Investigating patterns and extent of predation of hatchery-reared juvenile Nechako white sturgeon (Acipenser transmontanus) by North American river otter (Lontra canadensis) in the Nechako River, British Columbia, Canada

Abstract

Predation of fish released as part of conservation aquaculture programs may undermine conservation goals. Identification of factors influencing predation, therefore, can inform management decisions that minimize predation losses. For the endangered Nechako white sturgeon ( Acipenser transmontanus Richardson, 1836), the survival of individuals released as part of a conservation aquaculture program is threatened by river otter ( Lontra canadensis (Schreber, 1777)) predation. Through the recovery of sturgeon passive integrated transponder (PIT) tags from otter latrines, we set out to quantify the extent of predation, identify spatial patterns in predation including identifying predation hotspots, and understand the timing of predation. The recovery of 3.9% of PIT tags from the hatchery-released sturgeon represents a minimum predation estimate based on several identified factors. The distribution of predation hotspots varied by release cohort, with some consistent hotspots among cohorts. An apparent decrease in predation in recent years was seen in conjunction with fewer live captures and lower release numbers, suggesting some level of density-dependent predation. Results from this study can be used to contribute to management decisions related to Nechako white sturgeon recovery efforts, inform further research needs, and contribute to a growing knowledge of sturgeon predation.