Trying to quantify the juvenile fish population in a river as large as the Spey is difficult if not impossible. However one technique that can be used effectively is a time limited salmon fry survey. Using this protocol we electrofish in shallow, run/riffle habitat, for a standard period targeting salmon fry. With our new electrofishing gear we are able to set the countdown timer so that all our surveys last for a predefined period of three minutes actual fishing time.
This year we focussed almost exclusively on run/riffle habitat as this is considered to be the preferred habitat for fry. The results from this years extensive survey are shown in the graph below.
The sites are ordered from lower river on the left to upper on the right. For example the third site from the left, where 32 salmon fry/minute were recorded is at Brae Water beat 5. On the extreme right is the upper most site, located 1km downstream of Loch Spey, where no fry were found. There were only two sites where no salmon fry were found, both upstream of Spey Dam, although fry were found at 9 of the 11 sites surveyed above the dam.
The 2012 monitoring technique using the countdown timer on the electrofisher is different to that used in the past. In previous years the surveys were timed, based on total elapsed time from the start to the end of the survey. In order to calibrate the new technique with the old we also recorded the total elapsed time during each survey. The average calibrated number of salmon fry/min in 2012 was 4.04, compared with 1.9/min in 2011, despite the fact that almost a fifth of the survey sites in 2012 were upstream of Spey Dam where lower numbers of fish were expected. This is encouraging but as we were targeting run/riffle habitat higher numbers of salmon fry per minute were anticipated.
The Craigellachie sites were missed from the sequence in the survey plan but we managed to completed three sites there today. The results from these sites indicate that the increased number of salmon fry we found in 2012 is more than just an artefact of the new survey technique. At Craigellachie we did the usual sites i.e. the riffle above Telford Bridge, the glide in front of the fishing beat hut and a new site in the run between the Tunnel and Upper Slabs Pool. In 2011 19 salmon fry were found at the Telford Bridge site, today we found 110 and at the hut site we found 39 this year compared to 12 in 2011. The result from the Upper Slabs site was also good with 61 salmon fry recorded along with a few parr and many small eels. It should be noted that the total survey time at each site this year was 7 to 8 minutes, less than the 1o minute surveys completed in the past.
All three Craigellachie sites were quite different. The Telford Bridge site is a classic riffle for fry and the results from this site were equal to the highest recorded at any of our survey sites on the Spey this year. The Upper Slabs site was bouldery and more suited to parr, whilst the site in front of the hut was what I would consider sub-optimal fry habitat, i.e. glide rather than run/riffle with limited cover. This site was surveyed at the request of the ghillie to provide a direct comparison with previous years in a different habitat type.
Dougie Ross, the beat ghillie, was on hand to witness the surveys, and we were joined by one of his anglers at the Telford Bridge site. I would consider that all three sites were well populated with salmon fry, each supporting a density according to the habitat present. The results indicate a significant improvement in the numbers of salmon fry present in the river this year.
In conclusion we found that salmon fry are present from the bottom of the river almost to the very top, with only 2 sites from a total of 61 surveyed yielding no fry, although parr were recorded at these sites. The numbers varied from site to site but even with a new survey technique the calibration exercise carried out indicates that salmon fry numbers are significantly greater in real terms than those recorded in recent years.