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Some South Esk salmon numbers

Tuesday, September 25th, 2012

These bulletin blogs represent news about Finavon and the South Esk, and my views as a riparian owner. They are not the views of any other organisation, nor are they designed to promote the interests of any individual or organisation other than Finavon Castle Water and factors affecting the fishery. Tony Andrews

In the light of the publication of 2011 catch statistics for all Scottish salmon districts, it may be useful to revisit my blog of last summer when, based on calculations of smolt production and ICES/NASCO returning adult fish percentages, I concluded that the annual run of salmon and grilse into the South Esk is about 10,000.

What did the nets catch in the September 2012 extension period? The item of news that should interest anyone who knows the South Esk is the number of salmon and grilse caught by Usan Fisheries Ltd during the two week extension of the netting season into September. This “two weeks” was actually eighteen tides, and the total catch was 272, of which the main part was grilse. I have good reason to believe that my source is reliable. TA

In 2011 I wrote;

“While there’s no room for complacency, it is very encouraging that in 2011 there are good numbers of spring fish in the river. Of course one swallow doesn’t make a summer, but it is also true that the 2010 run of spring salmon indicated a reasonable return of adult salmon, despite the poor rod catches resulting from low water yet again. The evidence therefore suggests that there appears to be a surplus of spring salmon year-on-year. By “surplus” I mean an escapement of fish to spawn that allows the regeneration of numbers of adult fish well above the minimum number required for sustaining stocks to return to the river between the start of the season and the end of May each year. That for me is the meaning of the term ‘sustainable’.

Ken Whelan fishing Pheasantry in May 2010 (above)

We don’t know how many salmon and grilse run the South Esk. It is a pity that the Esk Board has not devoted some of its considerable resources to a proper assessment of South Esk stocks, and continues to make management decisions on the current guesswork basis. We only have rod catch statistics to tell us what the trends are. But I will hazard a guess that the five-year average of returning adults, based on 60% of Usan net catches and the declared rod catch, plus our own observations, is somewhere around 10,000 fish. That figure has not yet been challenged and reflects more the general ignorance of the numbers and structure of South Esk stocks than it does on the actual numbers of fish”.

I based that speculative figure on 1,500 MSW fish up to 31 May, 3,000 MSW salmon and grilse in June, July and August and 5,500 MSW salmon and grilse from 1 September until spawning time (ie including salmon that enter the river after the close season on 31/10).

Since these figures were not challenged, and in fact a number of scientists commented that the method of reaching them was logical and consistent with experience from other rivers, I think it is fair to quote them again here. Based on those figures I wrote the following:

Average number of South Esk salmon and grilse killed by mixed stocks nets = c. 2,500*

Total number of salmon and grilse returning to the River = c. 10,000*

Total number of spawning females, allowing for 20% in-river losses = c.4,000

Average weight of spawning hen salmon = c. 8 lbs

Average number of eggs deposited by each hen fish = 4,500

Total number of eggs deposited in South Esk catchment (4,500 X 4,000) = c.18 million

Number of smolts produced annually by S.Esk (say 1% of total deposited eggs) = c.180,000*

Assume smolts returning as grilse is about 8% and of MSW fish about 5% (average 6.5%)

6.5% of 180,000 = c. 11,700 salmon and grilse arriving off the Angus coast (PFA) prior to nets exploitation.

Looking at those figures now, I really don’t see much need to change them. Perhaps I would reduce the return average from 6.5% to 6% to reflect the downturn in grilse numbers, and the proportion of fish caught at Usan and attributed to the South Esk more like 40% than 60%, but I think that those are the only adjustments neccessary.

In the context of those (admittedly speculative) figures I was interested to see the 2011 catch statistics published by Marine Scotland last week for salmon and grilse caught in the South Esk District. These returns include net and rod fisheries of fish killed and fished caught and released by rods. Nets of course kill everything they catch.

Here are the 2011 salmon and grilse catch returns for the South Esk District

Salmon killed = 5,646

Grilse killed = 1,203

salmon caught & released = 518

Grilse caught & released = 85

Total South Esk District catch = 7,452 salmon & grilse

If we take the figures for the South Esk District nets (the only legal nets being those belonging to Usan Fisheries Ltd) we see that:

In May 2,307 salmon were killed: average weight 4.13 Kgs

In June 1337 were killed: average weight 4.26 Kgs

In July 1053 were killed: average weight 4.2 Kgs

In August 746 were killed: average weight 4.36 Kgs

The consistent average weight of fish throughout the season (about 9lbs) suggests that there was a predominance of MSW fish throughout the season, expressed either as some very large MSW salmon offset by the lower average weights of grilse, or (more likely) a reflection of very low numbers of grilse, which would typically average 2 Kgs.

The figure that stands out in the 2011 season is the large number of 2,307 salmon killed in May. There are a number of aspects relative to this figure that are worth comment:

1. The value of 2.307 of prime spring salmon is very high. One may assume a per fish value of £150 to £200, giving a gross income to Usan Fisheries Ltd for May month of £300,000 plus. No wonder the Usan business doesn’t want May removed from the netting season, as has already happened in February, March and April.

2. If the 2012 radio tracking data are used to indicate how many of these May fish were bound for the South Esk, we might assume, from the proportion of recorded tagged salmon in the South Esk, that 40% of those 2,307 salmon killed in May 2011 were South Esk fish.

3. Upper proprietors observed that there was a prolific run of spring salmon in 2011. Usan’s May return confirms that the spring run continued to be strong into May. Based on Usan’s May catch return we might assume that about 900 of those fish were of South Esk origin. That figure tallies with my guess that an average of 1,500 salmon enter the South Esk before the end of May.

4. Catch returns from Cortachy & Downie Park, Inshewan and Finavon indicate that there were good numbers of MSW salmon in the South Esk from March onwards, and of course with no netting taking place in March and April, these salmon had free access to the river. Moreover, none of the rod-caught salmon in those two months was killed. Spawning escapement in 2011, even with the 900 fish killed in May by Usan nets, was clearly significant.

It is important that the Marine Scotland radio tracking project fulfills its purpose, which is to find out where early running South Esk salmon spawn. The project has nothing to do with stock assessment beyond that single purpose, although people (such as I!) will inevitably extrapolate from the data to support their arguments. We need to have a health warning on such methodology because the data coming from the MS project are not fit for any purpose other than demonstrating where some spring fish go in the South Esk catchment.

Posted in History, River Report, Salmon | Comments Off on Some South Esk salmon numbers

Return to the Lemno Burn in low water

Sunday, September 23rd, 2012

Today was one of those September mornings that confirm childhood memories of golden autumn days. In the 1950s there were no high-roll bales of straw after the barley harvest. At that time the mechanised baler produced a rectangular bale that could easily be lifted by one person. But I rather like the haphazard jigsaw of the 6’0” high-roll bales in the harvested fields, even if it is impossible to lift them manually – or is it? Is there some giant of a farmer’s son somewhere in Aberdeenshire or Angus who routinely lifts and carries the huge bales from the fields to the steading?

This is the view looking south across the big field towards the Lemno Burn and the policy woodlands that line its banks. This is the section of the Lemno discussed in this bulletin blog.

So, today was a sunlit autumn Sunday, and I decided to extend the dogs’ constitutional with a wander up the Lemno Burn, which was very low after our long summer of spates. I wanted to see how the channel downstream of the A90 had developed since the volunteer day on 1^st April, and what I saw surprised and delighted me.

Low water stickle in the Lemno Burn just upstream from the Red Brae

On first inspection you might think that the differences between now and a year ago are marginal: there is still far too much silt in the long flat section 300 metres upstream of the Red Brae, but below that there is now plenty of gravel exposed by healthy streams, riffles and stickles. While the gravel is still covered with algae and it is obvious that agricultural enrichment is dominant, there are places where fish might spawn. The reduced tree canopy is letting far more light in than a year ago, with the result that grasses and wildflowers are starting to re-colonise the banks.

One of the main pools (above) in the Lemno Burn in the section where the high tree canopy was reduced by thinning in the winter of 2011/12. It was in this part of the lower Lemno that I observed large numbers of salmon and sea trout parr on Sunday 23rd September.

As I walked up the left bank of the burn in the margins of the woods that define the burn’s course, peering into the water I saw small fish in every single pool. At first it was just the odd fish darting for cover as I appeared above them. But when I reached the long flat pool about half way between Red Brae and the main road (A90) I saw literally hundreds of parr, ranging in size from about 5cms to 10 or 11cms in length. In some places there were shoals of these little fish numbering 40 or 50, quite closely packed together. When disturbed they darted around the pool individually, afterwards to return to a deeper section where the shoal reformed. I was able to get quite close to a small group of fish and study them in detail with the use of my Polaroid glasses. They were certainly parr, but I have no idea whether they were salmon or trout.

Woodland pools in the lower Lemno Burn are holding large numbers of salmon and sea trout parr. The abundance of juveniles is encouraging, but as yet we do not know the ratio of salmon to sea trout. Those data would be useful in understanding the role that the Lemno Burn plays in the makeup of South Esk stocks of both species.

The same pattern repeated itself all the way up to the village. There is absolutely no point in exaggerating, and every reason to try and report as accurately as possible what I actually observed. I estimate that in the lowest 800 metres of the Lemno Burn there are at least 500 salmon and sea trout parr, and there may be more than this because my estimate is pretty conservative. These juvenile fish look to be in good condition and, judging from the quality of the riparian habitat, there is probably plenty of food available. What I cannot say, and will avoid speculating, is whether the removal of about 40% of the tree canopy and obstructions from the bed of the burn have influenced the numbers of fish using this section. In other words I have no baseline for comparison.

Above: not a very good photo of the silty bed of the pool in which I observed a large shoal of salmon or sea trout parr (probably the latter I guess).

Thinking through the implications of the various bits of information on the Lemno Burn I have recently received:

A government scientist told me that the middle Lemno supports small numbers of very large parr (or did when it was electro fished a couple of years ago)
The farmer at the Meadows on the King’s Burn, the only major tributary of the Lemno, described his father finding dead salmon kelts on the banks of that burn in late winter in recent years.
My own observation on 23 September 2012 of large numbers of salmon and/or sea trout parr in the 800 metres of the Lemno Burn upstream of its confluence with the South Esk.

One could not possibly argue that all is well in the Lemno Burn, especially after the dredging vandalism carried out by the farmer to the section that runs parallel to the A90 just north of the Kirriemuir junction. There is no doubt that a lot of work needs to be done to increase the Lemno’s output of smolts. However, I am surprised and delighted to allay my concerns to some extent after what I saw today. These little fish are almost certainly in the second year of their lives and should smolt next year (April/May 2013). If, as may well be possible, the Lemno Burn is releasing two or three thousand pre-smolting parr into the South Esk each year, it is making a much better contribution to the overall stocks of salmon and sea trout of the South Esk than I had feared.

Autumn and a newly hatched Red Admiral butterfly Vanessa atlanta. The Rajah Brooke birdwing butterfly Trogonoptera brookiana is bigger, the Purple Emperor Apatura iris more regal and the Camberwell Beauty Nymphalis antiopa more exotic, but is there a more beautiful insect on earth than our very own Vanessa atlanta ? (even the Latin name is gorgeous!)

Wouldn’t it be interesting to learn what proportion of the fish I saw today were salmon or sea trout? I shall ask the Esk Trust to help us answer that question.

TA 23/9/2012

Posted in Fishing Report, Habitat improvements, River Report, Salmon, Sea Trout | Comments Off on Return to the Lemno Burn in low water

Thinking about the Lemno Burn

Monday, September 17th, 2012

The structure of a river catchment is one of the factors that determines the breakdown of the river’s stock of salmon – and maybe sea trout – into distinct populations. The shape of the catchment, altitude, gradient, topographical features (such as waterfalls), geology and chemical characteristics of its water, define a river’s migratory salmonids in terms of run timings and the predisposition of its salmon to return as grilse or multi sea-winter salmon, as well as variations in behaviour of sea trout. In big rivers, like the Tay or Dee, that may seem an obvious statement, but for a little river, such as the South Esk, we may overlook the importance of its smaller tributaries, and the role they play in the evolution of the characteristics of the stock of the whole river catchment.

The Lemno Burn just upstream of its confluence with the South Esk at Finavon. The photograph above was taken during a cleaning up operation by volunteers in April 2012, which involved moving tons of rubbish from the burn, whose gravel bed was covered by a thick blanket of gooey silt, up to 2′ 0″deep in places.

The Lemno Burn is a much abused drain for agricultural run-off and chemical enrichment from the intensively farmed Vale of Strathmore. There is anecdotal, but I think reliable, evidence that the Lemno was once an important spawning burn. Farmers upstream of Battledykes, through whose land the King’s Burn flows, tell of dead salmon kelts washed up on the banks of the burn after winter floods. As far as I am aware, there has not been any redd or official juvenile count in the King’s Burn in recent years. My guess is that it still supports a stock of salmon and trout, albeit a diminished one.

The photo above shows how the artificially wide channel and silting up of the burn has slowed the current and reduced scouring, even in a spate. By getting the water moving again we hope to reveal the good quality gravels beneath the silt and encourage fish to use the burn again.

Silt, sewage, pollution and utrification have severely damaged the habitat for spawning and juvenile salmon and sea trout once provided by this South Esk tributary. Despite the degraded condition of the habitat in some parts of the Lemno, electro fishing the middle and upper reaches by Marine Scotland scientists has revealed some very large parr, especially in the area of the confluence with the King’s Burn at Battledykes. There is no record of whether these fish were salmon or trout, or whether there is a mixture of the two. If we can restore the Lemno to a level that can support a diversity of aquatic life, it is likely that the burn will once again make a valuable contribution to the recruitment of salmon and sea trout.

Blocked by trees and accumulated rubbish, and full of the detritus of years of neglect and a thick ‘porridge’ of silt, the Lemno Burn is far from the ideal environment one would look for in an important tributary of the South Esk. But even in the photo above we can see the potential for restoration with the healthy flow and substrate of good quality gravel and cobble. If we can reduce the tree canopy to let the light in, we should have more phyto and zoo life in the burn, which should lead to providing the food necessary for healthy juvenile fish abundance.

Another photo (above) of the degraded channel of the Lemno Burn in its lower reaches. The accumulation of feet of glutinous silt at this point ensures no salmon or sea trout could spawn in this part of the burn.

If you walk up the Lemno Burn from its confluence with the South Esk at Finavon’s Red Brae Pool, the first thing that strikes you is the unnatural width of the channel downstream of the A90 dual carriageway. The channel is indeed an artificial one, because it was the lade of the roundstone dyke at Tannadice which was removed in 1946. Prior to that time the Lemno Burn joined up with the lade which provided water power for the mill on the Finavon Estate. When the water from the main river was diverted into the lade by a sluice on the south end of the dyke it combined with the water from the Lemno to make a sizeable stream. In low water the effect of the diversion was to discourage fish from running, with the result that they would gather in large shoals in the pools immediately above and below the Red Brae.

The last mile of the Lemno Burn, between the A90 and where the burn joins the South Esk, is a heavily wooded section. Over the years the tree canopy has spread out and removed all direct light from the sun. The photo above shows how the burn now looks after a major tree thinning operation in the winter of 2011/12.

In this summer’s blogs I have commented on the importance of one of these smaller tributaries – the Rottal Burn – and the rather surprising lack of our knowledge about its role in contributing to recruitment of juvenile salmon and sea trout prior to the start of the restoration project. It would I think have been useful to have had a baseline from which we could measure the effects of the project on populations of migratory fish using the burn. The lack of that baseline means that we may have to resort to guessing, which, for those of us who take an interest in the South Esk, is all too familiar a situation!

While the Rottal Burn is an upper catchment tributary and, as such, a natural destination for early running salmon – producing mainly S3 smolts (but maybe some S4s amongst them), the Lemno Burn is a middle catchment tributary. The Lemno Burn’s confluence with the main river at the Red Brae Pool on Milton Beat of Finavon Castle Water is about 15Kms from the tide at Bridge of Dun. The ‘plateau’, which I described in the previous blog, where there is about 500 metres of gentle gradient between two much steeper gradients, seems to be at about the right distance from the tide for migrating fish to rest. Spawning fish arriving at the mouth of the Lemno in the late summer and autumn may have used the burn to gain access to the King’s Burn at Battledykes. One of the radio receivers used in the tracking project is currently sited on the Lemno Burn. It will be interesting to see if any spring salmon use this burn.

The Lemno Burn may be more like the Pow Burn, which is the lowest of the South Esk’s tributaries and provides habitat mainly for sea trout, or like the tributaries of the upper catchment catering for the needs of salmon, or both species. It will be interesting to find out; and the best place to start is to clean up the lower reaches and improve conditions for spawning and juveniles further upstream. Work in progress.

TA 20 September 2012

Posted in Habitat improvements, History, River Report, Salmon, Sea Trout | Comments Off on Thinking about the Lemno Burn

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Some South Esk salmon numbers

Return to the Lemno Burn in low water

Thinking about the Lemno Burn

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