Caledonian Canal

Caledonian Canal

The Caledonian Canal, which provides a shipping route from the east to west coast of Scotland, was opened in 1822. The canal construction had a major effect on the Ness catchment e.g., Loch Ness was raised by several feet. Not only did the canal opening have a major impact on the catchment, it had a significant impact on the Ness salmon population. Soon after the opening of the canal the difficulties encountered by salmon smolts in navigating their way down the river, rather than entering the canal, were recorded in parliamentary reports.

Developments in acoustic tracking in recent years have provided hard evidence of, and quantified, the loss of salmon smolts within the canal.

The canal was built along the line of the Great Glen and links the three big lochs, Ness, Oich and Lochy. Loch Oich is the high point on the canal and according to Thomas Telford * “on the summit there is an inexhaustible supply of water”. Before the canal as built there was only one outlet to Loch Oich, that being the River Oich. Now there are three outlets, the River Oich plus the Caledonian Canal which flows east and west from Loch Oich. The water used by the  canal means that the flow in the River Oich is diminished on dry weather. Tracking of smolts has shown that significant numbers of smolts enter the canal at the west end of Loch Oich, entering the Lochy catchment. Some of these smolts have been tracked into the Minch around Mull. Smolts also enter the canal at the east end of Loch Oich at Cullochy. None of the smolts entering the canal at Cullochy have been found to reach the sea.

A similar problem can occur at Dochgarroch, and in 2020 large numbers of salmon smolts were filmed in the canal, resulting in questions being asked in the Scottish Parliament. There is a least a smolt by-wash channel at Dochgarroch, although the effectiveness of this is unknown. There is no by-wash as Cullochy, which means that the majority of the smolts exiting Loch Oich via the canal become entrained within, which invariably results in failure to reach the sea.

Although the impact of the canal on salmon smolts became evident as soon as it was opened, the availability of tracking data for individual smolts has highlighted the impact of the canal on what are now regarded as endangered salmon populations. We are in regular dialogue with Scottish Canals and we were very pleased to see that the Wild Salmon Strategy Implementation Plan 2023 – 2028 contains an action against Scottish Canals, and other organisations to resolve the issues – “1.17 Undertake a review of the risk to fish migration of the canal network and associated management structures [By 2025] (Scottish Canals – DSFBs and Trusts, SEPA, NatureScot)”

We are aware that Scottish Canals are commissioning an independent options appraisal to assess what measures can be implemented to reduce the impact of the canal on wild salmon. We look forward to working with Scottish Canals on this.

*. Contained within “The Caledonian Canal” by A.D. Cameron, 1972.