Date of Award

Spring 2001

Document Type



Life & Environmental Sciences

First Advisor

Grant Hokit

Second Advisor

John Addis

Third Advisor

Linda MacCammon


The effect of sedimentation on fish populations, especially the effect on reproduction, has been one of the most significant problems surrounding sedimentation pollution. Sedimentation has deleterious effects on the hatching and survival of trout eggs by reducing the egg’s access to oxygen and nutrients. To test for the effects of sedimentation, five streams in the Townsend, Montana area were examined. The effects of total suspended solids (TSS) as well as the individual effects of different particle sizes (clay, silt, sand) on trout reproductive success were measured. The number of rainbow trout hatchlings was not significantly associated with sand (p=0.794), silt (p=0.815), or clay (p=0.140). However, there was a significant negative correlation between TSS and trout numbers (p=0.043). Collectively, all the particles contributed to the reduction in trout hatchling numbers. Despite testing of individual particles, the individual effects of different particle sizes could not be observed, possibly because they could not be sufficiently isolated from the other particles within the sediment. The TSS results show a strong correlation between the amount of fine sediment and reproductive success of rainbow trout, supporting previous studies. Sedimentation does indeed lower the survival rate of salmonid eggs.