fishing boats

There are many different ways to catch or farm fish and shellfish, and some have a much lower environmental impact than others. Here we explain the different fishing methods and how sustainability can be improved.

Fisheries & Aquaculture Team

What does sustainability mean?

Below are some of the most common fishing methods that are used to catch the fish and shellfish on your plate. Each type of fishing activity can have completely different impacts, depending on where it’s happening and how well it’s regulated.

In all cases, we want to see better monitoring and reporting of fishing activity, especially where bycatch is an issue. We also want management plans for all species that fishers target, to stop too many fish or shellfish from being taken. We have a dedicated policy team working to achieving this. Read more about our policy positions and responses to public consultations.

The Good Fish Guide looks at all of these factors when deciding how sustainable fish and shellfish are.

Bottom-towed fishing

This is a term to describe all fishing gear that is pulled along the seabed. It’s also known as demersal fishing – demersal being the term that refers to the sea floor. It’s the most common way to catch fish in the UK. The main types are otter trawling, beam trawling, dredging, and demersal seining.

Otter trawling

Otter trawling involves towing a net over the seabed. The net is held open by two panels, known as otter boards. Fish are herded between the boards and into the net, which is then hauled onto the boat.

Demersal trawling - 4 _Fig 3.1_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Beam trawling

Beam trawling involves towing a net over the seabed. The net is held open by a heavy beam. There can be tickler chains or chain matting, which drag along the front of the net. They disturb the fish, causing them to swim up and into the net, which is then hauled onto the boat.

Beam trawling - 29 _Fig 2.1_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Dredging

Dredging involves towing a heavy steel frame, attached to a chainmail bag, over the seabed. There may be teeth at the front to flip shellfish into the bag. Boats can tow up to 20 dredges at once, depending on how big and powerful the boat is.

Scallop dredging - 5 _Fig 2.7_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Demersal seining

Demersal seining involves placing a net on the seabed and slowly closing it. As ropes move over the seabed to close the net, they herd fish into it. This method sometimes involves towing the net along the seabed. It is also known as flyshooting, Danish seining or Scottish seining, depending on how it's set up.

Scottish seining - 23 _Fig 1.2_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Impact

The main impact of these fishing gears is on seabed habitats. The level of impact is different depending on which fishing gear is used and where. Sandy seabed, for example, can recover very quickly whereas cold-water corals and maerl can take decades or centuries to recover. Demersal seining is the lightest gear and doesn’t dig into the seabed, whereas beam trawling and dredging are very heavy and can penetrate several centimetres, disturbing buried sea life as well as what’s on top of the seabed.

What are we working towards

We want to see better monitoring and reporting of all fishing activities, including bycatch. More data is needed to understand which habitats are affected and how, and urgent steps must be taken to prevent damage to vulnerable habitats.

In the UK, there are many Marine Protected Areas where seabed is supposed to be protected from damaging activities like bottom-towed fishing. Protections are missing in most of these sites, and UK governments need to do more to address this. We are campaigning on this right now.

Support our call for action on Marine unProtected Areas

Join our campaign

Longline

Longlining

Longlining uses a long fishing line with baited hooks. There can be hundreds of hooks on one line. The type and size of the hook, the bait used, and the position of the longline (at the surface, mid-water, or on the sea floor) vary depending on what fishers are trying to catch.

Pelagic lines - 84 _Fig 8.2_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Impact

The main concern with this method is that the baited hooks can attract various species, including seabirds, sharks and turtles. As the line can be left out for some time, these animals may drown before they can be released, although some are released alive.

This is of most concern in tuna, swordfish and marlin fisheries, where lines can be several kilometres long. In some areas, thousands of seabirds, sharks and turtles are caught and killed each year. Longlining in some parts of the world is responsible for some species falling to endangered levels.

What are we working towards

Better monitoring and reporting of bycatch is crucial. We also want to see steps taken to reduce impacts, such as using bird scarers, avoiding bait that attracts animals like turtles, and avoiding times or locations where these animals are most common.

Gillnets

Gillnetting

Gillnetting uses a net, suspended in the water, which is anchored to the seabed. It is kept vertical by buoys, to create a wall of netting that fish swim into and become entangled. The mesh size and length of time the nets are left at sea varies, depending on where they are fishing and what they are targeting.

Fleet of gill nets - 62 _Fig 7.5_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Impact

The main concern with this method is that it can accidentally catch other animals. It is difficult for animals to sense the nets, meaning that porpoises, turtles and seabirds can become entangled and die if not released in time. This is mainly an issue in areas where gillnets overlap with populations of these species.

What are we working towards

Better monitoring and reporting of bycatch is crucial. We also want to see steps taken to reduce impacts, such as using ‘pingers’ that make a noise to deter animals from approaching the nets, avoiding fishing at times or in locations where these animals are most common, and reducing the amount of time that nets are left in the water.

In tuna, swordfish and marlin fisheries, gillnets can be up to 7 km long. The scale of bycatch is vast, so we consider all tuna, swordfish or marlin caught by gillnet to be unsustainable.

Mid-water fishing

This is where fishing gear is pulled through the water and doesn’t touch the seabed. It’s also known as pelagic fishing – pelagic being the term that refers to the mid-water zone.

Pelagic trawl

Pelagic trawling involves towing a net through mid-water or at the surface. It can be towed by one boat or a pair of boats. Shoals of fish are targeted using equipment such as sonar.

Pelagic pair trawling - 22 _Fig 6.2_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Purse seine

Purse seining involves encircling a school of fish with a net, tightening it at the bottom so the fish can’t swim out, then hauling it onto the boat.

Purse seining - 3 _Fig 1.5_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Impacts

Impacts of these fishing methods vary a lot, depending on how well the fishing is monitored and where it’s happening. The main potential impact is bycatch of unwanted species. In some areas, this can include dolphins, porpoises and sharks.

What are we working towards

We want to see better monitoring and reporting of bycatch. We also want to see steps taken to reduce impacts, such as avoiding times or locations where vulnerable animals are most likely to be encountered.

Pots, traps and creels

Pots, traps and creels

Pots, traps and creels are small containers which are left on the seabed for a period of time, and later retrieved by boats. Bait is used to attract animals into them. They are usually made of wire and nylon netting and structured so that animals can enter but not leave. A boat can carry and set out anything from dozens to hundreds of pots at a time, depending on its size.

Fleet of pots - 57 _Fig 8.6_.jpg

Fleet of pots

Credit: Image supplied by Seafish: www.seafish.org

Impact

These are low impact fishing gears in general. One potential significant impact is that the ropes attached to the pots can entangle whales, dolphins or sharks in some areas. This is primarily a concern where there is a high overlap between populations of these species and potting. In many cases, we don’t understand how often this happens because it’s not well reported.

There are also concerns that unknown amounts of fish and shellfish are being used for bait – which could have impacts on the wild populations that provide the bait.

In many areas, potting can be unlimited. While it is a low impact method, if too many pots are being used one small area, this could start to affect seabed habitats.

What are we working towards

We want to see better monitoring and reporting of entanglement, and more innovations such as rope-less pots to reduce the risks. We also want to see more monitoring and fishing controls for pots, to make sure we understand bait use and catches, and don’t have too many pots in one place.

Pole and line or handline

There are many types of fishing that involve using rods and lines in some form. They include handline, pole and line, and troll. These methods are also known as one-by-one fishing because the fish are landed onto the boat one at a time.

Handline

Handlining varies depending on where it is happening and what species is being targeted. In general, it uses a baited line from a stationary boat. The fisher pulls the line in by hand, rather than using rods or poles.

Pole and line

Pole and line, or baitboat fishing involves a number of rods being set up on a boat. They might be operated by hand or mechanically. Bait is used to attract the target species.

Pole and line - 69 _Fig 8.4_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Troll

Trolling involves a number of fishing lines attached to large poles or rods at the back of a boat. They are slowly towed along near the surface. Artificial bait or lures can be used.

Trolling - 68 _Fig 8.5_.jpg

Credit: Image supplied by Seafish: www.seafish.org

Impact

These are low-impact fishing methods because they don’t usually touch the seabed, and so don’t cause habitat damage. Often, it’s easy to make sure the right fish are being caught, and if other species are accidentally caught as bycatch, they can usually be released alive.

However, if bait is being used it’s important to know which species and how much, so that the wild populations of ‘bait fish’ are not adversely affected.

What are we working towards

We want to see better monitoring of all fishing activity to understand catch levels and bait use. We also want management plans for all species that fishers target, including bait fish, to stop too many fish or shellfish from being taken.

Hand-gathering

Hand-gathering involves collecting animals (usually shellfish) from the shore or the seabed by hand, one at a time. Hand diving may involve boats and scuba equipment.

Impact

This is one of the lowest impact ways of catching fish or shellfish because there are rarely any seabed impacts, and no bycatch. It is still important to control these activities. In some areas, hand gathering is so extensive that beaches have had to be closed to prevent too many shellfish from being taken.

What are we working towards

We want to see better monitoring and reporting of hand gathering, to make sure it isn’t taking too many fish or shellfish.

All of these impacts are considered when we look at seafood sustainability. Check out the Good Fish Guide to find out how sustainable your fish or shellfish is, and get recommendations for alternatives.

Is the seafood on your plate endangered?

Search our Good Fish Guide to find out