The effects of temperature, body size and growth rate on energy losses due to metabolism in early life stages of haddock (Melanogrammus aeglefinus)

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Rates of routine respiration (R R, μl O2 fish -1 h-1) and total ammonia nitrogen excretion (E R, μg NH4-N + NH3-N fish-1 h -1) were measured on larval and juvenile haddock (Melanogrammus aeglefinus) to ascertain how energy losses due to metabolism were influenced by temperature (T), dry body mass (M D, mg) and specific growth rate (SGR, % per day). R R and E R increased with M D according to y = a·M Db with b-values of 0.96, 0.98, 1.14, and 0.89, 0.78, 0.74, respectively, at 10, 7, and 4°C, respectively. Multiple regressions explained 98% of the variability in the combined effects of M D and T on R R and E R in larval haddock: R R = 0.97·M D0.98 ·e0.092·T ; E R = 0.06·M D0.79 ·e0.092·T . In young juvenile (24-30 mm standard length) haddock, R R tended to decline (P = 0.06) and E R significantly declined (P = 0.02) with increasing SGR. O:N ratios significantly increased with increasing SGR suggesting that N was spared in relatively fast-growing individuals. Our results for young larval and juvenile haddock suggest: (1) nearly isometric scaling of R R with increasing body size, (2) allometric scaling of E R with increasing body size, (3) Q 10 values of 2.5 for both R R and E R, (4) metabolic differences in substrate utilization between relatively fast- and slow-growing individuals, and (5) that rates of routine energy loss and growth were not positively related. The measurements in this study will provide robust parameter estimates for individual-based models that are currently being utilized to investigate how variability in climatic forcing influences the vital rates of early life stages of haddock. Our results also stress that inter-individual differences in rates of energy loss should not be overlooked as a factor influencing growth variability among individuals. © 2008 Springer-Verlag.

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Marine Biology