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Uses of stable isotopes in fish ecology
Citation:
Church, R. Uses of stable isotopes in fish ecology. Presented at Otolith Workshop, October 25 - 26, 2012.
Impact/Purpose:
Stable isotope analysis is a very powerful and effective tool in studying fish ecology. It can help determine, diet (and changes in diet), habitat use (and changes in habitat use) as well as elucidate aspects of the physiological ecology of fish.
Description:
Analyses of fish tissues (other than otoliths) for stable isotope ratios can provide substantial information on fish ecology, including physiological ecology. Stable isotopes of nitrogen and carbon frequently are used to determine the mix of diet sources for consumers. Stable isotopes of nitrogen are very useful in determining trophic position of consumers. Nitrogen isotopes also are useful in determining nutrient sources to aquatic ecosystems (e.g., marine derived nutrients in streams with anadromous fish species). Stable isotopes of carbon in fish tissues may reflect a number of influencing factors in the aquatic environment, including flow velocities in streams, substrate type, energy sources (e.g., autotrophy vs. heterotrophy) and possibly temperature effects as well. Sulfur isotope ratios in fish can reflect the oxidation/reduction condition of local habitats and thus are useful in studying habitat use. Oxygen isotope ratios in water vary among water bodies, sometimes at fine scales, and, because they influence the ratios in fish tissues, can be used in identifying habitat use of fish. Controls on stable isotope ratios of hydrogen in fish have been studied only sparsely, but, like carbon isotopes, may be useful indicators of stream energetics and food sources. Changes over time in fish tissues can be useful in examining diet or habitat switching. Different tissues respond at different rates. Isotopic ratios in muscle directly reflect growth and tissue turnover and can change very slowly. Fin tissues respond on similar time scales to muscle. At low to moderate growth rates, epidermal mucus can respond an order of magnitude faster than either muscle or fins and thus can provide a rapid indicator of diet or habitat switches, given appropriate differences in end members. The combination of patterns or changes in muscle vs. mucus can thus provide a time history of diet and habitat use.