Congressional Briefing: Portfolio Effects in Fisheries

Mon, 01/24/2011

On January 24, 2011, Drs. Daniel Schindler and Robert Steneck presented recent science that illustrates the powerful influence population diversity has on the stability of fish stocks and, in turn, on the economic and social sustainability of human communities that depend upon them. The key to this stability is the “portfolio effect.”

It is common knowledge that species are going extinct at an alarming rate. Less well-known is the fact that genetically distinct populations within many species are going extinct as much as 1000 times faster than species themselves. For the first time, scientists have shown that high diversity at the population level makes species -- such as sockeye salmon -- less vulnerable to boom-and-bust cycles. Maintaining a diverse portfolio of populations helps species like salmon hedge against adverse conditions.

COMPASS brought Dr. Daniel Schindler, from the University of Washington, and Dr. Robert Steneck, from the University of Maine, to Capitol Hill to discuss the implications of their research into the portfolio effect. Schindler and Steneck drew connections between recent research results, published in journals such as Nature, and ongoing policy discussions.

Issues ranged from the Pebble Mine development in Alaska, where a proposed copper mine could disturb high quality habitat for salmon, to understanding how population diversity may be important in the decline of Steller Sea Lion populations in the Aleutian chain.

Some of their key take-home messages: 1) Population diversity (that is, a diverse portfolio of populations) helps keep fisheries robust, preventing frequent fisheries closures. The “portfolio effect” offers an important lens for understanding the significance of within-species diversity. 2) Diversity plays a key role for estuarine and open ocean species, whose breeding distributions may be more local than previously thought. 3) To avoid boom-and-bust cycles in natural resource stocks, protect diversity: Your weak stock today could be your strong stock tomorrow.