Physiological disturbances and behavioural impairment associated with the incidental capture of freshwater turtles in a commercial fyke-net fishery

摘要

ABSTRACT: Turtles are caught as bycatch in commercial fisheries in both inland and marine waters. Turtle mortality associated with bycatch is concerning, as life-history characteristics of turtles, including high juvenile mortality and delayed sexual maturity, make them particularly susceptible to population declines following small increases in adult mortality. In eastern Ontario, Canada, freshwater turtles are encountered as bycatch in an inland commercial fyke-net fishery. Although some temperate turtle species can tolerate prolonged submergence, their ability to withstand submergence decreases as water temperatures increase such that turtles may experience severe physiological disturbances and mortality following prolonged forced submergence. The purpose of our study was to evaluate the sublethal physiological consequences and related behavioural impairments associated with fyke-net capture for 3 species of freshwater turtles (eastern musk turtle Sternotherus odoratus, northern map turtle Graptemys geographica and painted turtle Chrysemys picta). Individuals that were entrapped for 3 h at elevated water temperatures (23 to 29°C) displayed considerably higher blood lactate and lower blood pH compared to free-living individuals. This trend was consistent across species and sexes. Despite having the largest increase in blood lactate, musk turtles did not exhibit behavioural impairment from entrapment, whereas both map and painted turtles displayed low responsiveness to behavioural assessments following entrapment. Our results suggest that sub-lethal responses can be used to identify potential harm or fitness impacts even in the absence of immediate mortality. Assessment of behavioural impairments, which could compromise activity and potentially result in post-release mortality, is important for protected and at-risk species that exhibit high juvenile mortality and delayed sexual maturity.