Marine Life

Researchers document seasonal migration in deep-sea for first time

written by Oceanographic Staff

For the first time, scientists have documented seasonal migrations of deep-sea fish across the seafloor, an important insight that will further scientific understanding of the underwater world.

The study was led by Nova Southeastern University (NSU) and the University of Glasgow. researchers analysed more than seven years of deep-sea photographic data from West Africa, linking seasonal patterns in surface-ocean productivity with observed behavioural patterns of fishes at 1,500m.

Deep-sea fish migrations

“We are extremely excited about our findings, which demonstrate a previously unobserved level of dynamism in fishes living on the deep sea floor, potentially mirroring the great migrations which are so well characterised in animal systems on land,” said Rosanna Milligan, Assistant Professor at Nova Southeastern University, who started the work at the University of Glasgow.

Most of the world’s surface consists of deep-sea areas, which have a water depth of greater than 200m. Recent advances in technology have hugely improved our ability to access and study deep-sea ecosystems. However, there are still many basic questions that we don’t have answers to.

“Animal migrations are really important in nature, because when animals move from place to place, they transport energy, carbon and nutrients,” said Dr. David Bailey, Senior Lecturer in Marine Biology at the University of Glasgow’s Institute of Biodiversity, Animal Health and Comparative Medicine. “We were only able to discover this behaviour because of the collective expertise and decade-long commitment of the Universities and industry partners. These kinds of long-term projects and the datasets they generate are vital to understanding ongoing change in the oceans and how they may be impacted in the future.”

This study now provides evidence of cycles of movement across the seafloor in deep-sea fish, with the study authors believing these movements could be happening in other locations across the world’s sea floor too.

“The work really adds to our understanding of movement patterns in deep-sea fishes and suggests reasons for their behaviours,” Milligan said. “Because we were able to link the abundances of fish observed at the seafloor to satellite-derived estimates of primary productivity, our results suggest that even top-level predators and scavengers in the deep oceans could be affected by changes filtering down from the surface of the ocean.”

This work was done using the Deep-ocean Environmental Long-term Observatory System (DELOS). The DELOS observatories are permanently left on the seafloor at a depth of 1,400m and house separate instrumentation “modules” containing oceanographic sensors, cameras and more. The modules are periodically recovered for data download and servicing using a remotely-operated vehicle (ROV).

Photograph courtesy of  DELOS Consortium.

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