Third of freshwater fish threatened with extinction

Freshwater fish are the most endangered group of animals on the planet, with more than a third threatened with extinction, according to a report being compiled by British scientists.
Richard Gray The Telegraph 30 Jul 11;

Among those at the greatest risk of dying out are several species from UK rivers and lakes including the European eel, Shetland charr and many little known fish that have become isolated in remote waterways in Wales and Scotland.

Others critically endangered include types of sturgeon, which provide some of the world's most expensive caviar, and giant river dwellers such as the Mekong giant catfish and freshwater stingray, which can grow as long as 15 feet.

The scientists have blamed human activities such as overfishing, pollution and construction for pushing so many species to the brink of extinction.

They also warn that the loss of the fish could have serious implications for humans. In Africa alone more than 7.5 million people rely on freshwater fish for food and income.

The precarious status of the species has been revealed in interim results from the International Union for Conservation of Nature's Red List assessment of freshwater fish.

Dr William Darwall, manager of the freshwater unit at the IUCN in Cambridge, said: "There are still some big gaps in our knowledge, but of the 5,685 species that have been assessed, 36 per cent of them are threatened.

"Compared to mammals, where 21 per cent are threatened, and birds, where 12 per cent are threatened, it is clear that fresh water ecosystems are among the most threatened in the world.

"Sadly, it is also not going to get any better as human need for fresh water, power and food continues to grown and we exploit freshwater environments for these resources."

The IUCN conducts assessments on the status of species around the world. It most recently completed an assessment of amphibians and found 30 of the planet's amphibians are threatened with extinction.

The assessments form the basis for conservation groups and governments to conserve biodiversity and protect the most threatened species.

There are an estimated 15,000 freshwater fish species that have been discovered and so far 5,685 of them have had their status assessed.

The preliminary results of the assessment were revealed at the annual conference of the Fisheries Society of the British Isles at Bournemouth University.

Professor Rudy Golzan, director of the centre for conservation ecology at Bournemouth University, said: "Freshwater biodiversity is a crucial issue and more important than people think. Billions of people rely upon freshwater species for food and work.

"We have to find ways of reducing impacts on these ecosystems while allowing people to continue to use the resources that freshwater environments have to offer."

In the UK a relative of the salmon, called the Gwyniad, is found in just one lake in Wales called Llyn Tegid, where it became trapped after the end of the last ice age.

The introduction of another fish called the ruffe, which preys upon the eggs and young Gwyniads, has seen their numbers fall to as low as 31 females since the 1980s.

The European eel, another species found in UK streams, rivers and lakes which is an important food source for many birds and other fish, has also declined by 90 per cent since the early 1980s.

Atlantic sturgeon, which is the source of one of the most expensive forms of caviar and were once common in rivers around Europe including the UK, is now only found in the Garonne river in France, where it has an estimated wild population of between 20 and 750.

The results show that in Africa around 28 per cent of freshwater fish are threatened while in Europe 38 per cent are threatened.

Among the most threatened with extinction are giant freshwater species such as the Mekong giant catfish, which can grow up to 10 feet long, may have as few as has just 250 individuals left in the wild.

The Mekong freshwater stingray, which grow up to 15 feet long and can weigh up to 1,300lbs, has suffered declines of up to 50 per cent in Thailand and Cambodia.

The giant Mekong salmon carp has also seen numbers plummet by more than 90 per cent due to overfishing and damage to its habitat.

Scientists fear that dam construction in China, Laos, and Thailand will further threaten these species by cutting off fish populations and preventing the species from reaching their spawning grounds.

Professor David Dudgeon, chair of ecology and biodiversity at the University of Hong Kong, said: "There are eight Chinese dams in the upper reaches of the Mekong river while there are another 11 dams planned downstream.

"They will prevent many threatened species from reaching their spawning sites upstream. The impact on the people there will be huge too as they will reduce flow by 70 per cent."

Other species such as the knifetooth sawfish, found in inshore estuaries of the Red Sea, Persian Gulf and Indonesia have seen numbers plummet due to over fishing.

The red tailed shark from lowland streams in Thailand and the Nilgiri shark in India are also critically endangered.