| THE SCALING OF SPECIFIC DYNAMIC ACTION IN ATLANTIC COD: FROM LARVA TO JUVENILE. |
| HUNT VON HERBING, I. University of Maine, Orono, ME 04469, i.vonherb@maine.edu; S. Hansen, J. Geubtner and A. McCollum |
| It has been 26 years since Malcolm Jobling first wrote what became a very famous review focused on adult fishes called, “The influences of feeding on the metabolic rate of fishes: a short review.” Over the intervening years new physiological methods enabling the measurement of total metabolic heat output (i.e. aerobic and anaerobic metabolism) in early life history stages have been developed. It is, therefore, time to revisit what we know about the patterns of post-prandial oxygen consumption in multiple life history stages in a single fish species, Atlantic cod (Gadus morhua). After feeding, fish experience an increase in metabolic rate (SDA), which is usually measured by an increase in metabolic rate (either heat output or oxygen consumption). Here, SDA is measured in larvae using a microcalorimeter or Thermal Activity Monitor (TAM) (increase in heat output), and is measured in juveniles using a swimming respirometer (increase in oxygen consumption). For larvae, SDA is reported from 4 to 42 days post-hatching, and from 0.25 to 1.82 mg dry weight; and for juveniles, from 115 to 180 days post-hatching and from 1.2 to 1.8g wet weight. Results from this study found that SDA occurs in first-feeding larvae (4 days post-hatching) and increased by a factor 1.67 with development and a three-fold increase in dry body mass. For juvenile cod, SDA increased by a factor of 1.48 with a nine-fold increase in wet body mass. In cod, for both the larval and juvenile stages, SDA took up a large proportion of metabolic scope. In larvae, SDA may set or exceed the small aerobic scope, leaving little energy for other activities, directing most of the available food energy to growth. In juvenile fish, SDA took up 14.83% to 44.01% of the scope for activity, leaving significantly more energy, compared to the larval stage, for other activities, such as swimming. |
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