Research Document 1997/79
Evaluation of age specific and length specific estimates of juvenile Atlantic salmon (Salmo salar L.) abundance in the Experimental Ponds Area as predictors of adult returns to the Gander River
By R. Knoechel, P.M. Ryan, and M.F. O'Connell
Abstract
Models are evaluated which use age-specific and length-specific estimates of Experimental Ponds Area juvenile salmon abundance to predict total adult returns to the Gander River, Newfoundland, the following year. Restricting the juvenile estimate to age classes older than 2+, either singly or combined, resulted in lower statistical precision than using all age classes together. Length-specific models deleted the smaller juveniles from the population estimate starting with those 110 mm and then worked upwards in 10 mm increments. Restricting the juvenile estimate to fork lengths >120 mm provided adult return estimates with the greatest statistical precision and also produced a predicted 1996 adult return that was closer to the observed value. Incorporating the 1996 observed adult return into the length-specific models again resulted in maximum precision for the >120 mm fork-length model. This model predicts a 1997 Gander River adult return of 53,620 which is well above the conservation spawning requirement of 21,828 small salmon.
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