Influence of Winter Conditions on the Age, Hatch Dates, and Growth of Juvenile Atlantic Menhaden in the Choptank River, Maryland
Since 1993, the Atlantic Menhaden Brevoortia tyrannus has experienced sustained low juvenile production (recruitment) in the Chesapeake Bay. We hypothesized that factors affecting wintertime larval growth in Atlantic Ocean shelf habitats carry over to juvenile growth and survival within the Chesapeake Bay. The effects of winter thermal conditions on the hatch dates and growth of larval and juvenile Atlantic Menhaden were examined using otolith increment analyses. During 2010–2013, truncated hatch date distributions for Atlantic Menhaden provided evidence of a winter recruitment bottleneck caused by cold temperatures. Hatch dates of surviving juveniles were skewed toward warmer months for years characterized by colder temperatures. Reduced larval growth rates, which were influenced by lower temperature and reduced food availability, carried over to juvenile growth rates for the same individuals. If larvae that are destined for ingress to the Chesapeake Bay predominately originate from early winter hatch, a recruitment bottleneck may occur, caused by either direct larval mortality or depressed larval growth rates owing to sublethal winter temperatures. Depressed larval growth rates, when not lethal, have the potential to carry over as reduced juvenile growth and survival after estuarine ingress.
Received January 20, 2017; accepted June 27, 2017Published online September 12, 2017