Fish Pass on the Dorset Frome

Louds Mill – dewatering cofferdam

Work has started on installing a fish pass at the Crump gauging weir at Louds Mill on the Dorset Frome to allow passage of salmon and sea trout.

The weir is a serious obstacle to upstream migration of salmon and a complete barrier to upstream movement of smaller fish. The new fish pass will be built adjacent to the main weir which will allow the fish free passage across a wide range of water flows.

The weirs at this site, complimented by the gauging weir on the Stinsford Channel, have provided a gauge of the total flow of the Frome immediately downstream of Dorchester for over 36 years.

The new project seeks to resolve the fish passage problem at the site and provide a sustainable solution to fish movement past the weir structures, especially for migratory salmonids, without affecting the gauging accuracy.

A decline in salmon numbers nationally has caused concern for some years. Work to improve spawning and freshwater habitats have been made by the Environment Agency and its partner organisations within numerous river catchments.

‘Work has gone on for a number of years to address the problems faced by salmon in the River Frome and this project will ensure that these and other fish species can easily reach the good quality spawning habitat found in the upper river. Whilst ensuring that the flow gauging facilities of this structure are not compromised and the flood risk to the adjacent properties are not increased,’ said Andy Martin, for the Environment Agency.

This project is the first in the country to integrate a Larinier fish pass into a gauging structure, without compromising the gauging accuracy. It will serve as a demonstration site for this type of technology.

This project links into the Environment Agency’s vision by helping to achieve the following themes:

–         An enhanced environment for wildlife by ensuring free passage of fish passed the Louds Mill site and thereby allowing the fish to breed more effectively.
–         A better quality of life – increased fish populations will lead to more opportunities for angling and the benefits this brings to individual anglers and the local economy.
–         Reducing flood risk by warning and forecasting high flows and modelling and design purposes.

The work, which is being carried out on the Environment Agency owned site and in partnership with the Frome Piddle and West Dorset Fisheries Association, is due for completion by November 2007.

Richard Slocock, Chairman of the Fisheries Association, said: ‘We are delighted to be working with the Environment Agency on this project and look forward to seeing the salmon ascend the pass this winter.’

Like many salmon rivers, the Dorset Frome has a ‘Salmon Action Plan’ that pinpoints the main threats to local salmon stocks and helps the Environment Agency and its partners decide how best to boost fish numbers.

The plan includes a conservation limit. This is a target for the number of salmon eggs needed to ensure enough young salmon survive in the river to sustain a healthy population.

At present, the Dorset Frome is failing to reach its salmon conservation limit.

At least 15km of spawning grounds will be opened up to salmon spawning by the new fish passes. Once built, the Environment Agency will monitor the biodiversity improvements and fish populations, using cameras in the fish pass and electric fishing surveys.