Iron storage disease has been reported in a large variety of managed collections of mammal species.
Differences in the amount and bioavailability of iron between natural forages and provisioned diets are most often cited when discussing possible etiologies for iron storage disease among affected species.
Our research goals were to compare the iron levels in the blood of wild and managed dolphins and to analyze fish for iron content from their native and non-native diets. Using this information, our goal was to determine if there is a correlation between diet and iron levels in dolphins.
Dolphin blood values for total iron, AST, ALT, and GGT were compiled from wild and captive populations. The wild population consisted of 180 individuals (93 males, 87 females) ranging from 1 year to 50 years old, provided by the Sarasota Dolphin Research Program. The managed collection data were collected from 12 cooperating marine mammal facilities. The managed population consisted of 118 individuals (58 males, 60 females) with an age range of less than 1 year of age to 59 years old.
Seven species of native fish from Sarasota Bay were used in the study (ladyfish, mullet, pigfish, pinfish, seatrout, spot, and toadfish). In total, 46 samples of native fish caught during 2009-2012 were analyzed for iron content. Native fish were caught during fish monitoring surveys conducted by the Sarasota Dolphin Research Program. Six species of non-native fish were used in the study from the managed population diets (herring, capelin, smelt, sardines, mackerel, and saury). In total, 109 samples of non-native fish from 2009-2012 were analyzed for iron content.
Wild dolphins’ iron levels decreased with age with a slight increase in advanced age. Managed dolphins’ iron levels increased with age. The native diet had an average iron consumption of 22.03 ppm per day and non-native (managed) diets ranged from 16.4 ppm – 17.5 ppm per day. It appeared that managed dolphins consumed less iron than wild dolphins. Wild and managed dolphins’ diet values were based on the average proportions of prey items consumed as reported. Further research is needed to determine the cause for iron overload observed in select dolphins that consume a non-native diet. Funding for this research was provided by the 2012 International Marine Animal Trainer’s Association (IMATA) research grant.
This article was published on page 17 in the January 2014 Nicks n Notches.