Comparison of monofilament and multifilament bottom trammel nets regarding catch efficiency and chondrichthyan bycatch in Çanakkale, Türkiye

Comparison of monofilament and multifilament bottom trammel nets regarding catch efficiency and chondrichthyan bycatch in Çanakkale, Türkiye | 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 Comparison of monofilament and multifilament bottom trammel nets regarding catch efficiency and chondrichthyan bycatch in Çanakkale, Türkiye Oğuzhan Ayaz, Uğur Altınağaç, Adnan Ayaz, Cahide Çiğdem Yığın This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9010448/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 This study aimed to evaluate the catch efficiency and chondrichthyan bycatch of monofilament and multifilament bottom trammel nets in the Çanakkale region, where small-scale commercial fishing is practiced intensively. The field trials of the study were carried out between September 2024 and March 2026. Within the scope of the study, a total of 8 units (800 m) of trammel nets were used. The trammel nets are equipped with a 42 mm inner mesh size, monofilament and multifilament materials and, have all other technical characteristics identical. 65 trials were carried out with these nets. The nets were deployed in the water for 36 hours in each trial. As a result of the trials, a total of 981 individuals and 622.3 kg of fish belonging to 20 species were captured. All species with economic value were classified as target, and other species without economic value were classified as discard. When the economic species caught in the nets were compared, multifilament trammel nets caught 1.22 times more than monofilament trammel nets. As a result of the statistical comparison, multifilament trammel nets caught more than monofilament trammel nets ( P < 0.05). In the discarded catch, monofilament trammel nets caught 1.62 times more than multifilament trammel nets. In addition, the ratio of priority conservation species within the total catch was calculated as 23.2% in monofilament trammel nets; this ratio was 12.5% in multifilament trammel nets. In the comparison made using repeated measures analysis of variance, the difference between them was found to be statistically significant ( P < 0.05). The study determined that the preference for monofilament material is not necessary for the nets used in the fishing of species such as cuttlefish, lobster, and scorpionfish in the region, and that multifilament trammel nets are more efficient than monofilament trammel nets in catching target species. Additionally, considering that a large part of the bycatch consists of conservation-priority chondrichthyan fish species, it was determined that the use of monofilament material in trammel nets is not suitable in terms of sustainable fisheries. It was established that the preference for multifilament trammel nets would enhance bycatch mitigation. Catch efficiency Chondrichthyan bycatch Monofilament Multifilament Bottom trammel nets Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 INTRODUCTION The coasts of Çanakkale are among the areas where small-scale commercial fishers intensively use trammel nets. It has been determined that sharks, which are among the endangered species, are also caught in these nets, which are generally used between 10 and 100 meters in the region (Cilasın et al., 2015 ). The use of trammel nets poses potential threats, especially to sharks, rays, and other chondrichthyans. Therefore, any information to be gained about these species provides an ecological approach for fisheries management. Chondrichthyans living in Turkish seas are mostly of Atlantic-Mediterranean and cosmopolitan origin, but also include species endemic to the Mediterranean and Red Sea migrants. According to their distribution in Turkish seas, there are 9 species in the Black Sea, 36 in the Marmara Sea, 59 in the Aegean Sea, and 62 in the Mediterranean (Bengil and Başusta, 2018 ). The long lifespans, slow growth, low fecundity, and late attainment of sexual maturity of chondrichthyans make them more sensitive to possible ecosystem changes and overfishing pressure. The global population decline in fish stocks has directed commercial fishers and fisheries management toward new target species caught as bycatch and toward alternative strategies for their utilization. As a result, sharks and rays are being exploited at high rates today (Stevens et al., 2000 ). According to the Turkish Statistical Institute (TUIK) data for the last decade in Türkiye, there is a significant decrease in the catch amounts of rays and sharks (TUIK, 2023). Although chondrichthyans, whose reproductive capacity is limited compared to bony fishes, are bycatch species in areas where commercial fishing is practiced, they are significantly affected by fishing pressure (Bengil and Başusta, 2018 ). For this reason, many chondrichthyan species are classified by the International Union for Conservation of Nature (IUCN) as vulnerable, endangered, or data deficient. Recently, sensitivity toward these species has been increasing in Türkiye, and with the regulation of commercial fisheries (Communique No. 4/1), species such as Squatina oculata (Bonaparte, 1837), Squatina squatina (Linnaeus, 1758), Squatina aculeate (Cuvier, 1829), Rhinobatos rhinobatos (Linnaeus, 1758), Rhinobatos cemiculus (Geoffroy Saint-Hilaire, 1817), Oxynotus centrina (Linnaeus, 1758), Mobula mobular (Bonaparte, 1824), Mobula japonica (Müller and Henle, 1841), Alopias vulpinus (Bonnaterre, 1788), Isurus oxyrnchus (Rafinesque, 1810), Raja clavate (Linnaeus, 1758), Squalus Blainville (Daudin, 1809) and Myliobatidae species have been added to Carcharhinus plumbeus (Savi, 1844), Cetorhinus maximus (Garman, 1888), Galeorhinus galeus (Linnaeus, 1758), Lamna nasus (Bonnaterre, 1788) and Squalus acanthias (Linnaeus, 1758), and all types of fishing for them have been banned in Turkish waters. However, these species continue to be bycatch. Due to the small number of studies conducted on this subject in Türkiye, the importance of studies to be carried out on these species is increasing. With the re-legalization of the use of monofilament nets under Communique No. 5/1 published by the Ministry of Agriculture and Forestry, General Directorate of Fisheries and Aquaculture, it has been observed that small-scale fishers have started to use nets equipped with both the walling and the inner netting entirely of monofilament material instead of multifilament trammel nets. While this shift brings a significant transformation in fishing practices, it necessitates a scientific evaluation of the impacts of such nets on bycatch species and catch efficiency. Within the scope of this study, by rigging two different bottom trammel nets whose materials consist entirely of monofilament and multifilament, it was aimed to compare the catch efficiency and discarded catch rates of these nets. It was intended for the findings to guide sustainable fisheries management and to form a basis for evaluating the ecological effects of legislative practices. MATERIALS AND METHODS The trials of this study were carried out between September 2024 and March 2026 in the regions of Morto Bay (1), Tekke Bay (2), Çukurçeşme Bay (3), Çifte Burunlar, and Alçıtepe (4), located within the borders of Çanakkale province (Fig. 1 ). The areas where the maritime studies were conducted were selected among the regions where commercial fishers in the area use bottom trammel nets most intensively. Trials within the scope of the study were carried out with a 7-meter-long commercial fishing vessel named "REMZİ KAPTAN 17," which has an engine power of 90 bhp. In the trials, a total of 8 units (800 m) of bottom trammel nets, consisting of 4 units of monofilament and 4 units of multifilament nets were used. To prevent variables such as region and depth between trials, each multifilament and monofilament trammel net was connected to the others sequentially. The nets were set in the water before dark in the evening, using the method employed by commercial fishers, and were deployed in the water for a total of 36 hours. During this period, diving was performed under suitable weather conditions to visualize the fish caught in the nets underwater. As a result of the trials, the length and weight of the live individuals of priority conservation species caught in the nets were recorded, and they were released with minimum harm. Other species and dead shark species were separated into different boxes according to the net materials and trial groups, and necessary morphological measurements were performed later. The trammel nets were equipped with a 42 mm inner mesh size and constructed using monofilament and multifilament materials, while all other technical characteristics were kept identical. The technical characteristics of the nets are given in Figs. 2 and 3 . When determining the target catch, all species with economic value were included in the target catch by considering the legal catch sizes. Economic species without a legal catch size were included in the target catch by determining the size at which they are commercially valued, based on interviews with fishers. Priority conservation species and other species with no economic value were evaluated as bycatch and discarded catch. Catch Per Unit Effort (CPUE) was calculated per 100 m of net per operation. The operational data obtained in the field studies were subjected to analysis to determine whether the difference was statistically significant on a numerical and weight basis according to the materials. The comparison of the total catch obtained according to the materials in each operation on a numerical basis was performed using one-way repeated measures analysis of variance (ANOVA). RESULTS A total of 20 species were caught during the trials. The number and weight of the target species caught are given in Table 1 , and the chondrichthyan bycatch and discarded species are given in Table 2 . During the study, 981 individuals and 622.3 kg of fish were caught with the trial nets. In the comparison of catch efficiency, multifilament bottom trammel nets with 42 mm inner netting caught a total of 506 individuals (279.8 kg), while monofilament bottom trammel nets caught 475 individuals (342.5 kg) (Tables 1 , 2 ). However, when the catch amounts of target species were examined, 430 individuals (165.1 kg) were caught with multifilament trammel nets, and 352 individuals (137.9 kg) were caught with monofilament trammel nets (Table 1 ). During the study, in terms of number, black scorpionfish ( Scorpaena porcus Linnaeus, 1758) ranked first with 468 individuals, followed by common cuttlefish ( Sepia officinalis Linnaeus, 1758) with 252 individuals, and smoothback angelshark ( Squatina oculata ). In terms of weight, smoothback angelshark ( Squatina oculata ) ranked first with 242.9 kg, followed by common cuttlefish ( Sepia officinalis ) with 185.9 kg and black scorpionfish ( Scorpaena porcus ) with 98.8 kg (Tables 1 , 2 ). While 16 species were caught with multifilament trammel nets, 20 species were caught with monofilament trammel nets. Among the priority conservation species, 2 individuals of common eagle ray ( Myliobatis aquila Linnaeus, 1758) were caught in monofilament trammel nets, whereas multifilament trammel nets did not catch any individuals of this species. When priority conservation chondrichthyan species were evaluated, these species accounted for 23.2% of the total catch in monofilament trammel nets, while this rate was calculated as 12.5% in multifilament trammel nets. Monofilament trammel nets increased the catch rate of priority conservation species by approximately 1.85 times compared to multifilament trammel nets. 110 individuals of priority conservation species were caught in monofilament trammel nets, and 63 individuals in multifilament trammel nets. Specifically, it was determined that individuals of Squatina oculata and Squatina aculeata , which are classified as "Critically Endangered" category, were caught in higher numbers in monofilament trammel nets (Table 2 ). When target species such as common cuttlefish ( Sepia officinalis ), black scorpionfish ( Scorpaena porcus ), common sole ( Solea solea Linnaeus, 1758), and common pandora ( Pagellus erythrinus Linnaeus, 1758) were evaluated, multifilament trammel nets caught 1.22 times more than monofilament trammel nets. As a result of the statistical comparison, multifilament trammel nets caught more than monofilament trammel nets ( P < 0.05). In the discarded catch, monofilament trammel nets caught 1.62 times more than multifilament trammel nets (Table 3 ). In the comparison made using repeated measures analysis of variance, the difference between them was found to be statistically significant ( P < 0.05). Table 1 The amount of target catches in the trammel nets Scientific name Multifilament trammel nets Monofilament trammel nets Common name Piece Weight (g) Piece Weight (g) Diplodus puntazzo Sheephead bream 4 1066 2 471 Diplodus vulgaris Common two-banded seabream 6 932 2 390 Pagellus bogaraveo Blackspot seabream 3 149 4 312 Pagellus erythrinus Axillary seabream 1 155 7 1376 Sarpa salpa Salema 8 6395 3 1768 Scorpaena porcus Black scorpionfish 264 56166 204 42594 Sepia officinalis Common cuttlefish 133 98335 119 87614 Solea solea Common sole 7 1229 5 1370 Spondyliosoma cantharus Black seabream 4 652 4 649 Umbrina cirrosa Shi drum 0 0 2 1332 Total 430 165079 352 137876 Table 2 The amount of chondrichthyan bycatch and discarded catches in the trammel nets Scientific name Multifilament trammel nets Monofilament trammel nets Common name IUCN Red List Status Piece Weight (g) Piece Weight (g) Squatina aculeata Sawback Angelshark Critically Endangered 5 2019 21 6828 Squatina oculata Smoothback Angelshark Critically Endangered 31 75002 55 167947 Raja radula Rough Ray Endangered 3 780 9 1769 Dasyatis pastinaca Common Stingray Vulnerable 4 1333 7 1749 Myliobatis aquila Common Eagle Ray Vulnerable 0 0 2 1446 Conger conger European Conger Least Concern 1 552 1 557 Scyliorhinus canicula Lesser Spotted Dogfish Least Concern 0 0 1 2105 Serranus scriba Painted Comber Least Concern 1 193 3 569 Torpedo marmorata Marbled Electric Ray Least Concern 20 30214 15 18716 Uranoscopus scaber Stargazer Least Concern 11 4657 9 2878 Total 76 114750 123 204564 Table 3 Catch quantities and catch per unit effort for monofilament and multifilament trammel nets Multifilament trammel nets Monofilament trammel nets Piece Weight (g) Piece Weight (g) Target Catch Quantity 430 165079 352 137876 Discarded Catch Quantity 76 114750 123 204564 Target Catch Efficiency (CPUE) 6.61 2540 5.42 2121 Discarded Catch Efficiency (CPUE) 1.17 1765 1.89 3147 In this study, Catch Per Unit Effort (CPUE) was calculated by dividing the total number and total weight of target and discarded catch by the number of fishing operations. CPUE values were expressed as individuals per 100 m per operation and g per 100 m per operation (Table 3 ). The percentage values of target catch and discarded catch in monofilament and multifilament trammel nets are given in Figs. 4 and 5 , respectively, based on the results of the trials. In multifilament trammel nets, the target catch rate was 85%, and the discarded catch rate was 15%. In monofilament trammel nets, these values were 74% and 26%, respectively. Dives were conducted to capture underwater images of the trial nets and the samples caught in them under suitable weather conditions. In the underwater photographs, it is clearly distinguishable that multifilament trammel nets are much more visible than monofilament trammel nets. Sample images are provided in Figs. 6 and 7 . DISCUSSION In the trials, multifilament trammel nets caught 16 species, while monofilament trammel nets caught 20 species of fish. In addition, while 110 individuals categorized as priority conservation species (Otero et al., 2019 ) were caught in monofilament trammel nets consisting of 55 Squatina oculata , 21 Squatina aculeata , 15 Torpedo marmorata , 9 Raja radula , 7 Dasyatis pastinaca , 2 Myliobatis aquila , and 1 Scyliorhinus canicular a total of 63 individuals were caught in multifilament trammel nets, including 31 Squatina oculata , 5 Squatina aculeata , 20 Torpedo marmorata , 3 Raja radula , and 4 Dasyatis pastinaca . This result indicated that the net material has a significant impact on the catch rate of these species. In the literature, no studies were found regarding the species diversity caught by nets that were fully constructed with both monofilament and multifilament materials. In our study, it is thought that this difference affects the fishing of priority conservation species, especially within the bycatch. This difference may be related to the lower underwater visibility of monofilament trammel nets is lower than that of multifilament trammel nets underwater (Ayaz et al., 2026 ). As a result of the statistical comparison, multifilament trammel nets caught more target species than monofilament trammel nets ( P < 0.05). On a numerical basis, target species were caught 1.22 times more in multifilament trammel nets than in monofilament trammel nets. In the discarded catch, monofilament trammel nets caught 1.62 times more than multifilament trammel nets. On a weight basis, while multifilament trammel nets caught 1.2 times more target species than monofilament trammel nets, monofilament trammel nets caught 1.78 times more discarded catch than multifilament trammel nets. In the comparison made using repeated measures analysis of variance, the difference between them was found to be statistically significant ( P < 0.05). A significant part of the chondrichthyan species caught during the study were in the high-risk group in the International Union for Conservation of Nature (IUCN) Red List category. The smoothback angelshark ( Squatina oculata ) and the sawback angelshark ( Squatina aculeata ) were evaluated as “Critically Endangered,” the rough ray ( Raja radula ) as “Endangered,” and the common eagle ray ( Myliobatis aquila ) as “Vulnerable.” Most of these species lead a benthic life and show high sensitivity to trammel nets. Therefore, revealing the differences in bycatch rates depending on the net material was important not only in terms of catch efficiency but also for the conservation of these species. Thomas et al. ( 2003 ) conducted a study on the coasts of India with three different net types: plain multifilament, monofilament, and multifilament trammel nets. As a result of the trials, they stated that for the amount of target shrimp, the net with monofilament material caught 1.5 times more than the plain multifilament net, and the multifilament trammel net caught 2 times more than the monofilament net. This situation reveals the importance of determining which type of net should be used according to the targeted species. In the trials, the target species catch rate was 74% in monofilament trammel nets and 85% in multifilament trammel nets. In a study conducted in the region, İbin and Ayaz ( 2022 ) calculated the target catch rate as 20% for 20 mm gillnets. Similarly, for a gillnet with the same characteristics and a 20 mm mesh size, this value was calculated as 13% (Ayaz et al., 2010). It is thought that this difference arises because nets with small mesh sizes catch more bycatch species in regions with high species diversity, and also not all economic species were included in the target catch group. As a result of the study, it was determined that multifilament trammel nets provided higher efficiency in target species fishing compared to monofilament trammel nets and significantly reduced the bycatch rate. Conversely, monofilament trammel nets markedly increased the catch rate of chondrichthyan fish species evaluated in the critically endangered and endangered categories by the International Union for Conservation of Nature. While the ratio of priority conservation species within the total catch was calculated as 23.2% in monofilament trammel nets, this ratio was 12.5% in multifilament trammel nets. These findings revealed that net material should be evaluated not only in terms of economic efficiency but also within the framework of ecosystem-based fisheries management. These findings suggest that regulatory authorities should reconsider the unrestricted use of monofilament trammel nets, particularly in regions where priority conservation chondrichthyan species are known to occur. Implementing material-based regulations, seasonal restrictions, or spatial management measures could significantly reduce the incidental capture of vulnerable and critically endangered species. In this context, encouraging or mandating the use of multifilament trammel nets may represent a practical and immediately applicable mitigation strategy. There is a need for studies aimed at material-based regulations for bycatch mitigation. Declarations 4. FUNDING This study was supported by the Scientific Research Coordination Unit of Çanakkale Onsekiz Mart University. Project number: FDK-2024-4783 This study was supported by the Scientific and Technological Research Council of Türkiye. Project number: 224O327 5.1. Clinical Trial Number Clinical trial number: not applicable. 5.2. Ethics Approval All processes and experimental protocols have been approved by Çanakkale Onsekiz Mart University, Animal Experiments Local Ethics Committee (No: 2024/03-02), (No: 2025/03-01) under the General Directorate of Agricultural Research and Policy surveillance. 5.3. Competing Interests The authors declare no competing interests. 6. Acknowledgements The author acknowledges financial support from the Scientific and Technological Research Council of Turkey (TÜBİTAK), BİDEB 2211 National PhD Scholarship Programs. This study was conducted within the scope of the PhD thesis of Oguzhan Ayaz at the School of Graduate Studies, Çanakkale Onsekiz Mart University. References Ayaz O, Altınağaç U, Ayaz A (2026). The Effect of Using Trammel inred Mullet Species Fishing nets on Catch Efficiency and By-Catch. Thalassas 42, 36. https://doi.org/10.1007/s41208-026-01062-y Bengil EGT, Başusta N (2018). Chondrichthyan species as by-catch: A review on species inhabiting Turkish waters. Journal of the Black Sea/Mediterranean Environment 24(3), 288-305. Cilasın ME, Öztekin A, Ayaz A (2015). Catching Efficiency and Catch Composition of the Trammel Nets (Marya Nets) Used in Çanakkale Region. Adıyaman University Journal of Science. 5 (2), 94-104. İbin T, Ayaz A (2022). Comparison of Catch Efficiency of Nets with Multifilament and Monofilament Materials in Çanakkale Coasts Çanakkale Onsekiz Mart University Journal of Marine Sciences and Fisheries, 5(Special Issue), 13-21. https://doi.org/10.46384/jmsf.1129911 Otero M, Serena F, Gerovasileiou V, Barone M, Bo M, Arcos JM, Vulcano A, Xavier J (2019). Identification guide of vulnerable species incidentally caught in Mediterranean fisheries. IUCN, Malaga, Spain, 204 pages. Stevens JD, Bonfil R, Dulvy NK, Walker PA (2000). The effects of fishing on sharks, rays, and chimaeras (Chondrichthyans), and the implications for marine ecosystems. ICES Journal of Marine Science 57, 476–494. https://doi.org/10.1006/jmsc.2000.0724 Thomas SN, Edwin L, George VC (2003). Catching efficiency of gill nets and trammel nets for penaeid prawns. Fisheries Research. 60, 141–150 Doi: 10.1016/S0165-7836(02)00057-7 Turkish Statistical Institute (TUİK) (2023). Fishery Products https://data.tuik.gov.tr/Bulten/Index?p=Su-Urunleri-2023-53702. 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. 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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-9010448","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":601832587,"identity":"7aacb6d6-5531-4c50-9627-6908658fb213","order_by":0,"name":"Oğuzhan 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nets\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9010448/v1/29823d0def0901604fbc5a6c.png"},{"id":104395185,"identity":"678fb320-380a-46e6-a6aa-d053840e2b13","added_by":"auto","created_at":"2026-03-11 11:01:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":114615,"visible":true,"origin":"","legend":"\u003cp\u003eTechnical plan of monofilament bottom trammel nets\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9010448/v1/9deb2690aaef0d53bfdd28b8.png"},{"id":104395184,"identity":"57067f40-3713-4f17-9d84-7c252f6246f5","added_by":"auto","created_at":"2026-03-11 11:01:08","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":11275,"visible":true,"origin":"","legend":"\u003cp\u003eCatch distribution in multifilament trammel nets\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9010448/v1/d1cd76dc6256bdf0dbccdbce.png"},{"id":104406175,"identity":"24087995-6859-4950-89db-cfc69b4e7dd6","added_by":"auto","created_at":"2026-03-11 12:24:58","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":10536,"visible":true,"origin":"","legend":"\u003cp\u003eCatch distribution in monofilament trammel nets\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9010448/v1/a22882589f69b087d6668605.png"},{"id":104395187,"identity":"d5ad166a-2f3e-41de-8c08-5801563b74cf","added_by":"auto","created_at":"2026-03-11 11:01:08","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":871409,"visible":true,"origin":"","legend":"\u003cp\u003eRough Ray (\u003cem\u003eRaja radula\u003c/em\u003e) in multifilament trammel net\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-9010448/v1/2c4e532a030b23c88ddd8408.png"},{"id":104395186,"identity":"bae8aac5-10ae-4fff-b6d6-89ef553f6776","added_by":"auto","created_at":"2026-03-11 11:01:08","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":628191,"visible":true,"origin":"","legend":"\u003cp\u003eSawback Angelshark (\u003cem\u003eSquatina aculeata\u003c/em\u003e) in monofilament trammel net\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-9010448/v1/7c713e1e876d65256e4ce0f3.png"},{"id":105562953,"identity":"586aba86-f329-4fb1-801b-ab7caf481a6e","added_by":"auto","created_at":"2026-03-27 12:45:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3191697,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9010448/v1/a23664fc-c45a-4d7e-8f4a-3f491f5f2e22.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparison of monofilament and multifilament bottom trammel nets regarding catch efficiency and chondrichthyan bycatch in Çanakkale, Türkiye","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe coasts of \u0026Ccedil;anakkale are among the areas where small-scale commercial fishers intensively use trammel nets. It has been determined that sharks, which are among the endangered species, are also caught in these nets, which are generally used between 10 and 100 meters in the region (Cilasın et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The use of trammel nets poses potential threats, especially to sharks, rays, and other chondrichthyans. Therefore, any information to be gained about these species provides an ecological approach for fisheries management.\u003c/p\u003e \u003cp\u003eChondrichthyans living in Turkish seas are mostly of Atlantic-Mediterranean and cosmopolitan origin, but also include species endemic to the Mediterranean and Red Sea migrants. According to their distribution in Turkish seas, there are 9 species in the Black Sea, 36 in the Marmara Sea, 59 in the Aegean Sea, and 62 in the Mediterranean (Bengil and Başusta, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The long lifespans, slow growth, low fecundity, and late attainment of sexual maturity of chondrichthyans make them more sensitive to possible ecosystem changes and overfishing pressure. The global population decline in fish stocks has directed commercial fishers and fisheries management toward new target species caught as bycatch and toward alternative strategies for their utilization. As a result, sharks and rays are being exploited at high rates today (Stevens et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). According to the Turkish Statistical Institute (TUIK) data for the last decade in T\u0026uuml;rkiye, there is a significant decrease in the catch amounts of rays and sharks (TUIK, 2023). Although chondrichthyans, whose reproductive capacity is limited compared to bony fishes, are bycatch species in areas where commercial fishing is practiced, they are significantly affected by fishing pressure (Bengil and Başusta, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). For this reason, many chondrichthyan species are classified by the International Union for Conservation of Nature (IUCN) as vulnerable, endangered, or data deficient.\u003c/p\u003e \u003cp\u003eRecently, sensitivity toward these species has been increasing in T\u0026uuml;rkiye, and with the regulation of commercial fisheries (Communique No. 4/1), species such as \u003cem\u003eSquatina oculata\u003c/em\u003e (Bonaparte, 1837), \u003cem\u003eSquatina squatina\u003c/em\u003e (Linnaeus, 1758), \u003cem\u003eSquatina aculeate\u003c/em\u003e (Cuvier, 1829), \u003cem\u003eRhinobatos rhinobatos\u003c/em\u003e (Linnaeus, 1758), \u003cem\u003eRhinobatos cemiculus\u003c/em\u003e (Geoffroy Saint-Hilaire, 1817), \u003cem\u003eOxynotus centrina\u003c/em\u003e (Linnaeus, 1758), \u003cem\u003eMobula mobular\u003c/em\u003e (Bonaparte, 1824), \u003cem\u003eMobula japonica\u003c/em\u003e (M\u0026uuml;ller and Henle, 1841), \u003cem\u003eAlopias vulpinus\u003c/em\u003e (Bonnaterre, 1788), \u003cem\u003eIsurus oxyrnchus\u003c/em\u003e (Rafinesque, 1810), \u003cem\u003eRaja clavate\u003c/em\u003e (Linnaeus, 1758), \u003cem\u003eSqualus Blainville\u003c/em\u003e (Daudin, 1809) and Myliobatidae species have been added to \u003cem\u003eCarcharhinus plumbeus\u003c/em\u003e (Savi, 1844), \u003cem\u003eCetorhinus maximus\u003c/em\u003e (Garman, 1888), \u003cem\u003eGaleorhinus galeus\u003c/em\u003e (Linnaeus, 1758), \u003cem\u003eLamna nasus\u003c/em\u003e (Bonnaterre, 1788) and \u003cem\u003eSqualus acanthias\u003c/em\u003e (Linnaeus, 1758), and all types of fishing for them have been banned in Turkish waters. However, these species continue to be bycatch. Due to the small number of studies conducted on this subject in T\u0026uuml;rkiye, the importance of studies to be carried out on these species is increasing.\u003c/p\u003e \u003cp\u003eWith the re-legalization of the use of monofilament nets under Communique No. 5/1 published by the Ministry of Agriculture and Forestry, General Directorate of Fisheries and Aquaculture, it has been observed that small-scale fishers have started to use nets equipped with both the walling and the inner netting entirely of monofilament material instead of multifilament trammel nets. While this shift brings a significant transformation in fishing practices, it necessitates a scientific evaluation of the impacts of such nets on bycatch species and catch efficiency.\u003c/p\u003e \u003cp\u003eWithin the scope of this study, by rigging two different bottom trammel nets whose materials consist entirely of monofilament and multifilament, it was aimed to compare the catch efficiency and discarded catch rates of these nets. It was intended for the findings to guide sustainable fisheries management and to form a basis for evaluating the ecological effects of legislative practices.\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\u003cp\u003eThe trials of this study were carried out between September 2024 and March 2026 in the regions of Morto Bay (1), Tekke Bay (2), \u0026Ccedil;ukur\u0026ccedil;eşme Bay (3), \u0026Ccedil;ifte Burunlar, and Al\u0026ccedil;ıtepe (4), located within the borders of \u0026Ccedil;anakkale province (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The areas where the maritime studies were conducted were selected among the regions where commercial fishers in the area use bottom trammel nets most intensively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTrials within the scope of the study were carried out with a 7-meter-long commercial fishing vessel named \"REMZİ KAPTAN 17,\" which has an engine power of 90 bhp.\u003c/p\u003e \u003cp\u003eIn the trials, a total of 8 units (800 m) of bottom trammel nets, consisting of 4 units of monofilament and 4 units of multifilament nets were used. To prevent variables such as region and depth between trials, each multifilament and monofilament trammel net was connected to the others sequentially. The nets were set in the water before dark in the evening, using the method employed by commercial fishers, and were deployed in the water for a total of 36 hours. During this period, diving was performed under suitable weather conditions to visualize the fish caught in the nets underwater. As a result of the trials, the length and weight of the live individuals of priority conservation species caught in the nets were recorded, and they were released with minimum harm. Other species and dead shark species were separated into different boxes according to the net materials and trial groups, and necessary morphological measurements were performed later.\u003c/p\u003e \u003cp\u003eThe trammel nets were equipped with a 42 mm inner mesh size and constructed using monofilament and multifilament materials, while all other technical characteristics were kept identical. The technical characteristics of the nets are given in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhen determining the target catch, all species with economic value were included in the target catch by considering the legal catch sizes. Economic species without a legal catch size were included in the target catch by determining the size at which they are commercially valued, based on interviews with fishers. Priority conservation species and other species with no economic value were evaluated as bycatch and discarded catch.\u003c/p\u003e \u003cp\u003eCatch Per Unit Effort (CPUE) was calculated per 100 m of net per operation. The operational data obtained in the field studies were subjected to analysis to determine whether the difference was statistically significant on a numerical and weight basis according to the materials. The comparison of the total catch obtained according to the materials in each operation on a numerical basis was performed using one-way repeated measures analysis of variance (ANOVA).\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003eA total of 20 species were caught during the trials. The number and weight of the target species caught are given in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, and the chondrichthyan bycatch and discarded species are given in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. During the study, 981 individuals and 622.3 kg of fish were caught with the trial nets. In the comparison of catch efficiency, multifilament bottom trammel nets with 42 mm inner netting caught a total of 506 individuals (279.8 kg), while monofilament bottom trammel nets caught 475 individuals (342.5 kg) (Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). However, when the catch amounts of target species were examined, 430 individuals (165.1 kg) were caught with multifilament trammel nets, and 352 individuals (137.9 kg) were caught with monofilament trammel nets (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). During the study, in terms of number, black scorpionfish (\u003cem\u003eScorpaena porcus\u003c/em\u003e Linnaeus, 1758) ranked first with 468 individuals, followed by common cuttlefish (\u003cem\u003eSepia officinalis\u003c/em\u003e Linnaeus, 1758) with 252 individuals, and smoothback angelshark (\u003cem\u003eSquatina oculata\u003c/em\u003e). In terms of weight, smoothback angelshark (\u003cem\u003eSquatina oculata\u003c/em\u003e) ranked first with 242.9 kg, followed by common cuttlefish (\u003cem\u003eSepia officinalis\u003c/em\u003e) with 185.9 kg and black scorpionfish (\u003cem\u003eScorpaena porcus\u003c/em\u003e) with 98.8 kg (Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). While 16 species were caught with multifilament trammel nets, 20 species were caught with monofilament trammel nets. Among the priority conservation species, 2 individuals of common eagle ray (\u003cem\u003eMyliobatis aquila\u003c/em\u003e Linnaeus, 1758) were caught in monofilament trammel nets, whereas multifilament trammel nets did not catch any individuals of this species. When priority conservation chondrichthyan species were evaluated, these species accounted for 23.2% of the total catch in monofilament trammel nets, while this rate was calculated as 12.5% in multifilament trammel nets. Monofilament trammel nets increased the catch rate of priority conservation species by approximately 1.85 times compared to multifilament trammel nets. 110 individuals of priority conservation species were caught in monofilament trammel nets, and 63 individuals in multifilament trammel nets. Specifically, it was determined that individuals of \u003cem\u003eSquatina oculata\u003c/em\u003e and \u003cem\u003eSquatina aculeata\u003c/em\u003e, which are classified as \"Critically Endangered\" category, were caught in higher numbers in monofilament trammel nets (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). When target species such as common cuttlefish (\u003cem\u003eSepia officinalis\u003c/em\u003e), black scorpionfish (\u003cem\u003eScorpaena porcus\u003c/em\u003e), common sole (\u003cem\u003eSolea solea\u003c/em\u003e Linnaeus, 1758), and common pandora (\u003cem\u003ePagellus erythrinus\u003c/em\u003e Linnaeus, 1758) were evaluated, multifilament trammel nets caught 1.22 times more than monofilament trammel nets. As a result of the statistical comparison, multifilament trammel nets caught more than monofilament trammel nets (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In the discarded catch, monofilament trammel nets caught 1.62 times more than multifilament trammel nets (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In the comparison made using repeated measures analysis of variance, the difference between them was found to be statistically significant (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\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\u003eThe amount of target catches in the trammel nets\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" 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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eScientific name\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eMultifilament trammel nets\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eMonofilament trammel nets\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCommon name\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePiece\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWeight (g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePiece\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eWeight (g)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eDiplodus puntazzo\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSheephead bream\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1066\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e471\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eDiplodus vulgaris\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCommon two-banded seabream\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e932\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e390\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePagellus bogaraveo\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBlackspot seabream\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e149\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e312\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePagellus erythrinus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAxillary seabream\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e155\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1376\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSarpa salpa\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSalema\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6395\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1768\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eScorpaena porcus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBlack scorpionfish\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e264\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e56166\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e204\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e42594\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSepia officinalis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCommon cuttlefish\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e133\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e98335\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e119\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e87614\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSolea solea\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCommon sole\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1229\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1370\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSpondyliosoma cantharus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBlack seabream\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e652\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e649\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eUmbrina cirrosa\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShi drum\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1332\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e430\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e165079\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e352\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e137876\u003c/b\u003e\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 \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\u003eThe amount of chondrichthyan bycatch and discarded catches in the trammel nets\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eScientific name\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eMultifilament\u003c/p\u003e \u003cp\u003etrammel nets\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eMonofilament trammel nets\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCommon name\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIUCN Red List Status\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePiece\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eWeight (g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePiece\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003eWeight (g)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSquatina aculeata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSawback Angelshark\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCritically Endangered\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e6828\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSquatina oculata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSmoothback Angelshark\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCritically Endangered\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e75002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e167947\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eRaja radula\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRough Ray\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEndangered\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e780\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1769\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eDasyatis pastinaca\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCommon Stingray\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVulnerable\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e1333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1749\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eMyliobatis aquila\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCommon Eagle Ray\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVulnerable\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1446\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eConger conger\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEuropean Conger\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeast Concern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e552\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e557\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eScyliorhinus canicula\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLesser Spotted Dogfish\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeast Concern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2105\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSerranus scriba\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePainted Comber\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeast Concern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e193\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e569\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eTorpedo marmorata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMarbled Electric Ray\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeast Concern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e30214\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e18716\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eUranoscopus scaber\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStargazer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeast Concern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e4657\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2878\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e76\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e\u003cb\u003e114750\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e123\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e204564\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \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\u003eCatch quantities and catch per unit effort for monofilament and multifilament trammel nets\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=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eMultifilament trammel nets\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eMonofilament trammel nets\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePiece\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWeight (g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePiece\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWeight (g)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTarget Catch Quantity\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e430\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e165079\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e352\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e137876\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDiscarded Catch Quantity\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e114750\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e123\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e204564\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTarget Catch Efficiency (CPUE)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2540\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2121\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDiscarded Catch Efficiency (CPUE)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1765\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3147\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\u003eIn this study, Catch Per Unit Effort (CPUE) was calculated by dividing the total number and total weight of target and discarded catch by the number of fishing operations. CPUE values were expressed as individuals per 100 m per operation and g per 100 m per operation (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The percentage values of target catch and discarded catch in monofilament and multifilament trammel nets are given in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, respectively, based on the results of the trials. In multifilament trammel nets, the target catch rate was 85%, and the discarded catch rate was 15%. In monofilament trammel nets, these values were 74% and 26%, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDives were conducted to capture underwater images of the trial nets and the samples caught in them under suitable weather conditions. In the underwater photographs, it is clearly distinguishable that multifilament trammel nets are much more visible than monofilament trammel nets. Sample images are provided in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eIn the trials, multifilament trammel nets caught 16 species, while monofilament trammel nets caught 20 species of fish. In addition, while 110 individuals categorized as priority conservation species (Otero et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) were caught in monofilament trammel nets consisting of 55 \u003cem\u003eSquatina oculata\u003c/em\u003e, 21 \u003cem\u003eSquatina aculeata\u003c/em\u003e, 15 \u003cem\u003eTorpedo marmorata\u003c/em\u003e, 9 \u003cem\u003eRaja radula\u003c/em\u003e, 7 \u003cem\u003eDasyatis pastinaca\u003c/em\u003e, 2 \u003cem\u003eMyliobatis aquila\u003c/em\u003e, and 1 \u003cem\u003eScyliorhinus canicular\u003c/em\u003e a total of 63 individuals were caught in multifilament trammel nets, including 31 \u003cem\u003eSquatina oculata\u003c/em\u003e, 5 \u003cem\u003eSquatina aculeata\u003c/em\u003e, 20 \u003cem\u003eTorpedo marmorata\u003c/em\u003e, 3 \u003cem\u003eRaja radula\u003c/em\u003e, and 4 \u003cem\u003eDasyatis pastinaca\u003c/em\u003e. This result indicated that the net material has a significant impact on the catch rate of these species.\u003c/p\u003e \u003cp\u003eIn the literature, no studies were found regarding the species diversity caught by nets that were fully constructed with both monofilament and multifilament materials. In our study, it is thought that this difference affects the fishing of priority conservation species, especially within the bycatch. This difference may be related to the lower underwater visibility of monofilament trammel nets is lower than that of multifilament trammel nets underwater (Ayaz et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2026\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAs a result of the statistical comparison, multifilament trammel nets caught more target species than monofilament trammel nets (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). On a numerical basis, target species were caught 1.22 times more in multifilament trammel nets than in monofilament trammel nets. In the discarded catch, monofilament trammel nets caught 1.62 times more than multifilament trammel nets. On a weight basis, while multifilament trammel nets caught 1.2 times more target species than monofilament trammel nets, monofilament trammel nets caught 1.78 times more discarded catch than multifilament trammel nets. In the comparison made using repeated measures analysis of variance, the difference between them was found to be statistically significant (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eA significant part of the chondrichthyan species caught during the study were in the high-risk group in the International Union for Conservation of Nature (IUCN) Red List category. The smoothback angelshark (\u003cem\u003eSquatina oculata\u003c/em\u003e) and the sawback angelshark (\u003cem\u003eSquatina aculeata\u003c/em\u003e) were evaluated as \u0026ldquo;Critically Endangered,\u0026rdquo; the rough ray (\u003cem\u003eRaja radula\u003c/em\u003e) as \u0026ldquo;Endangered,\u0026rdquo; and the common eagle ray (\u003cem\u003eMyliobatis aquila\u003c/em\u003e) as \u0026ldquo;Vulnerable.\u0026rdquo; Most of these species lead a benthic life and show high sensitivity to trammel nets. Therefore, revealing the differences in bycatch rates depending on the net material was important not only in terms of catch efficiency but also for the conservation of these species.\u003c/p\u003e \u003cp\u003eThomas et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) conducted a study on the coasts of India with three different net types: plain multifilament, monofilament, and multifilament trammel nets. As a result of the trials, they stated that for the amount of target shrimp, the net with monofilament material caught 1.5 times more than the plain multifilament net, and the multifilament trammel net caught 2 times more than the monofilament net. This situation reveals the importance of determining which type of net should be used according to the targeted species.\u003c/p\u003e \u003cp\u003eIn the trials, the target species catch rate was 74% in monofilament trammel nets and 85% in multifilament trammel nets. In a study conducted in the region, İbin and Ayaz (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) calculated the target catch rate as 20% for 20 mm gillnets. Similarly, for a gillnet with the same characteristics and a 20 mm mesh size, this value was calculated as 13% (Ayaz et al., 2010). It is thought that this difference arises because nets with small mesh sizes catch more bycatch species in regions with high species diversity, and also not all economic species were included in the target catch group. As a result of the study, it was determined that multifilament trammel nets provided higher efficiency in target species fishing compared to monofilament trammel nets and significantly reduced the bycatch rate.\u003c/p\u003e \u003cp\u003eConversely, monofilament trammel nets markedly increased the catch rate of chondrichthyan fish species evaluated in the critically endangered and endangered categories by the International Union for Conservation of Nature. While the ratio of priority conservation species within the total catch was calculated as 23.2% in monofilament trammel nets, this ratio was 12.5% in multifilament trammel nets. These findings revealed that net material should be evaluated not only in terms of economic efficiency but also within the framework of ecosystem-based fisheries management. These findings suggest that regulatory authorities should reconsider the unrestricted use of monofilament trammel nets, particularly in regions where priority conservation chondrichthyan species are known to occur. Implementing material-based regulations, seasonal restrictions, or spatial management measures could significantly reduce the incidental capture of vulnerable and critically endangered species. In this context, encouraging or mandating the use of multifilament trammel nets may represent a practical and immediately applicable mitigation strategy. There is a need for studies aimed at material-based regulations for bycatch mitigation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e4. FUNDING\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the Scientific Research Coordination Unit of \u0026Ccedil;anakkale Onsekiz Mart University. Project number: FDK-2024-4783\u003c/p\u003e\n\u003cp\u003eThis study was supported by the Scientific and Technological Research Council of T\u0026uuml;rkiye. Project number: 224O327\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5.1. Clinical Trial Number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eClinical trial number: not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5.2. Ethics Approval\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll processes and experimental protocols have been approved by \u0026Ccedil;anakkale Onsekiz Mart University, Animal Experiments Local Ethics Committee (No: 2024/03-02), (No: 2025/03-01) under the General Directorate of Agricultural Research and Policy surveillance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5.3. Competing Interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e6.\u003c/strong\u003e \u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author acknowledges financial support from the Scientific and Technological Research Council of Turkey (T\u0026Uuml;BİTAK), BİDEB 2211 National PhD Scholarship Programs.\u003c/p\u003e\n\u003cp\u003eThis study was conducted within the scope of the PhD thesis of Oguzhan Ayaz at the School of Graduate Studies, \u0026Ccedil;anakkale Onsekiz Mart University.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAyaz O, Altınağa\u0026ccedil; U, Ayaz A (2026). The Effect of Using Trammel inred Mullet Species Fishing nets on Catch Efficiency and By-Catch. Thalassas 42, 36. https://doi.org/10.1007/s41208-026-01062-y\u003c/li\u003e\n \u003cli\u003eBengil EGT, Başusta N (2018). Chondrichthyan species as by-catch: A review on species inhabiting Turkish waters. Journal of the Black Sea/Mediterranean Environment 24(3), 288-305.\u003c/li\u003e\n \u003cli\u003eCilasın ME, \u0026Ouml;ztekin A, Ayaz A (2015). Catching Efficiency and Catch Composition of the Trammel Nets (Marya Nets) Used in \u0026Ccedil;anakkale Region. Adıyaman University Journal of Science. 5 (2), 94-104.\u003c/li\u003e\n \u003cli\u003eİbin T, Ayaz A (2022). Comparison of Catch Efficiency of Nets with Multifilament and Monofilament Materials in \u0026Ccedil;anakkale Coasts \u0026Ccedil;anakkale Onsekiz Mart University Journal of Marine Sciences and Fisheries, 5(Special Issue), 13-21. https://doi.org/10.46384/jmsf.1129911\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eOtero M, Serena F, Gerovasileiou V, Barone M, Bo M, Arcos JM, Vulcano A, Xavier J (2019). Identification guide of vulnerable species incidentally caught in Mediterranean fisheries. IUCN, Malaga, Spain, 204 pages.\u003c/li\u003e\n \u003cli\u003eStevens JD, Bonfil R, Dulvy NK, Walker PA (2000). The effects of fishing on sharks, rays, and chimaeras (Chondrichthyans), and the implications for marine ecosystems. ICES Journal of Marine Science 57, 476\u0026ndash;494.\u0026nbsp;https://doi.org/10.1006/jmsc.2000.0724\u003c/li\u003e\n \u003cli\u003eThomas SN, Edwin L, George VC (2003). Catching efficiency of gill nets and trammel nets for penaeid prawns. Fisheries Research. 60, 141\u0026ndash;150 Doi: 10.1016/S0165-7836(02)00057-7\u003c/li\u003e\n \u003cli\u003eTurkish Statistical Institute (TUİK) (2023). Fishery Products https://data.tuik.gov.tr/Bulten/Index?p=Su-Urunleri-2023-53702.\u0026nbsp;\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":false,"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":"Catch efficiency, Chondrichthyan bycatch, Monofilament, Multifilament, Bottom trammel nets","lastPublishedDoi":"10.21203/rs.3.rs-9010448/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9010448/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study aimed to evaluate the catch efficiency and chondrichthyan bycatch of monofilament and multifilament bottom trammel nets in the Çanakkale region, where small-scale commercial fishing is practiced intensively. The field trials of the study were carried out between September 2024 and March 2026. Within the scope of the study, a total of 8 units (800 m) of trammel nets were used. The trammel nets are equipped with a 42 mm inner mesh size, monofilament and multifilament materials and, have all other technical characteristics identical. 65 trials were carried out with these nets. The nets were deployed in the water for 36 hours in each trial. As a result of the trials, a total of 981 individuals and 622.3 kg of fish belonging to 20 species were captured. All species with economic value were classified as target, and other species without economic value were classified as discard. When the economic species caught in the nets were compared, multifilament trammel nets caught 1.22 times more than monofilament trammel nets. As a result of the statistical comparison, multifilament trammel nets caught more than monofilament trammel nets (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). In the discarded catch, monofilament trammel nets caught 1.62 times more than multifilament trammel nets. In addition, the ratio of priority conservation species within the total catch was calculated as 23.2% in monofilament trammel nets; this ratio was 12.5% in multifilament trammel nets. In the comparison made using repeated measures analysis of variance, the difference between them was found to be statistically significant (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). The study determined that the preference for monofilament material is not necessary for the nets used in the fishing of species such as cuttlefish, lobster, and scorpionfish in the region, and that multifilament trammel nets are more efficient than monofilament trammel nets in catching target species. Additionally, considering that a large part of the bycatch consists of conservation-priority chondrichthyan fish species, it was determined that the use of monofilament material in trammel nets is not suitable in terms of sustainable fisheries. It was established that the preference for multifilament trammel nets would enhance bycatch mitigation.\u003c/p\u003e","manuscriptTitle":"Comparison of monofilament and multifilament bottom trammel nets regarding catch efficiency and chondrichthyan bycatch in Çanakkale, Türkiye","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-11 11:00:50","doi":"10.21203/rs.3.rs-9010448/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":"50499c9f-f87f-479d-81e9-45ce2fa7d3a9","owner":[],"postedDate":"March 11th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-20T17:39:38+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-11 11:00:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9010448","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9010448","identity":"rs-9010448","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}