The need to see a bigger picture to understand the ups and downs of Pacific salmon abundances

Abstract

There are more Pacific salmon in the ocean recently than in recorded history. Increases are believed to be related to shifts in climate but specific, biologically based mechanisms linking climate to increases are not known. At the same time, Pacific salmon abundances in Japan and on Canada's west coast are at historic low levels with attempts to stop the decline unsuccessful. Most juvenile salmon that enter the ocean die, resulting in large abundance increases and decreases from small changes in the already very low ocean survival. Because of this sensitivity to changes in ocean ecosystems and because of the recent basin-scale fluctuations in trends in abundance, I propose that it is time to see a bigger picture and improve the understanding of the biological mechanisms that most influence ocean survival. I leave it to readers to decide if my example of Pacific salmon is part of a more general need in fisheries science to better understand the biological mechanisms linking survival to climate.