Shedding Light on Past Assumptions: A Look at Life History Characteristics of Alewife (Alosa pseudoharengus)

Every spring, alewives (Alosa pseudoharengus) begin their annual spawning run into lakes and ponds along the northeastern coast of the United States and Canada.  They are a critical component in both marine and freshwater food webs, providing an important food source and exchange of nutrients.  Historically, alewives have been harvested for direct consumption and bait; however, population declines have limited this potential in recent decades.  Current understanding of factors affecting their populations is limited by the large lack of knowledge of alewives in freshwater habitats, especially pertaining to juveniles.  Past literature suggests that adults immediately spawn in their respective natal nursery and quickly migrate back to sea; however, our preliminary results based on sampling 20 freshwater lakes and ponds in Massachusetts suggest that there is a distinct delay between adult migration and adult spawning. Moreover, the resulting offspring exhibit a wide range of growth across all systems and mortality varies widely across lakes.  Growth and mortality may be explained by landscape characteristics (surrounding land use, distance of pond from ocean, river barriers).  This expanded knowledge of juvenile alewife life history may help guide management and restoration of alewife populations in freshwater environments.