THE EFFECTS OF FOOD DEPRIVATION AND SALINITY CHANGES ON REPRODUCTIVE FUNCTION IN THE ESTUARINE GOBIID FISH, GILLICHTHYS MIRABILIS

¹ Department of Zoology, University of California, Berkeley, California

1. Investigations were conducted to examine whether decreasing food availability or increasing salinity might be implicated in termination of the breeding season in the estuarine gobiid fish, Gillichthys mirabilis.

2. Seasonal variation in weight-length ratio and hepatosomic index were studied in two populations of this species. These two indices, taken as an indication of fattening (or energy accumulation), seem to be correlated with the reproductive cycle. Both indices begin to increase as the gonads regress, and continue increasing concomitant with recrudescence; they decline steadily through the spawning season.

3. The effects of starvation on gametogenesis in this fish vary with season. Starvation can induce gonadal regression in a relatively short period in fish in phases of active gametogenesis, but does not block the initiation of gonadal recrudescence.

4. The rate of gonadal regression at high temperatures is not accelerated by starvation, suggesting that temperature can act independently to cause gonadal involution.

5. High salinity does not cause gonadal regression nor prevent recrudescence in Gillichthys.