**This blog entry orginally appeared on the website oceanspaces.org.**/p>

If you’ve ever been fishing off the coast of California, you’ve likely captured a rockfish, and perhaps even captured a rockfish that you had to throw back.  If this is familiar to you, the sight of a blown up rockfish with eyes bulging, and something coming out of its mouth, is also likely familiar.  That gas-filled item in the fish’s mouth is actually the rockfish’s stomach. Scientists call this gassy condition in rockfish “barotrauma.”  Barotrauma occurs in rockfish for a similar reason the bends happens in divers: when surfacing from deep water, gas expands in enclosed body cavities.

When a rockfish is reeled from deep water, the gas in the swimbladder expands and usually leaks into the rest of the fish’s body, looking for an escape.  The excess gas may push the stomach inside out and out the fish’s mouth, and push the eyes from their sockets.  This phenomenon is why most of the time rockfish end up floating on the surface when you release them. They just have too much gas inside of them to get below the surface of the water on their own.

For seven species of rockfish that have been declared “depleted,” this is especially bad because mortality rates from a surface release are over 50% when captured at depths between 40 m – 60 m and 100% when captured at depths over 60 m [1].

There is something you can do to help increase their chances of survival.  Ongoing research shows that if rockfish are released with a deepwater release/recompression device immediately after capture, the survival rate can be quite high. This is often called recompression, because as the rockfish is assisted back to its original depth of capture, the gas inside of the rockfish recompresses and the fish is able to swim away on its own.

Deepwater release devices are basically some variation of a weighted, barbless hook or fish gripper device that you attach to your rod.  A weighted cage (an old milk crate works great) with a line attached to it also works.  You can make your own, or purchase one in a tackle store.

  
Watch an entertaining video demonstrating the use of various recompression devices!

 

 

Some of the exciting research on rockfish and recompression has shown the following:

  • High rates of survival 2 to 17 days after recompression in several species of rockfish that have been captured at depths up to 55 m and immediately recompressed [2-4].
  • Limited tagging data that show rockfish surviving over 1 year after recompression [5].
  • Rockfish species that hang out in the water column (black rockfish, blue rockfish, and yellowtail rockfish) don’t seem to get as much benefit from recompression as rockfish species that hang out on the ocean bottom (i.e.: canary rockfish, yelloweye rockfish) [2, 6].
  • Despite eyes bulging from their sockets, air bubbles in the eye, and stretched optic nerves, vision is recovered in rockfish 2 days after they have been recompressed [7, 8].
  • Rockfish can get gas bubbles (emboli) in several of their tissues when brought up from as shallow as 20 m, however if quickly recompressed these emboli will often disappear and not cause any long-term injuries [9, 10].
  • Yelloweye rockfish can still reproduce after experiencing barotrauma and recompression [11].
  • Several deepwater rockfish species captured at depths up to 150 m have the potential to survive if recompressed [12-14] .
  • Factors such as the species of rockfish [2, 4, 6], the amount of time a rockfish spends on deck before being recompressed [4], the temperature difference between the depth of capture and the surface [2, 4], and the depth of capture can affect the survival of rockfish that are recompressed [2, 6].

As a result of this research, several “best fishing practices” to help increase rockfish survival have been developed [15, 16] and are being adopted by state, federal and nonprofit organizations.  Some of these practices include:
Plan ahead – Be prepared with deepwater release devices appropriate for the ocean conditions and fishing depth. Have devices out and ready to go.
Avoidance – If you are catching fish that have to be thrown back, move to a new spot.
Land the fish quickly – It is not possible to alleviate barotrauma by slow reeling because the rate of gas-resorption in rockfish is days, not minutes.
Minimize handling – Minimize the amount you handle fish before release.
Time is of the essence – Recompress rockfish within 5 minutes of capture, but the quicker the better!
Get it down – Try to return your rockfish as close as possible to its depth of capture.

Several efforts are underway to help get the word out to recreational anglers about the benefits of using recompression devices. The angling community has developed an innovative program called FishSmart, whose goals include communicating to anglers the benefits of improving the survival of released fish and implementing best practices, identifying needed research to help improve the survival of released fish, and building strong partnerships between the recreational fishing community, fisheries management bodies, and conservation organizations to work toward sustainable sport fishing opportunities.

California SeaGrant has developed a brochure about barotrauma in rockfish and how to use various recompression devices.  Collaborative Fisheries Research West and California SeaGrant also funded the production of the entertaining outreach video shown above that explains why barotrauma occurs in rockfish and demonstrates how to use commercially available recompression devices.  Angler Merit McCrea, biologist Milton Love and fish artist Ray Troll are featured!

These outreach efforts are a great example of how anglers, researchers, and fishery managers can all work together to help steward our ocean resources for generations to come!

 

References
1.              PFMC, 2009-10 Pacific Coast Groundfish Fishery Final Environmental Impact Statement, in Pacific Fishery Management Council. 2009, Pacific Fishery Management Council: Portland, OR.
2.              Hannah, R.W., P.S. Rankin, and M.T.O. Blume, Use of a Novel Cage System to Measure Postrecompression Survival of Northeast Pacific Rockfish. Marine and Coastal Fisheries, 2012. 4(1): p. 46-56.
3.              Hochhalter, S.J. and D.J. Reed, The effectiveness of deepwater release at improving the survival of discarded yelloweye rockfish. North American Journal of Fisheries Management, 2011. 31(5): p. 852-860.
4.              Jarvis, E.T. and C.G. Lowe, The effects of barotrauma on the catch-and-release survival of southern California nearshore and shelf rockfish (Scorpaenidae, Sebastes spp.). Canadian Journal of Fisheries and Aquatic Sciences, 2008. 65(07): p. 1286-1296.
5.              Hannah, R.W. and P.S. Rankin, Site Fidelity and Movement of Eight Species of Pacific Rockfish at a High-Relief Rocky Reef on the Oregon Coast. North American Journal of Fisheries Management, 2011. 31(3): p. 483-494.
6.              Hannah, R.W. and K.M. Matteson, Behavior of nine species of Pacific rockfish after hook-and-line capture, recompression, and release. Transactions of the American Fisheries Society, 2007. 136(1): p. 24-33.
7.              Rogers, B.L., C.G. Lowe, and E. Fernández-Juricic, Recovery of visual performance in rosy rockfish (Sebastes rosaceus) following exophthalmia resulting from barotrauma. Fisheries Research, 2011. 112(1–2): p. 1-7.
8.              Rogers, B.L., et al., Utilizing magnetic resonance imaging (MRI) to assess the effects of angling-induced barotrauma on rockfish (Sebastes). Canadian Journal of Fisheries and Aquatic Sciences, 2008. 65(7): p. 1245-1249.
9.              Pribyl, A.L., et al., The response to forced decompression in six species of Pacific rockfish. Transactions of the American Fisheries Society, 2011. 140(2): p. 374-383.
10.           Pribyl, A.L., et al., Recovery potential of black rockfish, Sebastes melanops Girard, recompressed following barotrauma. Journal of Fish Diseases, 2012. 35(4): p. 275-286.
11.           Blain, B., The effects of barotrauma and deepwater-release devices on the reproductive viability of yelloweye rockfish, in Fisheries Academic Program. 2011, University of Alaska: Fairbanks.
12.           Smiley, J.E. and M.A. Drawbridge, Techniques for live capture of deepwater fishes with special emphasis on the design and application of a low-cost hyperbaric chamber. Journal of Fish Biology, 2007. 70(3): p. 867-878.
13.           Rodgveller, C., C. Lunsford, and P. Malecha, Recompression experiemnts on rougheye rockfish with barotrauma. Alaska Fisheries Science Center, Juneau, unpublished data.
14.           Wegner, N., J. Hyde, and A.L. Pribyl, Post-release survival of deepwater rockfish following field recompression. NOAA Southwest Fisheries Science Center, La Jolla, unpublished data.
15.           Loftus, A.J. and G.C. Radonski, Proceedings of the FishSmart Barotrauma Workshop. 2011.
16.           Loftus, A.J. and G.C. Radonski, Regional workshop on improving survival of angler caught and released fish. Available at: www.fishsmart.org , 2012.