Deep-sea trawling puts rare fish species on critical list
THE INDEPENDENT
Trend for deep-sea trawling puts rare fish
species on the ocean's critical list
By Steve Connor, Science Editor
05 January 2006
Deep-sea fish are being taken to the brink of extinction because the
dramatic collapse of shallow-water stocks is sending fishing trawlers
further out to exploit deeper waters.
Scientists believe the overfishing that has caused the demise of the
traditional catch of fish, such as cod and plaice, is now causing an
equally severe, long-term decline of more exotic, deep-water species.
Scientists believe the overfishing that has caused the demise of the
traditional catch of fish, such as cod and plaice, is now causing an
equally severe, long-term decline of more exotic, deep-water species.
Research into five North Atlantic species of deep-sea fish has found that
their numbers have fallen dramatically during the relatively short time
since trawlers began to exploit new deepwater fishing grounds off Canada.
Similar trends have been observed off the coasts of Britain and Europe,
where commercial trawlers have turned increasingly to deepwater
species over the past two decades, such as the orange roughy, which
can live for 150 years and take 25 years to reach sexual maturity.
Scientists in Canada said yesterday the decline in numbers has caused
many deep-sea fish to be deemed "critically endangered" under the
international rules on threatened species.
Jennifer Devine, Krista Baker and Richard Haedrich of Memorial
University in St John's, Newfoundland, analysed the declining catch of
deepwater species caught during a 17-year period in the Canadian
waters of the north-west Atlantic.
They analysed the five species in detail because they all live on, or near
the bottom of the sea floor. None of the species were taken in any
substantial number prior to the 1970s. The scientists found that all five
declined by between 87 per cent and 98 per cent over 17 years. They
extrapolated these figures to cover a period of three generations of the
long-lived fish and concluded that the real decline is nearer to 99 per cent.
"According to the IUCN [International Conservation Union] criteria,
these five species qualify as critically endangered in the north-west
Atlantic. The declines occurred on a timescale equal to, or slightly less
than, a single generation," the scientists report in the journal Nature.
The species -- roundnose grenadier, blue hake, spiny eel, spinytail skate
and onion-eye grenadier -- share many characteristics of all deep-sea fish.
They are long-lived, with a lifespan of about 60 years or more, and take
20 years or more to reach sexual maturity. All those features make them
vulnerable to extinction when fished commercially, said Professor Haedrich.
"The deep sea covers an enormous area of the world and it was thought
to be a place you can turn to for more fishing reserves. This is absolutely
not true," he said.
His colleague, Jennifer Devine, said that the study was one of the first to
analyse the effect of the trend towards harvesting deeper-water stocks.
"We know that fish communities in shallower waters have been
damaged due to overfishing and other environmental factors but no one
has really looked at the deep sea," Ms Devine said.
"There's a lot going on out there that's not really been taken notice of.
One step that should be enacted is the protection of deep-sea habitats,"
she said.
Richard Dixon, director WWF Scotland, said that the slow growth rates
of deep-sea fish -- some of which live for as long as 150 years -- make
them highly vulnerable to overfishing.
"With such long lifespans, the impact of modern fishing methods on
these deep-sea species is disastrous, as they can be wiped out of entire
areas within a single season," Dr Dixon said.
"There is a real danger that slow-growing, deepwater species will take
centuries to recover from current fishing, if they can at all. In European
waters, we should close deep-sea fisheries as a matter of urgency," he said.
Deep-sea fisheries are those below 400m and, in Europe, the main
species of commercial interest are the orange roughy, the roundnose
grenadier, argentines and deep-water sharks such as the Portuguese
dogfish.
In 1989, French trawlers discovered major fishing grounds for orange
roughy off the west coast of Scotland and the catch peaked at 3,600
tons in 1991. Three years later, that fell to just 180 tons and now stocks
are believed to be fished out.
According to the WWF the orange roughy fishery has virtually collapsed
in 20 years in European waters, argentines crashed in the Irish
deepwater fishery in 1990, roundnose grenadiers suffer very high levels
of juvenile mortality in trawls. For many species stocks are unknown.
"Whilst some of our commercial species such as mackerel and plaice
could recover within years given proper management, there is a real
danger that slow-growing, deep-water species will take centuries to
recover, if at all," said Claire Pescod, Marine Policy Officer for WWF
Scotland.
Some populations of deep-water sharks off Britain have declined by 80
per cent in just 10 years, Ms Pescod said. "We must act to close these
fisheries as a matter of extreme urgency."
Fishing by numbers
* The global annual total of wild fish caught in 1950: 20 million tons
* The global annual total of wild fish caught in 2001: 92 million tons
* Number of fishing boats in the world: 3.5 million
* The population decline of deep-sea five species in 17 years: 98 per cent
* Quantity of cod caught in the Atlantic Ocean in 1956: 2.1 million tons
* Quantity of cod caught in the Atlantic Ocean in 2004: 645,000 tons
* Proportion of the North Sea floor trawled at least once a year: 90 per cent
* Proportion of the total global fish catch that comes from deep-sea
species: 1 per cent
* Number of new fish species found on two deep-sea reefs in 2005: 750
* Number of dolphins and porpoises that are killed as "by-catch" in the
North Atlantic every year: 10,000
* Proportion of deep sea coral reefs considered to be severely damaged:
67 per cent
* Proportion of deep-sea coral reefs considered to be damaged beyond
recovery: 20 per cent
* Number of acres of reef estimated to have been destroyed in the past
30 years: 35 million
* The proportion of the adult cod population aged above five: 0.5 per cent.
* Percentage of cod less than two years old: 90 per cent
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