The continental shelf waters off the southeastern United States are home to over 100 species of demersal (seafloor-associated) fish. When caught, these fish sometimes experience injuries called barotrauma as a result of the pressure change from seafloor to the surface (see gallery). Barotrauma can vary in its severity, but sometimes results in expanded swim bladder gases that cause the fish to float. Unable to re-submerge, floating fish are destined to die without intervention.
Enter descender devices. These handy tools push or pull floating fish back down to a depth where gases recompress. Descender (or descending) devices can be as simple as an inverted milk crate or as complex as the SeaQualizer tool (which has an incorporated pressure sensor allowing a pre-specified release depth). One focus of my research has been evaluating the effectiveness of descender devices in increasing post-release (or discard) survival for a variety of species.
Our team has used conventional and electronic tagging to evaluate survival after descended release. Overall, we have shown that descender devices are very effective for increasing survival in several species of groupers, black sea bass, and red snapper.
See a descender device in action in the video below!
Papers on descender devices: