Research Document - 2010/005

2009 Update Status Report for Atlantic Whitefish (Coregonus huntsmani)

By R.G. Bradford, P. Bentzen, D.M. Campbell, A.M. Cook, A.J.F. Gibson, and J. Whitelaw

Abstract

The Atlantic whitefish (Coregonus huntsmani), considered to be anadromous by nature, is endemic to Canada (Scott 1987), and found only in the Province of Nova Scotia. They presently exist as a land-locked population within three small semi-natural lakes in the Petite Rivière. The lakes can not be accessed from the sea. Atlantic whitefish are listed and protected as endangered under the Canada Species at Risk Act (SARA). Analyses of both mitochondrial and nuclear DNA support their putative status as an ancient and highly discrete lineage of whitefish. However, the remaining population exhibits extremely low genetic diversity, and no genetic variation among the three lake contingents. The land-locked population is probably resource limited, generally small-bodied, short-lived, and limited in reproductive capacity when compared to members of the same population introduced into captive rearing. These traits of the land-locked population do not appear to have changed greatly over the past several decades. Somatic growth realized by Atlantic whitefish in a captive rearing environment is virtually the same as that of the anadromous population that existed on the Tusket River prior to 1982. A re-construction of the prevalence, location, and date of construction of man-made dams in southwestern Nova Scotia rivers in 1926 indicates that river accessibility was probably impeded in the decades prior to the first description of Atlantic whitefish as a species in 1922. Removal of many of these dams, and a strengthened regulatory framework concerning fish passage around existing structures suggest that the level of threat to recovery arising from inadequate fish passage is likely lower today than it may have been prior to 1922. Therefore, and in light of the only limited information about the past distribution of Atlantic whitefish, any watershed within Nova Scotia could be considered a potential candidate for Atlantic whitefish introduction, particularly watersheds lying within the bounds of their known former range. Information about past abundance or productivity of Atlantic whitefish populations is not sufficient to form a basis for establishing watershed-specific abundance recovery targets or the number of populations required to ensure long-term viability. The minimum census population size required to maintain genetic diversity is estimated to be in the vicinity of 550 – 2,000 mature individuals. An interim watershed specific abundance target above the mid-point of this range (i.e., above 1,275 mature individuals) is proposed.

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