Nutrient fluxes and the recent collapse of coastal California salmon populations

Canadian Journal of Fisheries and Aquatic Sciences
By: , and 

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Abstract

Migratory salmon move nutrients both in and out of fresh waters during the different parts of their life cycle. We used a mass-balance approach to quantify recent changes in phosphorus (P) fluxes in six coastal California, USA, watersheds that have recently experienced dramatic decreases in salmon populations. As adults, semelparous Chinook (Oncorhynchus tshawytscha) and coho (Oncorhynchus kisutch) salmon imported 8.3 and 10.4 times more P from the ocean, respectively, than they exported as smolts, while iteroparous steelhead (i.e., sea-run rainbow trout, Oncorhynchus mykiss) imported only 1.6 times more than they exported as kelts and smolts. Semelparous species whose life histories led them to import more nutrients were also the species whose populations decreased the most dramatically in California in recent years. In addition, the relationship between import and export was nonlinear, with export being proportionally more important at lower levels of import. This pattern was driven by two density-dependent processes — smolts were larger and disproportionately more abundant at lower spawner abundances. In fact, in four of our six streams we found evidence that salmon can drive net export of P at low abundance, evidence for the reversal of the "conveyor belt" of nutrients.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Nutrient fluxes and the recent collapse of coastal California salmon populations
Series title Canadian Journal of Fisheries and Aquatic Sciences
DOI 10.1139/f2011-054
Volume 68
Issue 7
Year Published 2011
Language English
Publisher NRC Research Press
Contributing office(s) Cooperative Research Unit Seattle
Description 10 p.
First page 1161
Last page 1170
Country United States
State California
Online Only (Y/N) N
Additional Online Files (Y/N) N