An ecological comparison of two endemic species of whitefish in Bear Lake, Utah/Idaho (Utah, Idaho)

Ecological traits of the endemic Bear Lake whitefish Prosopium abyssicola and the Bonneville whitefish Prosopium spilonotus were investigated. Spatial distributions indicated distinctive differences in depth contour preference. Catch per unit effort data indicated that Bonneville whitefish prefer shallow depths and warmer water temperatures, whereas Bear Lake whitefish prefer deep, cold water.; Diet differences between the two species were large. Differences in both age distribution and growth rate patterns were also observed. The Bonneville whitefish population was predominantly composed of juvenile age classes. Very large adults reached ages of 12–14 years. Bear Lake whitefish exhibited a different population structure with few young fish and larger proportions of older age classes. Some of these fish were aged over 35 years old. Both analyses suggest that the population structure of each species is the result of a stable or growing population.