Deep Sea Fishing and Animal Welfare

Deep Sea Fishing: Scale and Invisibility

Deep sea fishing — targeting species at depths of 200 meters to over 2,000 meters — has expanded dramatically in recent decades as nearshore stocks have been depleted. Bottom trawling, longline fishing, and deep-water gillnets now reach previously unexploited ecosystems, capturing species including orange roughy, grenadiers, deep-sea sharks, toothfish, and numerous others. These fishing operations occur in remote areas, largely invisible to consumers and policymakers, with minimal welfare consideration for the animals caught.

Scale: Deep sea fishing vessels operate across all the world's oceans, including international waters beyond national jurisdiction. The global bottom trawling fleet travels millions of kilometers annually. Bottom trawls damage deep-sea coral and sponge habitats that took centuries to form and capture enormous bycatch volumes alongside target species.

Barotrauma: A Unique Deep-Sea Welfare Issue

Fish and other organisms caught in deep water and brought rapidly to the surface experience barotrauma — injury caused by the rapid decrease in ambient pressure. At depth, fish body cavities contain gas at high pressure; rapid decompression causes these gases to expand, rupturing internal organs, extruding the swim bladder through the mouth, and causing severe internal damage.

Barotrauma Welfare Impacts: Fish suffering barotrauma experience severe internal injuries. Even fish that appear alive at the surface and are released as bycatch typically cannot dive back down and die at the surface from their injuries. The welfare costs of barotrauma affect not only target species but the enormous volumes of bycatch that deep-sea fishing incidentally captures.

Discard and Bycatch

Deep-sea fisheries have notoriously high bycatch rates — non-target species and undersized individuals captured and discarded. Some deep-sea trawl fisheries discard over 80% of their catch. Discarded fish that have experienced barotrauma effectively never survive. The welfare costs of deep-sea bycatch — fish, rays, sharks, invertebrates, and marine mammals — are enormous and essentially invisible in standard fisheries management accounting.

Deep Sea Shark Welfare

Deep-sea sharks are among the most vulnerable species to fishing impacts. Many deep-sea shark species grow extremely slowly, mature late, and produce few offspring — making them highly sensitive to fishing pressure. Deep-sea sharks are taken as both target species (for fins, liver oil, and meat) and as bycatch across all deep-sea fisheries. Their slow reproductive rates mean population recovery from depletion takes decades.

Shark Finning Welfare: Finning — removing shark fins at sea and discarding the body — continues in some deep-sea fisheries despite prohibitions. Finned sharks dumped alive into the sea cannot swim and die from suffocation or predation. This practice causes prolonged, severe suffering and has driven numerous shark species to near-collapse.

Deep Coral Destruction

Bottom trawling in deep water destroys deep-sea coral and sponge ecosystems that took centuries or millennia to develop. These ecosystems provide essential habitat for numerous species. While the welfare implications of habitat destruction are less direct than those of individual animal killing, the elimination of habitat that supports diverse communities of animals represents a second-order welfare harm of significant scale.

Marine Protected Areas: Establishment of marine protected areas (MPAs) in deep-sea regions provides protection for both habitat and the species that depend on it. High seas MPAs — in international waters beyond national jurisdiction — require international cooperation. The 2023 High Seas Treaty created frameworks for high seas area protection that could benefit deep-sea ecosystems and their inhabitants.

Improving Deep Sea Fishing Welfare

Several approaches can reduce the welfare costs of deep-sea fishing:

Gear modification: Excluder devices reducing bycatch of non-target species; gear designs reducing habitat contact
Depth limitations: Prohibiting fishing below certain depths protects the most sensitive deep-sea ecosystems
Bycatch reduction: Observer programs, electronic monitoring, and gear restrictions to reduce non-target capture
Catch limits: Science-based quotas preventing overexploitation of slow-reproducing deep-sea species
Area closures: Protecting the most sensitive deep-sea habitats from trawling entirely

EU Deep Sea Fishing Regulations: The European Union has banned bottom trawling below 800 meters in European waters and established some area-based protections for vulnerable marine ecosystems. These measures represent meaningful welfare progress, though enforcement and coverage gaps remain. International waters require separate governance frameworks through RFMO (Regional Fisheries Management Organization) regulation.

Consumer Action

Deep-sea fish species raise significant welfare and sustainability concerns. Orange roughy, grenadier, and similar deep-sea species are long-lived and slow-reproducing, making sustainable harvest difficult. Welfare-conscious consumers can consult seafood sustainability guides (MSC certification, Monterey Bay Aquarium Seafood Watch) that incorporate some welfare-relevant information alongside sustainability assessments. Reducing consumption of deep-sea species reduces both conservation and welfare pressure on these poorly understood but clearly feeling animals.