Hundreds of rare powan fish to be released into Loch Lomond in conservation effort

Published on Monday 22 March 2010 21:44

HUNDREDS of one of Scotland's rarest fish will this week be released into Loch Lomond as part of a project to try to save the species from extinction.

Baby powan that have been reared by schoolchildren over the past two months will be let out into the loch, where the fish are struggling to survive.

Powan, an ancient freshwater fish, only live in two places in Scotland –Loch Eck in Argyll and Loch Lomond.

The whitefish, which has been in Scotland since the last ice age, is under threat of extinction in Loch Lomond due to the spread of ruffe, an alien species that has bred out of control since it was introduced into the loch about 25 years ago.

The ruffe, although tiny, devour the eggs of the powan and have decimated populations.

Now local primary schoolchildren are helping the powan fight back, in a project funded by the Natural Heritage Grant Scheme.

They have been looking after eggs in incubators, and on Wednesday and Thursday, Luss, Arrochar, Drymen and Gartocharn schools will release about 400 hatched fish into the loch.

In addition, Scottish Natural Heritage has been carrying out a project to establish "refuge" populations of powan in other parts of Scotland, such as the Carron Valley reservoir, to make sure the species is preserved if it becomes extinct in Loch Lomond.

Dr Andy Burrows, senior biologist with Loch Lomond Fisheries Trust, which is running the schools project, said: "The powan is in the premier league of rare fish in the UK. They are very geographically limited and it's such a rare species that when one of these locations gets threatened in some way, it has a relatively larger impact."

Ruffe were once popular for use as live bait by anglers, a practice which has now been banned. It is thought this is how the species ended up in Loch Lomond.

"Now you find that when we do surveys, certainly during the summer months, more often than not it's the ruffe that's the most abundant species that we catch," said Dr Burrows. Whereas powan, a distinctive fish with a dark bluish or green back, have lived in Loch Lomond since they were trapped there by the receding ice 12,000 years ago, ruffe have been there for just a quarter of a century.

"They have only had 25 years to establish and they have just mushroomed, just exploded, in that time," said Dr Burrows.

A survey in the 1980s, before the arrival of the ruffe, showed a healthy population of powan in Loch Lomond. A similar survey carried out in 2006 showed numbers had substantially decreased, and it was discovered that powan eggs had become one of the favourite foods of the ruffe.

Dr Burrows said he hoped the project to boost numbers of powan in the loch would simultaneously raise awareness among children of the need to conserve native species, and the threats posed by alien creatures released into the wild.

The children have had to take great care to keep the eggs alive, by putting ice packs in the tanks to lower the temperature of the water, and fishing out dead eggs to avoid contamination.

Powan is a protected species and must not be caught by anglers.