Effects of Temperature and Photoperiod on Reproduction of Female Yellow Perch Perca flavescens: Plasma Concentrations of Steroid Hormones, Spontaneous and Induced Ovulation, and Quality of Eggs (original) (raw)

1997, Journal of the World Aquaculture Society

The involvement of photoperiod and temperature in the regulation of reproductive processes was investigated in female yellow perch. Initially, all fish kept indoors were exposed to the same water temperature (22" C) and photoperiod (15L:9D). By the end of August, following the first sampling, fish were submitted to different photothermal regimes. Group A, was maintained under photothermal conditions characteristic for southern Ohio. Group B, was submitted to a condensed lighfftemperature regime designed to accelerate photothermal changes. The mean gonadosomatic index in group A, gradually increased throughout the experiment. Gonadosomatic index in group A, was higher than that in group B, from February through April. The highest plasma concentrations of estradiol in group A, occurred in November and December and exceeded those in group B,. Plasma concentrations of testosterone in group A, were highest in December and tended to be higher in October and April than in other months. There was no difference in plasma testosterone between groups A, and B, except in March when concentrations of this androgen were extremely high in group B,. Ovulation occurred earlier in B regime fish in comparison to that of A regime fish. However, egg quality of fish from regime B was lower than that of fish from regime A. We conclude that the condensed photothermal cycle is not an entirely effective method of inducing out-of-season spawning in female yellow perch. These data suggest that although the compression of the photothermal cycle slightly accelerated spawning, it also caused disturbances in patterns and levels of plasma steroids, diminished ovarian and hepatic growth, and reduced the quality of eggs. Thus, temperature and/or photoperiod may have only a modifying effect on the onset of perch spawning, hut these environmental cues seem to markedly influence earlier stages of gonadal growth and development.