This is the first trial so far in Egypt through upgrading the fish production by revealing specific ovarian myxozoan and fungal infections that affect their fecundity. Fecundity comparison was held between noninfected and infected Oreochromis niloticus and Cyprinus carpio with either Myxobolus spp. or Icthyophonus hoferi.The myxosporean parasite, Myxobolus spp. (with higher prevalence in both species ) appeared as numerous white large rounded spores embedded in the ovarian tissue causing excessive fibrosis. The fungus /. hoferi inspite of its lower prevalence among the 2 species, the white capsulated cysts and separate colonies caused ovarian atresia and fibrosis with inflammatory oedema.
Drop of fecundity was represented by significant decrease in relative and absolute fecundity, total protein, gonadosomatic and hepatosomatic indices ranging from highly with 0. niloticus to moderately with C carpio. In O. niloticus ( more sensitive ) /. hoferi reflected a positive correlation with ovarian weight and gonadosomatic index, while Myxobolus spp. recorded a negative correlation between ovarian weight and the body parameters (weight, length & depth).
The results revealed that infection takes place among apparently healthy fish proving that gonadal periodical examination is the only way for detecting such infections.