Spatial and Temporal Diet Patterns of Subadult and Small Adult Striped Bass in Massachusetts Estuaries: Data, a Synthesis, and Trends across Scales

Kristen H. Ferry,Martha E. Mather

doi:10.1080/19425120.2011.642747

Abstract

AbstractSubadult and small adult (375–475 mm total length) striped bass Morone saxatilis are abundant and represent an important component of the recovered U.S. Atlantic coast stocks. However, little is known about these large aggregations of striped bass during their annual foraging migrations to New England. A quantitative understanding of trends in the diets of subadult and small adult migrants is critical to research and management. Because of the complexity of the Massachusetts coast, we were able to compare diets at multiple spatial, temporal, and taxonomic scales and evaluate which of these provided the greatest insights into the foraging patterns of this size of fish. Specifically, during spring through autumn, we quantified the diets of 797 migratory striped bass collected from 13 Massachusetts estuaries distributed among three geographic regions in two biogeographic provinces. Our data provided three useful results. First, subadult and young adult striped bass ate a season‐specific mixture of fish and invertebrates. For example, more juvenile Atlantic herring Clupea harengus were eaten in spring than in summer or autumn, more juvenile Atlantic menhaden Brevoortia tyrannus were eaten in autumn than in spring or summer, amphipods were eaten primarily in the southern biogeographic province, and shrimp Crangon sp. were eaten in all locations and seasons. Second, examining diets by season was essential because of the temporal variability in striped bass prey. Grouping prey by fish and invertebrates revealed the potential for predictable differences in growth across geographic locations and seasons, based on the output from simple bioenergetics simulations. Third, of the three spatial scales examined, region provided the most quantitative and interpretable ecological trends. Our results demonstrate the utility of comparing multiple scales to evaluate the best way to depict diet trends in a migrating predator that seasonally uses different geographic locations.Received March 3, 2010; accepted May 3, 2011

Highlights

U.S Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts, Holdsworth Hall, Amherst, Massachusetts 01003, USA
Despite the popularity of migratory striped bass Morone saxatilis as a sport fish, little is known about the diets of a common size-class (375–475 mm total length [TL]) composed of subadults and small adults that forage seasonally along the Atlantic coast
Previous diet studies have not focused on the complex of subadult and small adult striped bass that migrate and feed as adults, nor have previous studies compared insights about diets obtained by examining multiple spatial, temporal, and taxonomic scales

Summary

Introduction

U.S Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts, Holdsworth Hall, Amherst, Massachusetts 01003, USA. Despite the popularity of migratory striped bass Morone saxatilis as a sport fish, little is known about the diets of a common size-class (375–475 mm total length [TL]) composed of subadults and small adults that forage seasonally along the Atlantic coast. The recovered U.S Atlantic coast striped bass stocks are very abundant (e.g., 43 million in 2002 compared with 5 million in 1980) One reason for this recovery is that 8 of 14 recent year-classes have been moderately strong (>10,000,000: 1992, 1994, 1995, 2000, 2006) or very strong (>15,000,000; 1996, 2001, 2003; NEFSC 2008). This has resulted in an abundance of subadult and young adult migratory striped bass (>2 years), many of which participate in the coastal migration. Subadult and small adult striped bass migrants have been seasonally abundant predators in New England waters for more than a decade

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Conclusion