Fishing gear is rarely perfectly selective. Alongside the target species, nets, longlines, and trawls often capture marine mammals, seabirds, turtles, and non-commercial fish. This unintended catch is called bycatch.

Some bycatch is discarded at sea, often dead or dying; some is retained and sold. The ecological cost can be high, especially for slow-reproducing species such as sharks, rays, and albatrosses. Certain fisheries have historically discarded more biomass than they retained, prompting management reforms.

Technical solutions include turtle-excluder devices, bird-scaring lines, circle hooks, and real-time spatial closures. Certification programs and import regulations increasingly require demonstrable reductions in bycatch. Monitoring through observers and electronic systems is essential for measuring progress. Complete elimination is difficult, yet substantial reductions are achievable with existing tools and incentives.

• Non-target species caught during fishing
• Can include mammals, birds, turtles, and fish
• Often discarded dead or dying
• Reduced by gear modifications and management