Effects of Jaw Tagging on Growth and Scale Characteristics of Landlocked Atlantic Salmon, Salmo salar

Abstract

Recapture of 165 annual and biennial spawners of landlocked Atlantic salmon (Salmo salar) from 1239 fish tagged on the spawning grounds from 1953 to 1955 at the Fish River Lakes, Maine, showed that jaw-tagged females grew significantly slower than untagged female of identical ages and cycles. For most maturing male salmon, growth increments were not significantly reduced by jaw tagging. A tendency for decreased growth increments with increase in age was apparent for both tagged and untagged fish.Recognizable annuli were formed on the scales of 77–100% of 97 male salmon and of 74–97% of 187 female salmon between tagging and recapture. A significantly smaller percentage of females (74%) than males (100%) at large 1 year and recaptured on the spawning grounds had formed a recognizable annulus, but there was no significant difference between females (86%) and males (91%) recaptured by anglers. The significantly lower annulus recognition for annual female spawners was attributed to their demonstrated slower growth rate and possibly resorption of minimal marginal scale growth.Spawning checks were recognizable on the scales of 69–100% of 97 males and 49–78% of 187 females recaptured. Male salmon recaptured on the spawning grounds formed a significantly higher percentage of recognizable spawning checks than females (both annual and biennial spawners), but there were no significant differences between sexes for angler-recaptured fish. Lower reliability in spawning check recognition for females was attributed to less severe marginal resorption resulting in no spawning check being formed or obliteration of previous spawning checks by resorption of the small amount of marginal scale increment made by some annually spawning females, or both.