Assessment of the status, vulnerability and prognosis for Atlantic salmon stocks of the Southern Upland of Nova Scotia / P.G. Amiro.: Fs70-1/2000-062E-PDF

The status, vulnerability to extirpation, and prognosis for Atlantic salmon populations of the Southern Upland of Nova Scotia are assessed with respect to the impact of acidification and low marine survival. Management measures involving stocking and pH manipulation to enhance the probability of persistence of the stocks and to provide harvests are numerically assessed. A total of sixty-rive rivers was identified where 84.8 million square meters of salmon habitat remain. Previous categorization of status and vulnerability indicated fourteen rivers with pH less than 4.7 where populations were extirpated, twenty-four partially impacted (pH 4.7-5.0) and twenty-two low impacted (pH 5.1) rivers. Analysis of forty-seven rivers, based on mean winter pH in 1985 and 1986 and assumed marine survival rate of 10%, indicated that 55% or 26 of the rivers would become extirpated. At 5% assumed marine survival, 85% or 40 of the forty-seven rivers will become extirpated. At 5% marine survival even the low pH-impacted rivers will not provide surplus for harvest without enhancement i.e. hatchery supplementation. Hatchery supplementation in pH-impacted rivers without pH improvement was shown to be ineffective. Recent electrofishing has determined that 28% of rivers fished were void of salmon parr, a proportion that was in close agreement with projections from a model based on mean winter pH. Juvenile population survey and sampling are recommended to further validate the models and to provide tissue samples for genetic analyses that may document population structure among rivers of the Southern Upland.

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