Research Document 1998/126
Juvenile Atlantic salmon (Salmo Salar L.) abundance in the Experimental Ponds Area relative to adult returns to the Gander River as an index of marine survival: evidence for increased marine mortality in 1997
By R. Knoechel, P.M. Ryan, and M.F. O'Connell
Abstract
A marine survival ratio index was calculated as the number of adult salmon returning to the Gander River divided by the total juvenile salmon populations in the Experimental Ponds Area at the headwaters of the river in the previous spring. This survival index increased more than four-fold in the first four years (1992-95) following closure of the commercial fishery in 1992. The index dropped moderately in 1996 and then precipitously to pre-closure levels in 1997, suggesting that there has been a sudden decrease in marine survival despite the continued closure of the commercial fishery in insular Newfoundland. The observed 1997 Experimental Ponds Area juvenile abundance of 3112 would yield a predicted return of 25,643 small adults if the high survival observed during the early post-moratorium years (1992-95) was achieved but only 4,979 if the poor survival of 1997 was repeated. It is thus unlikely that the Gander River conservation requirement of 21,828 adult spawners will be met in 1998.
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