The Forgotten Pink Salmon in the Laurentian Great Lakes: An Unexpected Invasion With Insights for Three Oceans

ABSTRACT Introductions of species outside their native range, such as pink salmon ( Oncorhynchus gorbuscha ) in the Laurentian Great Lakes, can serve as unplanned experiments that provide new insights into ecological adaptation. We synthesize available information on the understudied Great Lakes pink salmon invasion and highlight how this case can inform research and management related to expansions and invasions of this species in the Pacific, Arctic and North Atlantic Oceans. Accidentally introduced to Lake Superior in 1956, pink salmon quickly spread to all five Great Lakes, displaying unexpected behaviours and life history plasticity. This invasion history demonstrates a remarkable ability of pink salmon to establish from a small founder population, colonize large areas, produce explosive year classes to rapidly increase in abundance, and complete a full life cycle entirely in freshwater. One of the most striking changes is a shift from their rigid 2‐year Pacific life cycle to a variable maturation age ranging from 1 to 4 years, likely influenced by prey availability as well as temperature and other environmental factors. We discuss implications for expansions elsewhere and outline five research themes necessary for understanding pink salmon dynamics in the Great Lakes with broader relevance for managing the species everywhere: (1) What drives rapid changes in abundance? (2) How do temperature extremes influence their ecology? (3) What causes departures from the 2‐year life cycle? (4) How important is it for the phenology of life history events to match new habitats? (5) What guides pelagic movements and straying in new habitats?