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    Effects of traditional and alternative mesh sizes in trammel nets on selectivity and catchability of Penaeus kerathurus (Forskal, 1775) in the Marmara Sea
    (Elsevier, 2025) Sen, Yusuf
    Penaeus kerathurus is one target species caught with trammel nets by small-scale fishers in the Marmara Sea. Generally, 40 mm mesh size is used in trammel nets. In the present study, alternative mesh sizes (36 mm, 44 mm) were compared with the 40 mm traditional mesh size for their effects on selectivity and catchability. A total of 27 species comprising 3777 individuals and weighing 123615 g were caught. Penaeus kerathurus constituted 72.4 % of the total number of individuals and 58.3 % of the total weight. The mean (+/- Ss) catch-per-unit-of-effort (CPUE) for the 40 mm mesh size for commercial fishers was determined to be 7.73 +/- 4.99 g/m.operation(-1), and 9.92 +/- 4.47 g/m.operation(-1) for the present study. The CPUE values for the 36 mm and 44 mm alternative mesh sizes were determined as 4.83 +/- 2.67 and 7.77 +/- 4.92 g/m.operation(-1), respectively. The highest CPUE value for individuals was detected with the 40 mm mesh size. The mean carapace length, total length and total weight of P. kerathurus significantly increased with mesh size. The model lengths of P. kerathurus were found to be larger than the carapace length at first sexual maturity in the Marmara Sea. So, traditional and alternative mesh sizes can be used to catch P. kerathurus. As a result, P. kerathurus fisheries in the Marmara Sea were described for the first time. Alternative mesh sizes did not significantly affect catch and bycatch composition, selectivity, but they decreased catching efficiency. New and additional modifications, innovations or changes can be made to trammel nets to promote sustainable P. kerathurus fisheries.
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    Estimation of Economic Losses in Trammel Nets Fisheries Using the Length-weight Relationship
    (Springer Int Publ Ag, 2024) Sen, Yusuf; Ozekinci, Ugur
    Trammel nets are used with nearly five days of soaking time to increase the catching efficiency of demersal fish under the control of commercial fishers in the Marmara Sea, Turkiye. The long soaking times can be deteriorate or damage individuals of fish species and economic losses. In this situation, the length and weight of fresh individuals can be measured, but damaged individuals can not be measured in length and weight or both. These losses can be revealed by relating of the length-weight relationship. The current study aimed to determine economic losses by estimating the length-weight relationships of known length and weight of fresh individuals, and by calculating the weight of damaged individuals depending on the length-weight relationships. The catching operations with different soaking times were conducted firstly from December 2020 to December 2021 and secondly from the winter and spring seasons of 2022 in the Marmara Sea, Turkiye. A total of 654 individuals of all species were caught and 185 of them were determined to be damaged. This shows that 30% of those caught were damaged individuals. The total weight of the damaged individuals was calculated to be 91.3 kg. The damaged fish were caught with a total of 2000 m trammel nets and it was determined that they caused an economic loss of 355.3 USD. When we consider the decline and overexploitation of fish stocks, these economic losses and damaged individuals with long soaking times for trammel nets are significant. So, the negative effects of long soaking times on catchable stocks should be evaluated by fisheries managers, and the long soaking times of trammel nets should be regulated for sustainable fisheries.
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    Estimation of spawning stock biomass and spawning areas of sardine, (Sardina pilchardus) with winter time ichthyoplankton sampling in the Sea of Marmara, Turkiye
    (Ege Univ, Fac Fisheries, 2024) Daban, Ismail Burak; Sen, Yusuf; Öztekin, Alkan; Ayaz, Adnan; Altinagac, Ugur; İşmen, Ali; Yuksek, Ahsen
    The spawning areas and spawning stock biomass of sardine were studied with ichthyoplankton sampling in the winter period from the 32 stations, in the Marmara Sea. The mean fish egg and larvae biomass in a unit area were calculated as 18.4 +/- 5.3 eggs/10 m(2) and 2.5 larvae/10 m(2), respectively. Three main spawning areas were detected as Karacabey Floodplain area, Gonen, and Buyukcekmece estuarine area. The larvae are mostly located in the western part. The batch fecundity of sardine was detected between 2415.9 and 16738.3, with a mean of 6899.8 +/- 255.7 eggs. The sex ratio (R), spawning fraction (S), mortality rate, and daily egg production (Po) were calculated as 0.53, 0.098, 0.62, and 9.25 eggs/m(2) in the Marmara Sea. The spawning stock biomass (B) is estimated at 2998 tonnes in the Marmara Sea. Both ichthyoplankton biomass and spawning stock biomass were found relatively lower. It is recommended to apply stricter management sanctions for the sustainability of sardine stocks.
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    Mollusc fauna of Kemer Bay (Sea of Marmara)
    (Ege Univ, Fac Fisheries, 2022) Bitlis, Banu; Ozturk, Bilal; Sen, Yusuf
    In the present study, mollusc species distributed in the Kemer Bay (Sea of Marmara) were determined seasonally (November, February, May, and August) in the years 2010 and 2011. The benthic samples were collected from different biotopes in 16 stations at depth ranging between 0.2 and 5 m by using a quadrate sampling gear. As a result of the evaluation of collected benthic materials, a total of 66 mollusc species belonging to 3 classes (Polyplacophora, Gastropoda, and Bivalvia) were identified. When the number of species and individuals are compared based on the seasons, maximum number of species (46 species) and individuals (168825 ind. m(-2)) were counted in autumn and spring, respectively. Mytilus galloprovincialis (Lamarck, 1819) and Mytilaster lineatus (Gmelin, 1791) were the most abundant species in all the seasons. Whereas, Bittium reticulatum (da Costa, 1778), Rissoa membranacea (Montagu, 1803), and Tricolia pullus pullus (Linnaeus, 1758) were characterized as species having the highest frequency index values in all seasons.
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    Occurrence of the Scavenger Crustaceans Natatolana neglecta (Hansen, 1890) (Isopoda: Cirolanidae) and Scopelocheirus hopei (Costa in Hope, 1851) (Amphipoda: Scopelocheiridae) on Bento-pelagic Fish Species in the Turkish Straits System
    (Inst Zoology, Bas, 2022) Mulayim, Aysegul; Ates, A. Suat; Sen, Yusuf; Ozekinci, Ugur; Acar, Secil
    The scavenger crustaceans Natatolana neglecta (Hansen, 1890) (Isopoda: Cirolanidae) and Scopelocheirus hopei (Costa in Hope, 1851) (Amphipoda: Scopelocheiridae), along with several other peracarid crustaceans, were recorded on demersal fish species in the Turkish Straits System. Samples were collected on (in) Raja clavata, Chelidonichthys lucerna, Trachurus sp., Scorpaena scrofa, Merluccius sp., Solea solea and Squalus acanthias captured by trammel nets at depth of 50 m on 26(th) January 2021. Natatolana neglecta, Scopelocheirus hopei and Nebalia abyssicola Ledoyer, 1997 are new for the fauna of the Turkish Straits System.
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    Post-Mucilage Distribution, Daily Growth, Mortality, and Hatch Date Timing of Sand steenbras Lithognathus mormyrus (Linnaeus, 1758) Juveniles in the Sea of Marmara
    (Istanbul Univ Press, Fac Aquatic Sciences, 2024) Daban, Ismail Burak; Sen, Yusuf; Öztekin, Alkan; Ayaz, Adnan; Altinagac, Ugur; İşmen, Ali; Yuksek, Ahsen
    Between 2021-2022, a dense mucilage disaster occurred in the Sea of Marmara in T & uuml;rkiye. Mucilage mostly covered coastal areas, which juvenile fish use for nurseries, growth, and protection. Due to Sand steenbras having been suggested as an environmental bioindicator species for Mediterranean coastal waters, this study attempts to reveal post-mucilage distribution and potential differences on the timing of hatching, daily age, growth, and mortality as revealed by the otolith microstructure. Individuals were sampled using beach seine nets from 12 equally spaced stations along the Sea of Marmara. Its presence and significant abundance in 10 out of 12 stations showed the Sand steenbras to be a common juvenile species for the Sea of Marmara. Hatching occurs between MayJanuary, with peak hatching occurring in October. When considering that the mucilage had completely disappeared from the environment in August, the first set of hatching months can be seen to coincide with the dense mucilage. Thus, Sand steenbras can be considered as able to reproduce under these environmental conditions. The daily age of the Sand steenbras juveniles ranged between 38-235 days, with a mean of 120.3 +/- 1.8 days. The daily growth and mortality rates were also calculated respectively as 0.226 mm/day and 4.11%.
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    Postmucilage biodiversity of shallow water fish assemblages: A case study in the Marmara Sea, Turkey
    (Tubitak Scientific & Technological Research Council Turkey, 2023) Daban, Ismail Burak; Sen, Yusuf; Ayaz, Adnan; Altinagac, Ugur; Öztekin, Alkan; Ozekinci, Ugur; İşmen, Ali
    A dense mucilage event occurred between November 2020 and August 2021 in the Marmara Sea, Turkey. In this study, the aim was to understand the effect of mucilage on coastal fish biodiversity. For this purpose, juvenile and small-sized adult fish species were sampled with an experimental beach seine at 12 equally-spaced stations around the Marmara Sea between November 2021 and April 2022. In total, 34 species belonging to 19 families were sampled. Approximately 70% of the total fish abundance were Atherina boyeri Risso, 1810, Chelon auratus (Risso, 1810) and Chelon saliens (Risso, 1810). Highest abundance was detected from S5 (Marmara Ereglisi) and S11 (Florya) comprising 17.3% and 14.2% of total abundance, respectively. Maximum species richness was found at S4 (Erdek) and S12 (Yalova Tigem), with 21 and 18 species, respectively. The highest biodiversity indexes were seen at S4, S8 (Karacabey floodplain area) and S12, whereas the lowest biodiversity index was found at S9 (Buyukcekmece). S4 and S8 should be monitored and protected by fisheries management authorities due to being nursery and protection areas for the Sea of Marmara. When the biomass and biodiversity of the coastal fish assemblages were compared with previous studies conducted before the mucilage event, it can be said that mucilage did not adversely affect recruitment success.
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    Presence of abnormal otoliths in hallucinogenic fish and their comparison with normal otoliths using light and scanning electron digital imaging
    (Wiley, 2024) Yedier, Serdar; Daban, Ismail Burak; Sen, Yusuf; Bostanci, Derya
    The otolith organs located in the inner ear of the fish are responsible for vital activities such as balance and hearing. Abnormalities in these organs can adversely affect the vital activities of the fish species. The main purpose of the study is to analyze the abnormalities in the otoliths of Sarpa salpa, known as the hallucinogenic fish. For that, 372 individuals of S. salpa are collected from the North Aegean Sea. As a result of the abnormality analyses in S. salpa otoliths, anomalies were detected such as various prominence structures on the surface of the otolith caused by accumulation and a more transparent appearance due to the different crystal structures in some parts of the otolith. These abnormalities were found in the left and/or right otoliths of male and female individuals in different total lengths. The percentage of individuals with abnormal otoliths of S. salpa is calculated as 52.42%. It was determined that there are statistical differences between the left and right otolith measurements of male and female individuals with abnormal and normal otoliths(p < 0.05). There is no relationship between the percentage of individuals showing abnormality and total length and sex. The current study presents for the first time abnormal otolith information on left and right otoliths in male and female S. salpa. It is thought that abnormalities in hallucinogenic fish otoliths could be related to genetic predisposition as well as stress due to nutritional preference, pollutants, and environmental factors.
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    The Effect of Bait and Soaking Times on Catch Efficiency and Species Composition of Trammel Nets
    (Central Fisheries Research Inst, 2024) Sen, Yusuf; Ozekinci, Ugur
    Trammel nets are used with long soaking times to increase catching efficiency in Turkiye commercial fisheries. In the present study aim to examine the effects of the baited trammel nets alternative method instead of the long soaking times of trammel nets. A total of 405 individuals from 37 species were caught, including 143 from 9 target species, 93 from 18 non-target species and 169 from 10 other species. 98 nondamage individuals of target species comprised only 24.2% of total catch. The baited trammel nets were found as 1.56,1.6,1.2 times more efficient than non-baited nets for 3,5,7 days soaking times in the non-damage individuals of target species. The nonbaited nets for only 1 day were determined as 1.5 times more efficient than baited nets. 109 damaged individuals (46.2%) were identified from the total target and nontarget species in the baited and non-baited nets. As the soaking times increased, the number of damaged individuals in target and non-target, also other species increased. The addition bait affected individuals, whereas statistically insignificant. Consequently, the baited alternative method of trammel nets with 3 days soaking time can be recommended instead of the long soaking times considering negative effects on species for Turkish trammel net fisheries.
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    The effect of gillnet twine thickness on catching efficiency and selectivity for common carp (Cyprinus carpio Linnaeus, 1758) fishery in Marmara Lake
    (Ege Univ, Fac Fisheries, 2022) Dereli, Hakki; Kebapcioglu, Turhan; Sen, Yusuf; Olcek, Zeki Serkan; Dincturk, Ezgi; Ulman, Aylin
    The effects of multifilament gillnet twine thickness on selectivity and catching efficiency for the common carp fishery were investigated in this study. Sampling was carried out with multifilament gillnets of two different twine thicknesses (with 210d/2 and 210d/3) on 140, 150, 160, 180, 200 mm mesh sizes between June 2015 and December 2016 in Marmara Lake, located in Western Turkey. Higher modal lengths and lower catch per unit effort (CPUE) values and lower sub-minimum landing size (MLS) individuals rate (excluding 180 and 200 mm mesh sizes) were obtained in the thick multifilament material (210d/3) with the same mesh size compared to thin material (210d/2). All mesh sizes in both twine thickness provided modal lengths above the MLS. However, the thin twine material had a higher nominal percentage of undersized fish (8%), greater than the 5% accepted limit for total catches when all mesh sizes are considered together. As a result, the modal lengths and spread values increased and the selectivity and catching efficiency decreased with the thicker twine material.
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    The length-weight relationship and condition factors of coastal small-sized adult and juvenile fish species following dense mucilage in the Sea of Marmara, Türkiye
    (Tubitak Scientific & Technological Research Council Turkey, 2024) Sen, Yusuf; Daban, Ismail Burak; Öztekin, Alkan; Ayaz, Adnan; Altinagac, Ugur; İşmen, Ali; Yuksek, Ahsen
    To understand the ecosystem health of the Sea of Marmara following the dense mucilage event in 2021, growth indicators (length-weight relationships and condition factors) of coastal fish species were investigated. For this purpose, individuals were sampled during experimental fishing trials with beach seine nets between November 2021 and March 2022 from the Sea of Marmara, Turkiye. A total of 32 fish species belonging to 19 families were obtained. A total of 12 juvenile and 20 small-sized adult coastal fish species were identified, and condition factors and length-weight relationships (LWRs) were calculated. The LWR results of this study reveal the first findings as Gasterosteus aculeatus for Mediterranean marine waters, as Umbrina cirrosa for Turkish waters, and as Pomatoschistus marmoratus and Pomatoschistus minutus for the Sea of Marmara. The b value of 17 species ranged between 2.586 and 3.566, all distributed within the expected range (2.5 and 3.5) for healthy stocks. In addition, the CF values were found slightly lower from the results of the previous studies. These differences may be a result of abnormal environmental conditions which cause mucilage to form and/or address varied life phases (juvenile/adult) of this study and compared previous studies. To better understand, multidisciplinary studies should be conducted that include case history as well as back-calculated predictions, as in this study.
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    Winter Time Ichthyoplankton Assemblages Following Dense Mucilage Event in the Sea Of Marmara, Türkiye
    (Central Fisheries Research Inst, 2024) Daban, Ismail Burak; Yuksek, Ahsen; Öztekin, Alkan; Sen, Yusuf; Altinagac, Ugur; Ayaz, Adnan; İşmen, Ali
    The community structure of ichthyoplankton after mucilage was investigated. For this purpose, three ichthyoplankton survey were conducted from 34 stations between December 2021 and March 2022. A total of 19 fish egg and 16 fish larvae species were identified. It was detected that the biodiversity of winter time ichthyoplankton was higher than previous studies. European Sprat, Sprattus sprattus had the highest mean biomass for both fish eggs and fish larvae, whereas Sardine, Sardina pilchardus had relatively low biomass. Karacabey Floodplain area, B & uuml;y & uuml;k & ccedil;ekmece estuarine area and Erdek Bay were the most important spawning areas for winter spawners. It was found that ecosystem health of the Marmara Sea was suitable for fertilization, hatching and larval growth soon after the mucilage and hydrological regime recover itself immidiatelly.