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Fish mucus as a rapidly responding tissue in diet switching studies
Citation:
CHURCH, M., J. L. EBERSOLE, K. RENSMEYER, R. Couture, D. Noakes, R. Barrows, AND P. J. WIGINGTON JR. Fish mucus as a rapidly responding tissue in diet switching studies. Presented at The 2009 Conference Oregon Chapter American Fisheries Society, Bend, OR, February 25 - 27, 2009.
Impact/Purpose:
We are using stable isotopes of C, N, O and S (H planned) to study the ecology of coho salmon in streams of the Oregon Coast Range.
Description:
We are using stable isotopes of C, N, O and S (H planned) to study the ecology of coho salmon in streams of the Oregon Coast Range. One aspect of our work focuses on the incorporation of marine-derived nutrients into the diet of overwintering coho salmon juveniles. These studies are complicated by the short time window of coho spawner returns relative to the time required for muscle tissues to show an isotopic response during periods of slow growth. To investigate fish mucus as a potentially more rapidly responding “tissue,” we performed diet switching studies of steelhead trout in a controlled hatchery setting using diets formulated to have either low δ15N (3 ‰) or high δ15N (13 ‰). Our work to date indicates that mucus responds significantly more rapidly than muscle tissue at growth rates approaching the most rapid we see in wild coho in our Coast Range streams. In contrast, rates of changes in mucus closely parallel those in muscle at hatchery growth rates well beyond what we see in the wild. In non-feeding fish, the composition (percent C, percent N) of mucus changes markedly within 1-2 days, as do δ13C and δ15N, which both show immediate declines. In ongoing work we are examining rates of change of δ13C and δ15N of mucus in slowly growing fish. Fish mucus composition probably is controlled by synthesis from both recently ingested food and recycled amino acids from tissue breakdown, with the relative contributions changing depending on nutritional status. Analysis of mucus in wild fish populations, for both elemental composition and stable isotopes, holds promise as a valuable tool in discerning ebbs and flows in nutritional status and diet sources over ranges of highly variable seasonal conditions.