Juvenile alewives (<em>Alosa pseudoharengus</em>): Size, growth, and date of emigration from natal lake

This dataset supports an investigation into how the growth of young alewives (Alosa pseudoharengus) is affected when they are unable to migrate from the lake in which they hatched to the sea. Fish were sampled at the outlet of Bride Lake in East Lyme, Connecticut, USA, during a non-drought year and a prolonged drought year in which their migration was blocked when the exit stream dried up for a prolonged period. Data taken on individuals include standard length and dry mass, daily age from earstones (otoliths), and measurements of daily growth marks on otoliths that permit estimation of daily growth over various periods after hatch. These data provide insight into within- and among-year variability in attributes of individuals who are undertaking a migration. Individuals undertaking migration are a non-random subset of the population, and their features (size, growth rate) influence migration performance, hence prospects for subsequent survival and growth. Variability in these features underscores the complex rules of the strategic decision to migrate and will help to inform management and conservation of this species of concern. Methods Juvenile Alewife were sampled at the outlet of Bride Lake in East Lyme, Connecticut, during a non-drought year and a prolonged drought year. We measured standard length and dry mass, determined daily age from earstones (otoliths), quantified condition as the residual from the overall relationship between mass and length, and estimated daily growth over the lifetime as well as in stanzas from 0 to 30 days, 0 to 100 days, and 70 to 100 days post hatch from the width of daily growth marks in the otolith.