Survival of Reef Fish after Rapid Depressurization: Field and Laboratory Studies
K. M. Burns and V. Restrepo
Undersized catch is a serious problem in reef fish fisheries. Current U.S. state and federal management plans enforce minimum size regulations for species in the grouper/snapper complex, but, to be effective, a high rate of postrelease survival must occur over all depths fished. Survival rates are known to vary by depth of capture, among other factors (Gitschlag and Renaud 1994). Rapid depressurization of physoclistic (closed swim bladder) fish caught at depth can be harmful, even lethal, to fish. Reef fish brought rapidly to the surface from any appreciable depth, experience rapid expansion of swim bladder gases leading to ruptured swim bladders, bloating, protrusion of internal organs and eyes, and emboli. Although Wilson and Burns (1996) proved that red grouper Epinephelus morio and scamp Mycteroperca phenax can potentially survive in high enough percentages to justify a minimum size rule, if fish are rapidly returned to habitat depth, severe abdominal bloating and stomach protrusion hinders the fish’s ability to return to depth on its own following release. Without an easy shipboard method of aiding the descent of these bloated, undersized fish, they become easy prey for sea birds and predatory fishes.