Atlantic Fisheries Research Document 1996/047

Ratio of adults to experimental ponds area juveniles in a prediction of Atlantic salmon (Salmo salar L.) returns to the Gander River, Newfoundland in 1996

By P.M. Ryan; R. Knoechel; M.F. O'Connell; E.G.M. Ash

Abstract

Spring population sizes of juvenile Atlantic salmon were determined by Schnabel multiple, mark-recapture methods in two Experimental Ponds Area (EPA) lakes at the headwaters of the Gander River from 1979-95. Juvenile abundance in 1995 was considerably higher than expected as indicated by a previously derived stock-recruit relationship between juvenile abundance and adults returning to the Salmon Brook fishway on a lower river tributary four years earlier.

Total river adult (small salmon <63 cm) returns were obtained over the period 1989-95 at the counting fence near the mouth of the river and the fish angled downstream of the fence. Changes in the ratios of returning small salmon to the juvenile abundance one year earlier were indicative of a more than fourfold (4.8 X) increase in the average marine survival of Gander River salmon following closure of the commercial fishery in 1992. Total river adult returns in 1996 were projected from 1995 juvenile abundance and the post-commercial fishery ratio of returning small salmon to the juvenile abundance one year earlier. Projections indicate that 37,014 small salmon will return to the Gander River to spawn in 1996 and will exceed the current target spawning requirement in 1996.

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