Applications of Stable Isotope Analysis to Tracing Nutrient Sources to Hawaiian Gobioid Fishes and Other Stream Organisms

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[edit] Author(s)

• Hobson, K. A.
• Smith, R.
• Jan, F.
• Sorenson, P.

[edit] Journal

Bishop Museum Bulletin in Cultural and Environmental Studies 3 (2007): 99-111.

[edit] Abstract

The measurement of naturally occurring stable isotopes of carbon (13C/12C, measured as d13C) and nitrogen (15N/14N, d15N) can be used to distinguish sources of nutrients to freshwater stream fishes and other organisms in cases where such sources are isotopically distinct. We used d13C measurements of fish muscle tissue to quantify relative contributions of allochthonous (leaf litter) and autochthonous (algae) nutrients to adult gobioid fishes at Hakalau Stream, Hawaii, 1996–2002. We also used d15N measurements to delineate trophic interactions among stream organisms. We detected a strong reliance on benthic algae vs. leaf litter. The Hawaiian gobioid fishes are amphidromous and have a marine larval phase. Newly arriving larval recruits into Hakalau stream were examined isotopically to investigate if this approach could be used to quantify their relative dependence on marine and freshwater nutrient contributions. On the basis of a three-source, two isotope mixing model, the stable isotope ratios of these recruits strongly resembled those of the freshwater algal-based food web and suggest that larvae spend sufficient time in the nutrient-rich plume to register ingestion of streamborne nutrients. However, further studies are now needed to contrast our stable isotope values of larval gobioids with known completely marine pelagic larvae.

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