Some Biological Aspects of Thornback Ray (Raja clavata L., 1758) in the Southeastern Black Sea

摘要

Feeding, 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 (r~2=0.91), W=0.008DW (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 preyitems found in the stomachs were anchovy (Engraulis encrasicolus), horse mackerel (Trachurus trachurus), whiting (Merlangus merlangus euxinus), goby (Gobius sp.), shrimps (Upogobia pusllla, Crangon crangori) and unidentified crab.