The relationship among spawning period, length at first maturity and depth distribution of Mullus barbatus and Upeneus moluccensis inhabiting the Northeastern Mediterranean coast of Turkey

This study examined the spawning characteristics and distribution of Mullus barbatus and Upeneus moluccensis in Babadillimani Bight, in the northeastern Mediterranean (near Mersin, Turkey) between of May 1999 and April 2000. Sampling was carried out monthly at depths of 0-50 m, 50-100 m and >100 m using commercial trawl net mesh size 22 mm knot to knot. The results showed no difference between the length at first maturity of males and females (t-test, P>0.001) in either M. barbatus or U. moluccensis. This length for the combined sexes was calculated to be 11.7 cm and 10.9 cm in M. barbatus and U. moluccensis, respectively. When monthly changes in the Gonadosomatic Index (GSI) values were evaluated, the spawning period was determined as July-November for M. barbatus and May-August for U. moluccensis. The mean total lengths from the individuals belonging to M. barbatus from depth layers of 0-50 m, 50-100 m and >100 m were calculated as 8.65 cm, 8.70 cm and 12.70 cm, respectively. Total lengths for U. moluccensis were calculated as 8.40 cm, 11.66 cm and 13.32 cm, respectively. The mean total length of M. barbatus and U. moluccensis increased from coastal areas to deeper waters. Therefore bottom trawl fishing must be conducted in waters deeper than 100 m for both M. barbatus and U. moluccensis.