FishSmart logo showing man thinking about fish smartlyFishSmart, a program driven by the fishing community, for the fishing community, works to improve the survival rate of released fish through teaching proper techniques for both freshwater and saltwater.  FishSmart does not just teach catch and release, but rather proper catch and release practices.

Across the nation, half of all fish caught are released.  In saltwater alone, nearly 500 million deep-sea fish species are caught each year and more than half are returned to the water, but not all survive.  By using careful catch and release techniques, more of these fish have a chance for survival.  Especially with some popular species of game fish, increasing the survival rates of released fish may be the only way to maintain healthy fish populations, now, and in the future.

FishSmart guides anglers with simple practices that improve the odds of released fish survival, including how to minimize injuring the fish. In certain areas of the country, special catch and release techniques should be practiced for deep water species.  Anglers who fish for deep-sea fish species, such as snapper, grouper and other deep-sea fish species in the Gulf of Mexico and South Atlantic, cod and black sea bass in the mid and north Atlantic, bottom fish (snapper and sea bass) in Hawaii, or rockfish on the West Coast and Alaska should be prepared to deal with fish suffering from the ill-effects of being brought rapidly to the surface.  But with the application of FishSmart techniques these fish can be released to survive for years to come.

Why Are Deep Water Fish Different?

All fish that are to be released require proper handling, but deep water fish can suffer from the effects of decompression when being brought to the surface while fishing and may require extra measures.  This does not mean you should not fish for them, rather it is important to be aware of the effect.  A little extra preparation is all it takes to release deep water species safely.

What Is A Swim Bladder?An angler holding a deep-sea fish species where its swim bladder has protruded out of its mouth

Successfully releasing deep-sea fish species  poses a challenge because of an organ called a swim bladder.  This gas-filled sac aids the fish by providing buoyancy. The fish can adjust its position in the water up or down by inflating or deflating the bladder slightly.

Unfortunately, with some deep-sea fish species, when you hook a fish, and bring it to the surface, the rapid ascent makes the fish's swim bladder swell like an over-inflated balloon.  The pressure at 100 feet under water, for example, is four times as great as at the surface.  So when a fish is brought to the surface from that depth, its swim bladder expands to many times its normal size. This is called decompression.  Decompression can happen in SCUBA divers as well, we call it the "bends" a serious medical condition that can be fatal.  With deep-sea fish species, the expanded swim bladder presses on other internal organs from the inside out.  Many times the fish's stomach will protrude from its mouth and its eyes will bug out. These effects are known as barotrauma.  Barotrauma is seen in such species as snapper, grouper and a few others.  Other deep water species such as freshwater salmon and trout, can adjust easily and will often go back down on their own after a while. 

It is particularly important to be prepared to release fish suffering from barotrauma because most are highly managed with season, area and size restrictions.  If you are planning to fish deep, plan to have a venting tool or a fish descender on board.  Some states require a venting tool be used, check with your state agency on their specific fishing regulations.

How Do I Release A Fish Suffering Barotrauma?A FishSmart diagram of how a deep-sea fish species swim bladder expands as it rises to the surface of the water

The antidote for decompression in fish is similar as in SCUBA diving - recompression.  For a diver, it means hours in a hyperbaric chamber.  For a fish, it's a lot simpler.  They just need to be returned to the depth from which they came, instead of being released at the surface.

The simple act of sending the fish back down into deep water will allow the swim bladder to recompress and shrink back down to normal size.  In studies of rockfish caught in California, fish returned to its original depth after less than two minutes at the surface, survived more than 80% of the time.  Getting them back down is easier than you think.  You can either release the extra pressure in the swim bladder with a venting tool, or send the fish back down to the bottom with a fish descender.

Venting Tools

A venting tool is simple in theory. It's a hollow needle that you insert into the fish's swim bladder to release the pressure.  Insert the needle into the side of the fish a few inches behind the pectoral fin and at a 45 degree angle and deflate the swim bladder. With the pressure released, the fish should be able to swim back down to depth on its own. Venting should not be done on small fish.  If an angler feels uncomfortable with this method,  they should use a descending device instead.  Check with your state agency on their specific fishing regulations.

A descender, a tool that FishSmart recommends using to release deep-sea fish speciesDescenders

There are several variations of descenders, but most consist of a weight and barbless-hook, or lip gripping device that lowers the fish to the proper depth like an elevator in reverse.  After a few moments down deep, the fish will shake free of the hook.  One example, the Seaqualizer, which was awarded the first FishSmart tackle award, is a pressure-sensitive descender that grips the fish's lip and can be preset to pop open at 50-, 100-, or 150-feet down.

Another variation (a DIY option) is a weighted cage.  An upside down milk crate with weights works just fine. The fish just swims out the bottom once it has been lowered far enough.  You can make your own release cage by painting the inside of a milk crate (available at office supply stores) with rubberized paint (dive shops often carry this for marking equipment) to smooth over the sharp edges and help protect the fish.  Next, zip-tie rebar or lead weights to the edges of the open end.  Flip it over, weighted side down and tie on a long line of your choice.  Instant fish descender.


FishSmart Related State Regulations and Guidelines

Always check with your state agency on their specific regulations if a catch and release venting tool is required, and learn how to use these tools before going fishing.  Some specific state and regional regulations:

But remember, before practicing special deep water release techniques, anglers should first follow the catch and release general guidelines for handling the fish properly to increase survival.

If you are a member of a state fish and wildlife agency, or a charter business click here to learn more about FishSmart's organization and mission.

Resources on barotrauma and catch and release research:


Photos courtesy of Florida Sea Grant and California Sea Grant.