WHOI scientists discover the elusive fish’s function within the meals internet.
Scientists on the Woods Gap Oceanographic Establishment (WHOI) have found that enormous sharks can spend prolonged durations within the ocean’s mesopelagic zone, positioned 200 to 1,000 meters (650 to three,300 toes) beneath the floor. This twilight area accommodates extra residing biomass than another a part of the ocean, but most of its creatures are too small to supply meals for big predators. This raises a central query: why do sharks linger there for therefore lengthy?
A current examine in Marine Ecology Progress Sequence factors to the importance of mid-sized predators, together with the bigscale pomfret, in connecting floor waters with the deeper ocean.
Till now, researchers had little info on how pomfret and different related fish journey, which made it obscure their ecological function. To beat this, the crew used satellite tv for pc monitoring tags to watch the actions of pomfret, a technique that had not often been utilized to deep-sea fish prior to now.
Monitoring the Pomfret
“The info exhibits bigscale pomfret are everlasting residents of the ocean’s twilight zone, and observe the sample of diel migration. This implies they keep deep in the course of the day and are available to shallower waters to feed at evening,” mentioned Martin Arostegui, lead creator of the examine and a analysis affiliate at WHOI. “Since these species spend a majority of their life on the move and in hard-to-reach places, it wouldn’t have been possible for us to tag enough of them during a few days at sea. Thus, we collaborated with a commercial longline fisher, Captain Danny Mears, who did that work as part of our research team.”
“Bigscale pomfret are so different from the tunas and swordfish we usually catch that we are fascinated by them whenever they show up in our gear,” Mears said. “My crew and I were excited for the opportunity to help with the satellite tagging for this study. It’s been very rewarding to see the data.”
Water Clarity and Migration
This new research also provides insight into how water clarity affects bigscale pomfrets’ migration patterns. When the fish moved from the Slope Sea to the clearer waters of the Sargasso Sea, their behavior changed noticeably. This indicates that water clarity influences the depth these fish occupy, which could impact food webs by changing the prey they target and their susceptibility to predators such as large sharks.
“We always talk about the mesopelagic layer like it’s this giant buffet for big predators—but we’ve been skipping over the species in the middle,” said WHOI biologist Camrin Braun, the senior author of the study and principal investigator of WHOI’s Marine Predators Group. “These mesopelagic fish are doing the hard work of connecting the deep ocean to the surface food web. If we don’t understand them, we’re basically trying to solve a puzzle with the middle pieces missing.”
Reference: “Movement ecology of a deep-pelagic mesopredator, the bigscale pomfret: implications for pelagic food web connectivity and fishery susceptibility” by Martin C. Arostegui, Danny Mears, Peter Gaube and Camrin D. Braun, 18 September 2025, Marine Ecology Progress Series.
DOI: 10.3354/meps14934
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