Hatchery Briefing Note

October 2008

The Board has a long history of catching up broodstock, stripping them and holding the resulting progeny in various hatcheries and incubators. The fish have historically been stocked out at all stages from eyed eggs to parr throughout various reaches of the catchment. This briefing note sets out why the Dee Board no longer operates the Dinnet Hatchery.

Factors Limiting Fish Production

At present there is no information to suggest that the numbers of eggs being laid down in redds are limiting the production of young salmon. In a few parts of the catchment, typically in areas of intensive agriculture, eggs are being smothered by excessive silt. However, on-going electro-fishing surveys indicate that the numbers of fry throughout the catchment are good and showing signs of naturally increasing.

The main factor limiting production of salmon smolts on the Dee is the survival of fry to parr. This is because in certain burns the parr habitat has either been smothered by silt or the cobbles and boulders have been removed to improve the drainage of nearby fields. The electro-fishing surveys have shown that certain areas do have a lack of parr for these very reasons. In short, where the parr habitat is good parr numbers are good and where it is poor parr numbers are poor.

Options Considered

(i) Hatchery

It is possible to strip fish and grow on the progeny to parr. However, once these fish are released into the tributaries they tend to die in much greater numbers than their wild cousins as they are not "streetwise" and are more susceptible to predation and competition with existing wild fish. In addition if parr are stocked into areas with little suitable habitat there will be little chance of them finding a suitable unoccupied territory and are again likely to die.

The earlier that these fish are released the greater their ability to acclimatise to wild conditions. Therefore the most successful stocking operations stock out either eyed eggs or first feeding fry. As there is currently no shortage of these stages in the wild and it is the fry to parr survival rate that is limiting the fish there is little point in carrying this out.

(ii) Habitat

As it is the lack of parr habitat that is limiting the production of fish one option is to improve these conditions so that more fish can survive. This is achieved by either stopping the silt smothering the parr habitat or by re-creating the cobble and boulder areas used by these fish.

Why Not Just Use Dinnet Hatchery?

The condition of Dinnet Hatchery was reviewed in early 2006 by an independent hatchery manager. The hatchery was found to be incapable of meeting the duty of care needed for the welfare of the fish. In short, due to the combination of the poor state of the hatchery and the banning of effective anti-fungal treatments, fish could not be looked after properly if they were brought into the facility. Therefore in order to meet this duty of care the hatchery would have required significant upgrading involving rebuilding the structure.

The hatchery had to be closed on these grounds and the options considered were whether to build a new hatchery or to concentrate on habitat improvement. The decision was taken not to rebuild the hatchery as it was estimated to only be adding less than a dozen rod caught salmon a year to the overall catch and the costs involved did not warrant the expenditure of up to £200,000.

The decision was taken to concentrate the limited financial resources available to the Board in restoring parr habitat. This was the main thrust of the LIFE project with the installation of 37 km of buffer strips to reduce the amount of silt going into the river and smothering the boulders and cobbles; 21km of riverbank coppicing to improve their stability and the availability of food for young salmon and finally the creation of 25,000m2 of new parr habitat through the addition of boulders. Recent electro-fishing results show that these habitat improvements are already resulting in increased numbers of salmon parr.

In 2008 the LIFE project finished. However, the Dee Board in partnership with the River Dee Trust have identified another 65 km of buffer strips that need to be installed and 30 km of coppicing that needs to be undertaken.

In addition a total of 31 obstructions to fish migration have been identified and work is progressing to clear these over the next few years. This is to allow fish access to good quality spawning and nursery areas which they previously could not reach.

These works, along with the new aim of restoring the parr habitat in the upper Dee catchment where the majority of spring fish are produced, will be undertaken over the next six years.

The possible use of a hatchery will always be considered as a potential fisheries management tool. However any decision taken will always be in the best interests of restoring the fish populations on the River Dee.