Distribution of U.S. Atlantic Salmon Postsmolts in the Gulf of Maine

Atlantic salmon Salmo salar of U.S. hatchery origin were captured as postsmolts by surface trawling during spatial surveys in late May to mid-June in the northeastern Gulf of Maine in 2002 and 2003. Most marked and unmarked postsmolts were from the Penobscot River, but some were also from the Dennys and other rivers of the Gulf of Maine. The capture rate of stocked smolts was very low(<= 0.01%), and it was highest for marked smolts from known rivers and proportional to numbers stocked. Marked postsmolts were caught 16-43 d after their release as smolts and 89-240 km from their river of origin. The rate of migration from different rivers differed and varied annually, and it accounted for some of the observed differences in capture rate. The weight of postsmolts from known rivers was greater than at smolt stocking and river exit, indicating early marine growth. The distribution of U.S. postsmolts from different rivers was similar, and they were often caught together, as were those from the same river. As a result of this close association during migration, postsmolt catches were aggregated at a few adjacent locations in several areas of the Gulf of Maine. Postsmolts crossing the Gulf of Maine were found east of Jordan Basin and most were along a corridor near shore at the eastern edge of the area surveyed along the southwest coast of Nova Scotia, Canada. Postsmolts of U.S. origin were found in areas used by other salmon populations also leaving the Bay of Fundy during May and June. This seasonal occurrence in a specific coastal area provides an opportunity to manage activities within that corridor to mitigate potential losses of Atlantic salmon from endangered and threatened populations in North America.