Using Acoustic Survey Data As a Tool for Characterizing and Forecasting Alewife Biomass

Hydroacoustic fisheries surveys have become standard for assessment of many fish species.  Such data can be used for stock assessment models, fisheries ecology, forecasting, and setting harvest levels.  Lakewide acoustic survey data from Lake Michigan will be used to highlight the potential of such surveys to go beyond "just monitoring".  One difficulty that has dogged efforts to forecast alewife biomass in Lake Michigan for more than a single year has been the volatility of the population.  Two primary sources of this volatility have been variable year class strength and variability in recruitment.  Utility of the survey data for short-term forecasts of alewife biomass will be explored to determine the degree to which such forecasts can be used to inform managers tasked with questions like "Should we maintain Chinook salmon stocking rates?"  The same acoustic data will be used to evaluate the influences of a number of biotic and abiotic factors on the survival of alewife from age-0 to age-1.  Both the forecasting analysis and exploration of factors influencing survival at early ages will allow evaluation of the degree of confidence managers can place in such assessments but can also inform our understanding of alewife ecology.