The Deep-See is pulled back on board after its first deployment. The vehicle is used for acoustic monitoring and gathering samples for eDNA analysis. (Photo by Andrea Vale © Woods Hole Oceanographic Institution)
The Deep-See is pulled back on board after its first deployment. The vehicle is used for acoustic monitoring and gathering samples for eDNA analysis. (Photo by Andrea Vale © Woods Hole Oceanographic Institution)

The daily cycle of instrument deployments and recoveries went into full swing today. The Deep-See was recovered smoothly at 10 a.m., and a few hours later the midwater trawl nets were reeled out into the Atlantic.

At sunset, it was time for the MOCNESS tow net to take a dive. WHOI marine ecologist Joel Llopiz and research assistants organized and spread five nets across the device’s giant metal frame. Once deployed, the MOCNESS began its journey to 1,000 meters (3,280 feet) below the surface. As the frame descended through the water, researchers opened and shut each net at specific depths, collecting samples between 0-1000 meters; 1000-500 meters; 500-300 meters; 300-100 meters; and 100-0 meters.

The MOCNESS awaits its first deployment. This high-tech tow net allows researchers to match what is found in nets at specific intervals with discrete properties of water at those depths. (Photo by Joel Llopiz © Woods Hole Oceanographic Institution)

The scientists are targeting the deep scattering layer, comparing the acoustic data showing up on the shipboard monitors with the creatures captured by MOCNESS at each depth.

“It being the first cast, and there being all new electronics on the MOCNESS, I was mostly happy to see that everything was working well,” Joel said. “And of course, I’m looking forward to seeing what’s in the nets, especially what’s matching up with what we’re seeing on the acoustics.”

WHOI marine ecologist Joel Llopiz monitors the data coming in from the MOCNESS during its first deployment. (Photo by Andrea Vale © Woods Hole Oceanographic Institution)

In the early hours of the morning, after four hours at sea, the MOC delivered its first haul of sea organisms. Katy Baker, a PhD. student at the University of Tasmania, described digging through the collection traps as being “like a kid in a candy store.”

The catch included a large anglerfish and a gulper (or pelican) eel: rare finds, considering the depth they normally reside in. Copious amounts of krill were collected in the 300-100 meter layer net, which allowed researchers to pinpoint the exact depth and time that each species was collected.

Katy Baker, a PhD. student at the University of Tasmania, examines a salp caught during a deployment of a MOCNESS tow net during an August 2022 research cruise. Salps often attach together to create chains, increasing their surface-area-to-volume ratio to filter feed more efficiently. (Photo by Andrea Vale © Woods Hole Oceanographic Institution)
Katy Baker cups four myctophids, two hatchet fish and a sawtooth eel in her hand. Myctophids, or lanternfish, sport bioluminescent lights on their underbellies, creating counterillumination that helps them blend in against the relatively sunlit surface above. (Photo by Andrea Vale © Woods Hole Oceanographic Institution)
A red Atolla jellyfish floats in a tray creatures caught in the MOCNESS nets. (Photo by Andrea Vale © Woods Hole Oceanographic Institution)
From left to right: a gulper eel, myctophids, an unidentified species, and a sawtooth eel line WHOI research assistant Julia Cox’s arm. Gulper eels are able to expand their mouths and stomachs to consume comparatively large prey. (Photo by Andrea Vale © Woods Hole Oceanographic Institution)

“It showed that our systems are working well,” said Julia Cox, a research assistant in the Llopiz lab. “The tow went really smoothly, and we got all the samples we wanted to get. It was a very successful tow overall, very promising.”

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