Applying the Krogh Principle to Find Shortcuts to Understanding Pacific Salmon Production

The Krogh Principle states that the selection of a particular animal can greatly facilitate understanding a particular mechanism. The principle could be applied to populations of Pacific salmon that are particularly productive within a region as a way of understanding more easily the mechanisms that regulate the productivity of all Pacific salmon. We show that an aggregate of Chinook salmon populations from the South Thompson River in the Fraser River drainage in British Columbia have anomalously high production, most likely related to their late ocean-entry life history. Similarly, sea-type Harrison River sockeye salmon from the same drainage also have a late ocean-entry life-history type and also have been exceptionally productive in recent years. These examples provide evidence that the exceptional production of late ocean-entry populations of Chinook and sockeye salmon may be caused by climate-related abundance increases in particular species of plankton in the early summer in the Strait of Georgia. The increased abundance of a preferred prey would allow the late ocean-entering juveniles to grow faster and be in better condition in the early marine period than the earlier ocean-entering juveniles. An understanding of the genetic, metabolic, and hormonal reasons for the improved productivity of these populations could help identify common mechanisms affecting productivity of other species of Pacific salmon.