Spatial Patterns in Condition and Feeding of Juvenile Weakfish in Delaware Bay

Abstract

Juvenile weakfish Cynoscion regalis were collected during July 1986 in Delaware Bay. Fish, ranging in size from 40 to 84 mm standard length, were analyzed for weight at length as a measure of condition and for gut fullness as a measure of feeding success. These data were compared among collections from the head of the estuary, the midbay region, and the mouth of the estuary. Condition and gut fullness were generally highest in the midbay region, lowest in the upper bay, and intermediate in the lower bay. The proportion of the diet consisting of mysids was also compared among the upper, mid, and lower bay collections. The mysid shrimp Neomysis americana dominated the diet in all bay areas. Despite their ubiquitous distribution throughout the estuary, the proportion of the diet consisting of mysids was generally highest in the middle bay, lowest in the upper bay, and intermediate in the lower bay. The upper bay is characterized by high turbidity and low illumination. These turbidity levels frequently extinguish all light on the bottom where juvenile weakfish feed and may reduce prey visibility and feeding success, causing reduced growth and condition in the upper bay. Patterns in feeding and condition suggest that growth rates may also vary spatially. Because feeding and growth are presumed important to survival and recruitment, it is possible that some bay nursery areas may potentially contribute more to recruitment.