What is a swim bladder and how are rockfishes different?

A swim bladder is a gas filled organ that allows fishes to regulate their buoyancy within the water column. By controlling how much gas is in the swim bladder, fish can easily ascend or descend in the water column without expending much energy. In many fish species this organ is connected to the esophagus, in rockfish however, this connection is absent and gas exchange is regulated solely by diffusion in and out of the bloodstream. This unique physiology makes rockfish susceptible to a phenomenon known as barotrauma. When a rockfish is quickly brought to surface, as occurs during fishing, the swim bladder expands with gas, at a rate faster than the fish can release it. This causes gas to leak into the body and cranial cavity compressing organs, causing bloating, bulging eyes, and expulsion of the stomach. This is a life-threatening condition and will quickly cause death if the fish is not returned to depth.

How can you help?

With almost 40 species in BC, rockfish are often incidentally caught by anglers and discarded as unwanted bycatch. However, these rockfish do not often survive due to barotrauma. They will often remain floating at the surface where they will die from their injuries or from predation by other species such as birds or marine mammals. Luckily however, the effects of barotrauma can be reversed and rockfish can survive incidental capture if quickly returned to depth. The use of descending devices will quickly bring rockfish back to depth, allowing the swim bladder to recompress, and the effects of barotrauma reversed. Research has shown that the quicker an individual is returned to depth, the greater the likelihood is of survival.

When out fishing always carry a descending device with you. Should you accidentally catch a rockfish return this species to depth as quickly as possible, ideally within 2 minutes of capture and aid in the conservation of these remarkable species! Find out more about barotrauma, guides, and different descending devices here.

Note: If you are catching a lot of rockfish in an area, particularly species which are threatened or endangered (see COSEWIC and SARA listings), the best thing to do is to move into another area.

Interested in learning more about rockfish? Check out our links below and additional resources here