American Shad Feeding on Spawning Grounds in the St. Johns River, Florida

Abstract

We evaluated the feeding habits of American shad Alosa sapidissima on spawning grounds in the St. Johns River, Florida. Feeding intensity in freshwater was generally low but highly variable. The items consumed were mainly pelagic (cyclopoid copepods and woody debris), although benthic (mollusks and sand) and surface (adult insects [Coleoptera, Hemiptera, and Odonata]) organisms occurred occasionally. The stomach fullness index varied by location for males, suggesting that ingestion is related to prey availability. Feeding by females also varied by location and continued during final oocyte maturation and active spawning. Egg cannibalism was suggested by the presence of some eggs morphologically similar to American shad eggs in the stomachs of males and females collected when females were running ripe. The results from diel sampling suggested that individuals consumed approximately 1.727 kJ/d in freshwater, which represents only a small fraction of the estimated daily energetic expenditure during the spawning run. Unlike iteroparous populations, Florida's American shad probably do not conserve energy for out-migration. While this low incidence of freshwater feeding did not maintain fish weight, it may increase available energy and thereby increase fecundity.