Prediction of Rainbow Trout Embryo Survival in Relation to Groundwater Seepage and Particle Size of Spawning Substrates

Abstract Several measures of the size composition of spawning substrates were used to describe the survival of preemergent embryos of rainbow trout Salmo gairdneri in a groundwater-fed streambed. Survival was not significantly related (P > 0.05) to the percentage of sediments smaller than 2.0 mm in diameter, the geometric-mean particle size, or fredle indices of substrate quality. However, survival strongly depended on the mean dissolved oxygen content and velocity of groundwater in redds. Dissolved oxygen concentrations were not related (P > 0.05) to measures of substrate size composition, and these variables accounted for only a limited proportion of the variance among redds in seepage velocities. These factors account for the lack of any significant association between survival and substrate size composition. The findings of this study imply that embryo survival models based on substrate size composition may not be entirely suitable for assessing the quality of spawning beds in groundwater-fed streams.