Research Document - 2006/027

Reproductive rates and rebuilding potential for two multi-sea-winter Atlantic salmon (Salmo salar L.) stocks of the Maritime provinces

By Chaput, G., and R. Jones

Abstract

The status of two multi-sea-winter Atlantic salmon (Salmo salar L.) stocks of the Maritime provinces of eastern Canada are compared and life history based characteristics and population dynamics are related to variations in abundance. Possible factors and life history stages which may be constraining the viability and the rebuilding potential of the stocks are discussed. The prognosis for the Miramichi River population remains positive as marine return rates appear sufficient for the population to replace itself. Size at age has increased and every female has the potential to produce more eggs than in the past, and there is a high survival to second and third spawning. Juvenile production remains high. The outstanding question is whether intra and inter-cohort competition of the juveniles is resulting in density dependent mortality of parr in the winter prior to smolting or whether reduced adult abundance is the result of reduced marine survival. Both factors are plausible for the Miramichi stock. The Saint John River population has generally failed to replace itself throughout the time period 1972 to 2004. For the last ten year classes, the lifetime egg production has been substantially below replacement. The dramatic decline in wild salmon reproductive rate strongly suggests that the increased mortality on the wild salmon post 1989 may in part be driven by a freshwater constraint associated with the environment at and above Mactaquac. Rebuilding potential for this stock in the absence of intervention is poor.

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