Bycatch from shrimp trawler (Credit: Eliott Norse, Marine Conservation Biology Institute/Marine Photobank)

Turtle Excluder Device (Credit: NOAA)

The incidental catch of non-target species in fisheries is known as bycatch. Bycatch can be separated into bycatch that is kept and landed as part of the commercial catch and bycatch that is discarded.

While bycatch issues are of concern across marine ecosystems and specific fisheries, some of the most notable impacts of bycatch are surface longline fisheries which target tuna and swordfish but also catch endangered species like sharks and turtles.

Bycatch is an issue in almost all fishing gear types, with the exception of some rod and reel fisheries, harpoon fisheries and diving where there is near 100 per cent selectivity. Bycatch can be reduced in some fisheries by modifying the fishing gear – for example, using turtle excluder devices (TEDs) in south Atlantic shrimp fisheries, and the Nordmore grate in north Atlantic shrimp fisheries. Bycatch can also be avoided by changing fishing behaviour, avoiding migratory routes for whales, fishing at different depths, using different baits which can be selective for certain species of fish and by fishing with lower impact gear.

In 2008, the Ecology Action Centre, Living Oceans Society and the Marine Conservation Institute completed a review of the impacts of all fishing gears used in Canada which provides data driven assessments on the relative impacts these gears on habitat and bycatch.

Waste Not Images of bycatch are upsetting to most people because it is blatantly wasteful and waste is something that goes against human sensibilities at a primal level. Homo sapiens are amongst the exceptions of animals that produce bycatch when acquiring their food. Most animals are highly selective in ensuring that they eat what they catch and kill. There are human cultures highly linked to the products of the ocean that also tend to not waste anything they catch. However, as seafood has become a global commodity and not a local subsistence resource, bycatch is often out of sight. One way around this issue is to make bycatch illegal. That is all fish likely to die upon release must be retained and accounted for. Although waste is unsettling to us, from an ecosystem perspective, it is generally not that important whether we eat the fish or discard the fish. It is actually more important to know that the species that are discarded are also being harvested at levels their populations can withstand.  A sustainable fishery requires an understanding of the population and ecosystem consequences of the bycatch species. The best managed fisheries have 100 per cent observer coverage so that the levels of bycatch can be fully accounted for and managed. With this type of management it is possible to have strict limits on the amount of bycatch.
There are many fisheries of all gear types that are successfully controlling their bycatch impacts. Support these fisheries whenever possible. If not from a known sustainable source simply do not buy it. Search for sustainable seafood