MEPS 236:233-240 (2002)  -  doi:10.3354/meps236233

Estimating turnover rates of carbon and nitrogen in recently metamorphosed winter flounder Pseudopleuronectes americanus with stable isotopes

Keith L. Bosley1,2,*, David A. Witting3, R. Christopher Chambers3, Sam C. Wainright2,**

1Fishery Resource Analysis and Monitoring Division, National Marine Fisheries Service, Northwest Fisheries Science Center, Hatfield Marine Science Center, 2030 S.E. Marine Science Drive, Newport, Oregon 97365, USA
2Rutgers University Institute of Marine and Coastal Sciences, 71 Dudley Road, New Brunswick, New Jersey 08901-8521, USA
3Coastal Ecology Branch, National Marine Fisheries Service, Northeast Fisheries Science Center, 74 Magruder Road, Highlands, New Jersey 07732, USA
*E-mail: **Present address: Department of Science, United States Coast Guard Academy, 15 Mohegan Avenue, New London, Connecticut 06320-8100, USA

ABSTRACT: Stable-isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) are widely used in the analysis of animal diets. However, using these stable-isotope ratios to infer dietary changes depends on precise knowledge of turnover rates of carbon and nitrogen. In the present study, carbon and nitrogen turnover rates were determined for recently settled juvenile winter flounder Pseudopleuronectes americanus in the laboratory using naturally occurring stable isotopes as dietary tracers. Flounder were reared at 13°C on a diet of rotifers Brachionus plicatilis of known isotopic composition from the time that the larvae began feeding until they reached metamorphosis and began to settle to the benthic habitat. At settlement, the fish were assigned to 1 of 2 temperature treatments (13 and 18°C). A subset of fish at each temperature was maintained on rotifers to serve as controls. The remaining fish were switched to a diet of brine shrimp Artemia sp. (known to be isotopically distinct from rotifers) and then sampled systematically over a 16 d period. Temperature had a significant effect on both carbon and nitrogen turnover rates. At 13°C, the half-life of carbon was 4.1 d (±0.6), and of nitrogen, 3.9 d (±0.7). At 18°C, the half-life of carbon was 2.2 d (±0.3), and of nitrogen, 3.1 d (±0.3). The change in isotopic composition closely followed predictions based entirely on the production of new tissue.

KEY WORDS: Stable isotopes · Diet shifts · Pseudopleuronectes americanus · Winter-flounder habitat · Temperature

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