Food Habits of Large Striped Bass in the Lower Chesapeake Bay and its Tributaries March 1997 - May 1998

Striped bass, Marone saxatilis, are dominant seasonal predators in Chesapeake Bay and support a large recreational and commercial fishery. This document presents the results of a yearlong ( 1997-1998) food habits study of large (\u3e 450mm or 18 inches) striped bass in lower Chesapeake Bay and adjacent ocean waters. These fish comprise the coastal migratory stock and are found in greatest abundance in Chesapeake Bay during the spring and fall. Fish were obtained from a variety of commercial, recreational and fishery-independent sources and were captured by gill, fyke and pound nets as well as recreational hook and line, otter trawl and electroshocking gear. From March of 1997 to May of 1998, stomach contents of 1,988 striped bass were examined. The frequency of occurrence, numerical abundance and weight of prey items in the stomachs were combined into an index of relative importance (IRI). This compound index identifies important food items in the diet of striped bass. Overall, menhaden, Brevoortia tyrannus were the dominant prey, not only in IRI but also by weight and frequency of occurrence. Menhaden became an increasingly important forage species as striped bass size increased. Anchovies were second in overall importance and first in numerical abundance. Seasonally, and at different locations, gizzard shad, spot and herring were next in importance in the diet. Blue crabs appeared infrequently in the stomachs sampled and contributed little to the overall weight of stomach contents. Other invertebrates were of lesser importance. Two measures of stomach fullness were employed, a stomach fullness index which measures the relative fullness of the stomach, and the percent frequency of empty stomachs. The highest percentage of empty stomachs was found during the spring months of March and April and also during the summer months of August and September. The highest percentage of full stomachs and the greatest stomach fullness values were found during the fall months of October and November. Gear type, season and location partially determined the fullness of the stomachs and the percentage of empty stomachs but no single variable accounted solely for the observed differences in stomach fullness