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Marine Ecology Progress Series

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MEPS 262:229-240 (2003)  -  doi:10.3354/meps262229

Relationship of RNA/DNA ratio and temperature to growth in larvae of Atlantic cod Gadus morhua

Elaine M. Caldarone1,*, Jeanne M. St. Onge-Burns1, Lawrence J. Buckley2

1National Oceanic and Atmospheric Administration National Marine Fisheries Service, Northeast Fisheries Science Center, Narragansett Laboratory, 28 Tarzwell Drive, Narragansett, Rhode Island 02882-1199, USA
2URI/NOAA CMER Program, Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA

ABSTRACT: The RNA, DNA, and protein content of larval cod Gadus morhua reared in the laboratory at 3 temperatures and 3 densities of prey was measured. The data were used to define a quantitative relationship between RNA/DNA ratio (R/D), water temperature (T), and protein-specific growth rate (SGR, % d-1). The nucleic acid content of each larva was determined with both a 2-dye flow-injection fluorometric assay (FIA) and a 1-dye/1-enzyme fluorometric microplate assay (MFA) in order to calibrate each methodology. The resulting equations were: SGR = 3.65 R/D + 1.02 T - 13.05 for FIA, and SGR = 4.03 R/D + 0.88 T - 11.16 for MFA. Measured growth rates ranged from negative (-8% d-1) to 20% d-1. Water temperature and larval R/D explained 37 to 39% of the variability in the observed growth rate. The models are applicable over temperatures ranging from 2.5 to 9.5°C and can be used to determine short-term growth rates of cod larvae collected from both the laboratory and field.

KEY WORDS: RNA/DNA ratio · Growth · Cod · Larvae · Temperature effects

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