Factors Affecting Recruitment of Age-0 Muskellunge in Escanaba Lake, Wisconsin, 1987–2006

Abstract

We modeled variation in recruitment (R) of age-0 muskellunge Esox masquinongy to identify factors influencing their abundance in Escanaba Lake, Wisconsin. Muskellunge R declined over the study period and ranged from 0.00 to 1.85 age-0 fish/km of shoreline (mean = 0.42 age-0 fish/km of shoreline). A Ricker stock–recruitment model determined that the following factors explained 88% of the variation in annual R of age-0 muskellunge between 1987 and 2006: abundance and age structure of the adult muskellunge population, abundance of bluntnose minnow Pimephales notatus, abundance of age-3 and older (age-3+) walleyes Sander vitreus, abundance of age-0 white suckers Catostomus commersonii, and coefficient of variation (CV) of May water temperatures. Abundance of adult muskellunge (≥76.2 cm total length) accounted for only 1% of the variation in R and showed no significant relationship with R. Abundance of bluntnose minnow improved the model fit to 40% of the variation in R and indicated that higher R was achieved with greater numbers of bluntnose minnow. The average age of adult muskellunge further improved the model fit to 59% of the variation in R, suggesting that R increased when more young adults were present in the population. The abundance of age-3+ walleyes enhanced the model fit to 69% of the variation in R and indicated that greater R occurred with high numbers of walleyes. The abundance of age-0 white suckers improved the model to explain 77% of the variation in R and indicated that more recruits occurred when numbers of age-0 white suckers were low. Finally, the CV of May water temperatures further improved the model to explain 88% of the variation in R and signified that lower variability in May water temperatures was beneficial to recruitment success. We interpret the model results to mean that muskellunge R in Escanaba Lake is regulated by the reproductive potential of the adult muskellunge population, forage availability, variation in May water temperatures, and other community dynamics.