecundity along with the seasonal differences in sexes and the growth rate (Gogoi and Goswaini, 2014). There may be significant variation in the sex ratio between species, and it differs at different periods in the same population, but in most cases, it is close to one, i.e., 1 male:1 female (Zin et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSpotted scat spawns throughout the year, with a peak in April - October in Nakhon Si Thammarat, Thailand (Sritakon and Songkaew, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The fish is also known to exhibit multiple spawnings during its reproductive period. Generally, the sex ratio is biased toward female dominance (Barry and Fast, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Gandhi, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Cai et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Regarding sexual dimorphism, generally females of \u003cem\u003eS. argus\u003c/em\u003e are larger and heavier than males of the same length group (Jency et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Gandhi et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Furthermore, morphometric observation on the length and weight relationship of fish is useful to determine condition indices and to equate life history and morphology of populations belonging to different regions (Petrakis and Stergiou, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Richter et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Moutopoulos and Stergiou, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Studies on the length - weight equation of spotted scat have been made in South-east Asia (Philippines, Thailand, and Malaysia) and India as well (Barry and Fast, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Sritakon and Songkaew, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Sawusdee, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Gandhi et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Hashim et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTherefore, the present study aimed to acquire information on the distribution as well as reproductive bionomics of \u003cem\u003eScatophagus argus\u003c/em\u003e to augment its aquaculture potential.\u003c/p\u003e"},{"header":"2. Material and Methods","content":"\u003cp\u003eFish samples of \u003cem\u003eS. argus\u003c/em\u003e were obtained from fishermen of the Ennore, Muttukadu and Mandapam coastal areas from November 2016 to February 2018. Fishes were brought to the laboratory in the ice box. Morphometric measurements such as total length, standard length and weight of the fish were made as per standard procedure (Barry and Fast, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Sawusdee, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Sritakon and Songkaew, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Gandhi et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Hashim et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Fish samples, thus collected, were analyzed for population structure, sex-ratio, and length - weight relationships. The stages of maturity of male and female fish were analyzed based on the size and texture of gonads (Murua et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Farrell et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Milton et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The gonadosomatic index (GSI) of the fish was calculated.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Histology\u003c/h2\u003e \u003cp\u003eGonads of both sexes in \u003cem\u003eS. argus\u003c/em\u003e at different size groups were dissected out and fixed in a 4% neutral buffered formaldehyde solution. The samples were dehydrated through a graded alcohol series and embedded in paraffin wax. Sections of 5\u0026ndash;6 \u0026micro;m thickness were taken and stained with hematoxylin and eosin. Photomicrographs were taken at various magnifications using a Leica DM 2500 (Germany) microscope.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e3.1 Diversity and morphological characteristics\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eA survey of \u003cem\u003eS. argus\u003c/em\u003e in fish landings indicated its distribution throughout the year in the coastal regions of Ennore, Muttukadu, and Mandapam. However, the size range of fish varied significantly in all sampling sites. The sex of the fish is distinguished by observing their head shape. In females, the head profile ascends at a constant slope, but males have a concave curvature in the head above the eyes. The spotted scat has a quadrangular and strongly compressed body; the body colour is uniformly greenish-silvery or coffee-brown. The mouth is small, not protrusible, and the teeth are small in several rows. The whole body is covered with ctenoid scales and round brown spots (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Reproductive performance and length-weight relationship\u003c/h2\u003e \u003cp\u003eThe gonadosomatic index (GSI) of female \u003cem\u003eS. argus\u003c/em\u003e is aptly related to the gonadal maturity of the fish (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The monthly GSI value in females ranged from 3 to 13%. The highest mean of GSI was registered in July (13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01%) and November 2017 (11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003%), indicating their peak spawning seasons.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eMales and females were found to mature at around 12.0 -12.5 cm total length (TL). In females, the weight of the fish ranged from 30 g to 800 g and the length was 15.3 cm with a range from 9.20 cm to 30 cm. The weight of males ranged from 55 g to 480 g and the length of 14.97 cm and the length ranged from 12 cm to 21.5 cm. The male and female sex ratio collected from Ennore and Muttukadu registered 1:2.4 (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The sex ratio was biased towards females up to 1:17 as recorded along the Mandapam coast as well.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFurthermore, the length (L) and weight (W) relationship showed W\u0026thinsp;=\u0026thinsp;0.0337 L\u003csup\u003e2.998\u003c/sup\u003e (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.9399, n\u0026thinsp;=\u0026thinsp;46) and W\u0026thinsp;=\u0026thinsp;0.055 L\u003csup\u003e2.804\u003c/sup\u003e (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.7465, n\u0026thinsp;=\u0026thinsp;19) for female and male, respectively (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The growth of \u003cem\u003eS. argus\u003c/em\u003e is \u0026ldquo;allometric\u0026rdquo; meaning that the increase in weight is not proportional to length.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Ovarian development\u003c/h2\u003e \u003cp\u003eBased on the colour, texture and size of the ovary, six different developmental stages were recorded (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA-F). These stages include virgin, developing virgin, immature, maturing, mature and ripe ovary. Each stage was characterized by the colour and size of the ovary as well as the nature of oocytes in the ovary. Virgin has small ovaries without visible oocytes. The ovarian wall is thin and identification of the onset of maturity is often difficult. In the developing virgin stage, the ovaries are small and at this stage, oocytes are in the primary growth phase. In the immature stage, the ovary is of medium size, occupying 5% of the body cavity, but is visible with opaque oocytes. At a maturing stage, ovaries occupy 10% of the body cavity; oocytes are seen as opaque and yellow. The mature stage represents larger ovaries occupying 25% of the body cavity. At a ripe stage, oocytes swell; ovaries become yellow and occupy more than 50% of the body cavity. In this stage, oocytes are seen as yellow with apparent blood capillaries.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSections through the ovary at different stages of maturity show five stages of oocyte maturation that include primary oocytes, previtellogenic oocytes, cortical alveolus, vitellogenic and mature oocytes (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eA-D). The characteristic features include oocyte size, the presence of a follicular layer, the number of nucleoli and the distribution of ooplasmic inclusions. The primary oocyte is small and measures around 33 to 40 \u0026micro;m in diameter. Previtellogenic oocytes are characterized by chromatin material inside the nucleus of the oocytes. The nucleolus is small, and oocytes measure from 50 to 67 \u0026micro;m in diameter. The cortical alveolus stage includes oocytes around 83 to 133 \u0026micro;m in diameter and characterized by the appearance of cortical alveoli marks (yolk vesicles). The vitellogenic stage represents oocytes with a size range from 134 to 320 \u0026micro;m in diameter and accumulation of yolk material, such as yolk granules and oil droplets. The mature stage represents oocytes in the size range of 185 to 400 \u0026micro;m in diameter with nucleus break-up and the ooplasm full of yolk bodies.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Testicular development\u003c/h2\u003e \u003cp\u003eBased on the morphology, colour and texture of the testis, six stages of testicular development are observed (Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eA-F). These stages include virgin, developing virgin, immature, maturing, mature and ripe testis. Virgin testes are generally tiny, translucent filaments that look like small tubes. At the developing virgin stage, the testis is characterized by a yellowish colour. Semen is not seen in the sperm duct even when squeezed. The immature testis is medium-sized and milt is seen in the sperm duct at this stage. Testes attain near full size but do not appear swollen. Maturing testis increases in size and is larger than the immature stage, and appears swollen. Sperm can be stripped and are visible when cut. Mature testis increase in size with full sperm that can be stripped around 100\u0026ndash;200 \u0026micro;l per fish. Ripe testes are larger and swollen fully with sperm and can be stripped of more than 200 \u0026micro;l per fish.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA histological study performed on the testis registered four stages of sperm maturation. These stages include spermatogonia, spermatocytes, spermatid and spermatozoa (Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eA-D). Spermatogonia are commonly found in groups or nests, but they sometimes occur solitary. Spermatocytes include primary and secondary spermatocytes that can be distinguished from each other with accuracy and are seen as the most actively dividing cells of the testis. Spermatids are small and tend to move towards the center of the seminiferous tubule. In the spermatozoa stage, spermatozoa occur within the lumen of the lobule. The fully formed mature spermatozoan is essentially comprised of a prominent head and flagellum (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe present study documents the distribution of \u003cem\u003eS. argus\u003c/em\u003e collected in Ennore, Muttukadu and Mandapam from South-east coast of India from November 2016 to February 2018. Distribution of this fish has been reported in other parts of the world (Wongchinawit and Paphavasit, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Gandhi et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Amarasinghe et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Sawusdee, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Gandhi et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe peak spawning season of \u003cem\u003eS. argus\u003c/em\u003e was evident with gonadal maturity during July and November (2017). Gandhi et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2014\u003c/span\u003e also reported the spawning of spotted scat twice in a season, during the south-west monsoon (June to August) and north-east monsoon (October to December) with peaks during July and November at the Mandapam coastal region. In South-China coastal waters, the spawning of this fish was during April - August and the peak spawning occurred during May and July. In Philippines, the initiation of spawning was from June to July and from April to October, with the spawning peak in August (Barry and Fast, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Cai et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eGonadal maturity of \u003cem\u003eS. argus\u003c/em\u003e registered 13% (GSI) in Indian waters, which is comparable to 14.7% (GSI) in Chinese waters (Cai et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). The monthly GSI value in females registered a maximum during July and November 2017. Gandhi et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2014\u003c/span\u003e also reported the first peak of GSI in females in July, which decreased in September and increased again in November.\u003c/p\u003e \u003cp\u003eIn this study, male and female \u003cem\u003eS. argus\u003c/em\u003e were found to mature first at a total length between 12.50 and 12.55 cm, with an average weight of 121. 94 g and 140.71 g, respectively. According to Barry. (1988)\u003csup\u003e,\u003c/sup\u003e the smallest male found with oozing milt was around 11.5 cm in length and 83.5 g in weight. This may be a reasonable estimate of the size at first maturity in male scat. Females were determined to be sexually mature by plotting their gonad weight as a function of standard length. The increase in gonad weights for fish longer than a total length of 14 cm and heavier than approximately 150 g indicates the size at which females reach first sexual maturity. Sritakon and Songkaew. (2011) reported the average length at first maturity of females was around 11.60 cm. The minimum age of reproduction for both males and females of \u003cem\u003eS. argus\u003c/em\u003e is achieved within the age of first year (Cai et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRegarding the sex ratio, it was biased toward females in Indian waters and fish collected from Ennore and Muttukadu registered at 1:2.4 and 1:17 along the Mandapam coast. An evaluation of the sex ratio in \u003cem\u003eS. argus\u003c/em\u003e showed that females were dominant in the population. Similar observations of female dominance in \u003cem\u003eS. argus\u003c/em\u003e were also reported in other waters (Gandhi et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Barry and Fast, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Cai et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Jency et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMorphometric measurements about the length and weight of \u003cem\u003eS. argus\u003c/em\u003e relatively showed a negative growth (b\u0026thinsp;\u0026lt;\u0026thinsp;3) pattern, indicating that the fish becomes more slender as length increases. A similar growth pattern in \u003cem\u003eS. argus\u003c/em\u003e was recorded in Thailand, India, Malaysia and Philippines waters (Barry and Fast, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Sawusdee, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Gandhi et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Hashim et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The growth of \u003cem\u003eS. argus\u003c/em\u003e is \u0026ldquo;allometric\u0026rdquo; i.e., the increase in weight is non-proportion to the length (W\u0026thinsp;=\u0026thinsp;0.0562TL\u003csup\u003e2.7021\u003c/sup\u003e, R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.93) ( Sawusdee, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Similarly, Gandhi et al. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) reported relationships between the total length and weight of each sex separately (Male W\u0026thinsp;=\u0026thinsp;0.005373 L \u003csup\u003e2.842\u003c/sup\u003e R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.97, Female W\u0026thinsp;=\u0026thinsp;0.002152 L \u003csup\u003e2.479\u003c/sup\u003e R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.98). Regression equation revealed that the values of b\u0026thinsp;=\u0026thinsp;2.842 and 2.479 are significantly different from 3, indicating that the LWR of this species departs significantly from isometry. The \u0026lsquo;b\u0026rsquo; values of spotted scat were quite similar to those observed by Barry and Fast. 1992 for the same species in the southern coastal waters of Panay Island, Philippines. The value of \u0026lsquo;b\u0026rsquo; may range between 2.5 and 3.5 (Shafiei et al., 2010). The slopes (b) of the regressions were less than 3 for both sexes, hence growth in the individual sex was found to be negative allometric which might be due to the deep, strongly laterally compressed body of spotted scat. \u003cem\u003eS. argus\u003c/em\u003e collected from the fish collection center at Gelang Patah, Johor Malaysian coastal also showed a similar allometric negative (b\u0026thinsp;\u0026lt;\u0026thinsp;3) indicating that the weight increment was lesser than the length increment (Hashim et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the majority of teleost fishes, five to eight stages of oocyte maturation have been reported (Murua et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Farrell et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Milton et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Shafiei et al., 2010; Abu El-Nasr, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). This study has documented ovarian development with six stages of oocyte maturation similar to many teleost fishes (Murua et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Shafiei et al., 2010; Milton et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In male spotted scat four stages of testicular development were registered (Abu El-Nasr, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Thus, this study provides baseline data on the reproductive performance and length-weight relationship of \u003cem\u003eS. argus\u003c/em\u003e, which would be helpful for the aquaculture potential of this species.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eFinancial interests\u003c/h2\u003e \u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eConflict of Interest Statement\u003c/h2\u003e \u003cp\u003eThe authors declare there is no conflict of interest.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCRediT author contribution statement\u003c/h2\u003e \u003cp\u003ePrapaporn Whaiprib: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing - original draft.\u003c/p\u003e \u003cp\u003eNarasimman Selvakumar: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing - original draft, Writing - review \u0026amp; editing.\u003c/p\u003e \u003cp\u003eKrishnamoorthy Dhanasekar: Writing - review \u0026amp; editing.\u003c/p\u003e \u003cp\u003eNatesan Munuswamy: Investigation, Supervision, Writing - review \u0026amp; editing.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eNo funding was received to assist with the preparation of this manuscript.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003ePrapaporn Whaiprib: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing - original draft.Narasimman Selvakumar: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing - original draft, Writing - review \u0026amp; editing.Krishnamoorthy Dhanasekar: Writing - review \u0026amp; editing.Natesan Munuswamy: Investigation, Supervision, Writing - review \u0026amp; editing.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eFinancial assistance to Dr. Prapaporn Whaiprib from Indian Council for Cultural Relations (ICCR), Ministry of External Affairs, Government of India, for Ph.D programme is gratefully acknowledged. Thanks are due to Council of Scientific and Industrial Research (CSIR) Government of India, New Delhi under CSIR-Emeritus scientist scheme (21(1069)/19/ EMR-II) and Dr. D. S. Kothari Post-Doctoral Fellowship by the University Grants Commission, New Delhi (F.4\u0026thinsp;\u0026minus;\u0026thinsp;2/2006(BSR)/BL/18\u0026ndash;19/0545).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbu El-Nasr TM (2016) Evaluation the quality of the oil waste histological changes in the ovaries of the whipfin fish, \u003cem\u003eGerres filamentosus\u003c/em\u003e (Cuvier, 1829) during the reproductive cycle in the Hurdhada Red Sea. Egypt. AENSI J., Adv. Environ. Biol. 10(4), 160\u0026ndash;173\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAdebiyi FA (2013) The sex ratio, gonadosomatic index, stages of gonadal development and fecundity of sompat grunt, \u003cem\u003ePomadasys jubelini\u003c/em\u003e (Cuvier, 1830). Pakistan J Zool 45(1):41\u0026ndash;46\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAmarasinghe US, Amarasinghe MD, Nissanka C (2002) Investigation of the Negombo estuary (Sri Lanka) brush park fishery, with an emphasis on community-based management. Fisheries Manag Eco 9(1):41\u0026ndash;56. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1046/j.1365-2400.2002.00250.x\u003c/span\u003e\u003cspan address=\"10.1046/j.1365-2400.2002.00250.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnney MK, Antony A (1988) Studies On Some Aspects Of Biology Of Two Estuarine Fishes \u003cem\u003eMegalops Cyprinoides\u003c/em\u003e And \u003cem\u003eScatophagus Argus\u003c/em\u003e. Ph.D. thesis, Cochin University of Science And Technology, India\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArocha F, Marcano. L, Silva. J (2010) Sex ratio at size of sailfish (\u003cem\u003eIstiophorus albicans\u003c/em\u003e) from the Venezuelan fishery off the Caribbean Sea and adjacent areas. Collective Volume Sci Papers ICCAT 65(5):1633\u0026ndash;1640\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarry TP (1988) Natural history of the spotted scat (\u003cem\u003eScatophagus argus\u003c/em\u003e). Spawning induction and pond culture of the spotted scat (\u003cem\u003eScatophagus argus\u003c/em\u003e Linnaeus) in the Philippines. 4\u0026ndash;31\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarry TP, Fast AW (1992) Biology of the spotted scat (\u003cem\u003eScatophagus argus\u003c/em\u003e) in the Philippines. Asian Fish Sci 5:163\u0026ndash;179\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBiswas G, Sundaray JK, Bhattacharyya SB, Kailasam M, Prem K, Krishna S, Ghoshal TK (2016) Evaluation of growth performance and survival of wild collected spotted scat, \u003cem\u003eScatophagus argus\u003c/em\u003e (Linnaeus, 1766) during rearing of fry to marketable size juveniles for aquarium trade at varied stocking densities. J Indian Soc Coastal agric Res 34:120\u0026ndash;126\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCai ZP, Wang Y, Hu JW, Zhang JB, Lin YG (2010) Reproductive biology of \u003cem\u003eScatophagus argus\u003c/em\u003e and artificial induction of spawning. J Trop Oceanogr 29(5):180\u0026ndash;185\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChakraborty BK, Mirza ZA, Miah MI, Habib MAB, Chakraborty A (2007) Reproductive cycle of the endangered sarpunti, \u003cem\u003ePuntius sarana\u003c/em\u003e (Hamilton, 1822) in Bangladesh. Asian Fish Sci 20:145\u0026ndash;164. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.33997/j.afs.2007.20.2.002\u003c/span\u003e\u003cspan address=\"10.33997/j.afs.2007.20.2.002\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCosta AM (2009) Macroscopic vs microscopic identification of the maturity stages of female horse mackerel. ICES Mar Sci 66:509\u0026ndash;516\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFarrell ED, H\u0026uuml;ssy K, Coad JO, Clausen LW, Clarke MW (2012) Oocyte development and maturity classification of boarfish (\u003cem\u003eCapros aper\u003c/em\u003e) in the Northeast Atlantic. ICES Mar Sci 69(4):498\u0026ndash;507. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://10.1093/icesjms/fss037\u003c/span\u003e\u003cspan address=\"https://10.1093/icesjms/fss037\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGandhi V (1998) Studies on the ecology and biology of butterfish \u003cem\u003eScatophagus argus\u003c/em\u003e in Mandapam coastal region. Ph.D. thesis, Madurai Kamaraj University, India\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGandhi. V, Venkatesan V, Zacharia PU (2013) Biometry analysis, length-weight relationship and sexual dimorphism of the Spotted Scat, \u003cem\u003eScatophagus argus\u003c/em\u003e (Linnaeus, 1766) (Perciformes: Scatophagidae) from Gulf of Mannar, southeast coast of India. J. Mar. biol. Ass. India. 55 (1), 12\u0026ndash;16. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://10.6024/jmbai.2013.55.1.01743-02\u003c/span\u003e\u003cspan address=\"https://10.6024/jmbai.2013.55.1.01743-02\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGandhi V, Venkatesan V, Ramamoorthy N (2014) Reproductive biology of the spotted scat \u003cem\u003eScatophagus argus\u003c/em\u003e (Linnaeus, 1766) from Mandapam waters, south-east coast of India. Indian J Fish 61(4):55\u0026ndash;59\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGhaffari H, Ardalan AA, Sahafi HH, Babaei MM, Abdollahi R (2011) Annual changes in gonadosomatic index (GSI), hepatosomatic index (HIS) and condition factor (K) of Largescale tonguesole Cynoglossus arel (Bloch \u0026amp; Schneider, 1801) in the coastal waters of Bandar Abbas, Persian Gulf. Aust j basic appl sci 5(9):1640\u0026ndash;1646\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGisha S (2007) Studies on Venom of the fish Scatophagus argus from Cochin estuary-a biochemical approach, Ph.D. thesis, Cochin University of Science and Technology, India\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGogoi R, Goswami. UC (2014) Length-Weight relationship and sex ratio of fresh water fish \u003cem\u003eAmblypharyngodon mola\u003c/em\u003e (HAM-BUCH) from Assam. Int J Fish Aquat 1(4):68\u0026ndash;71\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGupta S (2016) An overview on morphology, biology, and culture of spotted scat \u003cem\u003eScatophagus argus\u003c/em\u003e (Linnaeus 1766). Rev fish Sci aquac 24(2):203212. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://10.1080/23308249.2015.1119800\u003c/span\u003e\u003cspan address=\"https://10.1080/23308249.2015.1119800\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHasan T, Hossain MF, Mamun M, Alam MJ, Salam MA, Rafiquzzaman SM (2018) Reproductive biology of Puntius sophore in Bangladesh. Fishes 3(2):22\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHashim M, Abidin Z, Das DA, Mazlan SK, A.G (2017) Length-weight relationship, condition factor and TROPH of \u003cem\u003eScatophagus argus\u003c/em\u003e in Malaysian coastal waters. AACL Bioflux 10(2):297\u0026ndash;307\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJan M, Jan U, Shah GM (2014) Studies on fecundity and gonadosomatic index of \u003cem\u003eSchizothorax plagiostomus\u003c/em\u003e (Cypriniformes: Cyprinidae). J Threat Taxa 6(1):5375\u0026ndash;5379\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJency P, Honey S, Inasu ND, Joshi CO (2008) Sexual Dimorphism in spotted scat \u003cem\u003eScatophagus argus\u003c/em\u003e (Linnaeus). J Bombay Nat His Soc 105(3):349\u0026ndash;351\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKailasam M, Thirunavukkarasu AR (2011) Mass scale propagation of spotted scat. ICAR News 17(3):4\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMandal B, Kailasam M, Bera A, Sukumaran K, Hussain T, Makesh M, Thiagarajan G, Vijayan KK (2020) Gonadal recrudescence and annual reproductive hormone pattern of captive female spotted scats (\u003cem\u003eScatophagus argus\u003c/em\u003e). Anim Reprod Sci 213:106273. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.anireprosci.2020.106273\u003c/span\u003e\u003cspan address=\"10.1016/j.anireprosci.2020.106273\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMendon\u0026ccedil;a A, Isidro E, Menezes G, Rui Pinho M, Melo O, Est\u0026aacute;cio S (2006) New contribution to the reproductive features of bluemouth \u003cem\u003eHelicolenus dactylopterus\u003c/em\u003e dactylopterus from northeast Atlantic (\u003cem\u003eAzores Archipelago\u003c/em\u003e). Scientia Mar 70:679\u0026ndash;688. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3989/scimar.2006.70n4679\u003c/span\u003e\u003cspan address=\"10.3989/scimar.2006.70n4679\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMilton J, Bhat AA, Haniffa MA, Hussain SA, Rather IA, Al-Anazi KM, Hailan WA, Farah MA (2018) Ovarian development and histological observations of threatened dwarf snakehead fish, \u003cem\u003eChanna gachua\u003c/em\u003e. Saudi J Biol Sci 1822(1):149\u0026ndash;153. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://10.1016/j.sjbs.2017.03.011\u003c/span\u003e\u003cspan address=\"https://10.1016/j.sjbs.2017.03.011\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003eEpub 2017 Mar 16 Hamilton\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoutopoulos DK, Stergiou KI (2002) Length\u0026ndash;weight and length\u0026ndash;length relationships of fish species from the Aegean Sea (Greece). J Appl Ichthyol 18(3):200\u0026ndash;203. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://10.1046/j.1439-0426.2002.00281.x\u003c/span\u003e\u003cspan address=\"https://10.1046/j.1439-0426.2002.00281.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMurua H, Kraus G, Saborido-Rey F, Witthames PR, Thorsen A, Junquera S (2003) Procedures to estimate fecundity of marine fish species from field samples in relation to reproductive strategy. J Northwest Atlan Fis Sci 33:33\u0026ndash;54. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2960/J.v33.a3\u003c/span\u003e\u003cspan address=\"10.2960/J.v33.a3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePetrakis G, Stergiou KI (1995) Weight-length relationships for 33 fish species in Greek waters. Fish Res 21(3\u0026ndash;4):465\u0026ndash;469. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/0165-7836(94)00294-7\u003c/span\u003e\u003cspan address=\"10.1016/0165-7836(94)00294-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRichter H, Luckstadt C, Focken U, Becker K (2000) An improved procedure to assess fish condition on the basis of length-weight relationships. Archiv Fis Mar Researc 48(3):255\u0026ndash;264\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSawusdee A (2010) Population dynamics of the Spotted Scat \u003cem\u003eScatophagus argus\u003c/em\u003e (Linnaeus, 1766) in Pak Panang Bay, Nakhon Si Thammarat, Thailand. Walailak J Sci Tech 7(1):23\u0026ndash;31. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2004/wjst.v7i1.49\u003c/span\u003e\u003cspan address=\"10.2004/wjst.v7i1.49\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShafiei Sabet S, Imanpour MR, Aminian Fatideh B, Gorgin S (2010) Histological study of ovarian development and sexual maturity of kutum (Rutilus frisii kutum Kamenskii, 1901). World Appl Sci J 8(11):1343\u0026ndash;1350\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShafi S (2012) Study of fecundity and gonadosomatic index of \u003cem\u003eCarassius carassius\u003c/em\u003e (Linneaus, 1758- introduced) from Dal lake Kashmir. J Biology Agric Healthc 2(3):68\u0026ndash;75\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSivan G, Radhakrishnan CK (2011) Food, feeding habits and biochemical composition of \u003cem\u003eScatophagus argus\u003c/em\u003e. Turk. J Fish Aquat Sci 11(4):603\u0026ndash;608. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.4194/1303-2712-v11_4_14\u003c/span\u003e\u003cspan address=\"10.4194/1303-2712-v11_4_14\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSritakon T, Songkaew N (2011) Biology of Spotted Scat, \u003cem\u003eScatophagus argus\u003c/em\u003e (Linnaeus, 1766) in Nakhon Si Thammarat Bay. Southern Marine Fisheries Research and Development Center (Songkhla)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSu M, Duan Z, Shi H, Zhang J (2019) The effects of salinity on reproductive development and egg and larvae survival in the spotted scat Scatophagus argus under controlled conditions. Aqua Res 50(7):1782\u0026ndash;1794. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/are.14056\u003c/span\u003e\u003cspan address=\"10.1111/are.14056\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWongchinawit S, Paphavasit N (2009) Ontogenetic niche shift in the spotted scat, \u003cem\u003eScatophagus argus\u003c/em\u003e, in pak phanang estuary, Nakhon Si Thammarat Province, Thailand. Trop Nat His 9(2):143\u0026ndash;169\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZin T, Than AA, Naing TT (2011) Fecundity (F), gonadosomatic index (GSI), hepatosomatic index (HSI), condition factor (K) and length-weight relationship (LWR) in \u003cem\u003eChanna orientalis\u003c/em\u003e Bloch \u0026amp; Schneider, 1801. Universities Res J 4(2):47\u0026ndash;62\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"thalassas-an-international-journal-of-marine-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"thal","sideBox":"Learn more about [Thalassas: An International Journal of Marine Sciences](http://link.springer.com/journal/41208)","snPcode":"41208","submissionUrl":"https://submission.nature.com/new-submission/41208/3","title":"Thalassas: An International Journal of Marine Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Allometric, Population structure, Gonadosomatic index, Reproductive activity, Spotted scat","lastPublishedDoi":"10.21203/rs.3.rs-9166242/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9166242/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe study emphasizes reproductive biomomics, population structure and length-weight relationship of spotted scat, \u003cem\u003eScatophagus argus\u003c/em\u003e, off Indian waters. Sampling from Ennore, Muttukadu, and Mandapam along the South-east coast of India registered their occurrence during the south-west monsoon (June to August) and north-east monsoon (October to December) with peaks during July and November. There exists a biased sex ratio towards females in the spotted scat population. Reproductivity performance was assessed based on the gonad-somatic index, which aptly correlated with peak spawning season. This led to a description of six stages of ovarian and testicular development. Histological studies further revealed five stages of oocyte and four stages of sperm maturation. Morphometric analysis indicated that the total length (TL) of the fish in the samples ranged from 9.2 cm to 18.3 cm in females and 12.0 cm to 17.6 cm in males. Length-weight equations of w\u0026thinsp;=\u0026thinsp;0.0337 L\u003csup\u003e2.998\u003c/sup\u003e and w\u0026thinsp;=\u0026thinsp;0.055 L\u003csup\u003e2.804\u003c/sup\u003e were derived for females and males, respectively. The relationship showed that the exponent \u0026ldquo;b\u0026rdquo; value was below 3, with a negative allometric equation documenting compressed body shape. This study provides baseline data on the population structure, length-weight relationship, sexual maturity, and spawning periodicity of \u003cem\u003eScatophagus argus\u003c/em\u003e in Indian waters.\u003c/p\u003e","manuscriptTitle":"Reproductive bionomics of Spotted Scat, Scatophagus argus (Linnaeus, 1766) off South-east coast of India","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-01 19:05:37","doi":"10.21203/rs.3.rs-9166242/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"223880346622807939361993828293905420372","date":"2026-05-14T12:24:22+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-04T16:25:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"223688881995232176595962006547997994374","date":"2026-04-20T16:20:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"260687750118612397968118166015565072994","date":"2026-04-13T20:29:19+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-26T16:01:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-26T15:48:43+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-25T14:23:03+00:00","index":"","fulltext":""},{"type":"submitted","content":"Thalassas: An International Journal of Marine Sciences","date":"2026-03-19T07:13:11+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"thalassas-an-international-journal-of-marine-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"thal","sideBox":"Learn more about [Thalassas: An International Journal of Marine Sciences](http://link.springer.com/journal/41208)","snPcode":"41208","submissionUrl":"https://submission.nature.com/new-submission/41208/3","title":"Thalassas: An International Journal of Marine Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"1ac37241-4f99-4d6d-8d42-e29339c14170","owner":[],"postedDate":"April 1st, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"223880346622807939361993828293905420372","date":"2026-05-14T12:24:22+00:00","index":52,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-04T16:25:56+00:00","index":36,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-01T19:05:37+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-01 19:05:37","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9166242","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9166242","identity":"rs-9166242","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}