Research Document - 2010/055

Effects of pH, Temperature and Salinity on Age 0+ Atlantic Whitefish (Coregonus huntsmani) with Implications for Recovery Potential

By A.M. Cook, R.G. Bradford, B. Hubley, and P. Bentzen

Abstract

Endemic to Canada, the anadromous Atlantic whitefish only occurs in Nova Scotia, and spawning runs have only been documented in two watersheds. Since 1982, the global distribution of Atlantic whitefish has been limited to the Petite Rivière watershed, where a land-locked population persists within three small semi-natural lakes that cannot be accessed from the sea. Atlantic whitefish were designated as endangered by Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1984 and 2000; in 2006, a Recovery Strategy (DFO 2006) was developed which has the goal:

“to achieve stability in the current population of Atlantic whitefish in Nova Scotia, re-establishment of the anadromous form, and expansion beyond its current range.”

In order to acquire information to help guide recovery activities, a series of lab-based experiments were initiated in 2004 to assess the response of early life stages of Atlantic whitefish to water pH, temperature and salinity. This document describes the experiments and reports the outcomes. The results are then applied to available water chemistry data for rivers in Nova Scotia's Southern Upland (SU) region lying within the historical range of the species to assess recovery feasibility under a series of plausible life history scenarios.

The results show that Atlantic whitefish are tolerant to full seawater at early stages of development (larvae-juvenile) and exhibit increasing tolerance to pH through ontogeny such that:

Eggs<hatch<larvae=early juveniles<juveniles

Model simulations show freshwater resident populations can potentially survive in all watersheds in the SU region of Nova Scotia, as river specific median survival probabilities ranged from 0.20 to 0.96, with reduced survival occurring in the most acidified rivers. The inclusion of anadromous migrations into the simulations resulted in 30% increases in survival probability for Atlantic whitefish in the most acidified rivers, irrespective of the life stage in which the migration occurs.

Complete document (PDF, 626 KB)

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