Sustainable fisheries

Background

Through increasingly powerful fishing technology, we have put incredible pressure on the oceans resources. Economies and livelihoods are being irrevocably damaged. Certain stocks of fish have declined to the point where their survival is threatened. And other stocks of fish have been so substantially reduced in number that they could become similarly threatened. Unsustainable fishing methods are harmful to our oceans because they focus on maximising the number of fish caught regardless of long-term consequences.

The current crisis facing our fish stocks, and increasing reports of the impacts of fishing on the wider marine environment, have heightened consumer concerns and raised issues about the fish we eat.

Challenges and threats

Fisheries management bodies need to put in place measures to prevent overfishing and adhere to scientific advice. The catching capacity of the world's fishing fleets needs to be reduced before fishing can be sustainable. In addition to pressures from unsustainable fishing methods fish stocks are also affected by climate change and pollution from other human activities associated with exploitation of both marine and land-based resources.

Unsustainable fishing methods

Overfishing

• Recruitment overfishing - this is when adult populations are fished so heavily that the number and size of the adult population (spawning biomass) is reduced to the point that it does not have the reproductive capacity to replenish itself.
• Growth overfishing – this occurs when animals are harvested at an average size that is smaller than the size that would produce the maximum yield per recruit.

Bycatch
The term for marine creatures that are accidentally caught in fishing gear intended for other species.

Bycatch and Discards

Most fisheries catch marine creatures that were not originally targeted. This extra catch is known as bycatch. Of this bycatch some will have a commercial value and are landed by fishermen. However, a greater proportion is unwanted and is usually discarded (i.e. thrown back dead or dying over the side). In some cases this can lead to high levels of discarding of fish that otherwise could have helped re-build depleted stocks.

Unwanted bycatch is one of the main environmental effects of fishing and is a particular problem with management by TAC (Total Allowable Catch) and quotas. Once the TAC of a particular species has been reached, they will still continue to be caught by vessels targeting other species. In most cases, landing is illegal so they are thrown back dead or dying. In England and Wales around 40% of fish caught by commercial vessels are subsequently thrown away.

To put it in context, the amount of cod in the depleted fisheries around the UK being discarded is halting the rebuilding of these stocks. For example, in the North Sea, 51% of cod caught in langoustine (scampi) fisheries are discarded as they are undersized. Off the coast of Norway 61% of the total cod catch by langoustine trawls was discarded between 1995 and 2000.

It’s not just cod that suffers from bycatch and discarding in European waters. Around half of all plaice caught are discarded overboard, usually dead. The North Sea plaice and sole mixed beam trawl fishery, which accounts for the vast majority of catches, is the most wasteful of all – according to a 2000 report, up to 80% of the plaice catch is discarded in some areas. All in all, as much as 7kg of marine animals are killed by beam trawlers to produce 450g of marketable sole. The figure is similar for plaice. In the EU, it is estimated that beam trawlers targeting finfish discard 330,000 tonnes of marine life each year.

Over a quarter of a million marine turtles are caught each year on longlines worldwide.

Bycatch is a conservation problem of staggering global and regional significance because it is:

• Widespread
• Wasteful
• Inhibiting recovery of species at risk
• Preventing progress toward sustainable resource use at a time when fisheries and local communities are under economic pressure.

Fishing methods

Some fishing methods are known to destroy or alter the physical environment and change the habitat where fish live. Some types of fishing gear have more of an environmental impact than others, and are associated with the accidental capture of non-commercial species and gear-related damage to marine habitats and communities.

A vast array of fishing methods are employed by fishermen to catch the large number of commercially exploited species. As a general rule of thumb, traditional gear such as handlining (line caught), creeling, setting traps, and “diver caught” are better options because they tend to be less intensive, they have a lesser impact on marine habitats, and they tend to catch fewer juveniles and non-commercial species. Bottom trawling on the other hand, may cause damage to reefs and the seabed, and in some areas may have long-term environmental impacts.

Bottom trawling has been described as one of the most destructive of all fishing practices, comparable to forest clear cutting and agricultural ploughing on land. The bottom trawls targetting Nephrops (Scampi or Langoustine) scrape and plough into the mud, to a depth of 30cm or more. The trawls can leave deep, lasting furrows up to 6 m wide; flatten out natural contours; and compact sediments.