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    Age, Growth and Reproduction of the Thornback ray, Raja clavata (Linnaeus, 1758) in the Waters Off Gökçeada (the Northern Aegean Sea)
    (Springer Science and Business Media Deutschland GmbH, 2023) Yığın, Cahide Çiğdem; Cabbar, Koray; İşmen, Ali; Daban, İsmail Burak; Arslan İhsanoğlu, Mukadder
    In this study, the age, growth, maturity, and reproductive biology parameters of 262 Raja clavata, which were collected monthly from commercial trawlers off Gökçeada between February 2019 and February 2020, were estimated. The individuals comprise of 55.7% females and 44.3% males. The length of the females ranged between 23-84.2 cm (Disc width: 13.5-55.8 cm) and 11.2-74 cm (Disc width: 8-48.9 cm) for males. For age determination, age readings were performed on the vertebrae of 255 Raja clavata specimens (43.5% female, 56.4% male). The calculated von Bertalanffy growth parameters were estimated to be L∞= 93.04 cm, K=0.17 years-1, to=0.48 years for males, and L∞=102.46 cm, K=0.16 years-1, t0 =0.72 years for females. The minimum and maximum ages of the thornback rays ranged from 1 to 10 years. The first sexual maturity length of the population was measured to be L50 =57.7 cm in males, and L50 =66.1 cm in females.
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    Analysis of Demersal Fish Fauna off the Sea of Marmara, Turkey
    (Çanakkale Onsekiz Mart Üniversitesi, 2021) Daban, İsmail Burak; İşmen, Ali; Şirin, Murat; Yığın, Cahide Çiğdem; Arslan İhsanoğlu, Mukadder
    Demersal fish fauna of the Sea of Marmara, Turkey was determined by bottom trawl surveys between March 2017-December 2018 at 34 stations with the monthly samplings. During the study, a total of 61 teleost and 12 cartilaginous fish species belonging to 42 families were sampled. The target, bycatch and discard rates of CPUE were determined as 13.40%, 69.64% and 16.95%, respectively. In total, 53.9% of the CPUE was stemmed from Trachurus trachurus. Mustelus mustelus, Raja clavata, Merluccius merluccius and Merlangius merlangius had the highest CPUE with a mean of 77.63, 71.86, 71.72 and 72.68 kg/km2, respectively. The highest biodiversity was observed in the southwestern part of the Marmara Sea. With increasing depth, the species number of the teleost fish decreased, whereas the species number of the cartilaginous fish increased. The mean CPUE values of the economical demersal fish species were lower in comparison to those reported from other regions in Turkey. Evidence suggests fish stocks with shallower distribution is under heavier threat against fishing pressure. Since commercial trawling is banned in the Sea of Marmara, beam trawl fishery can be considered as the major threat to demersal fish stocks in the region.
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    Marmara denizi'nde parapenaeus longirostris (Lucas, 1846)'in populasyon yapısı, bolluk ve av oranlarının zamansal-alansal değişimleri
    (Çanakkale Onsekiz Mart Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2017) Arslan İhsanoğlu, Mukadder; İşmen, Ali
    In this study, temporal and spatial changes of catch per unit effort (CPUE-kg/h), stock amount (biomass-kg/km2), population structure of Parapenaeus longirostris, and current situation of the stocks, effects of beam trawl were determined in the Sea of Marmara. Samples were obtained by beam trawls monthly between October 2011-July 2014 and population parameters; size distributions, length-weight relationships, condition factor, growth-mortality parameters and sex rates were determined. The catch per unit effort value (CPUE) and abundance index of deep water pink shrimp were found 8,5 kg/h and 1545 N/h in the Sea of Marmara. The highest CPUE values were estimated region 2 (10,1 kg/h) and region 6 (15,1 kg/h). The lowest value was in region 5 (3,4 kg/h). According to depth contours, catch per unit effort values were determined as 8.8 kg/h in 50-100 m, 7 kg/h in ≥100 m. Biomass of the species was found 354 kg/km2 in the Sea of Marmara. The maximum value of biomass were in Tekirdag and Silivri and the lowest value was in the Yalova. 36288 individuals were measured, total length (TL), carapace length (CL) and weight (g) values were found as 34-175 mm (107 mm), 8-41 mm (22.6 mm), 0,2-28,9g (6,1g), respectively. Carapace length-weight relationship was calculated as W=0.0022*CL2.52. Growth parameters were determined as L∞=199,5 mm, k=0,47, t0=-0,5 in total length, L∞=36,8 mm, k=0,37, t0=-0.69 y in carapace length. Total mortality, natural mortality, fishing mortality and exploitation rates were found 1,60, 0,61, 0,99 and 0,62, respectively. Male-female ratio was found as 1:1,3.
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    Reproductive biology of Penaeus kerathurus (Forskal, 1775) (Decapoda: Penaeidae) in the Sea of Marmara, Turkey
    (De Gruyter Open Ltd, 2021) Arslan İhsanoğlu, Mukadder; Daban, İsmail Burak; İşmen, Ali; Cabbar, Koray; Yığın, Cahide Çiǧdem
    One of the economically important species is Penaeus kerathurus (Forskål, 1755), which is widespread in the Mediterranean ecosystem. This paper presents results of research on reproductive biology of Penaeus kerathurus in the Sea of Marmara. A total of 1404 specimens were dissected to determine the maturity stages, reproduction time, and length at first reproduction. The female-to-male ratio was 1:0.9. A high percentage of mature females was determined in April, May and July. Moreover, the value of the gonadosomatic index (GSI) decreased after July. The spawning period was observed between April and July, and its intensity increased in July. The carapace length at first sexual maturity was determined to be 39 mm.