Field Testing of New Monitoring Protocols to Assess Brown Trout Spawning Habitat in an Idaho Stream

Abstract

Abstract The effects of nonpoint source pollution on salmonid incubation and embryo survival to emergence were evaluated on Rock Creek in south-central Idaho. New monitoring protocols were applied to evaluate effects ofsediments and associated pollutants on spawning and recruitment of brown trout Salmo trutta. According to these new protocols, incubation success in artificial egg pockets is measured in terms of intragravel dissolved oxygen (IGDO), percent fine sediment (<2.0 mm) in the substrate, and survival of embryos and alevins to emergence. Mean IGDO concentrations and saturation levels were significantly less (P < 0.05) at stations affected by agricultural pollutants than at a control station. Up to 40% of IGDO measurements were below 6.0 mg/L, the proposed water quality criterion for salmonid spawning in Idaho streams. Mean values for percent fine sediment were also higher at all impacted stations. Survival to emergence at the control station ranged from 18 to 83% and averaged 48%. Survival at impa...