Effects of Parasitism on some Reproductive Indices in Sarotherodon Galilaeus (Linnaeus, 1758) in a Freshwater Habitat

Abstract

The reproductive activities and parasitic infestation of Sarotherodon galilaeus were investigated between 2016 and 2018 using standard methods. The sex ratio was 0.94:1 (male: female) and the male grew longer than females at maturity. Five stages of gonadal maturity were observed in male and female sexes. The gonado- somatic index of female was higher than that of males. Multiple spawning of four times in a year that spread across rainy and dry seasons was observed. Generally, low fecundity (1711+176 eggs) and relative fecundity (9+1 eggs per gram body weight of fish) values were recorded. The egg diameter ranged from 0.4 mm to

2.10 mm. Parasite species diversity in S. galilaeus showed three species, which comprised of one Acanthocephalan; Neoechinorhynchus rutili, (Mueller, 1780), the metacercaria of a Trematode Clinestomum tilapiae (Leidy, 1856) and a nematode Procamallanus laevionchus (Wedl, 1862). There was no significant (p≥ 0.05) difference between the weights of infested and uninfested male fish. However, significant difference between the weights of infested and uninfested female fish in the two years was observed; which indicated that the female fish body weight was affected by the parasitic infestation. Therefore, the parasitic infestation which affected the body weight of the infested female fish could also affect the Gonado-somatic index value, egg production, fecundity and relative fecundity values; which would inadvertently affect the reproductive capability of the infested fish in the aquatic environment.