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Bottom Trawling Cuts Wide Swath of Destruction

Elizabeth Whitman

UNITED NATIONS, Sep 16 2011 (IPS) - Bottom trawling, a method of deep-sea fishing, is threatening the existence of ecosystems in the deep oceans, wreaking nearly irrevocable havoc on thousands of species and the very habitat in which they live.

Even so, recent international efforts to limit the damage have been relatively ineffective, experts said this week at the United Nations.

Deep-sea bottom trawling is viewed as the most serious threat to fragile deep-sea ecosystems, which, once damaged, can take decades if not centuries to recover.

Over the past five years, the United Nations General Assembly (GA) has passed two resolutions in an effort to protect deep-sea areas and the biodiversity unique to them, yet many countries continue to flout the commitments to prevent adverse impacts on deep-sea species and ecosystems, commitments to which they agreed in 2006 and 2009.

Resolutions have not been fully implemented, nor are deep-sea fisheries being managed sustainably, scientists who attended a workshop last May to review fisheries management concluded. They published their findings in a report, which also stated that vulnerable marine ecosystems (VMEs) are not being sufficiently protected from the devastation that bottom fishing wreaks.

Ineffective resolutions

In 2006, the GA resolution called upon “regional fisheries management organisations” to assess, identify and manage areas particularly vulnerable to adverse impacts of bottom fishing, including closing certain areas if necessary.

The resolution in 2009 reiterated key elements of its predecessor, calling for the same fisheries management organisations to strengthen implementation of the earlier measures, a sign that they had not accomplished what they were intended to.

This week, the Deep Sea Conservation Coalition (DSCC) published a report noting issues such as a lack of regulation, lack of implementation of U.N. resolutions, and the ineffectiveness of areas closed to deep-sea fishing.

In some areas, it said, existing conservation efforts are often only move-on rules, where once a vessel catches a threshold weight of a certain species in a single trawl, it must leave the area and report it. The DSCC considered these rules “of limited value given the high threshold levels established as triggers” to move on from an established area.

Furthermore, “The deep-sea fisheries in the (North East Atlantic) area are characterised by extensive discarding, misreporting and non- reporting of catches,” said the DSCC report.

Destructive methods vs. fragile ecosystem

Bottom trawl fishing is a highly destructive and inefficient method of fishing that accounts for more than 95 percent of the bottom fish catch in the Atlantic, Pacific and Indian Oceans. It has been banned in international waters around Antarctica. In the northeast Atlantic, deep-sea fishing takes place at a range of 400 to 1,700 metres. Light can only penetrate to a depth of about 200 metres.

A boat, called a trawler, drags a funnel shaped net on or just above the bottom of the ocean floor, catching all that falls into the net’s path. In some instances, up to 50 percent or more of what is caught may be thrown back into the sea. Scientists estimate that zero percent of what is discarded, called bycatch, actually survives once returned to the sea.

Off the coast of Ireland, deep-sea fish abundance down to 1,500 metres has declined by 70 percent, studies have shown, although decreases in fish abundance have been observed down to a depth of 2,500 metres. The fact that deep-sea fishing does not reach to that depth shows how its impact extends far beyond the boundaries of areas directly fished.

Phil Weaver of the National Oceanography Centre in Southampton, UK, said during a panel at the U.N. on Thursday that deep-sea fishing can have an impact on an area close to three times that actually fished.

Bottom fishing “destroys complex seabed habitats… It reduces the three-dimensional complexity of the seabed,” Alex Rogers of Oxford University and a member of the group of scientists who met in May, told IPS. Ultimately, it eliminates habitats for organisms such as coral that in turn become habitats for yet more organisms, he added.

Despite the wide swath of destruction bottom fishing cuts, in the European Union’s fishing industry, the reported 43,000 tonnes of deep-sea catch in 2008 accounted for only 1.8 percent of all fish landed in the EU.

“Although the overall contribution to fish catch is low, the value to the individual vessels can be quite high,” Rogers explained. Thus continuing bottom fishing is profitable on a smaller scale, even if it represents only a tiny percentage of all fish caught.

Scientists estimate the deep sea to contain the majority of 750,000 undiscovered marine species worldwide. The deep sea is also home to coral reefs, some as old as 8,500 years. By destroying coral reefs, bottom fishing devastates entire ecosystems, destroying the very structure in which the ecosystem is contained and can thrive.

Deep-sea fish species are particularly vulnerable to harm, especially in comparison with shallow-water species. They grow slowly and reproduce late in their lives, and some species are known to live 150 years or longer.

Deep-sea fishing is also damaging because it lifts sediment off of the seabed, at which point it can be scattered and redistributed throughout the ocean, causing further environmental complications.

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