Hatch Dates, Growth, Survival, and Overwinter Mortality of Age‐0 Alewives in Lake Michigan: Implications for Habitat‐Specific Recruitment Success

Abstract

AbstractAlewivesAlosa pseudoharengusare key components of Laurentian Great Lakes ecosystems and spawn in multiple habitat types. Exploration of alewife early life history dynamics within these different habitats should help identify important recruitment processes. During 2001‐2003, we quantified physical (temperature, transparency) and biotic (chlorophylla, zooplankton densities) habitat factors and collected age‐0 alewives (using ichthyoplankton nets and trawls) in a nearshore region of Lake Michigan and Muskegon Lake, Michigan (a drowned river mouth lake connected to Lake Michigan). We characterized alewife hatch dates, individual condition, growth, mortality, and size‐dependent overwinter survival to infer differences in habitat‐specific recruitment success. Temperature, turbidity, chlorophyll‐aconcentrations, and densities of zooplankton prey were consistently higher in Muskegon Lake than in nearshore Lake Michigan. On average, young alewives in Muskegon Lake hatched earlier, grew faster, were in better condition (based on a biphasic length‐weight relationship), and had greater survival than alewives in Lake Michigan. By the end of the growing season, young alewives in Muskegon Lake obtained a larger size than those residing in nearshore Lake Michigan, suggesting that they were more likely to survive through winter (a period of intense size‐selective mortality) and ultimately recruit to the adult population.