Brute Ethics





Animal Ethics Encyclopedia

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Fishing - Deep Sea

Deep sea trawler Fishermen go out in large specialised boats along coasts or travel thousands of miles searching the seas and oceans for concentrations of fish to catch. Catches are as diverse as the tiny anchovy and large sharks. But concern, particularly about overfishing, is widespread and growing.

Fleets of industrialised fishing vessels fitted with powerful engines to tow giant fishing gear dominate the high seas. They process, pack and freeze fish in huge onboard plants and are equipped with sophisticated, expensive electronic equipment, such as:

  • Satellite navigation systems to show where a fishing vessel is by longitude and latitude.

  • Aircraft to spot and guide vessels to large schools of fish.

  • Echo-sounders to find fish and display the depth and shape of the ocean floor.

  • Net-recorders to display information about a net in use and the fish moving into it.

  • Satellite monitors to receive and relay information about weather, wind patterns, even fish location.

  • Four main techniques of deep sea fishing are:
  • Seining - (pronounced say-ning): encircling a shoal of fish with a net and drawing it tight around them.
  • Trawling - hauling a net through a shoal of fish on or above the seabed, trapping the fish in the net.
  • Long-lining - stringing out baits on a long line held up by buoys to catch fish who swallow the bait.

  • Netting - setting out nets with almost invisible mesh for fish to swim into and get snared.

Purse seining     Trawling     Long-lining

Which is purse-seining, trawling and long-lining?
Not drawn to scale.

Destructive Fishing

Some primary destructive methods of deep sea fishing are:

Purse Seine Netting

A fishing vessel herds a large school of fish. It unwinds a huge fishing net pulled around the school by its small boat and back to the fishing vessel. The bottom of the net is then drawn shut or 'pursed', trapping the fish. The fish, tuna are a favourite, cannot escape over or under the net and the whole lot is winched onboard.

Purse seining is an indiscriminate method of accumulating fish. The fishing net traps other marine animals, among them sea turtles, sea birds, dolphins and seals, and they all die.

Bottom Trawling

A fishing vessel drags a huge net over the ocean floor to catch bottom-living fish, such as cod, fluke, flounder and whiting, and shell fish like scallops and oysters. Sometimes a pair of vessels drag a net between them and the mouth of a net can be hundreds of metres across. Vessels also trawl their nets just above the sea floor for fish who live above it, like mackerel and bluefish. A winch pulls the net onboard when it is full, the catch spills onto the deck and then the equipment is redeployed. Fishing vessel also tow giant rigid steel-framed dredges along the sea bed instead of nets.

Bottom trawling catches non-target animals, rips up plants, destroys coral reefs and the structure of the ocean bottom and leaves the habitat and everything in its way smashed.

Longline Fishing

Long heavy nylon lines with thousands of baited hooks, set to sink just below the water surface and kept afloat by buoys, are unwound behind a fishing vessel. Longlines catch high-quality, high-value fish like tuna, marlin, snapper, swordfish and shark. Lines extend for dozens of kilometres, some over 100 km, with hundreds of shorter lines branching from the main line. A winch hauls the lines back on board. A fishing vessel can catch up to 40 tonnes or more of fish before returning to port.

Albatross, petrel fulmar and other seabirds fly down and seize the bait as the line is unwound. They get hooked, are pulled down and drown when the line sinks.

Drift Netting

A fishing vessel on the high sea unwinds a net to hang down from the surface like a curtain. The United Nations banned this kind of netting in the early 1990's. Nets were up to 70 km (40 miles) wide and made of non-perishable nylon. Primary targets were tuna and squid.

Drift nets were described as 'walls of death' for marine mammals like whales, dolphins, porpoises, fur seals, non-target fish, sea birds, sea turtles and other creatures. Non-target animals could not break free of the net and died. Nets cast adrift by fishing vessels remain a long-term lethal hazard for sea animals because of their non-perishable nature.


  • Scientists internationally warn that wild fish stocks are about to collapse, because modern techniques for catching fish are so effective and destructive. Uncontrolled fishing fleets will also empty the oceans of mammals, birds, sharks, turtles and destroy whole ecosystems.

  • Fishing boats use high technology equipment to hunt fish. Fishermen catch so many fish this way that populations of many fish species are decreasing and might go extinct.

  • Fishing boats use huge deep nets which may be scores of miles long to sweep up everything in their path - fish and no-target animals too.

  • Fish living in deep water are adapted to survive great pressure acting on their body surface. When hauled up to the surface (where the pressure is far less) their internal organs can burst.

  • Fishermen blame animals like seals, dolphins and fish-eating birds for their low catches of fish, call for them to be culled and kill them deliberately.

  • Fish, birds, marine mammals and smaller organisms depend on fish to eat. Commercial fishing takes so much of their food that they stave to death.

  • Fishermen discard fishing equipment which is then eaten and sticks in the digestive tract of animals, like turtles and otters, who then cannot digest their food and starve to death.


    Around 3.5 million boats fish the seas and oceans worldwide. Russia and US own the largest fleets of deepwater fishing boats. Japan and China consume the most fish.

    The worldwide total of wild caught fish today is 92 million tonnes, a 4.5 fold increase since 1950, when about 20 million tonnes was caught.

    The five countries in the table below caught nearly half the world total catch of fish in 2001. Britain ranked 21st at 0.7 million tonnes.

Table: Wild Caught Fish for 2001
World total & top five countries
World Total 92 million tonnes
China 16.5 million tonnes
Peru 8.0 million tonnes
US 4.9 million tonnes
Japan 4.7 million tonnes
Indonesia 4.2 million tonnes

Source: S Vannuccini (2003): Overview Of Fish Production, Utilization, Consumption And Trade. Food and Agriculture Organization of the United Nations, Fishery Information, Data and Statistics Unit. Data include shell fish. 1 tonne = 1 ton.

The World's Three Most Wild Caught Fish
(by weight)

1. Peruvian anchovy (Engraulis ringens).
Also called the Peruvian anchoveta.
7.2 million tonnes in 2001.
Maximum length 20 cm (8 ins). Prefers sub-tropical waters, swims in massive shoals, particularly off Peru and Chile. A filter-feeder on plankton.

2. Walleye Pollock (Theragra chalcogramma).
Also called Alaska Pollock.
3.1 million tones in 2001.
Length up to 80 cm (2 foot 6 ins). Lives throughout the north Pacific. Can live up to 15 years.

3. Chilean jack mackerel (Trachurus murphyi). 2.5 million tonnes in 2001. Length up to 70 cm (2 foot 4 ins). Found in south Pacific and south-west Atlantic. Feeds mainly on fish larvas and small shell fish. Can live up to 16 years.

Tonnage data from: Food and Agriculture Organization of the United Nations, Fishery Information, Data and Statistics Unit. 1 tonne = 1 ton.

For & Against: argue your case

Trawling Destruction
  • Claim: Bottom trawling destroys everything in its path and kills turtles, seals, sealions and dolphins when they get caught in trawl nets and drown.

  • Claim: Proposed measures to reduce the destruction of bottom trawling include:
  • Limit bottom trawling to rugged habitat where recovery of creatures is rapid.

  • Limit fishing activity to times when seals and sealions are less active.

  • Develop exclusion devices for nets, such as a grid across the opening with a mesh too small for large animals like turtles to get through.

  • Develop low-impact fishing methods and gear designed not to disturb the sea floor.
Long-line Deaths
  • Claim: Longlining kills hundreds of thousands of seabird annually. The birds seize the bait on the lines, are pulled under and drown.

  • Claim: Proposed counter measures to reduce seabird deaths are:
  • Use bird scare devices along lines.

  • Weight lines so they sink quickly.

  • Set out and unwind lines underwater and not on the surface.

  • Set lines at night when most seabirds are least active.

  • Do not discard offal around fishing boats which attracts scavenging birds.

Proposals vs Action
  • Claim: New measures are easy to devise; the challenge is to ensure fishermen adopt them. All the above proposals are just proposals. They are either not acted on or not acted on effectively.

  • Claim: The above proposals should be acted on by fishermen and be effective in reducing the number of untoward deaths.

  • Bycatch
  • Claim: Fishermen waste fish and resources because a quarter of the fish they catch they throw back into the sea.

  • Claim: Bycatch (the unwanted animals in a catch) is a problem partly dependent on pricing and the law:
  • Certain sizes and qualities of fish sell for more on the market so fishermen often throw back the cheaper catch until they have an optimum haul.

  • Governments impose catch quotas to protect stocks. Thus fishermen cannot legally take immature fish. Nor can they take fish of particular species once they catch a certain amount. However, fishermen cannot separate fish before they haul them on to their boat. So they haul in everything and throw back what they are not allowed to catch. But what they throw back is often dead or dying by this time.

Also see:

Fishing - Angling

Fishing - Farming

© 2004 Roger Panaman All rights reserved