Predation on Early Life Stages of Lake Sturgeon in the Peshtigo River, Wisconsin

Abstract

Mortality of early life stages can limit recruitment of fishes, and understanding the impacts of various sources of mortality has long been a goal of fisheries management. The impacts of predation on lake sturgeon Acipenser fulvescens are not well understood. The objective of this study was to identify and quantify sources of predation that affect lake sturgeon eggs, larvae, and age-0 juveniles in the Peshtigo River, Wisconsin, during 2006 and 2007. Egg bags were used to assess the rate of lake sturgeon egg consumption by crayfishes Orconectes spp. Potential piscine predators on eggs, larvae, or age-0 juveniles were captured using fyke nets, gill nets, hoop nets, and electrofishing for analysis of stomach contents. Crayfish consumed lake sturgeon eggs at an average rate of 9.4 eggs/d, and the population of crayfish within the lake sturgeon spawning habitat consumed an estimated 300,000 eggs during the incubation period. Numerous fish species were observed consuming lake sturgeon eggs, and piscine predators likely consumed most eggs that settled on the surface of the substrate. Within 862 predator stomachs, only a single lake sturgeon larva was observed, and there was no evidence of predation on age-0 juveniles. These results suggest that predation could limit recruitment at the egg stage, but it does not appear to be limiting to the larval and age-0 juvenile life stages in the Peshtigo River.