Annual cycle of ovarian development and sex hormones of grey mullet (Mugil cephalus) in captivity



grey mullet fingerling were imported to Iran in 1997 from Hong Kong and in
coastal fish pond of north part of Iran were successfully cultured in order to
obtain broodstocks and induce artificial reproduction. Seasonal changes in
serum concentrations of Testosterone, 17-β Estradiole (E2), 17-α
Hydroxy Progesterone and also the level of calcium, Triglyceride and
cholesterol in females grey mullet in captivity were measured by
Radioimmunoassay or colorimetry, respectively. Investigating of sex steroids in different
sexual maturity indicated that increasing of oocyte diameter and sexual
maturity development serum testosterone was increased significantly
(P < 0.05). Although Biochemical parameters concentrations in blood serum of
grey mullet diminished significantly until third stage of sexual maturity
(P < 0.05), their level showed a rising trend at the fourth stage. A
significant increase was observed in the serum protein and cholesterol
concentrations (P < 0.05), while, in contrast, serum Calcium ion and
triglyceride levels didn’t have significant differences in third and fourth
stages of sexual development (P> 0.05). These results suggest that the seasonal changes in serum lipids and
gonadal steroids were associated with reproductive development. The data also
support the hypothesis that the shortening photoperiod is a major factor in
stimulating reproductive activity in striped mullet.