Why do fish swim in schools? New study reveals unexpected benefits | The Optimist Daily
Today’s Solutions: July 19, 2024

BY THE OPTIMIST DAILY EDITORIAL STAFF

Schools of fish moving in synchrony have long captivated those lucky enough to observe this phenomenon, often appearing as a single, synchronized organism. A recent study provides insight into one of the primary advantages of this behavior: swimming in groups requires much less energy to navigate choppy waters.

The benefits of collective swimming

The study, published in PLOS Biology, discovered that fish swimming in schools waste far less energy than fish swimming alone. “We discovered that, when swimming at high speeds and high turbulence levels, fish schools reduced their total energy expenditure (TEE, both aerobic and anaerobic energy) by 63 percent to 79 percent compared to solitary fish,” the investigators wrote. This significant energy reduction is due to the physical and physiological benefits of group locomotion.

The turbulent sheltering hypothesis

Researchers presented the “turbulent sheltering hypothesis,” which states that fish in schools can shield one other from rough currents, making it easier to navigate turbulent waters. “Moving in turbulence is particularly challenging and energetically expensive for solitary fish,” the study authors stated. For example, solitary creek chub had a 22 percent reduction in maximum sustained swimming speed in turbulent conditions, but solitary Atlantic salmon had a locomotion cost of roughly 150 percent.

Experimental findings

Researchers tested their idea with giant danios (Devario aeqipinnatus). They saw the fish swim in groups of eight or alone in both smooth and rough water. High-speed cameras recorded their movements, while a respirometer measured energy expenditure and respiration rates. The findings revealed that fish in schools clustered closer together in turbulent water, whereas lone fish had to beat their tails harder to maintain speed in adverse currents.

Evolutionary and environmental implications

The study implies that locomotion efficiency plays an important role in the evolution of fish schooling behavior. “We show that being in a school substantially reduces the energetic cost for fish swimming in a turbulent environment, compared to swimming alone,” the researchers said. This observation lends support to the theory that schooling behavior helps individual fish reduce the increased energetic expenditure associated with swimming in turbulence.

Why does this research matter?

Understanding the energy dynamics of fish schools can aid in a variety of ecological and conservation endeavors. The hydrodynamic concepts discovered in the study could be used for habitat maintenance, aiding in the protection of certain species or the control of invading ones. Furthermore, the study’s findings may have implications for research into the energy dynamics of group movement in other aquatic and aerial creatures.

The researchers stressed the larger ecological implications of their findings. “Studies on animal locomotion and turbulence have profound implications for a better understanding of the planetary ecosystem, e.g., turbulence generated by groups of fish can contribute to vertical mixing of the ocean,” they stated. Vertical mixing is important for fertilizer dispersion and overall ocean health.

Swimming together allows fish to negotiate difficult seas more efficiently, which may have influenced the evolution of this habit. The work not only improves our understanding of fish ecology and hydrodynamics, but it may also have implications for conservation and other species studies.

Source study: PLOS Biology—Collective movement of schooling fish reduces the costs of locomotion in turbulent conditions

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