Early Life Stage Mortality Rates of Lake Sturgeon in the Peshtigo River, Wisconsin

Abstract

AbstractA thorough understanding of the early life history of lake sturgeon Acipenser fulvescens is critical for rehabilitation of this species. Recruitment of lake sturgeon is known to be variable, but the extent of that variation and mortality rates experienced by early life stages are unclear. The objective of this study was to quantify early life stage mortality and explore the variability in year‐class strength by estimating total egg deposition and abundance of larval and age‐0 juvenile lake sturgeon from the 2006 and 2007 year‐classes in the Peshtigo River, Wisconsin. Egg mats, drift nets, and visual surveys were used to collect lake sturgeon eggs, larvae, and age‐0 juveniles, respectively. Total egg deposition, larval abundance, and age‐0 juvenile abundance were higher in 2007 than in 2006. The magnitude of difference ranged from 2 times for eggs to 11 times for age‐0 juveniles. The rate of mortality from the larval stage to the age‐0 juvenile stage was higher in 2006 (98.26%) than in 2007 (90.46%); overall mortality from the egg stage to the age‐0 juvenile stage was also higher in 2006 (99.98%) than 2007 (99.93%). These results suggest that mortality rates for these life stages of lake sturgeon are high, and large variation in early life stage abundance may be common. Management strategies to reduce these mortality rates may increase recruitment and aid population recovery.