An Ecosystem Consumption Approach to Study Striped Bass Interactions With Menhaden On the Atlantic Coast

The recovery of the striped bass, Morone saxatilis, population along the Atlantic coast is unprecedented.  Along with the increase in striped bass abundance is an increase in their demand for prey, especially Atlantic menhaden, Brevoortia tyrannus, which is a primary prey item and a commercially important species.  We accumulated striped bass diet information from the Atlantic coast and used a bioenergetics approach to examine annual consumption of prey, particularly Atlantic menhaden. We estimated consumption within three regions of the Atlantic coast; Upper Atlantic (UPATL), Chesapeake-Delaware Bay (CBDEL), and North Carolina (NCARO), and on a broad, population-level scale for the entire coast  Estimated annual consumption (g fish^-1 year^-1) by striped bass was lower for all ages in the UPATL area and highest in NCARO area.  Estimated annual consumption increased with age but the effect differed among the three areas examined. The largest difference in annual consumption occurred at age-1 where striped bass in NCARO consumed 5144 (g fish^-1 year^-1) and striped bass in the UPATL and CBDEL consumed 1112 and 2854 (g fish^-1 year^-1) respectively.  As with total consumption, annual consumption of Atlantic menhaden was highest in NCARO and least in the UPATL.  Age-1 striped bass in NCARO consumed 6.5 and 3.8 times more Atlantic menhaden annually than age-1 in CBDEL and UPATL, respectively.  These differences in consumption were driven primarily by differences in water temperature and diet between the regions. Coastwide population-level consumption of Atlantic menhaden by striped bass has increased from 50´10³t in 1982 to over 250´10³t in 2010.  The total annual striped bass population consumption (tons) of Atlantic menhaden never equaled the commercial fishery landings but, by 1999, striped bass consumed only 14% less than the commercial landings.  However, by 1994 the striped bass population consumed more (by number) Atlantic menhaden than captured by the fishery. Direct competition between striped bass and the commercial fishery may be lessened because 75% of Atlantic menhaden consumed were age-0 and age-1 whereas the commercial landing primarily targeted age-2+ Atlantic menhaden.