DOWNSTREAM MIGRATORY BEHAVIOR OF HATCHERY-REARED, RADIO-TAGGED ATLANTIC SALMON (SALMO-SALAR) SMOLTS IN THE PENOBSCOT RIVER, MAINE, USA

Migratory patterns and timing of smelt movements of Atlantic salmon (S almo salar) were assessed by placing radio tags on salmon in 1990 and 1991 and releasing fish at Howland, Maine, about 91 km upstream from t he mouth of the Penobscot River. Fish movements were tracked by vehicl es on streamside roads and by airplanes. Fish released in April moved quickly into the main channel of the river, although 47% of the signal s ceased or became stationary within 10 km of the release site, owing to predation, battery failure, or cessation of migratory behavior. Onl y 3% of smolts were tracked over 40 km downstream. Of those fish activ ely migrating downstream, the passage rate averaged 3.7 km day(-1), ra nging from 0.5 to 15.7 km day-1.