1997 Volume 45 Issue 1 Pages 75-80
Gonadal maturation in hybrids of red sea bream _??_ ×black sea bream_??_and red sea bream_??_×silver bream_??_reared for 4 years in net cages on the sea was compared with that of red sea bream, black sea bream, and gynogenetic diploid silver bream. The gonads of both hybrids were clearly immature in their appearance compared with those of the parent species during the same period. The gonado-somatic index of the three parent species peaked in April with average values highr than 8 whereas the values for hybrids never exceeded 1. Histological examination of the gonads revealed spermatogonia, spermatocytes, spermatids, and spematogenesis in the males of both hybrids, but oocytes were not observed. From these results, it was made clear that both males and females of the two types of hybrids showed hybrid sterility.
