Dietary metal and macro-nutrient intakes of juvenile lemon sharks
Dietary metal and macro-nutrient intakes of juvenile lemon sharks determined from the nutritional composition of prey items.
Harri Pettitt-Wade, Steven P. Newman, Kristene T. Parsons, Samuel H. Gruber, Richard D. Handy.
ABSTRACT:
The trace element requirements of sharks are poorly understood and the dietary intake of metals from prey items in wild sharks has not been measured. In this study whole prey of nursery bound juvenile lemon sharks Negaprion brevirostris, from Bimini, Bahamas were analysed for carcass total protein, lipids, carbohydrates, ash content, energy, and elemental composition. Metal analysis included 415 prey items from 18 species (fish: Atherinidae, Belonidae, Gerreidae, Haemulidae, Lutjanidae, Scaridae, Sphyraenidae; decapod crustaceans: Penaeidae, Portunidae). There were some seasonal and location effects (North Sound versus South Bimini shark nurseries), but overall prey metal concentrations were broadly similar to reports for temperate species. Yellow fin mojarra Gerres cinereus dominate the shark diet, in which electrolytes were similar (Na 10, K 10, Ca 65, and Mg 2 mg g–1 dry weight) but trace metals were higher (Cu 2.4, Zn 96, Fe 63, Mn 0.7 µg g–1 dry weight) than in other prey fish species at Bimini. Swimming crabs (Portunidae) were an important source of dietary Ca, Mg, Cu and Mn for lemon sharks. The calculated daily dietary metal intakes (mg d–1) for Cu (0.17), Fe (1.2) and Mn (0.01) of lemon sharks are below previously estimated requirements of other fish. Dietary salt intake (272 mg Na d–1, 1% dietary salt) is similar to other fishes, but the Ca and Zn intakes are higher. Yellow fin mojarra contained 65% protein, 4% lipid, 23% ash. The average juvenile lemon shark (1.85 kg, 24.84 g daily ration) ate a very lean high protein diet (61.9% protein, 4.6% lipid, 24.9% ash, 8.6% carbohydrate), with a calculated energy intake of 397 kJ d–1. Overall, the data suggests the gross macronutrient composition of the shark diet is adequate, but some of the trace metals may be limiting in the diet of wild juvenile lemon sharks at Bimini.
Mar Ecol Prog Ser 433:245-260