What is Bycatch?

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

The seas around the UK are thriving underwater ecosystems. These waters provide essential habitats for a number of protected, endangered and threatened species of wildlife – also known as ‘sensitive marine species’. 

These species include common dolphin, grey seal, and seabirds such as fulmar and cormorant. Unfortunately, as these animals are often large and hunt in groups, and fishing gear has limited means of being selective, they are hard for fishermen to avoid and can end up as accidental catch – or “bycatch”. 

There are different ways in which wildlife gets caught by fishing vessels, depending on the gear used by fishermen to fish for their target catch. For example, some vessels use baited hooks on longlines, which seabirds grab at and are subsequently 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

It is difficult to determine the number of sensitive marine species that are captured in UK fisheries. A dedicated observer scheme for monitoring bycatch in UK fisheries, coordinated by the Sea Mammal Research Unit (SMRU), along with a catch sampling programme coordinated by Cefas, are working toward this. The Cetacean Strandings Investigation Programme (CSIP) also collects data on mortality-induced bycatch in stranded cetaceans. 

Key challenges for the current system of 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.

The International Council for the Exploration of the Sea (ICES) estimates the total harbour porpoise bycatch in all UK net fisheries to be 1,282 animals in 2017; whilst a recent Defra report estimated that overall fulmar bycatch in the offshore longline fishery could be around 4,500-5,700 birds every year.

Impacts of bycatch

The accidental capture of wildlife is both an animal welfare concern and a conservation concern. World-wide, bycatch is recognised as the biggest threat to the survival of sensitive marine species. Some small, isolated populations of marine mammals around the UK coastline are particularly vulnerable to population decline due to bycatch. 

Commercial fishing is an important livelihood for many coastal communities around the UK, and puts local seafood on our plates. Fishermen do not intend to harm wildlife when out fishing. The accidental capture of wildlife is often a distressing experience for those who care about the seas in which they fish, and the handling of caught seabirds, sharks and marine mammals can be traumatising. 

Wildlife bycatch also has a negative financial impact for fishermen, as equipment can get seriously damaged and extended periods of ‘downtime’ must be spent clearing nets of wildlife, which would otherwise have been spent pursuing commercial catch.




Fulmars, guillemots, cormorants and gannets are at a high risk of bycatch in some UK demersal longline and static net fisheries.

Marine Mammals

Marine Mammals

Harbour porpoises, common dolphin and both species of seals occurring round UK coasts are at risk of bycatch in certain UK static net fisheries.

Sharks, Rays & Skates

Sharks, Rays & Skates

Porbeagle, thresher, spurdog, blue skate and angelshark are at risk of bycatch in UK static net, longline and some trawl fisheries fisheries.

How Clean Catch UK is working to reduce bycatch

To reduce bycatch and improve the conservation and management of the UK’s sensitive marine species, more information about the populations, movements and distributions of these species is needed. Improved knowledge of current bycatch levels and information about post-release survival is also critical. 

The Clean Catch UK Regional Working Group and Local Focus Group are working together to gather data about the populations of sensitive species in South-west fisheries (ICES Divisions 7e-j) and current bycatch levels, through a collaborative research partnership with the fishing industry. The Clean Catch UK National Steering Group is bringing together scientists from around the UK to share knowledge and guide the work on-the-water in the South-west.

The scientists and fishing industry champions in the local, regional and national Clean Catch UK groups report back to Defra. Ultimately, Defra will use the data and information gathered by Clean Catch UK to develop practical and pragmatic management plans for England. 

Any interested parties are invited to contribute to this programme of research. 


Please contact us if you want to contribute to a local study to reduce bycatch or provide the programme with relevant, new research.

Contact Us

We use third-party cookies to personalise content and analyse site traffic.

Learn more