Jan. 9, 2006 — Several species of Atlantic deep-water fish have been so ravaged by overfishing that they should be classed as critically endangered, a rating that is even higher than for the giant panda and Bengal tiger, a study says.

Canadian biologists carried out an assessment of five deep-sea species to see how these fish were affected by a shift to deep trawling prompted by the collapse of shallow-water coastal fisheries.

Over 17 years, the five species declined by at least 87 percent and up to 98 percent, the scientists found.

"They meet the (World Conservation Union, IUCN) criteria for being critically endangered," the paper, published on Thursday in the British weekly science journal Nature, said.

"Our results indicate that urgent action is needed for the sustainable management of deep-sea fisheries."

The five species studied ranged from the common to the rare.

They were the roundnose grenadier (Coryphaenoides rupestris); onion-eye grenadier (Macrourus berglax); blue hake (Antimora rostrata); spiny eel (Notacanthus chemnitzi); and spinytail skate (Bathyraja spinicauda).

Population estimates were made from trawling surveys made by scientists in Canadian waters from 1978-94.

In addition, there was survey data for two of the species (the roundnose and onion-eye grenadiers) for the period from 1995-2003. In these two cases, the decline over the 26-year study period was 99.6 and 93.3 percent, respectively.

The authors, led by Jennifer Devine of Memorial University at St. John's, Newfoundland, said the findings provided powerful backing for anecdotal evidence that deep-water trawling is having a catastrophic impact on deep species.

"Deep-sea fish are highly vulnerable to disturbance because of their late maturation, extreme longevity, low fedundity and slow growth," they noted.

Some species cluster together in large numbers for spawning, which also makes them more susceptible to overtrawling.

The five species they studied live up to 60 years, grow up to more than a metre (3.25 feet) in length but only become sexually mature in their teenage years.

A quick, devasting decline in numbers of adult fish over three generations can drive a species to the brink of extinction because so few are left that can reproduce, according to the IUCN's criteria.

Deep-sea fish species were previously ignored by trawlermen in their quest for big, easier-to-catch "table" fish such as cod, tuna and halibut in coastal shelf fisheries such as the Grand Banks.

As these fisheries began to collapse in the 1960s and '70s, the trawlers turned their attention to species that live on the continental slope, the downward ridge between the coastal shelf and extreme ocean.

In this case, the main targets are the Greenland halibut and redfish. The other species get scooped up as "bycatch" — they are turned into fish paste, fish fingers or, ironically, ground up into pellets for fish farms.

Even if fishing quotas are rigorously restored, it takes years to restore a fishery if adult stocks fall below a given threshold.

A 2000 study of 90 seriously overfished areas in the North Sea and Atlantic found that only seven had fully recovered after 15 years of fishing restrictions.

The IUCN's Red Book on biodiversity lists "critically endangered" as its highest level of peril for species in the wild. Only two categories (extinct in the wild and extinct everywhere) are higher.

"Critically endangered" means a species faces an extremely high risk of extinction in the wild. The giant panda and Bengal tiger are listed as "endangered," meaning that they face a very high risk of extinction in the wild.