The high seas — international waters beyond national jurisdiction — cover 64% of the ocean's surface. They are home to blue whales, bluefin tuna, albatrosses, and billions of other animals, while being the least regulated ocean area for wildlife protection. The 2023 High Seas Treaty represents a potential turning point.
High-seas longline fishing for tuna, swordfish, and other pelagic species catches millions of non-target animals annually. Seabird bycatch: 300,000+ seabirds, mostly albatrosses and petrels, hooked and drowned annually. Sea turtle bycatch: estimated 250,000+ per year on high-seas longlines. Shark bycatch: hundreds of millions annually. Each bycatch event causes drowning death (for air-breathers) or hook injury and stress (for fish), followed by discard. High seas bycatch is one of the world's largest-scale marine welfare problems with no easy enforcement mechanism.
The 2023 High Seas Treaty (BBNJ Agreement) — the first international agreement specifically governing high seas biodiversity — provides legal frameworks for marine protected areas in international waters. If ratified and implemented effectively, it could reduce fishing pressure in critical habitat areas, benefiting the welfare of millions of marine animals annually.
Blue whales, sperm whales, humpbacks, and other cetaceans spend much of their lives on the high seas. Welfare threats: ship strikes (an estimated 18,000-25,000 cetacean deaths annually from vessel collisions); entanglement in high-seas fishing gear; underwater noise from commercial shipping (chronic stress effects on communication and navigation); and climate-driven prey changes affecting feeding success. Ship speed reduction (to 10 knots in key areas) significantly reduces strike mortality and is a welfare-positive shipping industry standard in some voluntary programs.
The mesopelagic zone (200-1000m depth) contains the world's most abundant vertebrate biomass — mesopelagic fish like lanternfish perform the ocean's largest daily migration (ascending at night, descending at dawn). Proposals to commercially harvest mesopelagic fish at scale for fishmeal raise major welfare concerns: the scale (potential catch of 1-10 billion tonnes) and the welfare of these billions of sentient fish during trawl capture and suffocation death.