Research Document 1998/46

Analyses of trends in returns of Atlantic salmon (Salmo salar) to rivers in Nova Scotia and Bay of Fundy, New-Brunswick, and status of 1997 returns relative to forecasts

P.G. Amiro, C.J. Harvie, S.F. O'Neil and T.L. Marshall

Abstract

This paper explores the spatial and temporal distribution of salmon return patterns among stocks of Nova Scotia and southern New Brunswick, the status of 1997 returns, the relative performance of wild and hatchery smolts and the condition of wild one-sea-winter returns to Morgan Falls, LaHave River. Temporal trends of small and large salmon returns were examined relative to time periods associated with the Salmon Management Plan of 1984 and the Newfoundland commercial salmon fishing moratorium of 1992. The analyses indicated a high degree of coherence among most Atlantic salmon stocks in the areas examined. Prior to the Salmon Management Plan (1970-1983), trends were generally increasing; trends over the years 1984-1997 were predominantly decreasing. Based on the 1984-1996 trends, 1997 returns were below expected returns in most data series. Low returns to the Liscomb, LaHave and Saint John fishways relative to forecasts, especially those based on 20-25 year forecast models, provide a strong indication of low recruitment in 1997 from both the 1995 and 1996 smolt classes. Estimated one-sea-winter and multi-sea-winter wild and hatchery returns to the Saint John and LaHave rivers were well below the forecast returns. Wild smolts migrating in 1996 from above Morgan Falls were 4.8 times more likely to survive to return than hatchery smolts. The condition of age 2.1 wild fish moving through the Morgan Falls fishway before August 1 over the years 1985-1997 increased significantly, while no temporal trends were detected in mean length or weight. The coefficient of skewness of the lengths of all age 2.1 wild fish increased significantly over the 1970-1997 period, indicating a decline in smaller fish of that age.

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