Food Habits and Organochlorine Contaminants in the Diet of Black Skimmers, Galveston Bay, Texas, USA

Abstract

-More than 500 food items of nestling Black Skimmers (Rhynchops niger) were identified representing 18 species of fish and 2 invertebrates. Food items were obtained by ligaturing nestlings and by collecting potential food items found near nests. Seven fish species composed 87% of the skimmers diet by frequency of occurrence and a single species, the tidewater silverside (Menidia peninsulae), accounted for 25% of the sample. The three heaviest fish species, striped and white mullet (Mugil cephalus and M. curema) and Gulf menhaden (Brevoortia patronus) made up 70% of the skimmer's diet by weight. DDE and polychlorinated biphenyls (PCBs) were the only contaminants consistently detected in the Black Skimmer diet, caracass, and egg samples. DDE was present at 0.01 ppm wet weight in only 3 of 5 fish samples. PCBs were detected in all food samples and were about 18 times higher in skimmer carcasses than in fish. Eggs contained 14 times the level of PCBs detected in the fish diet. Polychlorinated styrenes (PCSs) were present in 2 of 5 fish samples at 0.01 and 0.26 ppm. PCSs were detected in 1 of 20 eggs at 0.6 ppm. Received 9 March 1988, accepted 20June 1988.