Deep-Sea Fish Welfare: Barotrauma and Discarding

Deep-sea fish caught in trawl and longline fisheries suffer severe barotrauma injuries when brought to the surface, causing welfare concerns even when animals are returned alive.

Key Facts

Barotrauma in fish brought rapidly from depth includes gas bladder rupture, eye protrusion, intestinal herniation and organ damage
Rockfish and other physoclist (closed swim bladder) species are most severely affected by barotrauma
Recompression using weighted descent devices (fish are returned to depth with devices that bring them back down) significantly improves survival
Discard mortality rates vary by species - barotraumatised deep-sea species often have very low survival even if returned alive
Mandatory recompression device use is now required in some US West Coast fisheries for rockfish species

Welfare Considerations

Barotrauma causes intense, acute suffering - the rapid pressure change causes physical injuries equivalent to decompression sickness in divers, with gas bubble formation in tissues and rupture of internal organs. Fish returned to the surface with protruding eyes and everted gas bladders are often in extreme distress and rarely survive without recompression. The welfare case for mandatory recompression devices in deep-sea fisheries is strong - the technology is simple and inexpensive, and significantly improves both welfare and conservation outcomes by returning viable animals rather than dying ones. Where discard is required by catch composition rules, recompression should be the mandatory accompaniment for physoclist species.

What You Can Do

Support mandatory recompression device requirements in deep-sea and rockfish fisheries
Advocate for catch-and-release fishing guidance that includes species-specific recompression advice
Choose deep-sea fish from certified fisheries with documented low-discard or recompression practices
Support research into barotrauma prevention technologies including slower surface retrieval methods