| Unusual or unnatural elevation of suspended sediment in streams is known to adversely affect Pacific salmon (Oncorhynchus spp.) at different life stages, yet conspicuously lacking is knowledge of the effect of suspended sediment on egg fertilization and spawning success. Rainbow trout (O. mykiss), and sockeye (O. nerka) and coho (O. kisutch) salmon were used to investigate the impact of different concentrations of suspended sediment particles on the ability of sperm to successfully fertilize eggs. The fertilization process was simulated both in the field and in the laboratory using two different controlled flow water flumes with concentrations of suspended particles up to 47,000 mg·L −1. Egg fertilization success was assessed at eyed stage after incubating eggs in the streambed at the field location, or in artificial laboratory egg incubation (Heath) trays. Results suggest that suspended sediment concentrations greater than 1,500 mg·L−1 could negatively impact the percent of eggs successfully fertilized, and that large (>25%) reductions in the percent of successful fertilizations could occur when suspended sediment levels are in excess of 8,300 mg·L−1. In the absence of other experimental information, the negative relationship between suspended sediment concentration and fertilization success derived herein serves as a preliminary guideline for environmental management decisions and fisheries impact assessment, though differences between the experimental conditions created by the flume and the natural spawning environment must also be considered. |
