New device aims to reduce fish bycatch mortality

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A new device intended to improve the odds that a fish will live after catch and release is showing promise for use in deep sea fishing, thanks to a partnership among UNH researchers and students, a local business and a N.H. charter boat captain.   

The device, dubbed the “BaroSafe System,” is a three-foot-tall cylindrical steel cage attached to a rope and pulley system that is stationed on the deck of a boat. The device will allow anglers to place half a dozen unwanted fish into the cage, lower them deep into the ocean and open the bottom trap door so the fish can swim out at their depth of capture. Early results indicate that the BaroSafe System helps prevent unnecessary fish mortality, which is important in the health of fish populations, explained Erik Chapman, fisheries specialist for N.H. Sea Grant/UNH Cooperative Extension.

Metal cage sits on deck of boat.

Above: The BaroSafe System, ready for deployment.

Men on boat discuss details of metal fish cage.

Above: Erik Chapman (R) talks with Ben Brickett (L) from Blue Water Concepts about the BaroSafe device deployment.

“The BaroSafe System has the potential to save large number of fish and may have real impact on sustainability of fisheries in New England and around the world,” said Alex Brickett, program manager at Blue Water Concepts in Eliot, Maine, who helped to develop the device.

Fish that are brought up from the ocean may experience barotrauma — injury caused by the transition from deep, cold waters at higher pressure to shallow, warmer waters at lower pressure. Some fish species are able to tolerate barotrauma better than others; Gulf of Maine fish like cusk and redfish are particularly sensitive to barotrauma and often will not survive being brought to the surface and thrown back overboard. This is what fisheries managers refer to as “bycatch mortality.”

Young man holds redfish caught by rod and reel.

Above: An Acadian redfish, native to Gulf of Maine waters, experiences symptoms of barotrauma when brought to the surface.

An estimate of the bycatch mortality rate is used in computer models to help determine management regulations. A larger bycatch mortality rate may lead to a decrease in the number of fish that fishers are allowed to keep, Chapman said. He noted that recent regulations that limited fishermen to just a handful of fish like cod and haddock have coincided with fewer booked charter boat trips in N.H. Fishermen want to do whatever they can to help decrease bycatch mortality and increase the number of fish they can keep, he added.

Rather than toss an unwanted fish overboard at the surface, scientists and engineers have been working on developing equipment that would bring the fish down to its depth of capture quickly in hopes of lessening the impacts of barotrauma. Brickett worked on an early prototype of the BaroSafe System while he was a senior at UNH — he received an Undergraduate Research Award to develop equipment that would help lobstermen return undersized lobsters to depth quickly. This effort rolled into future discussions with UNH staff and local fishermen about how to apply the technology to fish bycatch.

Similar equipment has been developed elsewhere that can return one fish at a time to their capture depth, but Chapman and others felt that there should be a better solution.

“That kind of one-fish-at-a-time effort is really high maintenance and not the most efficient use of time,” Chapman explained. “The charter boat captains were asking for equipment that was quick and easy to use when their clients were on board fishing, something that isn’t in the way of the fishing equipment and won’t require deckhands to spend a lot of extra time attending to it,” he said.  

With development funding provided by N.H. Sea Grant, Chapman worked with Chris Glass, UNH research professor of zoology and ocean sciences, Mark Godfroy, a charter boat captain out of Seabrook, N.H., and the engineers at Blue Water Concepts to design a prototype based on Brickett’s undergraduate project. This spring, the team conducted a test-run of the BaroSafe System at sea with help from students in the UNH Fisheries and Aquaculture Club.

After catching fish using rod-and-reel on Godfroy’s boat, the team practiced using the device to return fish to various depths. A GoPro camera was attached to the side of the device to take underwater video footage of the process and determine the efficacy of the device. The UNH students recorded water temperature data and the fish species captured and the depth at which they were returned. Half a dozen redfish — the species most visibly experiencing barotrauma — were placed in the device and lowered to near the bottom of the ocean. Video footage revealed they swam out of the cage once the door was released, and those lowered the deepest did not pop back up on the water’s surface — a sign that indicated the redfish likely survived the catch-and-release experience.


“From an engineering perspective, the device accomplished all intended goals,” Brickett said. “It worked better than we anticipated, which is rare with a novel technology,” he added.

Streamlining the set-up on board the boat to ensure ease of use and client safety is continuing, but subsequent trials of the BaroSafe System have elicited positive feedback from Godfroy’s fishing clients, with many of them requesting turns to push the button that lowers the device full of fish into the water.

Young man places fish in metal cage.

Above: A deckhand on Mark Godfroy's fishing boat places a fish in the BaroSafe device for its return to deep waters.

“If we can prove that we can release fish with zero mortality, maybe the regulations will change for people who work with device like this,” Godfroy said. “Maybe it will allow us to keep two more fish each trip. My customers want to make sure the fish stay alive so they can catch them later,” he added.

Widespread adoption of the technology is a slow process, Chapman noted, but the team is moving forward with the efforts to get the device ready for other fishermen to use on their boats.

“Working with engineers, fishermen and fisheries scientists all trying to solve the same problem has been great,” he said. “Overall, it’s one of the more enjoyable and potentially successful projects I’ve worked on.”

Check out more photos from this project. For more information, please contact Erik Chapman at or 603.862.1935.

N.H. Sea Grant promotes the wise use, conservation and sustainable development of marine and coastal resources in the state, the region and beyond. Located at the University of New Hampshire, NHSG is part of a national network of programs located in our coastal and Great Lakes states as well as in Puerto Rico and Guam.  

Rebecca Zeiber, N.H. Sea Grant Science Writer