The effect of temperature and ration size on specific dynamic action and production performance in juvenile hapuku ( Polyprion oxygeneios )

The duration and magnitude of specific dynamic action (SDA) are largely comprised of the physiological costs of post-absorptive protein synthesis and could have a functional link to growth and feed conversion in fish. However, evidence has been found in several species to both support and oppose this hypothesis. To determine if SDA is positively linked to the production performance of a novel finfish aquaculture species, SDA was measured in juvenile hapuku Polyprion oxygeneios at two temperatures with two different ration sizes (i.e. 15°C with a 0.75% and 1.5% body weight ration and 21°C with a 1.5% and 3% body weight ration) and compared to the specific growth rate (SGR) and feed conversion ratio (FCR) of hapuku raised for 6weeks at the same levels of temperature and ration size. A marked effect of temperature on SDA was found and the magnitude of SDA was significantly higher for the shared ration size (1.5% body weight) at 21°C than 15°C. However, only the peak of the SDA response (SDApeak) and the total energy used during the response (SDA energy) increased with ration size at both temperatures. Higher SDA parameters were linked with higher growth performance in juvenile hapuku under certain scenarios but, because SGR was significantly lower at 21°C than 15°C for the shared ration size of 1.5% body weight, the SDA–growth relationship was not consistent and was likely under the interactive influence of temperature and ration size. Indeed, in some scenarios higher SDA provided greater growth at 21°C but the higher maintenance cost (i.e. MO2standard) of fish at this upper temperature may have constrained fish growth when only a 1.5% body weight ration was delivered. FCR was not positively related to SDA so this study does not support the hypothesis that SDA predicts the production performance of juvenile hapuku across a range of temperatures and ration sizes.