Farmed fish benefit from exercise training, no matter the species, say Australian researchers.
A new study by Murdoch University researchers Dr Essie Rodgers and Dr Daniel Gomez Isaza has revealed that exercise regimes can help fish reach marketable sizes at an accelerated rate, boosting production efficiency for fish farming operations.
The researchers compiled data from almost 70 research studies spanning 31 species in an effort to quantify the effects of exercise training on growth rates and feed conversion ratios.
The study, published in the journal Reviews in Aquaculture, found that exercise training significantly increases growth rates across a wide range of finfish species - not just naturally "athletic" salmonids but also non-salmonid commercial aquaculture species such as yellowtail kingfish.
Exercise for fish in both sea-based and land-based aquaculture is increasingly recognised as an important factor in promoting growth and supporting fish welfare by simulating natural environmental conditions.
To achieve this, fish farmers can adjust the water flow in tanks or enclosures to encourage fish to swim against the current, or use so-called "aquatic treadmills" to give fish a workout.
However, until now, the aquaculture industry did not have a comprehensive picture of the relationship between exercise and growth across different farmed species and different exercise protocols.
In their study, the Murdoch University researchers wanted to find out if exercise was equally beneficial across different species, and to determine optimal training protocols.
The findings showed that fish that had been exercised by manipulating water currents grew around 10 per cent quicker than fish kept in still water.
“Using statistical methods, we show that regardless of training regime used, fish that were exercised grew much faster than fish that were not exercised,” Dr Rodgers said.
"We also found that all species of fish benefitted from exercise training, and not just athletic fish like salmon.”
Importantly, feed converstion rations were unaffected by exercise, which indicates that exercised fish were just as efficient at converting food into body mass as "control" fish.
Exercise training was also associated with decreased variability in growth rates, leading to not only larger fish, but fish that are more uniform in size.
Isaza said they had identified optimal training regimes or ‘workouts’ which would be useful to fish farmers.
“We found a large number of studies that have exercised fish, but many use different training regimes, like different water speeds, durations and species,” he said.
The ideal training regime identified through the research included continuous exercise rather than intermittent at target speeds for longer periods of time.
"Overall, our findings show that exercise can be a powerful tool in promoting rapid and more uniform growth in finfish," the researchers conclude.
"These findings, coupled with numerous welfare benefits associated with exercise, provide a strong case to widely adopt exercise as tool in fish farming."
The original research paper can be accessed here: The growth-promoting effects of exercise in finfish: A systematic review and meta-analysis, 27 November 2023. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd.