Updated information on Atlantic salmon (Salmo salar) populations in Nova Scotia’s southern upland (SU; Salmon Fishing Areas 20, 21, and Part of 22) of relevance to the development of a 2nd COSEWIC status report

Abstract

The purpose of this research document is to summarize and update the present status and recent trends of Atlantic Salmon populations in the Southern Upland (SU) Designatable Unit (DU 14) of relevance to the development of the status report by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Based on genetic evidence, regional geography and differences in life history characteristics SU Atlantic Salmon is considered to be biologically unique (Gibson et al. 2011) and its extirpation would constitute an irreplaceable loss of Atlantic Salmon biodiversity. Within the SU DU, there are at least 72 rivers thought to contain, or to historically have contained Atlantic Salmon. The assessment of stock status is based on abundance of adults, juveniles and smolts in selected rivers, and the available data indicate that the abundances of SU Atlantic Salmon populations are low and declining. Region-wide comparisons of juvenile density data from more than 50 rivers indicate significant ongoing declines and provide evidence for river-specific extirpations. As of the most recent regional electrofishing survey, presence can be documented in 41% (22 of 54) of rivers that were assessed. Annual adult abundance data from four rivers show declines of 95% to 100% from maximum abundance, and Salmon returns to the SU index rivers (LaHave and St. Mary’s) have been below the conservation requirement every year for the past 3 generations of available data. The regional estimate for Atlantic Salmon predicts that in 2019 the SU DU would be have produced less than 4% (2.42–6.35 million eggs) of the estimated regional conservation requirement of 187.95 million eggs. A number of threats to Atlantic Salmon are identified in the freshwater and estuarine/marine environment of the SU DU, including habitat fragmentation, invasive fish species, acidification of freshwater habitat, illegal fishing/poaching, salmonid aquaculture, and marine ecosystem change.