Nutrient composition of whole crayfish eaten by hellbender salamanders (Cryptobranchus alleganiensis spp.)


Dierenfeld E, McGraw K, Fritsche K, Kerr K. 2007. Nutrient composition of whole crayfish eaten by hellbender salamanders (Cryptobranchus alleganiensis spp.). In Ward A, Hunt A, Maslanka M, Eds. Proceedings of the Seventh Conference on Zoo and Wildlife Nutrition, AZA Nutrition Advisory Group, Knoxville, TN.


Four species of native Missouri crayfish identified as foods of the Ozark hellbender salamander (Cryptobranchus alleganiensis bishopi), were analyzed for nutrient content including water, proximate composition (crude protein, crude fat, crude fiber, and ash), as well as vitamin A, vitamin E, total carotenoids, and select mineral concentrations. Additionally, fatty acids in crayfish were examined and compared with krill as a possible substitute food item for captive and/or larval salamanders. Crayfish collected from running streams (n=5 samples) contained less water than those collected in standing water (n=ll samples); 62 – 65% vs. 74 – 80%, respectively. On a dry matter (DM) basis, crayfish collected in native streams contained less protein (34 to 41%) than “farmed” crayfish (54 to 60%) and more ash (43 to 51% vs. 31 to 36%, respectively. Fat content in whole crayfish ranged from 2 to about 4.5% of DM. Overall, vitamin A concentrations in whole crayfish were low (755 to 2951 IU/g of DM, whereas vitamin E concentrations were relatively high (140 to 808 IU/g DM); crayfish sampled from “farmed” areas contained about twice the concentration of these nutrients as stream-living crayfish. Total carotenoids were also considerably higher in farm-raised crayfish, 55 to 75 mg/kg compared to 12 to 34 mg/kg in stream-living animals. All crayfish displayed high calcium content, 10-20% of DM, likely due to incorporation of this mineral within chitinous exoskeletons, whereas phosphorus levels ranged from 0.8 to 1.2% of DM. Both macromineral and trace element concentrations varied by habitat from which the crayfish were sampled. These nutrient differences are likely the result of nutrients in commercial diets fed to fish in the managed fisheries operations from which the crayfish were sampled. The comparison of molar ratios of fatty acids in crayfish compared with marine krill suggest that krill are not an equivalent nutritional substitute; krill contain higher levels of saturated fatty acids, and a very different distribution of n-3 to n-6 fatty acids than do crayfish. These initial data provide some baseline information for developing more optimal feeding programs for endangered species that consume crayfish, including the Ozark hellbender salamander.