Artificial Stocking
Wouldn't life be easy if we could correct all the problems and damage done to our rivers by releasing artificially reared fish? There is seldom a more controversial topic in fishery management than that of artificial stocking, but is this a solution for the Wye and Usk and what drives the polarisation of views?
Stocking can work: one only has to look at any of our reservoirs which can be made to hold considerable numbers of Rainbow trout, stocked to order and secure in the confines of their environment, ready to deliver instant sport and bred large enough to evade most of the likely predators (but not all!). But can it work for salmon, which have to travel 2000 + miles to feed and then negotiate their way back to their natal rivers to spawn?
There are several techniques in the artificial stocking toolbox:
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Translocation of adult fish above obstructions.
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Egg boxes, directly into a tributary.
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Hatcheries producing fry, parr and smolts.
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Reconditioning kelts (spawned fish) to increase egg collection without depleting wild egg deposition.
History of Artificial Stocking of Salmon in the Wye and Usk.
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19th Century- A small number of Rhine fry are stocked into the Wye, probably less than 300 or less than one thousandth of one percent of the run at the time. Legend has it that this small stocking created the run of large salmon on the Wye. However, no subsequent stocking with vastly greater amounts has produced any measurable change.
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Mid 1950s - A hatchery was started at Abercynrig to compensate for smolts lost in the cooling process of Uskmouth power station. Cooling water was subsequently taken from another source. Abercynrig is now used to supply smolts to the Taff to mitigate the effects of the Cardiff Bay Barrage and, since 2008, has been rearing Wye fish.
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1974 - A hatchery is commissioned at Glasbury (Wye). Up to 350,000 fry are stocked out per year over the next 18 or so years. Incidentally, the start of the decline in Wye stocks is traceable to 1974.
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1993 - Results of a 10-year tagging survey in Wales show a 0% return of hatchery smolts to the Wye compared to a 9.2% return of tagged wild smolts.
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1994 - The Wye Salmon Fishery Owners Association (WSFOA) commissions a study by Dr Alasdair Stevens into the causes of problems with Wye salmon. They are advised to remove all barriers, erosion problems and water quality issues and only to consider a hatchery having corrected these issues. A CEFAS/NASCO report in 2009 came with much the same advice.
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1995 - Green Bottom Hatchery starts in the Severn catchment to stock the Wye. Closed in 2001 following poor results and indeterminate cause for deaths of brood stock and progeny.
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1996 - Three cock fish and one 12lb hen were lifted over an illegal barrier on the Garth Dulas, an upper Wye tributary. The upper Garth Dulas was subsequently populated with fry for some 4km by this single hen fish. Survival rates of fry and parr were substantially higher than those usually experienced in a hatchery. This is an example of a very successful form of artificial stocking.
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2002 - The Wye and Usk Foundation constructs a hatchery at Painscastle and commences a pilot rearing scheme with 8 hen and 8 cock fish. Fed-up fry are put into the upper river.
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2003 - The catch-up is split between the Painscastle and Clywedog hatcheries. A follow-up survey shows success with the Painscastle fish, but zero survival of the Clywedog fish.
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2004 - All caught-up fish are sent to Painscastle. The discovery of signal crayfish at Painscastle limits the number of sites that can be used for stocking out i.e. sites that don’t contain native White claw crayfish.
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2008 - Painscastle hatchery is closed. EAW now rearing all Wye fish at Abercynrig hatchery in the Usk catchment. Limits remain at 30 hen and 30 cock fish.
Our Policy
Declining numbers of rod caught fish are symptomatic of problems in the river and/or at sea. The Foundation's policy is to deploy methods that deal with the cause rather than the symptoms. For example, in 1900 the river Wye was over-netted but had an almost pristine and unbarred tributary system. The reduction in netting (cause) resulted in a spectacular turn around as shown in the graph below.
This is an example where a hatchery would not have resolved the issue as the cause of the decline (extensive river netting) would not have been corrected.
Similarly, on the Tyne the toxic state of the estuary prevented fish entering and leaving the river. When the water quality improved in mid 60's sufficiently to allow fish passage, the river became a salmon fishery again (it was a very good one before industry curtailed the runs, incidentally). The improvement was spectacular and helped further by the removal of the northeast drift nets. Complicating the understanding of the issues behind the recovery was a hatchery that was built to mitigate the effect of the Kielder reservoir. This blocked off 7% of the catchment, which at the time already supported a good and improving population of salmon. The success of the Tyne recovery has often been incorrectly attributed to this hatchery. A long term assessment by the Environment Agency shows that it only accounts for 2% - 7% of the fish returning to the river. Please click here for the Tyne report.
Today, both the Wye and Usk face a complexity of problems rather than any single issue. Not least is a seemingly inexorable decline in the % survival of smolts at sea. This long term sea survival decline has been met with further reductions in exploitation of salmon: the WUF buy off of the estuary putchers and nets in 2000; the legal Irish drift net cessation in 2007 and the 2010 buy-off of the Lydney Park putchers. Other methods of ensuring more fish reach the redds have included a catch and release incentive scheme for anglers.
Our strategy is to deliver permanent in-river works including barrier removal, water quality improvements, habitat restoration and reducing estuarial salmon exploitation. This has several advantages:
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It is durable and sustainable. It benefits a wide range of species, including salmon, trout and other riverine species.
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It is substantially cheaper per fish - particularly in respect of barrier removal and net buy-offs.
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It can be demonstrated to work.
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Funding can be obtained for these works.
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Risks to the whole stock are spread out, compared to the intermittent hatchery disasters i.e. not all eggs are in one basket.
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It makes the best use of existing salmon stocks.
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Natural selection avoids genetic issues.
What we see as the arguments for artificial stocking for Wye and Usk:
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If there is sufficient adult stock and uncommitted and unlimited funds, plus sites that are inaccessible to wild fish or where wild fish spawning is impossible could be stocked and overall salmon numbers thereby increased. This situation may not exist on the Wye.
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Carefully selected and consistently good quality aquaculture can, in limited circumstances, achieve juvenile fish densities that are consistent with those achieved in the wild...but at a price.
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It can make good 'population bottlenecks'. For example, shortage of spawning gravels, or egg mortality.
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Understanding the hatchery process requires no particular skills, knowledge of fisheries, or concept of other issues - it can be assumed there will be more fish in the river as a result.
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It provides a "feel good factor".
And the arguments against stocking for Wye and Usk:
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It is very expensive. Year on year costs need to be met and if the stocking process stops, the river reverts to its previous level without necessarily achieving any expansion of stock. The pre-existing problems remain.
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Stocking is limited by the areas suitable for planting out fish and availability of broodstock.
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Stocking might be at the expense of permanent improvements.
- The long-term assessment of results of historic stocking the Wye and Usk (NRA 1993) are very, very poor.
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When salmon stocks are below their conservation target and there are barriers that could be opened or water quality issues, there is evidence to show that artificial rearing is not the best option.
Broodstock is taken at the expense of wild spawning and never allowed for in any calculations.
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The survival rate post release of reared fish is substantially lower than that of wild fish.
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Hatcheries are prone to catastrophes, often resulting in an overall net loss to the river. These inevitable events seldom receive the full glare of publicity.
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There are dangers of mixing the genetics of fish whose unique survival mechanisms have evolved to succeed against challenging and changing circumstances and provide a possible solution to impending problems such as climate change.
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The same applies to concerns over the loss of genetic integrity with respect to individual strains and different classes of fish. Please see the result of JR Hutton's long term scale reading survey.
The table above shows the complex ability of salmon to spend variously 1-3 years in the river and 1-4 years at sea, returning in spring or summer.
Additionally, there are a number of regulatory and legal considerations. The Wye and Usk site plans, drafted by the Countryside Council for Wales, regulator of both the Special Areas of Conservation, state that a hatchery should not be a method used in the management of the two rivers. The Agency has a set of practical constraints about sites that may be stocked and numbers of fish that may be caught up. This is rigidly limited to 30 cocks and 30 hens on the Wye.
In conclusion:
The achievable levels of stocking will never, on their own, restore the Wye nor will a hatchery sort out the causes of the Wye's decline. We therefore must pursue other permanent and sustainable methods. The Usk still requires restoration work to optimise salmon productivity and this is the best use of available funds for both rivers.
Further reading:
Please click here for the Environment Agency policy on stocking.
