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    Decade of microplastic alteration in the southeastern black sea: An example of seahorse gastrointestinal tracts
    (Academic Press Inc Elsevier Science, 2023) Onay, Hatice; Minaz, Mert; Ak, Kubra; Er, Akif; Emanet, Muammet; Karsli, Baris; Bilgin, Sabri
    Unconscious and excessive use of plastic supports the diversity and abundance of microplastics (MPs) in marine environments. As a result of MP exposure, organisms in the marine environment are faced with adverse scenarios up to death. In this study, ten-year MP composition was investigated in gastrointestinal tracts (GITs) of low-mobility seahorses (90 individuals per period) from the Southeastern Black Sea. Seahorse GITs sampled during both 2012 and 2022 contain 102 and 135 MP items, respectively. The number of MPs per unit individual seahorse and unit seahorse weight was higher in the 2022 period. On the other hands, no significant differences were observed between the MP lengths of both periods. The majority of MPs in both sample periods were materials shorter than 1000 mu m. Of the eight found synthetic polymers, five belonged to the 2012 period, while seven were observed during the 2022 period. Additionally, the most abundant synthetic polymer for both periods is polyvinyl stearate (PVS). As a result, 43% of the total plastic material belonged to the 2012 period, while 57% was observed in the 2022 period. Considering both the diversity of polymers and the abundance of plastics, the region was adversely affected by plastic materials in the 2022 period.
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    Güney Doğu Karadeniz’de Beam Trol ile Avlanan Liocarcinus depurator (Crustacea: Decapod: Brachyura)’ün Üreme Biyolojisi
    (2021) Onay, Hatice; Bilgin, Sabri
    Bu çalışma Aralık 2012- Kasım 2013 ayları arasında Güney Doğu Karadeniz’de beam trol ile avlanan Liocarcinus depurator (Crustacea: Decapod: Brachyura)’ün üreme özelliklerini belirlemek amacıyla yürütülmüştür. İyidere, Merkez ve Çayeli istasyonlarından 2 m genişliğinde kirişli trol (Beam trol) kullanılarak 0-30+ metre derinliklerde örnekleme yapılmıştır. En yüksek GSI değerleri dişilerde Ağustos- Kasım aylarında, erkeklerde ise Mart ayında tespit edilmiştir. %50 cinsi olgunluk erkekler için 32,28 mm (KG) dişiler için ise 28,19 mm (KG) olarak hesaplanmıştır. Bu çalışma sonuçları L. depurator türü üzerinde yapılacak daha sonraki çalışmalar için önemli bir kaynak olacaktır.
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    Güney Doğu Karadeniz’de Beam Trol ile Avlanan Liocarcinus depurator (Crustacea: Decapoda)’ün Boya Dayalı Büyümesi
    (2022) Onay, Hatice; Bilgin, Sabri
    Bu çalışma Aralık 2012- Kasım 2013 ayları arasında Güney Doğu Karadeniz’de beam trol ile avlanan Liocarcinus depurator (Crustacea: Decapod: Brachyura) türünün mevsimsel ve mevsimsel olmayan büyüme özelliklerini belirlemek amacıyla yürütülmüştür. İyidere, Merkez ve Çayeli istasyonlarından 2 m genişliğinde kirişli trol (Beam trol) kullanılarak 0-30+ derinliklerde örnekleme yapılmıştır. Toplamda 2715 adet L. depurator (%39,4 yumurtasız dişi, %7,8 yumurtalı dişi ve %52,8 erkek) biyolojik olarak incelenmiştir. Karapas genişliği, yumurtasız dişilerde 6,8- 37,5 mm, yumurtalı dişilerde 17,3- 35,0 mm, erkek bireylerde 10,1- 51,3 mm olarak hesaplanmıştır. L. depurator türünün büyümesi mevsimsel büyüme modelinde hesaplanan Rn değeri dişi için 0,766, erkek için ise 0,676 olarak , mevsimsel olmayan büyüme modeline göre hesaplanan Rn değerinde dişi için 0,434 erkek için ise 0,597 olarak hesaplanmıştır. Büyümeeki sezonsal salınım (C) dişiler için 0,703 erkekler için 0,990 olarak hesaplanmıştır. Mevsimsel von Bertalanffy büyüme denklemi parametreleri erkek için K = 1,739 yıl-1, L∞ = 36,4 mm WP= (0) olarak, dişiler için ise K = 1,692, L∞ = 35,0 yıl-1 WP = (4,73), Φ´=(3,317) mm ve olarak belirlenmiştir. Erkek bireyler için büyümenin en yavaş olduğu zaman, Aralık ayı sonu Ocak ayı başı (WP = 0), dişi bireyler için ise Mayıs ayının ikinci haftasından sonra (WP = 4,73) olduğu tespit edilmiştir. Bu sonuçlar L. depurator türünün Karadeniz’de mevsimsel büyüme özelliği gösterdiğini ortaya koymuştur.
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    Güneydoğu Karadeniz'de (Rize kıyıları, Türkiye) Deneysel Krişli Trol ile Örneklenen Yengeç (Crustacea: Decapoda: Brachyura) ve Mollusca (Bivalvia, Gastropoda) Türleri
    (2019) Bilgin, Sabri; Onay, Hatice
    Bu çalışma, Karadeniz'in Türkiye sularında (Rize civarında) bulunan yengeç ve mollusca türlerini belirlemek amacıylayürütülmüştür. Toplamda 146 örnekleme 15 mm torba ağ gözü açıklığına sahip deneysel krişli trol ile Aralık 2012 ve Kasım 2013 tarihleriarasında aylık olarak gerçekleştirilmiştir. Çalışmada 5 familyaya ait (Portunidae, Eriphiidae, Xanthidae, Grapsidae, ve Inachidae) 7 yengeç türü(Eriphia verrucosa, Pachygrapsus marmoratus, Macropodia longirostris, Carsinus aestuarii, Liocarcinus depurator, Polybius navigator veXantho poressa) ve Bivalvia sınıfına ait 5 tür (Scapharca inaequivalvis, Mytilus galloprovincialis, Donax trunculus, Chamelea gallina, Pitarrudis), Gastropoda sınıfına ait ise 3 tür (Rapana venosa, Nassarius reticulatus, Gibbula sp.) olmak üzere toplamda 8 mollusca türübelirlenmiştir.
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    Karadeniz’de Karaya Vuran ve Kazara Yakalanan Yunuslar (Cetacea) Hakkında: Ölüm Nedenleri, Beslenme Özellikleri ve Gebelik Durumu
    (2018) Bilgin, Sabri; Onay, Hatice; Köse, Ozay; Yeşilçiçek, Tuncay
    Bu çalışma, Kalkan dip uzatma solungaç ağlarıyla yapılan avcılıkta Karadeniz’de yaşayan iki yunus türünün (Mutur, Phocoena phocoena ve Tırtak, Delphinus delphis) karaya vuran miktarı ve ölüm nedenleri ile bazı üreme ve beslenme özelliklerinin belirlenmesi için Rize kıyı şeridinde yürütülmüştür. Dip uzatma kalkan ağlarıyla kazara yakalanan yunuslar (71 Mutur ve 4 Tırtak) ağlara dolanarak boğulmuş ve yunuslar kalkan ağlarına zarar verememiştir. Karaya vuran yunusların (6 Mutur ve 4 Tırtak) %60’ı P. phocoena, %40’ı ise D. delphis türüdür. Karaya vuran yunusların muhtemel ölüm sebeplerinin avcılık sırasında ağlara kazara takılıp boğulmaları ve deniz kirliliği olduğu belirlenmiştir. P. phocoena türü Haziran ve Temmuz aylarında çiftleşmeye başlamakta, Mayıs’tan sonra ise doğum gerçekleşmektedir. Çalışmada 52 Mutur ve 6 Tırtak midesi incelenmiştir. Hem sayısal varlık hem de bulunuş frekansı açısından Mutur başlıca Hamsi (% N 86; %FO %63), Mezgit (% N 12; %FO %25) ve İstavrit (% N 2; %FO %11) balıkları ile Tırtak ise Hamsi (%N 8, %FO 43) ve İstavrit (%N 5 %FO 43) balıklarıyla beslenmiştir.
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    Seasonal Growth and Reproduction of the Black goby, Gobius niger (Osteichthyes: Perciformes: Gobiidae) in the southeastern Black Sea Region of Turkey
    (2020) Bilgin, Sabri; Onay, Hatice
    Seasonal growth pattern and reproductive biology of the black goby, Gobius niger (n=568; 2.1–14.6 cm TL), were monthly studied in southern Black Sea between December 2012 andNovember 2013. The seasonal von Bertalanffy growth parameters, computed from ELEFAN,were estimated as L∞= 11.9 cm TL, K= 0.701 year-1, C= 0.633, and WP= 0.492 for the Hoenigseasonal model and as L∞= 12.1 cm TL, K= 0.680 year-1for non-seasonal von Bertalanffy model.The size at sexual maturity (Lm) was estimated as 8.9 cm TL. The Gonadosomatic index (GSI)ranged between 0.60 in December and 8.57 in April 2013 (mean 3.82±0.82) for females and 0.61in October 2013 and 2.90 in May 2013 (mean 1.70±0.26) for males. The seasonal growth waspronounced probably due to reproduction activity which extended investment of energy inreproduction causing slower growth. The GSI development was related to photoperiod and themonthly variations of GSI values indicating that the intensive spawning occurred between April2013 and August 2013. During spawning time, the mean GSI value of females (6.04±1.18) was2.9 times higher than the mean GSI values of males (2.08±0.42) (P< 0.05). The results of thisstudy were offered as biological input parameters regarded as a reference for the conservationand management of the Black Sea stocks of the black goby.
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    Spatial and Temporal Distribution of Liocarcinus depurator (Crustacea: Decapod) Caught by Beam Trawl in the Southeastern Black Sea
    (2021) Onay, Hatice; Bilgin, Sabri
    This study was carried out to determine the temporal and spatial distribution of Liocarcinus depurator (Crustacea: Decapod) caught by beam trawl in the southeast Black Sea between December 2012 and November 2013. Sampling was executed at depths from shoreline to deeper 30 m by using a 2 m wide beam trawl from İyidere, Merkez and Çayeli stations. L. depurator was determined most intensely (1000 m2) at 0-5 m depth at Çayeli station and during the summer season. L. depurator started to migrate from shallow to deeper in autumn and left the coast completely in winter. It approached the shore again in the spring and spread at all depths in the summer season. In addition, while it was distributed in three different habitats according to CPUE values, the highest CPUE value was calculated at Çayeli station, which has a macroalgae structure.
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    Spawning Period and Size at Maturity of Scaldback, Arnoglossus kessleri Schmidt, 1915 (Pleuronectiformes: Bothidae), Caught by Beam Trawl in The Black Sea, Turkey
    (Istanbul Univ Press, Fac Aquatic Sciences, 2020) Bilgin, Sabri; Onay, Hatice
    The scaldback, Arnoglossus kessleri, is a small fish that belongs to the Bothidae family. This species is a demersal fish inhabiting sandy and muddy bottoms where it lives, generally buried in the sand. Even in Turkey, the biology of A. kessleri is unknown, and there are very few complete studies of the biology of this fish in the Mediterranean Sea, including the Aegean Sea and the Sea of Marmara. To describe the spawning period, size at maturity (L-m), and length at maximum yield per recruit (L-opt) of A. kessleri, and to assess the differences in these parameters from other populations, a total of 12 months samplings were conducted between December 2012 and November 2013 in the Black Sea. The monthly fluctuation of the GSI values showed that the spawning period was between June and September in the study area. The L-m was estimated as 5.76 cm for females and 6.03 cm for males. The L-opt was calculated from the empirical relationships between the L-opt and L-m, and it was determined as smaller than L-m for both sexes (L-opt = 5.55 cm for female and L-opt = 5.82 cm for male) and also the reproductive load, L-m/L-max, of females was estimated as a bit (1.4%) larger than males. The results of this study were offered as biological input parameters regarded as a reference for the management of the Black Sea stocks of the scaldback species.
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    Spawning Period and Size at Maturity of the Thornback Ray, Raja clavata (Linnaeus, 1758), (Elasmobranchii: Rajidae) in the Black Sea
    (2020) Bilgin, Sabri; Onay, Hatice
    To describe the spawning period, size at maturity ($L_m$), reproductive load ($L_m/L_{max}$), length at maximum yield per recruit ($L_{opt}$) of thornback ray (Raja clavata); and to assess the differences in these parameters from other populations, a total of 18 months samplings were conducted between February 2011 and December 2013 in the southeast Black Sea. A total of 265 (160 females and 105 males) specimens of thornback ray were examined. The mean total length (L) of females was significantly greater than the mean total length of males (p<0.05). The GSI analysis revealed that thornback ray showed reproductive activities throughout the year. The $L_m$ was estimated as 75.44 cm for females and 71.71 cm for males. The Lopt was estimated from the empirical relationships between the $L_{opt} and L_m$, and it was larger than Lm for both sexes.
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    Weight-Length Relationships (WLRs) of Scaldback, Arnoglossus kessleri Schmidt, 1915 (Pleuronectiformes: Bothidae), Caught by Beam Trawl in the Southeastern Black Sea (Rize, Turkey)
    (2019) Bilgin, Sabri; Onay, Hatice
    The Scaldback, Arnoglossus kessleri, is an endemic fish to the Mediterranean and Black seas. The present study wasconducted to determine the weight-length relationships (WLRs) of this endemic species caught by beam trawl on the Rize province coasts of thesoutheastern Black Sea, Turkey and to compare the WLRs parameters of A. kessleri from different geographical locality for contributingfisheries management of this fish species in the Black Sea. The WLRs parameters showed that A. kessleri exhibited positive allometric (orhyperallometric) growth characteristics for male and combined data (Pauly’ t test, P < 0.05) and isometric growth for female (Pauly’ t test, P >0.05). The values of coefficient (r) for female, male and combined data of this species are different from zero (P < 0.05), indicated that A.kessleri has higher correlation in the WLRs equations. In addition to this, to compare the estimations calculated from the present study withother studies, log(a) values were plotted against values of slope (b), proved to be consistent with previous studies data for unsexed A. kesslerispecimens. This study provides new basic information on the WLRs for A. kessleri populations, in support of sustainable fisheries managementof this species and especially of the coastal waters in the Black Sea, Turkey.