The bioecologic characteristics of the spiny dogfish in the South-Eastern Black Sea

SUMMARY The Bioecologic Characteristics of the Spiny Dogfish in the South-Eastern Black Sea Spiny dogfish, Squalus acanthias, were sampled from Turkish coast of Black Sea to study growth parameters (K, to and L^), reproduction, and their diet compositions. Fish were caught by using longline and commercial purse seiners. In all sampled fish, 86.2 % the fish were female. Caught female fish total length and age were ranged between 43.3- 144.8 cm and 3-34 years, respectively. Male fish were younger (2-24 years old) and shorter (38.1-123 cm) than female fish. For ageing, first and second spines were used; however, the ages based on readings of the 2nd spines were used to estimate the ages of spiny dogfish with badly worn spines. The relationship was found Y=0.64*(2Çm)174 (1^=0.88); where Y is the estimated age in years from conception, 2Cm is the second spine base diameter. The length-weight relationships were W (body weight, kg)=0.0000004*L(body length, cm)3'51 (^=0.96) for females, W=0.0000008*L332 (^=0.98) for males, and W=0.0000005*L3-42 (1^=0.98) for both sexes. The estimated von Bertalanffy gowth equations were 1^=145. l*(l-e^14(H-2-69))) for females, Lt=144.1*(l-e-°067(t"('1 My) for males, and Lt=154.4*(l-e-0094(t+2'18)) for both sexes. The length and age at first maturity was 87.57 cm and 10.49 years for males and 102.97 cm and 11.99 years for females, respectively. Based on data collected over 2 pregnancy cycles (22-24 months), fertilization of eggs occures in June- August and breding occures in September-November. A total of 515 embryos was sexed, of which 252 (49 %) were male and 257 (5 1 %) were female. Embryo size at birth was 26-29.4 cm and 65-70 gr. The fecundity of the spiny dogfish increases with increasing length. The ratio of empty stomachs and stomach diet composition were affected by sampling gears and seasons. Stomach content data from 175 spiny dogfish showed that the major dietary components based frequancy of occurence were 66.8% fishes and 14.5% crustaceans. Keywords: Spiny Dogfish (Squalus acanthias), Black Sea, Growth, Food Composition, Reproduction, Fecundity. vm