The country's rivers support one of the largest Atlantic salmon resources within Europe. The cold water fish, found in temperate and arctic regions of the Northern hemisphere, has a complex migratory lifecycle in both marine and freshwater phases, and experts believe climate change is affecting both of these stages.

Speaking at a conference on Climate Change and the UK's Aquatic Ecosystems, 2007, Dr Harriet Orr from Lancaster University said: "While we can limit the worst effects of climate change by reducing emissions, we need to start thinking about how we adapt our river management practices for unavoidable climate change. Our rivers, and the fish within them, are particularly vulnerable and we need to start planning for that now.

"Most of the species and communities in rivers have a limited range of temperature tolerance. An increase of 2-3 degrees Celsius in temperature, along with changes in flow, could see some species, such as larval insects like stoneflies or mayflies, change distribution, decline in population or even become extinct."

These issues could have grave consequences, as these insects are important to the juvenile salmon's diet, as climate change affects the whole ecosystem and not just the individual salmon.
In addition climate change is altering weather patterns by increasing rainfall, causing an increase in the frequency of river spates which can wash out salmon eggs. This in turn decreases the number of juvenile salmon (parrs) and therefore decreases the numbers of returning salmon (grilse).

Another issue of climate change was highlighted by Professor Chris Todd at the Scottish River & Fishery Management Trusts AGM.
Prof Todd of St. Andrews University said: "The decline in the body weights of grilse probably is due to a lack of feeding at sea, which itself is being driven by ocean climate changes. Since the early 1990s, sea surface temperatures in the North Atlantic have risen by an average of 0.5 to 1.5C per decade and the ocean remains unusually warm."

This has resulted in malnourished salmon, many of which do not survive to go on and spawn. If they are able to spawn, they generally have poorer quality eggs, perhaps resulting in fewer parr returning to sea to complete the migratory lifecycle.

Within the marine phase of the life cycle, climatic change has also been linked to the increase in salmon mortality at sea. There is roughly the same number of salmon leaving the rivers out to sea, but fewer are returning. The main cause is thought to be linked to climate change affecting sea temperatures and currents, which in turn reduces feeding opportunities for salmon, as cold water food sources are migrating to more northern latitudes, removing themselves from the salmon's diet.

Climatic change is also thought to have played a part in the loss of over £1million of fish at an Irish salmon fish farm. A small jellyfish, Pelagia nocticula, normally associated with the warmer waters of the Mediterranean, infiltrated salmon cages killing the fish in November 2007. This was thought to have been as a result of climate change, as the waters have warmed around the UK, creating move favourable living conditions for the jellyfish.

In national and local press there have been reports of declining wild salmon stocks. Aquaculture, which is the rearing of aquatic organism, has been blamed as the main culprit due to sea lice infestations. However, this may not be entirely justified.

Bob Kindness, of UHI, Aquaculture and Fisheries Centre, Seafield, said: "Salmon farming is often blamed exclusively for the decline in wild salmon, but, given the fact that salmon numbers are poor in areas where there are no farms, there are obviously other factors that are much more influential. Perhaps the problem is that, while it may be considered relatively easy to deal with salmon farms by removing them, dealing with problems such as predation and climate change are much more difficult."

To try and combat the effects of climate change, most river trusts have implemented good practice schemes to try and combat declining salmon numbers. One such scheme was on the River Carron, Ross-Shire, where restocking was started in 2001, after there was an all time low catch of salmon in the river.

Restocking was carried out by collecting eggs from wild fish stocks, to increase smolt production throughout the river and stocking the river with all stages of growth, from eggs to smolts.

The river operates a catch and release policy, with a few being held for future brood stock. The fish caught are placed within a keep net and then released. This keep net enables research to be carried out and allows for the recording of the fish's individual measurements and statistics, which could help to devise future management strategies.

One of the problems that has been discovered whilst restocking is the increased occurrence of spates. However, the scheme has been highly successful and should be continued to counteract the possibility of increased spates caused by climatic change within the region.

Overall there are many factors known to influence the survival rates and declining stocks of Atlantic wild salmon. However, the role that climate changes plays appears to be increasing.

Catch and release policies can help the numbers to stabilise, whilst restocking can help to increase the numbers in the freshwater phase. With a continual increase in temperature of waters in and around the UK, the effects of climate change is set to continue, leading to an uncertain future for wild salmon.