The importance of measuring biotic and abiotic factors in the lower egg pocket to predict coho salmon egg survival
Abstract:Based on results from simulated redds of coho salmon Oncorhynchus kisutch, the amount of fine sediment <0·5 mm in the lower half of the egg pocket, rather than the entire egg pocket of the redd, was a strong predictor of egg survival to hatching ( r2 = 0·62). The relationship was much stronger than observed in other studies, which typically ignore egg pocket structure. Abundance of a fish egg-eating worm, Haplotaxis ichthyophagous, an oligochaete that may have been attracted to fine sediment and dead eggs in the egg pocket, was also associated with a decrease in egg survival. The worm, however, accounted for little of the variance in survival compared to fine sediment. Only 10% fine sediment (<0·5 mm) in the lower pocket was required to decrease survival from 100 to 5%. Other abiotic factors had weaker (gravel permeability) or non-existent (dissolved oxygen) correlations with survival.
Document Type: Regular Paper
Affiliations: Department of Botany, P. O. Box 3165, University of Wyoming, Laramie, Wyoming 82071, U.S.A.
Publication date: March 1, 2003