0+ monitoring Burn of Brown

The Burn of Brown has been stocked for a number of years principally because there is what is considered to be a partially inaccessible waterfall just above its confluence with the Lochy, which it joins at the Bridge of Brown. The confluence with the Lochy is at about 1000′ so it is a proper high altitude tributary. A walk over confirmed it to be a nice looking burn with high fish densities evident in the pools. Judging by the recent gravel deposits, divots and water flowing over grass it looks as if there had been a recent high water event.

In the centre left of this photo the burn can be seen flowing over a grass bank; the previous channel looks as if it has been smothered with deposited gravel

The next photo shows the upper Burn of Brown. The sinuosity and extensive gravel deposits indicate a highly mobile but entirely natural watercourse.

Upper Burn of Brown

The Burn of Brown had been stocked with 90,000 0+ parr on the 4th Oct 2011. We monitored 3 survey sites on the 11th Sept 2012, the first with a multiple, three run, survey technique to establish absolute fish numbers and the other two with a single run. I extrapolated the total fish densities for the single run sites.

The first site (three run site) was about 500m upstream of the spectacular rock gorge. The burn narrows to about 3′ width at this point through impressive rock formations providing a popular venue for outdoor activities such as river canyoning.

Burn of Brown rock gorge

The first survey site consisted of a mixture of fry and parr habitat, generally shallow with undercut banks on the left.

Burn of Brown site BB3, upstream view

The results at this site were encouraging with good densities of salmon parr – higher in fact than the trout density.

The second site was further upstream. This site consisted of a deep pool and glide with great cover provided by boulders and the roots of a large alder tree. Densities of both salmon and trout parr were excellent.

Burn of Brown BB5 downstream view

In order to gather data from a representative range of sites the upper site selected was shallower with mainly run habitat but good cobble cover. Here the results for both salmon and trout parr were less although trout fry were more abundant.

Burn of Brown BB6 upstream view

The results and classification from each site are shown below.

Based on these figures I estimate that the parr numbers within the stocked area of the burn to be as follows:

The estimated number of salmon parr (1866) is likely to be a slight overestimate as one of the survey sites was in one of the best areas of habitat in the burn, however it is clear that there were more salmon parr than trout parr in the stocked section of the burn. Survival from the original 90,000 stocking was just over 2% but then the initial stocking density was very high for such advanced fish.

I was quite impressed by the densities of salmon parr present.

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