Post-Smolt Emigration Times and Migration Through the Gulf of Maine

Emigration of Atlantic salmon smolts from Maine rivers now occurs two weeks earlier than it did in the 1960s. This shift is consistent throughout the Atlantic salmon’s range, and has been attributed to changing environments in the ocean and in coastal rivers (reduced snowpack, earlier ice out, and fluctuating water inputs). Multiple hypotheses exist on how this shift could challenge post-smolt survival: mismatch in environments, shifting forage bases, and predator fields. Recent telemetry assessments of Atlantic salmon smolt migrations from Maine rivers to the Scotian Shelf have provided novel information on fish entry and exit from the Gulf of Maine. To better understand the potential impacts of these shifts, we combined migration-timing data with telemetry speeds to simulate spatial-temporal distributions. Our goal was to illustrate theoretical changes in spring distribution of post-smolts in the Gulf of Maine. Highlighting these differences in timing through the Gulf of Maine is a first step in identifying the Atlantic salmon’s response to a changing environment.  The implications of this shift are unknown, but we believe visualizing them will inform modelers and managers to further explore spatial-temporal approaches.