Relative contributions of organochlorine contaminants, parasitism, and predation to reproductive success of eastern spiny softshell turtles (Apalone spiniferus spiniferus) from southern Ontario, Canada

Abstract

We examined hatching success, predation rates, rates of parasitism, sex ratio, and egg viability in eggs of the eastern spiny softshell (Apalone spiniferus spiniferus), a threatened species in Canada. Eggs were monitored from three populations, located at Thames River, Rondeau Provincial Park, and the Long Point National Wildlife Area, in southern Ontario, Canada in 1998. Concurrently, we measured organochlorine pesticides, PCBs, dibenzo-p-dioxins and furans from eggs from the same nests. Contaminant concentrations in eggs were similar among sites. There was no correlation between hatching success, parasitism and depredation rates, or the proportion of hatchlings that were males with total PCBs or individual pesticides, but there was a positive correlation between egg viability with concentrations in eggs of total PCBs, and with five pesticides. We found no evidence that the reproductive success of softshell turtles was compromised due to organochlorine contamination. The most important factors determining hatching success of eggs was predation, followed by egg viability and parasitism.