Science Serving Maryland's Coasts

Jennifer Rohrer, Virginia Polytechnic Institute and State University

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Project Title: 

Diet analysis and Aging of the Young-of-Year Bluefish, Pomatomus saltatrix, in the Chesapeake Bay


Bluefish (Pomatomus saltatrix) is an important commercial and recreational fish that utilizes Chesapeake Bay along the U.S. Atlantic coast during its annual migrations. Little research has been done on feeding ecology, growth, and habitat utilization of bluefish in Chesapeake Bay. Thirty young-of-the-year bluefish collected from previous research programs, along with l0 bluefish recently captured by Maryland DNR and, 7 bluefish from personal seining efforts were included in analyses. Diet analyses of all 47 YOY bluefish from the Upper, Middle, and Lower Chesapeake Bay regions were used to estimate regional patterns and changes in diet with age/growth. Bluefish <75mm had higher gut fullness values and a more varied diet that included primarily fish, but also crustaceans and polychaetes. Bluefish >75mm preyed almost exclusively on fish, mainly bay anchovy, with an occasional crustacean or polychaete. Otolith daily increments of 20 YOY bluefish were counted to determine age, hatch dates, and growth rates. Hatch dates were predominantly in two distinct periods, spring and summer, possibly indicating two distinct cohorts. The hatch dates suggested a spring-spawned cohort (March 3l-May 15 hatch dates), and a summer-spawned cohort (July l3-August 25 hatch dates). The allometric equation describing the weight-length relationship of YOY bluefish is W=(1 x 10-6) (L3.337). An average growth rate of l.52mm/day was estimated from the slope of the linear regression of length on otolith increments (=age).