Development of a captive breeding program for the Florida apple snail, Pomacea paludosa: Relaxation and sex ratio recommendations

Stock enhancement of the Florida apple snail, Pomacea paludosa, is a potential management strategy for the conservation of the endangered snail kite which is dependent upon the snail as its predominant food source. Reliable culture techniques that provide high growth and survival rates for juvenile snails have been established; however, additional research is needed to improve breeding in captivity. The goals of this study were to efficiently relax the snails to identify the sex in order to conduct a study to understand the effect of different sex ratios on reproductive output. Of the seven chemical solutions used to relax the snails, benzocaine mixed in methanol was the most effective. To examine the effect of sex ratio, 10 snails were stocked into 75 L tanks within a recirculating aquaculture system at the ratios of 3 F:7 M, 5 F:5 M, 7 F:3 M, and 8 F:2 M for 8 weeks. There was a significant positive relationship between the number of egg clutches produced and a higher number of females in the tank. However, there were no significant differences in the number of eggs per clutch, egg diameter, percent hatch rates, female production (egg clutches per female per week), or the number of juvenile snails produced per female. The number of copulations was observed for the first three weeks of the experiment. When standardized to the number of copulations per male snails, no significant differences between treatments were detected. Our results suggest that a female-biased sex ratio may prove optimal and cost effective for large-scale captive breeding production. Future studies should determine the minimal proportion of males needed to limit the loss of genetic diversity in a female-biased stock enhancement program.

► Benzocaine mixed in methanol is recommended for the relaxation of the apple snail.
► Egg clutch production was higher in female-biased sex ratios.
► A successful captive breeding program for the apple snail has been developed.