Age, Growth, and Hatch Dates of Juvenile Atlantic Menhaden in Warm and Cold Winter Years in the Chesapeake Bay

Historically, Chesapeake Bay served as the central nursery habitat for the shelf-spawning Atlantic menhaden, but over the past two decades juvenile production has fallen to <20% of its former level. Otolith-derived hatch dates have indicated that most recruits originate from spring-ingressed larvae, rather than larvae entering in early- and mid-winter. We hypothesized that prolonged exposure to low winter temperatures and low food availability in the Chesapeake was sub-lethal to larvae, shaping subsequent recruitment patterns. Hatch dates and back-calculated growth rates of juvenile menhaden were compared between cold- and warm-winter years with varying chlorophyll phenology. In addition, summer juvenile abundance from 1995-2012 was evaluated with respect to preceding winter temperatures. During 1995-2012, average winter temperatures ranged from 3.7⁰C to 8.5⁰C and exhibited an overall warming trend. However, we failed to detect differences in hatch-date distributions between warm- and cold-winter years. We observed higher growth rates in 2006, which were associated with warmer winter conditions coupled with early spring chlorophyll concentrations. Although early growth conditions were favored with warmer winters, hatch-date distributions of recent years and a long-term retrospective analysis failed to detect a strong influence of winter severity on early juvenile menhaden survival within the Chesapeake Bay.