Evidence of abalone (Haliotis rubra) diet from combined fatty acid and stable isotope analyses
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Abalone are common herbivores throughout temperate and tropical waters, and yet the contribution of red and brown macroalgae to the diet of wild abalone remains unclear. In the northern hemisphere, adult abalone are considered to consume predominantly brown algae, but in the southern hemisphere abalone are thought to prefer red algae. Conventional methods such as gut content analysis and feeding trials provide some insight into diet choice, but the associated biases of these techniques create uncertainty surrounding the aforementioned variability in abalone diet. We use combined stable isotope and fatty acid analysis to determine the relative contribution of red algae, brown algae and detritus/microalgae to the diet of wild abalone in Tasmanian waters. Stable isotopes of carbon suggest that brown algae and/detritus are a more important source of carbon than red algae. Fatty acid analysis confirmed the larger contribution of brown algae to the diet of abalone, and also identified the bacterial and diatom component of detritus to be an important contributor to abalone diet. These results show combined use of chemical tracers to be a promising technique for resolving abalone diet, and challenge current perceptions regarding spatial variability in abalone diet choice.
KeywordsDetritus Carbon Isotope Macroalgae Fatty Acid Profile Brown Alga
We thank B. Connell, S. Fava, S. Ibbott, and R. Kilpatrick for assistance in the field. Thanks to G. Edgar and J. Valentine who helped with identification of red algae species. The assistance of B. Mooney, M. Miller, K. Wheatley with laboratory processing and interpretation of fatty acid profiles were especially helpful. Thanks to J. Oakes for advice with analysis of detrital samples. D. Holdsworth managed the CSIRO GC-MS facility. Advice from A Revill was useful in modelling and interpretation of stable isotope values. Comments on the manuscript by C. Mundy, S. Shepherd and two anonymous reviewers are appreciated and helped to improve the manuscript. Thanks to M. Morffew for creating the map.
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