Movement Patterns and Size‐Class Influence Entrainment Susceptibility of Lake Sturgeon in a Small Hydroelectric Reservoir

Abstract

AbstractHydroelectric development is considered a threat to the recovery of Lake Sturgeon Acipenser fulvescens populations, in part because of injury and mortality concerns caused by interaction with hydroelectric facilities. Lake Sturgeon resident in small impoundments may be particularly susceptible to entrainment, depending on movement and habitat usage patterns. Using acoustic telemetry, we monitored coarse‐scale movements of 99 juvenile, subadult and adult Lake Sturgeon captured throughout a 10‐km‐long hydroelectric reservoir. Overall, adults moved over larger ranges than did smaller size‐classes. However, all size‐classes utilized habitat immediately upstream of hydroelectric facilities, and during the 18‐month study period, 27% of subadults tagged in the lowermost section of the reservoir, and 8.7% of adults tagged throughout the reservoir were entrained. Movements of juveniles and subadults were generally restricted to extended sections (2–6 km) of contiguous deepwater habitat (>15 m), and passage through the two shallow river narrows that subdivide the reservoir were rare. Over half of the tagged adults (52%) moved upstream or downstream through one or both river narrows, albeit infrequently. Initial residency influenced entrainment susceptibility for juveniles and subadults but not for adults. Results suggest that Lake Sturgeon resident in small impoundments are susceptible to entrainment. However, the presence of river narrows, which function as natural movement restrictors, may largely preclude susceptibility of juveniles and subadults resident in upstream sections.