The California Academy of Sciences is using a unique hyperbaric decompression chamber to prevent piercing the swim bladder when bringing up fish from the deep.
According to CAS’s Matt Wandell the chamber is fairly simple in design and can bring a fish up to to surface pressure in around 20 hours or so without adverse effects.
Aside from burst swim bladders, fish, like humans, can also get decompression sickness when exposed to rapid changes in pressure during capture.
“Bent” fish are most likely widespread in the live reef fish trade, as most of the species that have been examined were found to suffer symptoms of decompression sickness after capture from shallow depths of 10 to 15 metres.
Although most of the barotrauma damage occurs internally and thus is invisible, there are some external symptoms. At any given depth a fish’s body will absorb nitrogen gas through the gills and into the blood stream until equilibrium and saturation is reached.
If decompression is slow, the excess nitrogen can be removed via the blood to the gills. During capture of the fish, however, rapid decompression saturates the rate of nitrogen elimination. The stationary bubbles that accumulate in the bloodstream and tissues lead to the symptoms of decompression sickness.
In many fish, especially benthic dwellers that do not usually swim up and down the water column, the drastic increase in the volume of gas during depressurisation at capture will inflate the swim bladder. The size of the inflated swim bladder at the surface increases with depth of capture and the swim bladder will rupture when the volume of gas becomes too great.