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 and November 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 Hoenig seasonal model and as L∞= 12.1 cm TL, K= 0.680 year -1 for 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 0.61 in October 2013 and 2.90 in May 2013 (mean 1.70±0.26) for males. The seasonal growth was pronounced probably due to reproduction activity which extended investment of energy in reproduction causing slower growth. The GSI development was related to photoperiod and the monthly variations of GSI values indicating that the intensive spawning occurred between April 2013 and August 2013. During spawning time, the mean GSI value of females (6.04±1.18) was 2.9 times higher than the mean GSI values of males (2.08±0.42) (P< 0.05). The results of this study were offered as biological input parameters regarded as a reference for the conservation and management of the Black Sea stocks of the black goby.
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 L opt was estimated from the empirical relationships between the L opt and L m , and it was larger than L m for both sexes.
This study was carried out in order to determine some biological characteristics of the fish species of Spicara flexuosa, which is distributed on the Eastern Black Sea coast, and to contribute to the management of the picarel in all the seas of our country. Between October 2015 and September 2016, 599 fish samples were obtained and examined in the laboratory. It was determined that the examined individuals were distributed between the ages of I-VII which 31.22% of the population was male and 68.78% was female. The minimummaximum total length values of the samples were between 8.7 and 21.8 cm; and the weight values ranged from 7.1 to 129.94 g. It has been determined that the mean total length of males is statistically different from that of females (P<0.05). Von Bertalanffy growth equilibrium was calculated as "L∞=22.71 cm TL, K=0.243 year-1 , t0=-2.306 year-1 ; W∞=118.27 g" for females, "L∞=38.34 cm TL, K=0.063 year-1 , t0 =-6.381 year-1 ; W∞=755.37 g" for males, and "L∞=33.42 cm TL, K=0.080 year-1 , t0=-5.381 year-1 ; W∞=401.24 g" for all individuals. The length-weight relation of all individuals was found as W= 0.0118*L 2.9727 (R 2 =0.9487). When the ratio of gonadosomatic index (GSI) data and gonadal maturity stages were examined over the year, it was determined that the reproduction of the picarel in the Black Sea occurred between June and September.
Özet 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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