Much concern has been expressed about the juvenile salmon densities in the middle reaches of the Dulnain, one of the Spey’s most significant tributaries. Our earlier salmon fry index surveys found that salmon fry were present throughout the Dulnain although numbers were much higher in the lower reaches. Today we completed single run surveys at three locations at Balnain, Inverlaidnan and Dalnahaitnach in order to try and quantify the parr density. I joined the team just before they started at the Inverlaidnan site. The Dulnain, even this high up is still a large river and the mean width was over 15m. This is wider than recommended in the SFCC protocol but a one run survey was only ever going to provide an indication of the minimum density present.
The site at Inverlaidnan was called D21. The photo below shows the type of habitat present. There was a high percentage of boulder and cobble providing loads of cover.
We surveyed an area of over 300m2 and captured 94 salmon fry and 34 salmon parr along with a few trout. Calculated densities will be shown below.
After processing the catch we moved up to the end of the road at Dalnahaitnach where we completed another survey site just upstream of the remains of the old bridge. It can be seen from the photo below that the habitat at the site was good for parr. There is a vast area of similar habitat in the upper and middle Dulnain. Our site started above the upper riffle in the photo.
Quite a lot of fish were caught in the site which was 19m long. Salmon were dominant with only 1 or 2 trout present. Below are a few photos of the fish processing.
Back in the office densities of both salmon and trout fry were calculated. I like to use the SFCC national classification system to classify site results. This system is based on over 1600 results from across the country. The table is colour coded to make results more visual.
A salmon fry density greater than 42.1/100m2 is in the top 20% of Scottish results ( A class or Excellent) according to the SFCC classification and between 20.3 and 42.1/100m2 is in the second 20% band (B class or Good). For salmon parr anything between 9.1 and 15.8/100m2 is B class. It can be seen then that the juvenile salmon densities at the three sites are all in the moderate to excellent category. Full details of the classification scheme can be found here (Godfrey, 2005).
The average size of the fry and parr decreased with altitude. The Dulnain is no rich limestone stream and the invertebrate population is relatively sparse but the fish that live there are adapted and grow accordingly.
All in all it was yet another fascinating day on the river. The results indicate that the Dulnain supports a moderate to excellent density of juvenile salmon, and confirm its status as a significant smolt producer.
If anyone wants to joins us on an electrofishing trip please get in touch, assistance is always welcome.