Factors affecting growth of killifish, Aphanius dispar, a potential biological control of mosquitoes

Abstract

Preliminary experiments were carried out on the growth of killifish, Aphanius dispar. The motivation of the study was to obtain information for growing the fish on a commercial scale for their use as biological control agents of mosquito larvae. Growth of fry in the laboratory was found to be exponential, where the degree of variance in size among the fry increased with age. Grading the fry was shown to be effective in reducing the significant differences in their growth rates observed prior to grading. The effects of temperature, salinity and feeding rate on the growth of wild adult fish were also investigated. There were significant increases in growth rates of adult fish as temperature was increased from 18°C to 23°C. Further increases in temperature, to 27°C, did not further affect growth. Significant differences were also found among growth rates of fish kept at salinities from 8 to 56 ppt. Growth was found to be lowest at 40 ppt, and increased steadily as salinities approached the two range limits. Growth rates were found to increase significantly as feeding rates increased from 0% to 4% body weight (BW)/day. Further increases up to 10% BW/day did not result in further increases in growth. Regressing mean growth rates on feeding rates showed 1.6% BW/day to be the maintenance feeding rate at which fish neither gained nor lost weight.