Dam removal and salmon science


Pacific salmon face grim times.  The plight of Canada's Fraser River sockeye has fixated fishers, scientists, and the state for decades.  Concern has grown since the 1990s as annual runs went from bad to frightening, but then last summer’s run was bafflingly great.  The Canadian government federal government in Ottawa formed the Cohen Commission in November 2009 to assess the situation.  It is still grinding through a very complex set of riverine and oceanic factors, and it is not clear members can reach consensus by their current deadline of June 30.

Evolve or die:  that seems to be the theme of many recent events. The Cohen Commission is grappling with a range of issues that include, but are not limited to, rising river temperatures, degrading ocean conditions, and harmful effects from salmon farms.  Many members seem inclined to blame a combination of the above and perhaps more, but scientific explanations for how elements interact lag behind, and controlled experiments [pdf] may not be possible.

We are witnessing very rapid changes in ecology, technology, and politics, all of which are selecting for dynamic traits.  Populations and arguments incapable of adapting may well go extinct, and this applies to fish and environmentalists.

Environmental change may moot even cutting edge research.  A forthcoming study from ICES has linked population-level shifts in Pacific salmon abundance to climate change.  Findings are complicated by the ever changing extent of artificial fish propagation and by assumptions about relationships between abundance and harvests that seem debatable, but the take home message is chum and pink salmon have done better than sockeye and much better than chinook and coho, and success corresponds to more northerly ocean ranges, itself a proxy for climate change.  Even worse news came last week in the journal Science, when researchers announced that the Fraser’s warming waters pose lethal risks to sockeye.  The authors try to be hopeful but admit that “warming river temperatures could exert strong selective pressure for physiological adaptation,” which is a polite way of saying some stocks must evolve or die.