Although good catch data form angling and netting exist for the there is a need to develop a reliable and independent means of assessing the numbers of salmon ascending and descending the Spey. The Spey Fishery Board took a huge step towards achieving this goal during the 1990’s with the installation of a split-beam acoustic counter from a Seattle based company Hydroacoustic Technology Inc. The ambitious project funded through a generous donation from the late Martin Wills Trust, examined the feasibility of operating a counter in the lower Spey during 1996 to 2001.
Various potential monitoring sites were examined on the lower Spey and a semi-permanent site was established approximately 16km from the river mouth. The results were positive indicating that acoustics could be used to monitor fish passage in the turbulent waters of the Spey. Fish count data was collected for several years and compared with rod catch data to produce a model for determining adult fish runs see SFB Annual Report 2004 p42-43. A full report on the project is available Brotherston 2002. The acoustic counter program concluded in 2001.
VAKI Counter Installed
A VAKI fish counter (www.vaki.is) was installed in the River Dullan, a tributary of the Fiddich. The installation was funded through the CASS LIFE project with additional assistance from the whisky distillers DIAGEO. The Dullan has two water offtake weirs to supply distillery cooling water and these were recently fitted with Denil fish passages to improve fish access. The VAKI counter was installed on the lower Mortlach weir in July 2007.
The fish pass through two infrared scanners within the counter and an infrared image is collected and stored in the operating computer. Upstream fish also trigger a camera system allowing the species of fish ascending to be determined from digital images. Although this depends on clear water conditions to be effective.
Salmon, sea trout and brown trout have all been recorded ascending through the counter. In general the trout migration begins late July and extends to November, with peak passage in late October/early November. Salmon passage is later in the year although some do ascend as early as September the majority wait until late November to complete their spawning run. The majority of the trout have migrated soon after spates and typically at night although, even in low steady flows, a few trout make their way up the fish passage each evening. The pattern is similar for salmon.
Initiall installation provided excellent data but during 2010 and 2011 riverworks nearby and repairs to the weir have prevented effective counter operation. However, plans for re-installation are underdevelopment for 2012.
Truim Fish Counter
Scottish and Southern Energy (SSE) have installed a resistivity counter on the River Truim fish ladder near Dalwhinnie. The installation was completed in 2008 and supported by funds from the CASS LIFE Project. During 2010 and 2011, 134 and 106 fish respectively, were recorded passing over the counter. The fish passage includes salmon and trout so some work is still required to apportion the fish to species.