A new study on Alaska sockeye salmon shows that population diversity within a species plays a vital role in maintaining stable fisheries.
The study, published in the 3 June edition of the journal Nature and led ecologist Daniel Schindler and fisheries biologist Ray Hilborn, both of the University of Washington, quantifies for the first time how much a fish species depends on this “portfolio effect.”
Sockeye salmon are finely tuned to the individual streams and lakes in which they were born, resulting in incredible population diversity. Without this diversity, the Bristol Bay sockeye fishery would close 10 times more frequently — once every two or three years versus once every 25 years, said the study’s authors.
“Mother Nature does a pretty good job dealing with uncertainties — climate change, for instance — by producing a diversity of populations,” said Schindler. “In terms of fisheries, we need to have a longer-term vision for the viability of populations; the populations that are strong now are not necessarily going to be strong in coming years, so we need to protect weaker populations, too, as insurance for the future.”
The study’s authors said fisheries managers need to prioritize preserving population density within a species. This requires aggressive protection of the habitat networks that ultimately generate and maintain population diversity, both of which will become increasingly important as a first line of defense against climate change.
“We believe this new evidence is a game-changer for managing species and entire ecosystems,” said Schindler. “Population diversity of species is often overlooked by managers and conservationists. Yet, in general, current rates of population loss are probably a thousand times higher than species loss.”
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