Swimming performance of juvenile white sturgeon (Acipenser transmontanus): training and the probability of entrainment due to dredging

Abstract

Summary White sturgeon, Acipenser transmontanus (Richardson), are at risk of entrainment from dredging, with young-of-the-year fish at greatest risk. To evaluate this entrainment risk, swimming performance trials were conducted in a laboratory swim tunnel with hatchery-reared juvenile white sturgeon with varying experience levels including: naive (only tested once), tested (re-tested after being kept in no flow) and trained (re-tested after kept in flow for nearly three weeks). Individuals of various sizes (80–100 mm TL) and all experience levels were strongly rheotactic (> 80%), but endurance was highly variable among fish. Small juveniles [ 93 mm TL) naive fish (42–45 cm s−1), all of which had lower escape speeds than trained fish (72 cm s−1). Behavior was also highly variable among fish. Overall, benthic station-holding behaviors were least frequent in small fish, intermediate in medium and large fish, and most frequent in trained large fish. Probability of entrainment of juvenile white sturgeon can be reduced by maintaining dredge head flow fields at less than 45 cm s−1 for wild-spawned fish or by rearing hatchery fish to > 93 mm TL and exposing the fish to moderate flow velocities (10–12 cm s−1) prior to their release.