Reproductive biology of a Red Sea goby, Silhouettea aegyptia, and a Mediterranean goby, Pomatoschistus marmoratus, in Lake Timsah, Suez Canal

Abstract

The reproductive biology of the Red Sea goby Silhouettea aegyptia, and Mediterranean Pomatoschistus marmoratus, has been studied in Lake Timsah, Suez Canal. Male: female sex ratio was 1: 1 7 in S. aegyptia and 1: 2 7 in P. marmoratus. Size at first maturity was 20 mm (s.l.) in S. aegyptia and 24 mm in P. marmoratus. The breeding season of S. aegyptia extended from March to September with most gonadal activity in May, whereas in P. marmoratus, it stretched from. November until the following April with a peak in February. Hepatosomatic index for both species exhibited monthly fluctuations and an inverse correlation with gonadosomatic index was evident. Oocyte size‐frequency distribution indicated several modes at 400, 600 and 800 μm during the breeding season. Fecundity of S. aegyptia ranged from 152 to 782 with an average of 468 eggs, whereas in P. marmoratus it varied between 293 and 1300 with an average of 603 eggs. Fecundity was related curvilinearly to fish length, body weight and ovary weight. Recruitment of young fish to the adult populations occurred in late July and early August for S. aegyptia and during March for P. marmoratus. Life history pattern indicated that both species of gobies are successful colonists of Lake Timsah, Suez Canal.