Exercise training reduces the flesh firmness of juvenile hāpuku (Polyprion oxygeneios) with a hypertrophic reduction in muscle fibre density

Abstract

Consumers base the organoleptic quality of fish on factors such as texture, which can be altered by exercise. The effect of exercise on the fillet firmness of hāpuku (Polyprion oxygeneios) was investigated to determine whether exercise would yield a firmer and more desirable product. To achieve this, the firmness and muscle fibre density (MFD) of fillets from fish exercised for 8 weeks at 0.0, 0.75 or 1.5 body lengths/second (BL s−1) was assessed. Firmness was significantly lower in the 0.75 BL s−1 and 1.5 BL s−1 exercised fish than the 0.0 BL s−1 group. MFD was also significantly lower in the exercise treatments. This is explained by an increase in the median fibre size with exercise implying that exercise stimulated muscle fibre hypertrophy, leading to lowered MFD. Assuming that firmer flesh is perceived to be more desirable, exercise may have little value in the production of hāpuku.