The role of selected environmental factors and sex ratio upon egg production in three-spine sticklebacks, Gasterosteus aculeatus

Abstract

We compared the fecundity of female sticklebacks (Gasterosteus aculeatus) breeding in salt marsh tide pools with that of fish breeding in the laboratory. Although total egg production was higher in the laboratory, there was no significant difference in clutch sizes between the two groups. In the field, physicochemical factors (water temperature, levels of dissolved oxygen, pH, and salinity) explained a statistically significant but small amount of the variation in the various measures of reproduction (daily egg production, total egg production, clutch size, interspawning interval) used. The results of a laboratory experiment concerning the effect of sex ratio upon female reproduction showed that this variable had little effect. The time spent on the breeding grounds appears to be the principal factor determining the seasonal fecundity of this species.