Abstract
Migration is a widespread but highly diverse component of many animal life histories. Fish migrate throughout the world’s oceans, within lakes and rivers, and between the two realms, transporting matter, energy, and other species (e.g. microbes) across boundaries. Migration is therefore a process responsible for myriad ecosystem services. Many human populations depend on the presence of predictable migrations of fish for their subsistence and livelihoods. Although much research has focused on fish migration, many questions remain in our rapidly changing world. We assembled a diverse team of fundamental and applied scientists who study fish migrations in marine and freshwater environments to identify pressing unanswered questions. Our exercise revealed questions within themes related to understanding the migrating individual’s internal state, navigational mechanisms, locomotor capabilities, external drivers of migration, the threats confronting migratory fish including climate change, and the role of migration. In addition, we identified key requirements for aquatic animal management, restoration, policy, and governance. Lessons revealed included the difficulties in generalizing among species and populations, and in understanding the levels of connectivity facilitated by migrating fishes. We conclude by identifying priority research needed for assuring a sustainable future for migratory fishes.
Highlights
Migration is an adaptive and widely expressed behavior within the animal kingdom
How does land use change affect the delivery of accurate cues for migrating fishes?
We explore key questions related to conservation management below
Summary
Migration is an adaptive and widely expressed behavior within the animal kingdom. Species’ movements among habitats, whether by solitary individuals or as synchronized collective displacements by many animals, facilitate exploitation of patchy and seasonally variable resources, which is key to species’ reproduction and persistence (Baker, 1978; Jørgensen et al, 2008). Recent evidence suggests that stress levels and nutritional status can both impact migration distance and success in salmonids (Bordeleau et al, 2018; Birnie-Gauvin et al, 2019a) Few such studies exist, but these can shed light on the mechanistic links between internal state and migratory behavior. But these can shed light on the mechanistic links between internal state and migratory behavior These synergies are especially important given ecological consequences of recent human-mediated trait changes to fish populations (Jørgensen et al, 2007; Palkovacs et al, 2012; Rahel and McLaughlin, 2018). We provide a series of questions to guide future inquiry into the effects of fish internal state on movement and migration: 1. What are the internal physiological drivers of, and triggers for, migration?
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