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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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    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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    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.