What is bycatch?

Bycatch is the unintended capture or entanglement of non-target species in fishing gear.

The seas around the UK thrive with life. Among the many dazzling species found in our waters are a number that have been designated as protected, endangered, and threatened, because they are particularly sensitive to human impacts.

Common dolphin, grey seal, and seabirds such as fulmar and cormorant are all examples of these “sensitive marine species”. Unfortunately, they can sometimes be hard for fishermen to avoid and can end up being accidentally caught in fishing gear – an event known as “bycatch”.

There are different ways in which sensitive marine species can be caught by fishing vessels, depending on the gear that fishermen use for their target catch. For example, seabirds may grab at baited hooks on longlines, causing them to be dragged underwater. By contrast, marine mammals such as harbour porpoise are most vulnerable to accidental capture in nets and trawls, in which they can become entangled.

Monitoring bycatch

Bycatch significantly affects a wide variety of sensitive marine species. For example, the UK Bycatch Monitoring Programme (BMP) estimated that 502–1,560 harbour porpoises were bycaught in UK fisheries in 2019; while a recent JNCC report found that cormorants, northern fulmars, and guillemots are the seabirds most likely to become incidental bycatch in the UK. However, as in many other parts of the world, it’s hard to determine the exact scales of sensitive marine species bycatch.

Several initiatives are working to provide important data: the Bycatch Monitoring Programme, a dedicated observer scheme for monitoring bycatch in UK fisheries coordinated by the Sea Mammal Research Unit (SMRU); a catch sampling programme called the Observer Programme, coordinated by Cefas; and the Cetacean Strandings Investigation Programme (CSIP), which collects data on stranded cetaceans which show signs of having been bycaught.

Key challenges for bycatch monitoring revolve around the low levels of observer coverage across UK fisheries (less than 5% of commercial fishing activity is observed), and the limited space aboard fishing vessels for people and monitoring equipment. Added to this, there’s still much to learn about the population sizes, movements, distributions, behaviours, and post-release survival of many sensitive marine species – knowledge of which could help us develop effective ways to mitigate bycatch.

Impacts of bycatch

Bycatch is a major concern for both animal welfare and conservation. Globally, bycatch is one of the greatest threats to sensitive marine species, and can contribute to the decline of certain populations of these animals. This is particularly the case for some small, isolated populations of marine mammals around the UK coastline. Such losses have a knock-on impact on the ecosystems of which sensitive marine species are a vital part.

The consequences of bycatch don’t end with marine ecosystems. Commercial fishing is an important livelihood for many coastal communities around the UK. It puts local seafood on our plates and provides a source of important nutrients. Fishermen don’t want to harm wildlife when out fishing. Having to handle bycaught seabirds, sharks, and marine mammals can be a distressing and even traumatising experience – and can pose a safety risk to the person trying to free them.

Sensitive species bycatch also costs fishermen money. Fish catches and gear can be damaged or lost in the course of non-target animals being caught or entangled. Extended periods of downtime may need to be spent freeing or removing them, and repairing gear afterwards – all of which takes time away from the actual work of fishing.

Seabirds

Seabirds

Fulmars, guillemots, cormorants, and gannets are among the seabirds at high risk in some demersal longline and static net fisheries.

Marine Mammals

Marine Mammals

Harbour porpoise, common dolphin, harbour seal, and grey seal are at risk in some static net fisheries.

Sharks, Skates & Rays

Sharks, Skates & Rays

Porbeagle, thresher, blue skate, flapper skate, and angelshark are among the species at risk in static net, longline, and some trawl fisheries.

Bycatch is the unintended capture or entanglement of non-target species in fishing gear.

Monitoring bycatch

Impacts of bycatch

Seabirds

Seabirds

Marine Mammals

Marine Mammals

Sharks, Skates & Rays

Sharks, Skates & Rays

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