Explanatory note: The following article of PEW Charitable Trust refers mainly to sport fishing but we want to share this article because of the interestingness of the concept and because it may be useful at some point, to be applied in some manual commercial fishery or for scientific purposes.
Millions of deep-dwelling ocean fish that are caught and released die each year from the rapid pressure changes they undergo when they are hauled to the surface—a loss that is harming the health of some fish populations.
Now there’s a simple, affordable, and reusable device that can help fish survive their trip to the surface and back, and the South Atlantic Fishery Management Council is hosting public hearings on the topic this month. Members will discuss a proposal to require that fishermen have the tool on board so they can be ready to release fish safely and improve the animals’ chances of survival. The hearings will be webcast at 6 p.m. EDT Tuesday, April 30, and Wednesday, May 1. The council is accepting written comments from noon April 16 to 5 p.m. May 10.
When fish ascend rapidly, gases build up that cause their organs to expand, leading to a condition known as barotrauma, which is similar to the bends in humans. Once returned to the water, fish sometimes have trouble swimming back to their preferred depth before the damage becomes fatal. But a weighted device clipped to a fish’s jaw helps it sink quickly, improving the chances that its organs will return to their normal size in time.
There are several types of descending devices; some include a pressure switch that releases fish at preset depths. A top-of-the-line, reusable descender can cost about $50; the tools are also attached to line so fishermen can easily retrieve them.
A new video by Brendan Runde, a graduate research assistant in North Carolina State University’s Department of Applied Ecology, shows a red grouper recovering from barotrauma with the help of a pressure-switch descending device.
YouTube video: Red grouper with barotrauma recompressed with SeaQualizer descender device - NC State CMAST
The South Atlantic council’s proposal, Snapper Grouper Regulatory Amendment 29, would require the devices on fishing boats that catch snapper and grouper species. For years, the council has been trying to reduce the number of red snapper caught incidentally when fishermen target other species. Too many red snapper die from barotrauma, which experts say is slowing the population’s recovery from years of overfishing.
Council members have asked the body’s Law Enforcement Advisory Panel to ensure that the regulation clearly defines a “rigged and ready” requirement for the devices, meaning they are on board and ready to use. The council also is developing a research and monitoring plan to better understand use of the devices and track compliance if the proposal is approved. Combined, these two steps would maximize use of the devices and measure how well the regulation helps fish populations recover.
Education efforts have increased fishermen’s awareness of barotrauma and how descending devices can help. For example, NOAA’s Bycatch Reduction Engineering Program recently awarded $81,000 to the South Carolina Wildlife Federation to work with the South Atlantic council in educating fishermen about the tools, fish handling techniques, and best practices for releasing fish under a range of conditions and locations. The program is providing 500 free descending devices to anglers who complete an online tutorial or attend one of 12 educational workshops. And Yamaha and other marine supply manufacturers, in partnership with state and federal fishery managers, are promoting best practices for releasing fish through the FishSmart Conservation Project.
Left, the Set the SeaQualizer, $55, to a specific depth, and the jaws automatically pop open to release bottomfish at the proper atmospheric pressure. Al medio Attach the RokLees by EcoLesser, $30, to a fish’s mouth. Once it’s deployed to a suitable depth, jerk the rod tip to open the descender’s jaws and free the fish. Right the Blacktip’s Catch & Release Recompression Tool, $55, utilizes a heavy weight to clamp shut its jaws on a fish’s mouth. Once the weight hits bottom, the jaws open and release bottom-dwellers like rockfish. (graphics: Kevin Hand)
Catch and release is a common practice. Fishermen often discard nontarget species and fish that are illegal to keep because they are too small, out of season, or exceed a catch limit.
But mortality of discarded fish is one of the biggest challenges facing many fish populations. In the South Atlantic, a recent stock assessment found that 28.5 percent of recreationally caught red snapper die after release—more than 460,000 fish in 2017. For commercially caught red snapper, the proportion that die after release is 38 percent, and some other species’ mortality rates are even higher.
YouTube vieo NOAA: Down Scope: Saving Snapper & Grouper from Barotrauma
Another stock assessment reported that nearly all snowy grouper die after they are thrown back, mainly because they are hauled up from very deep water. And more than 7.6 million black sea bass—about 13 percent of the fish released by anglers—died after release from 2012 to 2016, according to the most recent stock assessment and the National Oceanic and Atmospheric Administration’s fisheries statistics.
Descending devices show strong potential to benefit both fish and fishermen. Along with other measures The Pew Charitable Trusts has supported during the past 10 years, such as science-based fishing limits and protecting spawning habitat, reducing the number of fish lost to barotrauma will lead to more robust fish populations—a win for fishermen, the U.S. marine ecosystem, and all who rely on healthy fisheries.