Abstract
Induced-swimming can improve the growth and feed conversion efficiency of finfish aquaculture species, such as salmonids and Seriola sp., but some species, such as Atlantic cod, show no or a negative productivity response to exercise. As a possible explanation for these species-specific differences, a recent hypothesis proposed that the applicability of exercise training, as well as the exercise regime for optimal growth gain (ERopt growth), was dependent upon the size of available aerobic metabolic scope (AMS). This study aimed to test this hypothesis by measuring the growth and swimming metabolism of hapuku, Polyprion oxygeneios, to different exercise regimes and then reconciling the metabolic costs of swimming and specific dynamic action (SDA) against AMS. Two 8-week growth trials were conducted with ERs of 0.0, 0.25, 0.5, 0.75, 1, and 1.5 body lengths per second (BL s−1). Fish in the first trial showed a modest 4.8% increase in SGR over static controls in the region 0.5–0.75 BL s−1 whereas the fish in trial 2 showed no significant effect of ER on growth performance. Reconciling the SDA of hapuku with the metabolic costs of swimming showed that hapuku AMS is sufficient to support growth and swimming at all ERs. The current study therefore suggests that exercise-induced growth is independent of AMS and is driven by other factors.
Highlights
There is ample evidence in the literature showing that induced swimming, or exercise training, can improve the growth and feed conversion efficiency of many species of farmed fish (Davison, 1989; Palstra and Planas, 2011; Davison and Herbert, 2013)
Non-linear regressions did not provide convincing evidence that ER was positively linked with weight-specific growth (SGR) for either trial 1 (F = 1.91, R2 = 0.56, P > 0.05) or trial 2 (F = 0.56, R2 = 0.27, P > 0.05) (Figure 1A)
With their active ecotype and high aerobic metabolic scope (AMS) (∼350–500 mg O2 kg−1 h−1), show exercise-induced growth at relatively fast swimming speeds (Walker and Emerson, 1978; Houlihan and Laurent, 1987; Jørgensen and Jobling, 1993; Bugeon et al, 2003) and provide data to support the upper end of the Davison and Herbert (2013) model
Summary
There is ample evidence in the literature showing that induced swimming, or exercise training, can improve the growth and feed conversion efficiency of many species of farmed fish (Davison, 1989; Palstra and Planas, 2011; Davison and Herbert, 2013). Exerciseinduced growth is often perceived as a paradoxical concept as it seems illogical that fish can expend considerable energy on exercise whilst committing to the extra expense of accelerated growth. To stand any chance of exploiting the economic gains of exercise-induced growth in aquaculture, an indepth understanding of how fish balance the metabolic costs of growth and exercise needs to be ascertained, in the case of information-poor species that are new to farming
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