Dietary metal and macro-nutrient intakes of juvenile lemon sharks determined from the nutritional composition of prey items

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% 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. KEY WORDS: Dietary metal · Trace element · Electrolyte · Energy intake · Proximate composition · Nutrition · Negaprion brevirostris · BiminiResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 433: 245-260, 2011 mation of their survivability rank on the list (Sundström 2005). Adequate food intake is a critical factor in the survival of any species. For sharks, research has mainly focused on measuring the energy content and the gross nutritional profile (protein, fat, carbohydrate) of teleost prey species so that the energy requirements of the sharks can be calculated (Wetherbee et al. 1990, Lawson et al. 1998, Eder & Lewis 2005. Such information is used to aid understanding of bioenergetics, survival strategies and fish husbandry; as well as to inform conservation measures for the protection of top predators. Yet it is well known in fish nutrition that the energy, protein, fat or carbohydrate content of the food are not the only factors that may limit the growth or health of fishes. Other ingredients in the food such as vitamins and minerals can also have significant effects on fish health (Halver 1989). There has been extensive research on the trace metal requirements of teleost fish, especially those used in aquaculture, and many teleosts need a few milligrams per day of each...

Accounting for body mass effects in the estimation of field metabolic rates from body acceleration

“…This difference converts to 232.591 kJ day -1 (Jobling, 1995). Given that yellow fin mojarra (Gerres cinereus), the primary prey of juvenile lemon sharks in Bimini have an average mass of 41.38 g and energy density of 15.58 kJ g -1 (Pettitt-Wade et al, 2011), this 232.591 kJ difference represents 0.96 mojarras, or a 25% increase in the expected daily energetic requirement of a shark. With such clear improvements over other modelling techniques, we strongly recommend the covariate-corrected modelling approach for establishing ṀO2 predictive equations across different body sizes.…”

An appetite for invasion: digestive physiology, thermal performance, and food intake in lionfish (Pterois spp.)

“…Average gross energy density was 13.79± 0.87 kJ g −1 (wet mass), similar to the energy density of demersal western Atlantic reef fish that lionfish would prey upon (Schwartzkopf and Cowan, 2017;Welicky et al, 2018). Pettitt-Wade et al (2011) found no difference in the energy density of small forage fish including A. stipes between seasons in The Bahamas, so this energy density was used for all treatments and experiments.…”