Swim bladder inflation failure affects energy allocation, growth, and feed conversion of California Yellowtail (Seriola dorsalis) in aquaculture

This study examines the effects of swim bladder inflation failure, a common developmental abnormality in finfish aquaculture, on the energy allocation, growth, and development of California Yellowtail (Seriola dorsalis). Health and fitness metrics including oxygen consumption, aerobic scope, critical swimming speed, feed conversion ratio, and growth rate, were monitored over a 32-week growout period in three groups of S. dorsalis: aquaculture-reared fish that failed to inflate their swim bladders (uninflated), aquaculture-reared fish with properly inflated swim bladders (inflated), and wild-caught individuals (wild). After the growout period, the uninflated fish had significantly lower body mass (636.1 ± 80.4 g vs. 758.6 ± 92.7 g inflated), shorter body length (36.5 ± 1.9 cm vs. 39.6 ± 2.0 cm inflated), and smaller girth (21.5 ± 1.2 cm vs. 23.2 ± 1.1 cm inflated) than the inflated fish. In addition, the uninflated fish had the least efficient feed conversion ratio (2.08 uninflated vs. 1.49 inflated, 1.41 wild), needing 39.8% more feed than the inflated fish, and 47.8% more feed than the wild fish to gain equivalent mass. These differences in growth and feed conversion appear to be primarily attributed to differences in energy allocation. Measures of oxygen consumption using a swim tunnel respirometer at two time points during the growout period showed that uninflated fish had significantly higher metabolic costs than both the inflated and wild groups over a large range of the swimming speeds tested. In addition, the uninflated fish were often observed swimming faster in their growout tank, likely to generate enough lift to compensate for the lack of a buoyant swim bladder. The wild-caught fish had the lowest feed conversion ratios and had significantly lower metabolic costs than both the inflated and uninflated aquaculture-reared fish at the beginning of the growout period (shortly after capture from the wild). The results of this study show that rearing S. dorsalis without a functional swim bladder is not economically feasible based on their poor growth and feed conversion ratios, and suggest that there is room for improvement in the metabolic efficiency of cultured S. dorsalis with properly inflated swim bladders.