A bioenergetics approach for determining the effect of increased striped bass population on its prey in the Chesapeake Bay

Anthony S. Overton, Jennifer C. Griffin and F. J. Margraf
University of Maryland Eastern Shore Maryland Cooperative Fish and Wildlife Research Unit1120 Trigg Hall Princess Anne, Maryland 21853 (410) 651-7663;FAX (410) 651-7662; Aoverton@umes-bird.umd.edu

The purpose of this study is to examine the predatory demand and prey species contributions to the production of striped bass in Chesapeake Bay. We collected adult striped bass to examine diet composition. Specimens were collected from April 1998 through December 1999. Angling was the primary sampling method however seining, gillnetting, and electroshocking were also used. Sand shrimp (Crangon spp) made up over 74% of the numerical diet and 2% of the biomass. Bay anchovy (18%), blueback herring(1%) and menhaden (1%) were the next most numerous prey items found in the diet. Gizzard shad (28%) contributed the greatest proportion to the total diet biomass. Menhaden (20%) contributed the next highest percentage to the biomass followed by blueback herring (13%). Blue crab made up approximately 1% of the total diet biomass and frequency of occurrence. Consumption varied among cohorts and showed seasonal differences. Age 1 striped bass were closest to reaching their predatory demand throughout the sampling period. The consumption of blue crabs and blueback herring was low for all cohorts. The dominant prey species, relative to biomass, changed over the collection period. Blueback herring dominated in April, gizzard shad dominated the May-June and September-October collections, and Atlantic menhaden dominated the November-December collection. Bay anchovy occurred throughout the collection period and dominated the July-August collection. The diversity of striped bass diets may reflect the abundance and distribution of its prey items. It is speculated that current prey abundances may not be able to support the increased striped bass population. Changes in prey abundances may adversely affect the health of the striped bass.