Stocking With Smolts
Stocking salmon rivers with late parr and smolts can have several benefits and a few “potential” drawbacks. In evaluating those we must measure the benefits agains the potential risk.
Benefits:
1. Increased salmon population:
Long term stocking programmes in Iceland, Denmark and Scotland has proven beyond any doubt that Stocking salmon rivers with smolts can help replenish a declining salmon population in rivers where natural reproduction is limited or has been impacted by factors such as habitat degradation, pollution and overfishing both in the freshwater and marine phase of the lifecycle. This can help maintain and restore a sustainable fishery. Examples of this are Ranga in Iceland, Skjern in Denmark and Carron on the West coast of Scotland, all of which have, over the past 20 years, bucked the downward trend in production of wild Atlantic Salmon seen in every other river in Scotland and the wider UK.
2. Economic benefits:
Salmon fishing is a popular recreational activity that can generate significant economic benefits for local, mainly fragile rural communities, including direct revenue from fishing licenses, tackle sales, lodging, and tourism. The last economic study by Glasgow Caledonian University was carried out 20 years ago in 2003, when directly, the industry generated an annual income in the region of £120m (now £80m), as well as 2800 rural jobs in Scotland. Stocking smolts and late Parr will help support and enhance these economic benefits by ensuring a healthy and abundant salmon population during those times of greater pressure due to the effects of climate change in the form of larger and more frequent floods and other variables such as increased predation both in fresh and salt water..
3. Ecological benefits:
Salmon are a keystone species that play a “crucial” role in the ecosystem by transferring important marine-derived nutrients to freshwater and terrestrial ecosystems. So vital are those nutrients, in the absence of salmon, the Dee fishery board recently sought to replace them by planting out the legs of dead Deer in upper tributaries. Stocking salmon rivers with smolts will help maintain this ecological balance and support the overall health and diversity of the ecosystem because as everyone knows, nothing substitutes for the real thing.
Perceived Potential Drawbacks (PPD)
1. Genetic risks:
We are told that stocking salmon rivers with smolts from hatcheries can introduce genetic risks to the wild population. Hatchery-raised smolts may have lower genetic diversity, adaptability, and survival rates compared to wild salmon. This can lead to decreased resilience and long-term sustainability of the wild population. However, in those rivers mentioned above, in 20 years, or 4 generations of salmon this has proven not to be the case. In actual fact on going Genetic sampling on the Carron River in Scotland would suggest quite the opposite.
2. Competition and predation:
One of the perceived problems associated with stocked smolts is, they may face competition and predation from other fish species in the river, which can reduce their survival rates. Additionally, stocked smolts may compete with wild smolts for limited food resources, potentially impacting the overall ecosystem balance. Those are arguments used by protagonists, however, given we have clear lead from rivers using such stocking methods, I believe, given the stock status in our rivers the time for debate is over and we need to bring in experts in the field to deliver the correct solutions.
3. Disease transmission:
Hatchery-raised smolts can carry diseases or parasites that can be transmitted to wild salmon and other fish species in the river. This can lead to increased mortality rates and negatively impact the overall health of the river ecosystem. As far as I know there has never been a single instance of this in any in river hatchery and again lead should be taken from those with experience in the filed.
Conclusion:
Stocking salmon rivers with smolts and late Parr is a useful tool to support and enhance salmon populations where stocking with smaller fish has been proven time and again not to be, especially in rivers facing significant challenges to natural reproduction. Mitigating against potential genetic risks, competition, predation, and disease transmission should be in the hands of those people with a proven track record in replenishing salmon populations on other rivers. At this stage their experience over those with a record of failure should be being utilised at all cost. A £120m, potentially £300m and 2800 jobs industry are dependant on it.
Long-term monitoring and adaptive management strategies should be implemented to ensure the sustainability and ecological integrity of stocked salmon populations and the overall river ecosystem.
How Important is Genetic Integrity?
A few years back Marine Scotland Science (MSS) published a series of reports relating to salmon stocks in various river systems as part of the ‘Focusing Atlantic Salmon Management on Populations (FASMOP) project. This £1 million project was to identify genetically distinct breeding populations of wild salmon from a range of rivers throughout Scotland. Turn the clock on 10 years and the £1m The FASMOP project is never talked about. Why? Because despite costing a huge amount of money and covering several important river systems, it failed to identify the predicted distinct populations of salmon many biologists claimed existed across Scotland. The main reason given for the absence of genetically distinct populations was - The mixing of salmon from different parts of the river system but somewhat strangely, did not include the possible mixing from salmon straying from other rivers.
One by-product of this failure should have been for each river to explore its potential for “proper” smolt stocking case studies and not simply wasting hatchery fish as has always happened in the past.
Genetic Research on the Carron river in the west of Scotland are cutting edge and are leading the field here in Scotland. What the initial study proves is that Stocking with, in the case of this river, late parr, does in fact work well and has nothing but positive impact on the river and economic prosperity of this fragile area of Scotland. This should provide the benchmark and see such schemes being rolled out all over Scotland. We sit in a unique part of the world with the most amazing and precious resource, a resource which if properly managed would secure future prosperity of generations to come.
Time for a U turn Marine Science Scotland!!!!!
Excellent blog Ian, for me Peter Gray proved restocking worked when done in this way on the river Tyne and still does. All the EA wished to do was discredit his work saying the Tyne restocked itself naturally! oh yeah! dream on. How else can the out of control predation on parr and smolts be counteracted. It is one of the only tools we have in the locker to achieve this.
David Stevenson
Spot on, Ian. The problem is the `scientific consensus`, they will not and cannot, admit that their opposition to stocking, in many instances, is wrong. They`ve been taking the research money and finding the evidence doesn`t stack up, exactly the same as the FASMOP project, hence the silence. They have a poor view of anglers, ghillies etc. I went to a scientific conference five years ago about the decline of the salmon, it was two days, mid week; the scientists pointed to the lack of anglers in the audience and said it was evidence of how much we cared. I explained that whilst I was retired and they were paid to attend, the anglers were out working at their day…
Thank you for this. I shall read it as soon as I can take a break!