No abstract

Age 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 ¼ 0.0014*TL 3.1672 (R 2 ¼ 0.98) for females, TW ¼ 0.0012*TL 3.1947 (R 2 ¼ 0.98) for males and TW ¼ 0.0012*TL 3.1915 (R 2 ¼ 0.98) for both sexes. The parameters for von Bertalanffy growth curves were estimated as L inf ¼ 137.70 + 9.38 cm, K ¼ 0.159 + 0.047, to ¼ 2 2.180 + 0.90 for pooled data.

Samples of 525 Scorpaena porcus (Linnaeus, 1758) were collected from the southeastern Black Sea between January 2002 and May 2003 for information on age, growth, lengthweight relationships and stomach contents. Total length of sampled fish ranged from 4.6 to 22.9 cm and total weight from 1.3 to 220 g. The sex ratio (1 : 1.61) was biased toward females (P < 0.05). Positive allometric growth was determined in the collected samples. The length-weight relationship for all individuals was described by the parameters a = 0.0149 and b = 3.09, with r 2 = 0.99. The sample was composed of five age-classes (0-7 years). Three growth models were used to identify the growth characteristics: von Bertalanffy, L t ¼ L inf ½1 À expðÀkðt À t 0 ÞÞ; logistic, L t ¼ L inf =½1 þ ððL a À L 0 Þ=L 0 Þ½expðÀrtÞ; and Schnute and Richards, L t ¼ L inf ½1 þ aexpðÀat c Þ ðÀ1=bÞ . Among these, the Schnute and Richards model was best fitted to the data as L t ¼ 21:34½1 þ 2:38expðÀ0:34t 1:58 Þ ðÀ1=0:99Þ The diet was composed of Carcinus mediterraneus (18.2%), Crangon crangon (12.1%), unidentified crab species (10.6%), Gobius sp. (4.6%), Palaemon sp. (4.5%), Macropipus sp. (4.5%), Engraulis encrasicholus (1.5%), Gastropoda (1.5%), and unidentified remains (34.9%).

Summary Presented are length–weight relationships for Rhinobatos rhinobatos, Rhinobatos cemiculus, Gymnura altevela, Dasyatis pastinaca, Rhinoptera marginata, Pteromylaeus bovinus, Torpedo nobiliana, Raja miraletus and Raja clavata captured by gillnet, longline and bottom trawl fishing between May 2010 and July 2011 off the east coast of Iskenderun Bay, Turkey.

This study reports the parameters a and b of the length-weight relationships for seven fish species (Gobius niger, Mesogobius batrachocephalus, Mullus barbatus, Neogobius melanostomus, Raja clavata, Scorpaena porcus, Uranoscopus scaber) from the southeastern Black Sea.