Movement And Mortality Of Atlantic Salmon Kelts (Salmo Solar) Released Into The Penobscot River, Maine

The Penobscot River is home to the last remaining major run of Atlantic salmon (Salmo salar) in the United States and the subject of a century-long stocking effort. Since the 1970s, most kelts have been released to the estuary after they spawn in a hatchery, and the iteroparous share of the run has declined to <1%. We tagged with a radio transmitter 55 kelts that had spawned at a hatchery in 2015, and released them at two locations (head of tide and -50 km upstream) to assess 1) when kelts leave the river, 2) whether release location influences the timing of river exit, and 3) whether kelts from the upper river could outmigrate through the hydroelectric complex of the river. The kelts were tracked from November 2015 to July 2016. Although fish from both release groups left the system within one month, the majority (84%) overwintered in freshwater. Many (71%) kelts that overwintered in freshwater made upstream movements in November and December. There was no difference in upstream movement rates, timing of outmigration, or survival between the release groups. Survival to outmigration was 23.6%. This low survival to outmigration may have contributed to the precipitous decline in iteroparous Atlantic salmon from the Penobscot River over the last four decades.