Dulnain electrofishing – one year on

Last summer we surveyed the Dulnain in detail. The electrofishing  sites in the Dulnain mainstem last year held good salmon fry densities but much lower parr densities. We promised then to revisit these sites a year on to see if the 2012 fry numbers had translated into higher parr densities. The intention was to resurvey four sites in total and today we managed to survey three, the other involves a major expedition on an estate road and will have to wait for a later date.

The furthest downstream site today was at Balnaan Bridge in the lower river a couple miles upstream of the village of Dulnain Bridge. This site has been surveyed on a number of occasions providing a nice history for comparison.

The electrofishing site at Balnaan (Balnain). The river here is wide and shallow and the site consists of a transect across the river of about 6.5m. The same area has been surveyed eight times since 2003.

The electrofishing site at Balnaan (Balnain). The river here is wide and shallow and the site consists of a transect across the river about 6.5m long giving a site area of 131m2. The same area has been surveyed eight times since 2003. There was a high incidence of moss and weeds covering the substrate providing good cover but making fish capture difficult.

The results from this years survey and previous years are results are shown in the table below.

Electrofishing results from the Balnaan site. Previously there has always been an excellent density of salmon fry at the site and it was the same this year. The salmon parr density today was the highest recorded. The Dulnain is very low at the moment but the width was only about 10% less than that recorded last year.

Electrofishing results from the Balnaan site. There has always been an excellent density of salmon fry at the site and it was the same this year. However the salmon parr density today was the highest recorded at the site. The Dulnain is very low at the moment but the wetted width was only about 10% less than that recorded last year.

The middle site was several miles upstream of Carrbridge just upstream of Inverlaidnan Bridge. The river here is quite different in character with big boulders and little weed growth. The third site was a couple miles further upstream at Dalnahaitnach. Again a different bit of river with faster flows dominated by riffle and run habitat.

Survey site at Inverlaidnan.

Survey site at Inverlaidnan.

Survey site at Dalnahaitnach

Survey site at Dalnahaitnach. I haven’t figured out a way to highlight areas in the picture above on the blog but I will show the survey area clearly during the presentation in Aberlour on Thursday. The site here was 18m long by about 9m wide giving an area of 164m2.

The results from all three sites over the last two years are shown in the table below.

Results from the 3 sites surveyed on the Dulnain today along with last years results. The average widths measured each year are also shown.

Results from the 3 sites surveyed on the Dulnain today along with last years results. The average widths measured each year are also shown. The site widths were approximately 15% less this year than last due to the low water.

It can be seen that the salmon fry densities were in the excellent category in all 3 sites, the same for the salmon parr. The results are classified and colour coded according to the Scottish Fisheries Centre Coordination Moray Firth region corrected for stream width. Salmon fry and parr densities were higher at all 3 sites than found in 2012.

The size of the fish declined in an upstream direction and at Dalnahaitnach the smallest of the one year old parr were about 58mm. 65 out of the 70 parr found in the sites looked like one year olds with the other 5 older fish (all judged by size distribution, scale reading will confirm or otherwise in due course). Most of the smaller parr were on the lean side.

Tjree year classes of juvenile salmon from the Dalnahaitnach site on the Dulnain. Note the lean condition of the middle fish (looks like the right size to be a one year old parr).

Three year classes of juvenile salmon from the Dalnahaitnach site on the Dulnain. Note the lean condition of the middle fish (looks like the right size to be a one year old parr in this part of the river).

These are encouraging results and it was nice to see the good fry densities last year translated into excellent parr densities. The densities found today and the lean condition of the parr in the upper sites suggest that if anything the food available is being shared between too many mouths……

 

There are 2 comments for this article
  1. Stuart brabbs at 11:03 pm

    Interesting post Brian. Smolt trap next year to see how many parr survive to smolt stage?

    • Brian Shaw Author at 8:29 am

      Thanks Stuart, the challenge would be trying to quantify the run, you will have noted the width of the channel in the upper sites? The Dulnain can experience very high flows during snow melt in the spring!!

      Brian

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