MEPS 293:241-252 (2005)  -  doi:10.3354/meps293241

Estimating growth in haddock larvae Melanogrammus aeglefinus from RNA:DNA ratios and water temperature

Elaine M. Caldarone1,*

1National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northeast Fisheries Science Center, Narragansett Laboratory, 28 Tarzwell Drive, Narragansett, Rhode Island 02882-1152, USA

ABSTRACT: Five biochemically based variables (RNA, DNA, protein content, RNA:DNA [R:D] ratio, protein:DNA [pro:DNA] ratio) were evaluated as potential indirect measures of growth in larval haddock Melanogrammus aeglefinus. Larvae were reared in the laboratory from hatch to 47 d post-hatch under temperature (T)-controlled conditions (6, 8, and 10°C) and, to produce a variety of growth rates, were starved or reared at 1 of 3 prey levels. The nucleic acid content of the larvae was measured with a spectrofluorometric microplate assay, and the protein-specific growth rate (SGR,% d–1) was estimated from the difference in mean protein content between consecutive sampling intervals. Larval haddock growth rate was best described by R:D or pro:DNA ratios. The growth models developed were: SGR = 4.61R:D + 1.18T – 17.31 (R2 = 0.52) and SGR = 0.92 pro:DNA + 1.10T – 24.97 (R2 = 0.52). These models can be used to estimate recent growth of larval haddock collected from both the laboratory and field. A combined haddock/Atlantic cod Gadus morhua growth model was calculated as: SGR = 4.67R:D + 0.96T – 15.30 (R2 = 0.45). This model will be used to estimate recent growth of haddock and cod larvae collected during a multi-year field sampling effort on Georges Bank.

KEY WORDS: RNA:DNA ratio · Growth · Haddock · Larvae · Nutritional condition · Nucleic acids · Fluorometric microplate assay · Temperature effects

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