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Öğe Age and Growth of the Bluemouth Rockfish, Helicolenus dactylopterus (Delaroche 1809) from the North-Eastern Mediterranean Sea, Turkey(Zoological Soc Pakistan, 2015) Demirhan, Sefa Ayhan; Akbulut, FatihIn the recent study,. age, growth and length-weight relations-hip of Helicolenus dactylopterus (Delaroche, 1809) were investigated. A total of 525 specimens were collected from bottom-trawl research surveys and commercial trawl fishery along the southern continental slope of the Iskenderun Bay between June 2012 and May 2014. Age was determined by reading whole sagittal otoliths. Fish ranged froth 9.3 to 20.9 cm in total length, which corresponded to fish between 1 to 8 years old. Growth parameters were estimated using the standard Von Bertalanffy growth model (k=0.064, L infinity=35.419 cm and to =-4.797 for combined sexes). Length-weight relationships were estimated for females (W=0.0385L(2) (6645)) and males (W=0.0345L(2 7089)). The low level of maximum length registered in this study could be related to high pressure level of trawl fishery during the last two decades in Iskenderun Bay.Öğe Age and growth of the Bluemouth Rockfish, Helicolenus dactylopterus (Delaroche 1809) from the North-Eastern Uediterranean Sea, Turkey(University of Punjab (new Campus), 2015) Demirhan, Sefa Ayhan; Akbulut, FatihIn the recent study, age, growth and length-weight relationship of Helicolenus dactylopterus (Delaroche, 1809) were investigated. A total of 525 specimens were collected from bottom-trawl research surveys and commercial trawl fishery along the southern continental slope of the Iskenderun Bay between June 2012 and May 2014. Age was determined by reading whole sagittal otoliths. Fish ranged from 9.3 to 20.9 cm in total length, which corresponded to fish between 1 to 8 years old. Growth parameters were estimated using the standard Von Bertalanffy growth model (k=0.064, L?=35.419 cm and to =-4.797 for combined sexes). Length-weight relationships were estimated for females (W=0.0385L2.6645) and males (W=0.0345L2.7089). The low level of maximum length registered in this study could be related to high pressure level of trawl fishery during the last two decades in Iskenderun Bay. Copyright © 2015 Zoological Society of Pakistan.Öğe Age and growth of the common guitarfish, Rhinobatos rhinobatos, in Iskenderun Bay (north-eastern Mediterranean, Turkey)(Cambridge Univ Press, 2008) Basusta, Nuri; Demirhan, Sefa Ayhan; Cicek, Erdogan; Basusta, Asiye; Kuleli, TuncayAge and growth of the common guitarfish (Rhinobatos rhinobatos) were estimated from the north-eastern Mediterranean coast of Turkey. A total Of 115 common guitarfish (66 females and 49 males) were sampled. Age determinations were carried out using vertebral sections. Alcian blue dying techniques were used to enhance the visibility of the band on vertebrae. The techniques have been used for the first time on elasmobranchs vertebrae successfully in this study. A total of 97 vertebrae Of 115 were visible on the vertebral band in this study. Male and female common guitarfish ranged in age from 1 to 15 and 1 to 24 y respectively. Total length ranged from 42 to 147 cm for females and 39 to 124 cm for males. The relationships between total length (TL) and total weight (TW) were presented as TW = 0.0014*TL3.1672 (R-2 = 0.98) for females, TW=0.0012*TL3.1947 (R-2 = 0.98) for males and TW=0.0012*TL3.1915 (R-2 = 0.98) for both sexes. The parameters for von Bertalanffy growth curves were estimated as L-inf = 137.70 +/- 9.38 cm, K= 0.159 +/- 0.047, to = -2.180 +/- 0.90 for pooled data.Öğe Biological observations on the common guitarfish Rhinobatos rhinobatos from Iskenderun Bay (Turkey, Eastern Mediterranean)(Brill, 2009) Cek, Sehriban; Basusta, Nuri; Demirhan, Sefa Ayhan; Karalar, MuratHistological examination of the gonads showed that spermatogenesis occurs in every male R. rhinobatos collected in autumn and winter months of the year. The testis was composed of lobes having numerous spermatocysts in a dorsoventral zonated arrangement. Present results suggest that since R. rhinobatos have a cystic mode of spermatogenesis it can be used as a model for biomedical and toxicological studies. Eight stages of maturation for females and seven stages of maturation for males were identified. Moreover, vitellogenic oocytes were consistently found in every female collected during the summer months. In vitellogenic oocytes, yolk is present as pleomorphic droplets and very often; small yolk droplets have a crystalline configuration. These data suggest that both sexes are reproductively active at different times of the year. Both, the right ovary/testis and the left ovary/testis were functional. Ripe oocytes in the ovaries were usually symmetrically distributed. The population consisted of aplacental viviparous individuals with lecithotrophic embryo development. Although, sex ratios of R. rhinobatos were not significantly different from the expected 1:1 ratio (p>0.05), slightly female biased sex ration were recorded. (C) Koninklijke Brill NV, Leiden, 2009Öğe Dietary overlap in spiny dogfish (Squalus acanthias) and thornback Ray (Raja clavata) in the Southeastern Black Sea(2007) Demirhan, Sefa Ayhan; Seyhan, Kadir; Başusta, NuriBu çalışmada mahmuzlu camgöz (Squalus acanthias) ve vatoz (Raja clavata) türlerinin besin kompozisyonu ve aralarındaki besinsel rekabet araştırılmıştır. Bölgede, mahmuzlu camgöz ve vatozun besininin genel olarak kabuklulardan ve balıklardan oluştuğu tespit edilmiştir. Mahmuzlu camgözün beslenme stratejisinde ana kriter besinin bulunabilirliğidir. Kış mevsiminde ortamda yoğun olarak bulunan hamsi, mahmuzlu camgözün bu dönemdeki ana besinidir. Bu durum, mahmuzlu camgözün besin kompozisyonunu ve diyet genişliğini etkilediği gibi, dolayı olarak vatozun besin komposisyonu ile olan diyet benzerliği ve rekabetini de etkilemektedir. Çalışmada bu iki türün besin benzerliği indeksi %38 olarak bulunmuştur. Ayrıca vatozun besin kompozisyonu üzerinde mahmuzlu camgözün besin örtüşme değeri 1,38 olarak bulunmuştur. Bunun yanında daha dar bir diyete sahip olan mahmuzlu camgözün besin kompozisyonu üzerinde vatozun besin örtüşme değeri 0,36 olarak bulunmu?tur. Sonuç olarak, R. clavata kış mevsiminde hamsi ve mezgit ile, yılın kalan döneminde yengeç, kayabalığı türleri, diğer demersal balık türleri ve mezgitle beslenirken, mahmuzlu camgöz beslenme konusunda seçici davranmamakta ve ortamda bulunan her besin maddesini tüketebilmektedir.Öğe Life history of spiny dogfish, Squalus acanthias (L. 1758), in the southern Black Sea(Elsevier, 2007) Demirhan, Sefa Ayhan; Seyhan, KadirAge, growth parameters and food of Squalus acanthias L., spiny dogfish sampled from the SE Black Sea were studied. First and second dorsal spines were used for ageing. Spiny dogfish from age classes I to 38 were identified with an age distribution of 2-38 years for females and 1-27 for males. The length-weight relationship was W = 0.0000004 x L-3.5 and W = 0.0000008 x L-3.32 for females and males, respectively. The estimated von Bertalanffy growth parameters were; L-infinity = 137.73 (+/-1.22) cm, K = 0.1263 (+/-0.0073) (year(-1)), t(0) = 1.67 (+/-0.25) (year) (r(2) = 0.93) for females, L-infinity = 123.78 (+/-4.85) cm, K = 0.168 (+/-0.024) (year(-1)), t(0) = 2.62 (year) (r(2) = 0.96) for males and L-infinity = 136.76 (+/-1.42) cm, K = 0.133 (+/-0.006) (year(-1)), t(0) = 2.15 (+/-0.178) (year) (r(2) = 0.95) for sexes combined. They feed mainly on fish (IRI% = 97.63) and crustaceans (IRI% = 2.23). Whiting was the main prey item in all seasons (IRI% = 87.81) except for winter where they feed mainly on anchovy (IRI% = 96.46). The stomach fullness and dietary component were affected by the gear used as well as seasons. It was concluded that the abundance and availability of the prey are main factors for the spiny dogfish feeding strategy in the Black Sea. (C) 2007 Elsevier B.V. All rights reserved.Öğe Maturity and fecundity of spiny dogfish (Squalus acanthias L., 1758) in the Eastern Black Sea(2007) Demirhan, Sefa Ayhan; Seyhan, KadirÖzet: Bu çalışmada Doğu Karadeniz'deki mahmuzlu camgözün eşeysel olgunluğa ulaşma boyu ve yaşı ile döl verimliliği araştırılmıştır. Eşeylerin % 50'sinin eşeysel olgunluğa ulaştığı yaş ve boy değerleri dişi ve erkek bireyler için sırayla 11,99 yıl ve 102,97 cm ile 10,49 yıl ve 87,57 cm olarak tespit edilmiştir. Dişi eşeyin iki yıllık döl verimliliği ise 19,4 yumurta ve 12,9 yavru olarak hesaplanmıştır. Embriyo ve yumurta üretkenliği ile birey boyları arasında doğrusal bir ilişki olduğu tespit edilmiştir (embryo üretkenliği için Fe = 0,09 x TLp + 2,12, r = 0,5 ve yumurta üretkenliği için Fo = 0,27 x TLp - 21,59, r = 0,7).Öğe Seasonality of reproduction and embryonic growth of spiny dogfish (Squalus acanthias L., 1758) in the Eastern Black Sea(2006) Demirhan, Sefa Ayhan; Seyhan, KadirBu çalışmada Doğu Karadeniz'den örneklenen mahmuzlu camgözün (Squalus acanthias 1. 1758) mevsimsel üreme döngüsü ve embryo gelişimi incelenmiştir. Mahmuzlu camgözün gebelik süresinin Ağustos, Eylül, Ekim aylarında başladığı ve yaklaşık 23-24 ay sürdüğü belirlenmiştir. Çalışmada döllenmiş bireylere 30-45 m derinlikte Haziran-Ağustos aylarında rastlanmıştır. Dölyatakları boş yada dölyataklarında tam gelişmiş embriyo taşıyan dişi bireyler ise sıcaklığın 10 °C olduğu 50-60 m derinliklerde yakalanmıştır. Yavruların yaklaşık olarak 28-29 cm boy ve 68-78 gr ağırlıkta doğdukları tahmin edilmiştir. Embriyo ve yumurta gelişimi ise sırasıyla TLe = 0,8124 - 0,334 x mo + 0,1289 x mo2 - 0,03 x mo3 (r = 0,92) ve Do = 0,7364 x 0,1503 x mo + 0,0221 x mo2 - 0,004 x mo3 (r = 0,94) şeklinde kübik fonksyonlarla tanımlanmıştır.Öğe Some biological aspects of thornback Ray (Raja clavata L., 1758) in the Southeastern Black Sea(2005) Demirhan, Sefa Ayhan; Engin, Semih; Seyhan, Kadir; Akamca, ErhanFeeding, reproduction and growth of thornback ray {Raja clavata L., 1758) were studied from the South-eastern Black Sea near the Georgian border. Females made up 56% and males 44% of the individuals. The total length (TL) of females ranged from 34.3 to 88.2 cm (21.5-62.7 cm disc width (DW)), and males from 48.0 to 95.0 cm (35.5-61.0 cm DW)). The total length-weight (TL-W), disc width-weight (DW-W) and total length-disc width (TL-DW) relationships were $W=0.001TL^{3.42}$ ( $r^2$ =0.91), $W=0.008DW^{3.21}$ ( $r^2$ =0.94) and DW=0.65TL+2.47 ( $r^2$ =0.88), respectively, for the sexes combined. The total length at 50% maturity (TL50) was about 64.03 cm (44.24 cm DW) for males and about 66.72 cm (47.27 cm DW) for females. Out of 50 stomachs examined, 70% of them were empty. The prey items found in the stomachs were anchovy (Engraulis encrasicolus), horse mackerel (Trachurus trachurus), whiting (Merlangus merlangus euxinus), goby (Gobius sp.), shrimps (Upogobia pusilla, Crangon crangon) and unidentified crab.
