Why Life History Diversity is Critical to Salmon Survival

This year’s Chairman’s Council Luncheon featured a presentation by Dr. Nathan Mantua, Climate Impacts Group, highlighting the need to protect and restore salmon life history diversity as a strategy to ensure they persist through anticipated environmental changes brought on by climate change.

Salmon as a species employ a diverse set of life history types, resulting in a wide range of variations within spawning timing, freshwater rearing periods, smolt migration timing, and ocean migration patterns. Historically, salmon have relied on this diversity in tandem with a second strategy – massive population sizes – to carry them through periods of environmental change. Now, as we face a future climate certain to be different from what it is today, we must ask ourselves if salmon have the resources they need to survive into the future.

The 2008 and 2009 commercial salmon fishery collapse in California suggests that, in areas where few wild fish are present, perhaps they are ill equipped to deal with environmental changes. In that case, a population of monoculture hatchery fish encountered unfavorable ocean conditions during the out-migrant life history phase, and very few survived to adulthood. A more diverse assemblage of Chinook populations with various life history traits would have buffered overall abundance during this unfavorable period. In this example, hatcheries were part of the problem, but it’s possible that they don’t have to be.

Long Live the Kings believes hatcheries can play a positive role in the effort to recover wild salmon. In his Chairman’s Council presentation, Dr. Mantua outlined a “climate insurance” program for wild salmon. He called for the protection and restoration of complex and connected freshwater and estuary habitat combined with a management approach that will build abundance and diversity. This makes necessary a harvest managed so that enough adult salmon could spawn to fill habitat niches. LLTK is exploring the potential for limited, targeted use of supplementation to build abundance in key watersheds where the habitat and harvest conditions described by Dr. Mantua exist.

Download Dr. Mantua's presentation slides here.