Study Finds Fish Expend Significant Energy Just to Stay Still

Researchers discover hovering is far more metabolically demanding than previously thought for many fish species.

Published on Feb. 27, 2026

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A new study has found that many fish species expend far more energy than expected just to remain suspended in the water column, a behavior known as hovering. The researchers measured the metabolic rates of 13 different fish species and found that hovering can nearly double their energy expenditure compared to resting. This challenges the long-held assumption that fish can remain motionless with minimal effort due to their swim bladders. The findings shed light on the hidden energetic costs of everyday fish behaviors and have implications for the design of efficient underwater robots.

Why it matters

Understanding the true energetic demands of common fish behaviors like hovering is crucial for building accurate models of fish ecology and evolution. The study shows that even seemingly effortless actions require significant energy investment, which could impact factors like foraging, predator avoidance, and reproduction. The insights also have practical applications for engineering more efficient underwater vehicles.

The details

The researchers combined metabolic measurements and high-speed video to analyze the energetic costs of hovering across 13 different fish species. They found that metabolic rates during hovering were almost twice as high as during rest, with some species expending even more energy. This is because fish must make continuous, precise adjustments with their fins to counter the slight misalignment between their center of mass and center of buoyancy, which creates a constant torque. Deep-bodied fish were more inherently stable and hovered more efficiently, while elongated species required more frequent fin movements and had higher energetic demands.

  • The study was conducted in 2026.

The players

Otar Akanyeti

Senior Lecturer in Artificial Intelligence and Robotics at Aberystwyth University.

Valentina Di Santo

Assistant Professor of Marine Animal Biomechanics at the University of California, San Diego.

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What they’re saying

“Hovering, the behaviour that allows a fish to remain suspended in one place, is far more energetically demanding than scientists once believed.”

— Otar Akanyeti, Senior Lecturer in Artificial Intelligence and Robotics (Mirage News)

“Our results show that the story is more complex. A fish that hovers must do more than balance weight and buoyant force; it must also control its posture.”

— Valentina Di Santo, Assistant Professor of Marine Animal Biomechanics (Mirage News)

What’s next

The researchers plan to further investigate how different fish species' body shapes and fin arrangements impact their energy expenditure during hovering and other common behaviors.

The takeaway

This study upends the long-held assumption that fish can remain motionless in the water with little effort, revealing the hidden energetic costs of even simple behaviors like hovering. The findings have important implications for understanding fish ecology and evolution, as well as informing the design of more efficient underwater robotics.