2014 Season: Numbers up the fish pass to date:
22 Salmon 36 Sea trout
On 3rd October 2014 the first salmon ascended the Culter Dam in over 200 years, thanks to a fish pass we installed on the dam just days earlier. This dam, at Peterculter, is the largest man-made obstruction on the River Dee.
Why install a fish pass on the Culter?
The fish pass has opened up 76 miles of habitat in the previously inaccessible Culter burn for migratory salmon and sea trout to re-establish natural populations in.
Only the lowest one mile of burn is below the dam and so accessible to salmon and sea trout. The spawning and rearing habitat in this part of the burn is fully utilised, resulting in high juvenile fish densities. High juvenile fish densities mean lots of competition and higher mortality rates. Creating more rearing habitat for juveniles will result in lower mortality rates and so higher fish production.
Once habitat restoration work is completed in the Culter catchment we expect to see an additional 1,500 salmon returning to the Dee each year.
These salmon may be available to the catch and release rod fishery as far up river as Banchory, as our radio tracking studies show how fish may wander up to 20km upstream from where they eventually spawn.
Monitoring Fish Pass Success
A Vaki fish counter is installed at the top of the fish pass to record how many fish are using the pass to ascend the dam. The counter records the length of each fish. We assume that all fish longer than 50cm are salmon, fish between 30 and 50cm length are sea trout and fish less than 30cm are brown trout. In practice, there is some size overlap, particularly between small salmon and large sea trout. Our scale data show we would expect 6% error in these classifications.
An infra red image of the first salmon to ascend the dam in over 200 years
Culter Catchment Restoration
Culter Dam is the first and most important step in removing a total of four obstructions and re-establishing natural habitat of the Culter catchment. Weirs further upstream, on the Loch of Skene and Waterton Loch were also barriers to migratory fish. However, the Board and Trust have worked to ease these obstructions in 2014: A fish pass was installed at the outflow of Loch of Skene, whilst work at Waterton Loch involved the creation of a 40m bypass channel for fish to travel upstream of the dam. We aim to tackle the remaining obstruction in 2015.
Fish Pass Construction
Step 1 - Stabilise the dam wall with 50 tonnes of hardcore and concrete
Step 2 - Transport pre-fabricated Alaskan denil fish pass to site
Step 3 - Install the one-metre sections of the fish pass
Step 4 - Completed fish pass on the Culter Dam
Culter Dam Background
Culter Dam is a remnant of a large paper mill that closed in the 1980s. For over 200 years the dam has prevented fish from accessing the Culter Burn, which is the second largest tributary of the Dee. Since 2007 the River Dee Trust and Dee District Salmon Fishery Board have removed or eased 27 man-made structures from the River Dee's tributaries. The aim of this work is simple: To allow fish to gain access to their natural spawning and rearing grounds.
The work on the Culter Dam was delivered jointly by the Trust and Dee DSFB, entirely funded by two businessmen Martin Gilbert and Stewart Spence, without which the work would not have gone ahead.
Fish passes on the Loch of Skene and Waterton Loch have been supported by SEPA's Water Environment Fund and with the support of Dunecht Estate. Thank you to Aboyne Photographics for the great photos.