Swimming Kinematics of Deep-sea Fishes

Summary

In this study, SUNY Geneseo students have characterized how fishes swim across habitat depths to 20,000 ft, finding that deep-sea fishes swim consistently slowly, likely due to cold temperatures in the deep sea.

Abstract

Although the deep oceans represent Earth's largest habitat, the challenges of studying deep-sea organisms in situ have limited our understanding of adaptation, ecology, and behaviour in these important ecosystems. One fundamental trait of fishes that remains largely unexplored in the deep ocean is swimming, a vital process for movement, migration, and dispersal in marine habitats. Deep-sea conditions such as temperature, pressure, and food availability could each impact the speed and efficiency of swimming in fishes. To investigate swimming kinematics of fishes with increasing depth, we analysed in situ video of bony fishes across a 6000-m depth gradient. We compared open-source videos of fishes from National Oceanic and Atmospheric Administration (NOAA) Ocean Exploration with tank-based recordings of shallow-water relatives from Puget Sound, Washington, USA to understand how both habitat depth and phylogeny influence swimming in fishes. We analysed kinematics in four dominant demersal fish groups, the orders Anguilliformes, Gadiformes, Ophidiiformes, and Perciformes. Deep-sea fishes swam consistently slowly. Swimming kinematics varied across temperature, oxygen, body elongation, and depth. These results suggest that swimming kinematics do not change linearly with increasing habitat depth in fishes and that the impacts of deep-sea conditions such as low temperatures, high pressures, and low nutrient availability on swimming behaviour need to be considered independently of one another. These findings provide insight into the evolution of fish form and function in the deep ocean.

Primary research questions

1. How have fishes evolved to swim in the deep ocean?
2. How does swimming in deep-sea fishes compare to swimming in their shallower-living relatives?

What was known?

Our research builds on anecdotal observations of deep-sea fishes swimming slowly and a few published measurements of swimming speeds in deep-sea species.

What or how does your research add to the field or topic?

This is the first study to investigate swimming in deep-sea fishes across habitat depth within taxonomic orders, allowing us to compare the swimming patterns of closely related species that live at different depths. In this study, deep-sea fishes swam consistently slowly, rather than decreasing swimming speed as depth increased, suggesting that temperature, rather than pressure is likely driving the slow swimming behavior of deep-sea fishes.

Implications for research

These findings provide new insights into how deep-sea conditions drive evolution.

Notable information

This study features four SUNY Geneseo alumni from the Department of Biology, including co-lead authors Brett Woodworth '22 and Jessica Palmeri '21.