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Rockfish Barotrauma

Update: September 2022
New paper – Hailey L. Davies, Shane Gross, Dana R. Haggarty, Francis Juanes (August, 2022)- PHOTO DIARY – Conserving Rockfishes: Barotrauma and Descending Devices in the Northeast Pacific, Fisheries Magazine.

Get the app that alerts you when you enter a Rockfish Conservation Area.

Update: Fisheries Notice March  25, 2019
The use of a descending device is now required by condition of licence to assist in the conservation and survivability of rockfish being returned to the water. Because of their closed swim bladders, rockfish brought to the surface suffer barotrauma, causing the swim bladder to inflate and reducing the probability of their survival upon release. Handle catch as little as possible, using wet hands to preserve the protective slime coat, and return to the water at depth of capture as quickly as possible (under two minutes). To avoid catching rockfish, move to another fishing location.”


This photo is of a Yelloweye Rockfish that has died from barotrauma, also known as “pressure shock”. 

Yelloweye Rockfish that has died of barotrauma. Reduced water pressure causes the air in the swim bladder to expand and push out the esophagus and eyes. BUT this is a reversible condition whereby the fish can survive through use of a “fish descender”. Photo: Hildering. 

Many rockfish species are particularly sensitive to reductions in pressure since the air in their swim bladders expands substantially. The swim bladder is a buoyancy control organ and even when slowly reeled in from a depth of only 20 m (60’), a rockfish’s swim bladder can expand to three times its size, putting pressure on the fish’s organs.

As is the case with the Yelloweye Rockfish in the photo, the swim bladder can expand to the point of causing the fish’s eyes to bulge out of their sockets and its esophagus to be pushed out of its mouth (the esophagus is the first section of the digestive tract). I know this is likely a sight that may not enhance your appetite for your rockfish catch but please read on since, contrary to the thinking of many, this IS reversible whereby the rockfish stands a good chance of survival.

Colossal “management” errors were made with overfishing slow-growing rockfish. Many species are extremely long-lived, slow to sexually mature, and the big, old females are the most fertile – producing the most eggs and hatching the largest number of healthy young.

For example, Yelloweye Rockfish are believed to have a lifespan of up to 118 years. They don’t reproduce until they are at least 12 years old, and the old females can incubate up to 2.7 million eggs! Know that there are 38 species of rockfish off the coast of British Columbia. 

This means that species are very slow to reproduce whereby, if you catch lots, especially the big females, you can devastate populations very quickly.

Another nail in the coffin of rockfish is that many adults also have high site fidelity so that by fishing one area, you can wipe out a community of fish. Click here for my blog on having found back the SAME individual rockfish in the SAME spot after EIGHT YEARS. This is why Rockfish Conservation Areas (RCAs) are essential, where it is most often illegal to do any hook and line fishing (see restrictions here). 

But, what is you accidentally catch a rockfish outside these areas?

There are studies that support that if you were to quickly recompress the fish, it would stand a very good chance of survival, even where it appears dead at the surface. The fish could be brought back to depth with barbless weighted hooks, or commercial “fish descenders”.

This video make the life-saving potential of fish descenders very clear.

From Island Fisherman Magazine: “Common types of descending devices include a simple, inverted barbless hook, a spring-loaded clamp, and a pressure-release clamp. Of the different devices available, the most effective and simplest to use is a depth pressure activated release device, the Seaqualizer . . . Automatically opening at preset depth, the motion of the boat or the actions of the rockfish as it descends will not prematurely release the fish.

Examples of fish descenders:
Seaqualizer Fish Release Tool (~ $60 CAN)
(Recommended by various fishing organizations and publications)
Shelton Fish Descender (~$8 CAN) 
SeaQualizer SeaYaLater Fish-Release Hook (~$20 CAN)”

If you can act quickly enough (which is essential) you can even use and inverted, weighted milk crate. See clip below AND this link for making your own descending device.

How wonderful it would be if more people would undertake the effort to recompress the fish, knowing how dire the situation is for many rockfish species. Imagine the further positive impact if people would choose to return the depleted species to depth even when they haven’t reached their catch limit, especially the big, highly productive females.

But, even if there was to be such enlightenment, many rockfish populations are so depleted that they need far more protection.

Again, Rockfish Conservation Areas (RCAs) are essential. These should be areas known to be the territory of depleted rockfish populations. Since these are no-fishing zones, there is no chance of barotrauma and the rockfish populations that live in the area are given the time to rebuild to have more sexually mature fish and more big old super mamas.

In summary, it’s so easy to contribute to rockfish conservation:
(1) Respect Rockfish Conservation Areas knowing that you usually cannot do ANY hook and line fishing there; and
(2) Invest in a fish descender for rockfish caught outside RCAs.

Long live rockfish!

Fantastic video showing how rockfish that appear dead at the surface due to barotrauma fully can revive at depth! From the Coastside Fishing Club:

Video from Alaska Department of Fish and Wildlife showing a summary of homemade and commercial fish descenders. 

Entertaining and super informative video “How to save a life – a rockfish life” by fish guru Milton Love with a rap song by Ray Troll:

Source: Protecting Rockfish – Fisheries and Oceans Canada

Get the app that alerts you when you enter a Rockfish Conservation Area

Government of Canada

Examples of fish descenders

Research on the effectiveness of fish descenders

8 Responses to “Rockfish Barotrauma”

  1. Jacqui

    I had no idea that they could survive if released! We don’t fish for rockfish anymore, they are far and few between now. Thanks for the great info MD!

    • The Marine Detective

      My friend, it was a surprise to me too to find out how great their chances of survival are. From one source: “In experiments with several species of common Southern California rockfish, 83 percent of fish caught at depths between 217 feet and 350 feet, survived when returned to depth within 2 minutes. The odds of a fish dying following recompression nearly doubled with every 10-minute increase in time at the surface. Tagging and recapture studies showed some released fish were still alive 1.5 years later.” Therefore, their are efforts in California to have fishers recompress the fish using “tools” like this
      So simple . . .

  2. Anonymous

    Believe it or not, the answer to the mystery of whales beach themselves can stated in only one


    Barosinusitis in diving sea mammals is a pressure-related injury in the sinuses and air sacs

    located inside their heads.

    It is well-known that rapid and excessive changes in the surrounding water pressure can cause

    physical trauma in all diving mammals, including man.

    Severe oscillations in pressure are common above the epicenter of certain shallow-focused

    undersea earthquakes, especially those located in the rift valley of mid-ocean ridges. Scientists

    called these seismoacoustic waves seaquakes until the 1950s when the name was changed to

    T-Phase Waves.

    But not all earthquakes generate whale-dangerous T-Phase Waves (aka: seaquakes). Only

    events that occur in specific places and in a specific manner generate T-Phases that are

    dangerous to diving whales and dolphins.

    Navy sonar, oil industry airguns, and underwater explosives also induce rapid and excessive

    changes in pressures surrounding the diving whales and dolphins. These man-made devices

    cause the exact same barosinusitis injury as caused by seismoacoustic waves generated by

    undersea earthquakes.

    In toothed whales, the sinuses and air sacs serve as acoustic mirrors reflecting sound inside their

    heads in such a fashion to enable their echo-navigation system to function properly. An injury in

    this critical part of their biosonar system naturally disrupts echo-navigation, causing the animals

    to lose their normally excellent sense of direction. It also prevents them from diving and feeding


    Lost at sea, the flow of the surface currents direct the injured whales/dolphins downstream from

    the point of injury. This control over the swim path of the injured sea mammals happens

    because water is 800 times denser than air. The increased density induces a powerful drag

    (resistance) to swimming in any direction except downstream with the flow. Thus, surface

    currents quickly point lost whales and dolphins headfirst into the path of least resistance or least


    The whales/dolphins will recover from a slight barotraumatic injury within a week or so. On the

    other hand, surface currents are likely to deposit those that do not recover on a sandy beach

    because current just happens to be the same energy that carries each grain of sand to build the

    beach in the first place. In general, whales/dolphins are directed to beaches that are building

    sand; not to beaches that are eroding.

    Hungry sharks sense the whales/dolphins are in trouble. They move in close and wait for an

    opportunity to snatch any weakened pod member that falls behind.

    Unable to navigate or dive and terrified by the pack of starving predators trailing them, the

    wounded whales/dolphins huddle together in a tight group for protection against sharks and

    killer whales. They swim downstream with the flow of the surface currents. The idea that

    individuals will follow a pod leader to the beach, or be drawn in by the distress calls of a

    beached member out of some sort of strong social bond is an over-glamorized false concept.

    Rather, individuals are highly-stressed and have no idea which way to swim to safety. They will

    follow any whale that ventures out in hopes that this individual knows the way to open water.

    They abide by a herd instinct, remaining close to their pod mates because they are in dreadful

    fear of becoming the next shark attack victim if they swim away from the herd. It appears as if

    the Pod has close social ties but in fact the action of each individual is focused on self


    Said differently, it is the whale with the least fear that appears to human observers as a pod

    leader when in fact this individual is just as lost and confused as the rest of the pod.

    Landmasses that extend out to sea opposing the flow of the surface currents, serve to trap sand,

    flotsam, seaweed, and lost sea mammals swimming with the flow. Cape Cod is the best

    example of such a natural trap in the United States. Cape Sorrel in Tasmania and Golden Bay

    in New Zealand are also natural traps for non-navigating whales/dolphins.

    The reason for the increased strandings in Cape Cod during the 2011/2012 stranding season

    was the drastic increase in oil survey activity off the coast of Canada and West Greenland.

    Normally the dolphins swim away from the oil survey boats long before they are injured;

    however, the rocky coast of northeast Canada and western Greenland consist mainly of one

    small cove after the next. The dolphins dart into these coves to avoid the loud booms. The

    survey vessel blocks their escape route when it tows the airguns along the openings of the


    The survey crews could prevent these deaths if they would simply reduce the volume of air

    supplied to the airguns as they cross the mouth of the coves.

    I do not advocate the halt of oil exploration; however, I only ask that the oil industry and the US

    Navy stop denying the existence of barosinusitis and start listening to ways to prevent it. We

    can solve the problem by owning up to the truth and using simple precautions in the operations

    of oil survey vessels and sonar ships.

    The reason the Navy and the oil industry will not admit barotrauma involves the numerous “best

    available scientific information” clauses in the Marine Mammal Protection Act of 1972. This

    law mandates that our governments protect marine mammals to the limits of the “best available

    scientific information.”

    However, the control over developing “best available scientific information” is now solely in the

    hands of the US Navy and the oil industry since these two organizations fund 98% of all marina

    mammal research worldwide.

    It’s like putting the tobacco industry in charge of lung cancer research.

    The Navy and oil industry are not going to fund a study into barosinusitis since they are afraid

    they will shoot themselves in the foot. Instead, they fund research that covers up barotrauma in


    As long as they can muddy the waters on the “best available scientific information,” they can

    skirt around the laws and do as they please. On the other hand, if they would fund research on

    preventing barotrauma and barosinusitis in marine mammals, simple procedures could be put in

    place that would allow the oil industry to extract offshore oil and the Navy to practice using

    sonar and still save the lives of the thousands of whales and dolphins that are killed every month.

    Capt. David Williams, Chairman
    Deafwhale Society, Inc.
    (a 501-c non-profit whale research corporation devoted solely
    to understanding why marine mammals beach themselves.)

    • The Marine Detective

      Hello David, I hesitated with approving this comment. While the information is of great value, the issue is of great importance, and your dedication greatly to be respected, the information’s placement here is not ideal – on an item to do with fish, not cetaceans. I will at some point do an item on seismic and sonar impacts on cetaceans and will then reference your work. All the best.

  3. Hella

    Wow! Nature’s perfect workings. Thank you for sharing, Jackie.

  4. Heather Lane

    Fish are washing up on the beaches here in the Gulf of Papagayo, Costa Rica and there is both red tide present and several shrimp boats. Dead fish were not washing up on shore before the shrimp boats arrived. I know they kill a ton of by-catch but locals are saying that the eels, puffer fish, pargo and all other fish washing up on shore are killed by the red tide. Many of the pargo (snapper) have these bulged eyes/pressure shock….wouldn’t that mean that they were killed by shrimpers from being pulled up to the surface in the nets? Or could the red tide cause pressure shock as well?
    Thank you, Heather


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