Absolute darkness and effects on growth and reproductive performance of female sterlet (Acipenser ruthenus) brooders

Meknatkhah, Bahman; Rahmati, Mehdi

doi:10.22124/japb.2026.33203.1585

Absolute darkness and effects on growth and reproductive performance of female sterlet (Acipenser ruthenus) brooders

Articles in Press

Document Type : Research Paper

Authors

National Center for Stock Enhancement and Conservation of the Caspian Sea Sturgeons and Perch Genetic Resources (Dr. Yousefpour), Siahkal, Guilan, Iran.

10.22124/japb.2026.33203.1585

Abstract

This study aimed to investigate the comparison of absolute darkness with natural photoperiod on growth indices, some physiological parameters and reproductive performance in female sterlet (Acipenser ruthenus) brooders for 6 months. Fish with an average weight of 1052.8 ± 255.8 g were grown under natural or darkness photoperiods and at the termination of experiment, growth performance was measured. The results showed growth parameters except condition factor were insignificant between two treatments (p>0.05), while a better performance was achieved in absolute darkness. However, germinal vesicle position displayed lower value after 6 months of rearing in natural photoperiod (p<0.05). The plasma concentrations of total protein, progesterone and 17β-estradiol revealed no significant changes between treatments (p>0.05). After reaching to optimal reproduction temperature, fish were induced by LHRHa2. The results of this part of study showed the responded brooders to hormonal injection was higher in natural photoperiod (80%) compared with the darkness (33.3%) (p<0.05). There were no significant difference in reproductive performance between two treatments (p>0.05). The results of this study demonstrated while numerical values of growth of sterlet brooders were higher in absolute darkness, the negative impacts were obviously found in this condition in pre-spawning period and can delay final maturation.

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