This year we are surveying the Avon (pronounced A’an) intensively as part of the three year catchment rota. The Avon mainstem is too large to survey effectively by quantitative surveying so we used the same fry index survey technique as used on the Spey mainstem. The protocol is identical to that used in the Spey mainstem survey so the results will be directly comparable. As this technique has not been used on the Avon before the only benchmark are the Spey mainstem results
Today we completed 6 sites, 5 on the Avon and 1 in the lower Livet for comparison. Normally we would expect to do more sites using this type of survey but we needed to select suitable survey sites and access, plus we found a lot of fish! To aid site identification the river was split the river into 500m long sections numbered sequentially from the confluence upstream. There are 120 x 500m sections and we wanted a survey site approximately every 2.5km.
Our first site was opposite Ballindalloch Castle in the lower reaches. Ideally we want sites that will be resilient to a range of flows so that factor had a heavy bearing on our site selection.
The next site was upstream of the Ballindalloch Filling station next to the golf course. Here the substrate was coarser but it was very productive.
The Avon gillie Alan Thomson helped us with the site selection on the upper part of the Ballindalloch Estate water. The third site was below the Haugh Pool in Beat 3 (a lovely looking bit of water).
The next site was the riffle between the Kelt Pool and Gray’s Run towards the upper end of the Ballindalloch Water.
On the way home we stopped where the bridge at Drumin crosses the lower Livet. I have often admired this river vista whilst traversing the bridge so it was a pleasure to complete a site in the warm sunshine just upstream of the road.
This was a very interesting day as we hadn’t used this survey technique before in the Avon. The mean salmon fry number from the 6 sites today was 147, and for salmon parr it was 43.8, really good results, although as noted above we don’t really have any benchmark from the Avon for comparison. The gradient of the Avon is much higher than the Spey and it appears to be almost universally good parr habitat. There are acres of habitat in the Avon similar to that which we surveyed today. We try to select representative habitat; it is clear from todays surveys that the lower Avon is currently supporting a large population of salmon parr.