Descending and Venting

Recent closures of several Gulf reef fish fisheries like red snapper and grouper have focused attention on the importance of successful release of fish caught in deeper water. These fish are particularly susceptible to mortality from barotrauma, the bloat and internal organ damage caused by pressure change. If discard mortality can be reduced, there is hope that the severity of closures and bag limits can be lessened.

Deep-water Release Working Group

Scientists and fisheries managers from across the nation have formed a deep-water release working group to evaluate the especially difficult problem of increasing the survival of fish caught from deep water. These fish are particularly susceptible to mortality from barotrauma, the bloat and internal organ damage caused by pressure change.

The working group members are looking at field trials on the U.S. West Coast that indicate the survival of some reef species can be significantly increased using rapid descending techniques that quickly return the fish to capture depth while minimizing injury. Research shows high survival rates for rockfish in depths up to 300 feet. (Watch this dramatic video of the release of a yelloweye rockfish.)

Florida Sea Grant has become part of the deep-water release working group, in an effort to generate information on the usability and practicality of these descending tools and techniques in the Gulf of Mexico.

Options of Last Resort

The most important concept of improved catch-and-release practices is to get the fish back in the water with a minimum of handling, and as quickly as possible. If a fish can get back down without intervention from the angler, neither venting nor descending are necessary.

However, 'floaters' are not a pretty sight. Fish caught from deep water experience significant damage when brought quickly to the surface. When intervention is required, venting and descenging gear may be helpful, but they also must be considered options of last resort, because they increase handling and time out of water.

Providing anglers with a variety of options that are best suited to local fishing conditions and practices may be the best solution for improving survival of deep-water released fish. Additional research is needed to learn more about improving release and fisheries management techniques.

Venting

Currently, venting is the required practice for releasing deep-water reef fishes caught in the Gulf of Mexico. It releases gases trapped in the fish's body cavity, allowing the fish to swim back to its normal habitat depth. Fish venting can be a useful method for returning fish back to depth. Evidence has shown that it can be helpful for some species, but the research for many other species is either lacking or inconclusive.

Why vent?

Reef fish taken from depths of 50 feet or more may undergo expansion of the gases in the swim bladder as they are brought quickly to the surface on hook and line. Swimbladders can expand only so far before they burst. When the swimbladder bursts, the gases escape into the fish's body cavity, where they can continue to expand.

The pressure exerted by the gases on the fish's internal organs is considerable, and can result in serious injury to the fish. Often the pressure is sufficient to push the stomach out of the mouth, and the intestines out of the anus.

Moreover, if the fish is released in this buoyant condition, the fish may float away and die from exposure to the elements, or become an easy target for predators.

Visit the Florida Sea Grant webpage on Fish Venting for a complete description of venting, tools and regulations.

Fish Descending

Fish descending devices may prove to be a more effective practice as they result in less injury to the fish. Providing anglers with a variety of options that are best suited to local fishing conditions and practices may be the best solution for improving survival of deep-water released fish.

As of April 2013, the Gulf of Mexico Fishery Management Council is considering changing the regulation that requires anglers to vent reef fish caught in the Gulf of Mexico. Use of all types of venting and descending devices is currently permissible in the Atlantic.

SLIDESHOW -- What are Fish Descending Devices? -- A brief slideshow of the devices at The Marine Scene Plus!

NEW FACT SHEET -- What are Fish Descending Devices? -- Reviews the kinds of tools and techniques that Florida Sea Grant extension agents and volunteer anglers are using in experimental trials around the state.

ADDITIONAL VIDEOS -- Rough video cuts of some previous descending field trials, as well as additional photos, can be found at Florida Sea Grant Flickr.

Additional Resources

Visit the FishSmart.org website for a summary of deep-water release workshops since March 2011.

PowerPoint

Watch Fish Venting: How to Use Venting to Improve Survival of Released Fish, a 12-minute PowerPoint-to-Flash tutorial covering the how and why of using venting and deep release rigs to mitigate the effects of barotrauma in reef fish.

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