Hydroacoustic tracking of the endangered Atlantic whitefish (Coregonus huntsmani); comparative analysis from wild and hatchery reared populations

Atlantic whitefish (Coregonus huntsmani) are an endangered species located in only three lakes in Nova Scotia, Canada. Conservation efforts are directed toward increasing their range and number of viable populations. Current stocking programs use hatchery reared fish. The goal of the study was to determine the survival and distribution of hatchery reared Atlantic whitefish after release. Comparative hydroacoustic tracking experiments were performed to examine the survival, depth preferences and movements of hatchery reared and wild Atlantic whitefish. Hatchery reared fish were released to a non native lake whereas wild fish were released back to their native lake. Hatchery reared fish were 'lost' from the study lakes through presumed predation at a much higher rate (67 %) than wild released (6.5 %). Mortality rate in wild released fish was higher (50 %) than hatchery reared fish (20 %) and were likely due to the increased stress associated with handling or tagging. Movements were tracked over 248 and 342 days for wild captured and hatchery reared fish respectively. Hatchery reared fish were slow to disperse from the release site (mean ± standard error; 12 ± 3.2 days) and swam at the surface of the water for extended periods, which could have led to the unknown losses of these fish. After dispersal throughout the lake, however, the hatchery-reared fish were distributed in depths similar to those of the wild released fish, an important finding for the use of hatchery-reared fish in conservation. Results are discussed to improve hatchery practices for fish destined for stocking.