A Comparison of the Diets of Gulf Killifish, Fundulus grandis Baird and Girard, Entering and Leaving a Mississippi Brackish Marsh

We examined the diets of Gulf killifish, Fundulus grandis Baird and Girard, collected monthly from March through July 1988 with unbaited minnow traps during two sampling periods: (1) on flood tides before they reached the marsh surface, and (2) on ebb tides as they left the marsh. Thirty-five prey taxa, plant parts, and detritus were identified from the stomach contents of 110 Gulf killifish (mean SL = 55 mm, range = 30-82 mm). Fiddler crabs, Uca longisignalis Salmon and Atsaides; amphipods, mostly Corophium louisianum Shoemaker; tanaidaceans, Hargeria rapax (Harger); and hydrobiids, Littoridinops palustris Thompson, were their most important prey. Killifish diets differed both quantitatively and qualitatively relative to the habitat in which they were feeding. Fiddler crabs and polychaetes were consumed more frequently and in greater numbers in the intertidal zone, whereas more amphipods were eaten by killifish feeding in subtidal and low intertidal areas. Gulf killifish consumed a greater volume of food when they had access to the marsh surface than when they were confined to subtidal areas.