Bob Kindness
Stock recovery is good news for the Carron – but not for the critics
THIS year has been designated the International Year of the Salmon and it finds wild Atlantic salmon struggling across their entire range. Catch figures for 2018 have recently been released and show that the rod catch for Scotland of 37,196 is the lowest since official records began in 1952.
To put this in context by making comparisons with the past, one beat on the Aberdeenshire Dee recorded a total catch of 343 salmon for February alone in 1957. This year the whole of the Dee is struggling to reach that total for the first three months of the season.
I have also seen a photograph of an opening day catch for one rod on the Dee in the 1950s of 34 salmon laid out on in rows on the grass.
It should also be remembered that in the past the commercial netting of salmon by both fixed engine and net and coble took place all round the coast of Scotland, as well as within rivers. In the 1960s, the annual catch
was as high as 500,000 salmon and yet there was no shortage of salmon in the rivers.
Through the middle of the twentieth century salmon were indeed plentiful and exploitation by nets and rods was easily sustainable.
However, throughout the latter part of the last century salmon numbers began to drop and this decline, apart from for a few individual years, has continued until today.
The main approach taken by the authorities to try to arrest this decline has been to reduce exploitation. The commercial netting was gradually reduced through buy-outs until it was eventually stopped completely in 2018.
The thought behind this was that all the fish saved from the nets would get into the rivers to bolster rod fisheries and increase the number of spawning fish.
Unfortunately, although rod fisheries were maintained to some extent throughout this period of reducing exploitation, overall salmon numbers continued to drop.
The next move was to reduce exploitation by anglers. A ban on the sale of rod-caught salmon was introduced, voluntary catch-and-release became normal practice for many fisheries and, most recently, mandatory catchand-release has been introduced for spring stocks for all rivers and for the entire season for rivers where stocks are unsustainable. Despite all this, the numbers continue to drop.
The problem is that although reducing exploitation in order to try to preserve what you have is obviously a good thing to do, the reality is that it is simply not achieving enough to counter the ever increasing difficulties facing wild salmon.
What needs to happen is, rather than just reducing exploitation, we need to increase abundance so that despite all the losses occurring in salmon stocks, there are sufficient surviving to both maintain rod fisheries, which are economically important, and enough spawners to maintain stocks. Culprits
Before trying to answer the question of how to increase salmon abundance we should consider what factors are the likely culprits in reducing stocks.
The popular perception is that the main problems are in the marine environment, with poor survival as a result of factors such as climate change, lack of feeding, over fishing and aquaculture, although I fail to see how the lack of fish on the east coast can be blamed on salmon farming when there are no cage sites on that side of the country.
While it is fair to say that marine survival is much lower now than it was in the past, less than five per cent compared to a figure of over 20 per cent, the problem is not just at sea and does not just involve the culprits already mentioned.
All is not rosy within our rivers and at the river mouths. In all the deliberations about the poor state of salmon stocks, one major factor is seldom mentioned and that is the ever increasing number of salmon predators.
The list is a long one and includes goosanders, merganzers, cormorants, herons, otters and, at the river mouths, seals and dolphins, and they are all fully protected.
For most rivers the worst offenders are goosanders and merganzers, the fish eating ducks. These birds will target the smolt run when they are pairing up prior to breeding. Then the mother and young will feed on fry and parr through the summer before the young fledge in August and usually leave the river.
The mothers are very diligent, will never leave their young and are capable of fledging broods of up to 12 young. The damage done to salmon stocks is horrendous.
The penny is now beginning to drop regarding in-river predation, with results from rivers such as the Dee using telemetry showing that a very high percentage of smolts from the upper river do not reach the sea.
Unfortunately, little can be done about predation as the sort of population controls that would be necessary to make a difference would never be sanctioned. We simply have to live with them.
It is also highly likely that, even if current marine projects can identify what the problems are at sea, we will be able to do little about them, at least in the short term.
We therefore need to accept the low level of marine survival and take what steps we can to ensure that even with that low level we can still get enough fish returning to our rivers to keep anglers happy and maintain stocks.
While fixing the problems at sea and dealing with the predators may be a step too far, one approach that is within our powers is to increase abundance by increasing the number of smolts successfully leaving our rivers.
Successful approach
Steps have been taken on several rivers in an attempt to increase smolt production by improving habitats and opening up hitherto inaccessible parts of the river by removing obstructions such as dams and weirs.
The success of this approach has been limited to date and has certainly not arrested the decline in salmon. The reason is quite simple. Creating more habitat is only worthwhile if there is insufficient existing good habitat to accommodate the young stock that you already have.
If a river has under utilised habitat, then creating more habitat will make little difference in the short term since you are simply spreading out what you already have.
However, habitat improvements are certainly beneficial if combined with increasing the numbers of young fish at the same time.
In an ideal world we would leave this to nature because, as is often said, ‘nature knows best’. But in the case of salmon it is highly unlikely that leaving it to nature will achieve the outcome we desire.
“Definitive evidence on stocking related to a Highland river in the heart of the aquaculture zone is of sectors’” great importance for both
Most species produce enough offspring to replace themselves with perhaps a little extra. In the case of salmon, an average sized hen will produce approximately 5,000 eggs, of which about 50 will reach the smolt stage, providing there are no disasters.
At a marine survival level of four per cent this would result in two adults returning to the river, which is replacement level with no opportunity for an increase in numbers.
When this is combined with the fact that we now have less spawning fish, it is clear that, at best, nature will keep the stocks of salmon ticking over but will not increase abundance.
In reality, natural spawning is not very efficient, hence the large number of eggs produced by each hen.
Last winter a short video was posted of a small hen grilse spawning in the River Ness. She dug a shallow redd, which would have been susceptible to wash-out in a spate; as she deposited her eggs the cock produced a cloud of milt to fertilise them, which has to happen before the eggs reach the gravel, but several eggs were washed away in the current and then four brown trout moved in for a feed. The number of fry emerging from the redd would only be a fraction of the number of eggs produced by the hen.
In stark contrast, artificial spawning is extremely efficient. As an example taken from the stocking programme on the River Carron, for a batch of 6,400 eggs stripped from one MSW hen last winter, only 12 failed to reach the eyed stage and a further 25 failed to hatch.
Almost all the rest reached the feeding stage and, all things being equal, all of them will reach the stocking-out stage.
This means that in excess of 6,000 autumn fry could be stocked out, a figure that is at least 10 times the number of equivalent fry had the hen been left to spawn naturally.
Artificial spawning, the use of hatcheries and the development of appropriate stocking programmes have to be considered if we are to increase the smolt output to a level that will make a real difference.
We need to at least double the number of smolts to potentially get an acceptable number of returning adults. This is exactly what has been achieved on the River Carron, where a stocking programme has been in operation for more than 20 years.
The story of the stocking project has been well documented, describing the journey from a near empty river to one achieving record catches, but it is worth highlighting some salient points:
• Initial recovery achieved using stock from
captive broodstock;
• Stock then maintained using both captive broodstock and wild broodies caught on rod and line;
• Stocking using all life stages from eyed ova to smolts;
• Stocking into all parts of the catchment, from the headwaters to above the tidal water;
• Ability to demonstrate the success of stocked autumn fry through to the smolt stage from a tagging programme and the use of a rotary screw trap. On a par with the expected success from wild fish with no signs of domestication;
• Use of the screw trap over the last 12 years to estimate smolt output at more than double what might be expected from natural production. Autumn stocking replaces wild stock lost through the winter (spates) and summer (predation) and goes out after most of the young goosanders have fledged and left the river;
• Using known stocked hens as broodstock and achieving the same high level of success from eggs and fry as from wild hens. No indication of lack of fitness. Unfit fish do not return from the North Atlantic;
• Achieving excellent catches throughout the years of the stocking programme. Catches are at historically high levels for salmon and especially for grilse. Catch figures portray a very telling story, with the average yearly catch from 1952 to 2003 (pre-effect of stocking) being 57 for MSW salmon and 23 for grilse in contrast to the years from 2004 to 2018 (post-effect of stocking) when the figures rose to 92 MSW salmon and 131 grilse. The 2018 salmon catch was higher than the 10-year average, indicating that catches are holding up well at a time when the general trend across the country is a downward one.
Samples of over 300 sea trout and finnock in both 2017 and 2018 showed that more than 90 per cent of the fish were carrying no sea lice and had no fin damage, despite the fact that the River Carron is in the centre of a very busy salmon farming area.
Fin clips for DNA analysis from all broodstock used in the programme have been taken since 2011, clips from screw trap smolts and rod caught salmon since 2013.
This last point is possibly the most important. There is a great deal of scepticism in certain quarters regarding whether stocking works and whether it damages wild stocks. It is fair to say that it is being actively discouraged.
In the case of the River Carron, there is no doubt that, in the absence of any other plausible reason, the initial stock recovery was as a result of the early stocking.
However, what is of more interest to the salmon angling community is to what degree is stocking influencing salmon catches after the initial recovery took place. In other words, what proportion of the rod catch is coming from stocking and what is coming from natural spawning.
DNA analysis of the fin clips collected over the years would provide the answer and would be extremely informative for decision makers who want to improve salmon stocks around the country.
Unfortunately, the process of analysing the DNA is expensive and requires a significant amount of funding.
Definitive evidence on stocking related to a Highland river in the heart of the aquaculture zone is of great importance for both salmon farming and wild salmon sectors.
Every effort needs to be made to gather this evidence so proper decisions can be taken on the way forward to boost our wild salmon stocks and salmon fisheries.