Research Document - 1999/030

Annual and decadal change in Atlantic salmon (Salmo salar) abundance in eastern Canada.

By G. Chaput and E. Prévost

Abstract

The data series of returns and at-sea survivals of Atlantic salmon to monitored rivers in eastern Canada are used to address three issues: 1) whether returns and sea survivals in 1997 were unusual, 2) whether there were spatial and or temporal correlations in the returns and sea survivals, and 3) whether there are spatial patterns in the returns trends in the last decade. The survival rates to 1SW salmon and 2SW salmon observed for the 1997 returns were among the lowest observed in the recent 5-year and 10-year time periods. There was a broad scale pattern of decline from the previous year in survival rates of 1SW and 2SW salmon across the monitored rivers of eastern Canada in 1997. The probability of such a broad scale decline by chance alone was less than 4%. There was a broad spatial scale decline in the small salmon returns to eastern Canada in 1997 relative to 1996 with declines observed in over 80% of rivers. The trends in returns of small salmon and large salmon provide a geographically segregated picture of abundance patterns for four geographic areas of eastern Canada. Strong declines characterise the rivers of the Bay of Fundy and Atlantic coast of Nova Scotia. Rivers in Québec are characterised by declining or relatively stable abundance. The southern Gulf of St. Lawrence rivers are defined by declining through stable through slight increased abundance. Finally, insular Newfoundland rivers are characterised by stable through increasing through strongly increasing abundance. The contrasts in the patterns of evolution of the returns over the last decade prevent the formulation of any general statement regarding an overall improvement or deterioration of Atlantic salmon status in eastern Canada.

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