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

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. © Inter-Research 2005.