From salmon to shad: Shifting sources of marine-derived nutrients in the Columbia River Basin

Ecology of Freshwater Fish



Like Pacific salmon (Oncorhynchus spp.), nonnative American shad (Alosa sapidissima) have the potential to convey large quantities of nutrients between the Pacific Ocean and freshwater spawning areas in the Columbia River Basin (CRB). American shad are now the most numerous anadromous fish in the CRB, yet the magnitude of the resulting nutrient flux owing to the shift from salmon to shad is unknown. Nutrient flux models revealed that American shad conveyed over 15,000 kg of nitrogen (N) and 3,000 kg of phosphorus (P) annually to John Day Reservoir, the largest mainstem reservoir in the lower Columbia River. Shad were net importers of N, with juveniles and postspawners exporting just 31% of the N imported by adults. Shad were usually net importers of P, with juveniles and postspawners exporting 46% of the P imported by adults on average. American shad contributed <0.2% of the total annual P load into John Day Reservoir, but during June when most adult shad are migrating into John Day Reservoir, they contributed as much as 2.0% of the P load. Nutrient inputs by American shad were similar to current but far less than historical inputs of Pacific salmon owing to their smaller size. Given the relatively high background P levels and low retention times in lower Columbia River reservoirs, it is unlikely that shad marine-derived nutrients affect nutrient balances or food web productivity through autotrophic pathways. However, a better understanding of shad spawning aggregations in the CRB is needed.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title From salmon to shad: Shifting sources of marine-derived nutrients in the Columbia River Basin
Series title Ecology of Freshwater Fish
DOI 10.1111/eff.12348
Volume 27
Issue 1
Year Published 2018
Language English
Publisher Wiley
Contributing office(s) Western Fisheries Research Center
Description 13 p.
First page 310
Last page 322
Country United States
Other Geospatial Columbia River, John Day Reservoir