Teleost aquaculture performance is fundamentally constrained by species-specific physiology, particularly the capacity for oxygen transport and utilisation, from gills through to mitochondria. Deliberate exercise conditioning has been shown to improve growth and feed conversion in salmonids. However, research on whether these benefits and underlying physiological mechanisms are applicable to other commercially valuable teleosts, is promising but limited, particularly in emerging aquaculture species.
This study examined whether sustained and entrained optomotor-induced exercise elicited measurable adaptations in mitochondrial respiratory function and cardiac morphology in juvenile Australasian snapper (Chrysophrys auratus) and yellowtail kingfish (Seriola lalandi), two commercially significant New Zealand species with contrasting baseline activity levels, ecological niches, and oxidative capacities. Kingfish and Snapper were assigned to True Control, Static Light, or Moving Light treatment groups across a conditioning period of six or eight weeks, respectively. Mitochondrial oxygen flux in ventricular tissue and red skeletal muscle was measured via high-resolution respirometry (Oroboros O2k) using a substrate-uncoupler-inhibitor-titration protocol. Cardiac morphometrics were assessed through allometric scaling and relative ventricular mass (RVM%).
Neither species exhibited statistically significant overall treatment effects in mitochondrial flux. However, targeted post-hoc comparisons revealed tissue-specific responses; Snapper red muscle CI Leak was significantly decreased under Static Light relative to both True Control and Moving Light, whilst Kingfish red muscle ETS capacity differed significantly between Static and Moving Light groups. Cardiac allometry diverged between species; Kingfish ventricular mass scaled isometrically, Snapper exhibited significant negative allometry, and RVM% did not differ by treatment in either species.
These findings suggest exercise-induced physiological plasticity in juvenile teleosts is subtle, tissue-specific, and species-dependent rather than a uniform whole-organism response, with implications for how conditioning protocols are designed and interpreted across aquaculture species with differing physiologies. Longer duration of exercise trials may be required in order to produce observable, significant changes within muscle/cardiac structure and mitochondrial efficiency.