From the Telegraph.co.uk

Fishermen may have landed a record haul of salmon last year, but the "King of fish" are becoming lighter and smaller because of climate change, according to new research.

A major study of the iconic species in Scotland has revealed that the average grilse, young salmon which have been at sea for just one year before swimming back to their home rivers to spawn, are a third less heavy and have shrunk by nearly a tenth.

Scientists also say that there are a third less salmon in the Atlantic than 40 years ago and twice as many as previously are dying at sea before reaching their rivers, perhaps because of the reduced size.

The Scottish research, part of the most comprehensive international study of Atlantic salmon ever undertaken, will come as a disappointment to fishermen and conservationists.

Commercial fisheries in the salmon's feeding grounds off West Greenland and the Faroes has been stopped and anglers return their catch rather than taking it home to eat.

At first it appeared the measures were working with 100,000 salmon landed in Scotland last year, the most since records began in 1952.

But Professor Chris Todd, professor of marine ecology at St Andrews University, said it was not just the numbers of salmon that was a concern but their quality.

He said that by monitoring an unnamed major Scottish river for the past 17 years he had found that the weight of the average grilse had fallen from 5.3lbs (2.4kg) to 3.74lbs (1.7kg), and that its length had shortened from 23 to 21 inches (59 to 54cm).

"It is pretty dramatic and very worrying," he said. "The fat content in the fish has also declined by about 80 per cent. People may be catching lots of fish but the quality is comparatively poor compared to the historical record. Also larger fish tend to produce more eggs. We don't yet know about the effect on egg quality – skinny fish may produce poor quality fish. It could be a vicious circle with big impacts for the future of the species."

Prof Todd said he suspected that climate change was the cause of the shrinking salmon as the water temperatures increase and force the plankton that the young salmon feed upon further north.

"They are going to a particular area and it is a matter of chance if they are finding food. It is like getting to the restaurant and finding it's not open," he said.

"To find salmon that have now spent three, four and five winters at sea – the very big fish – is rare. Despite the closure of fisheries and coastal netting – and the effects of catch and release by anglers – the number of fish coming back to their rivers has been going steadily down as has the quality. Something quite unusual is happening and all the problems point to this happening at sea."

The research is part of the £5.5m seven year SALSEA project on Atlantic salmon, that will be delivered to a symposium in September at La Rochelle, France

I am sorry but I find the argument that everything adverse equates to 'global warming' polarised and unlikely to yield anything constructive in terms of a solution. It is correct that salmon have been reducing in size but they have been doing so - steadily - over the last century. This would be a consistent finding on every river holding Atlantic salmon: UK or otherwise.

If Prof Todd was correct and that the effect was purely marine, with the quantity of plankton driving the effect then the size would be open to variability. Some might remember that during the 1980's and 1990' metereologists were warning of an imminent ice age, if Prof Todd were correct we should have seen an increase in multi sea winter fish. In fact the opposite was true; particularly marked on the Upper Tay an area I am sure he has marked for monitoring the multiseawinter fish.

Plankton's growth rate responds fast to changes in temperature. While it is entirely possible that a short term trend may be consequent upon a localised lack of food it goes no way in explaining the observations over the last century. (The most dramatic decline seen in MSW fish was seen during a relatiely cool period.) If Dr Todd was correct then it should be possible to determine a relationship between size of fish caught that year and the direction the Pacific current. There is a reason fisherman do not pay much heed to the flow of this current when deciding what breaking strain to purchase that year.

And that is the point. We need solutions. Nothing is going to be gained by attributing causes that we can do nothing about. The sea is not going to get cooler cause we want it to. If you want bigger fish you need to think how to get them and if there is not enough data on the species you study think laterally. Fortunately there is lots of data on: Birth Size/ Final size/ Mortality rates in humans. It is interesting that in my hometown of Glasgow, in 1929 (the height of the last major depression), not only was birth size significantly smaller than those born in 1928 or 1930, so was final size and mortality rate. The increase in mortality continued right throughout the lives of those born in 1929. Glasgow was in a horrendous situation at the time - even today - think of your average Glasweigan - wee Jimmy isn't it?

Stress in utero is the most significant predictor of birth weight. This in turn is the strongest predictor of final size - no matter what you eat during your life. It takes two generations to change this effect - wee jimmy's grandchild that lives in New Zealand or Canada is no longer 5' 3 - 5' 7 but a strapping 6ft plus. Being born in 1929 meant you carried an increased risk of mortality. The reason the figures were so meticulously gleaned from the Glasgow population was because of the appauling mortality figures. If we applied the same principles to salmon and that being born at a time of stress meant you lived less time, this would favour survival of those fish that spawned younger.

It is simple and, at the end of the day, so might be the solutions. Look at the environment the salmon is born into before you blame other factors. This principle has already worked wonders on the Tweed and will, in my opinion, always serve us better than looking too far afield.

AcEgEnE

*****. There's bigger and more fish running the Kyle of Sutherland now than there has been for donkeys year.

And I really do fish for salmon and seatrout in the highlands which is more than these bunch of fannys do.

made me smile dj.
report has been mentioned in another post in salmon threads.
as i mentioned there, this does seem to be a year of big fish, so lets see how the grilse run shapes up!
regards
bert

It's a classic genetic population response to predation too, smaller, more numerous sexually mature individuals = higher chance of species continuation. Added to the poorer marine feeding and you have smaller fish with lower fat reserves.

Loch Lomond 1927 -

3x 21lb; 7x 22lb; 2x 22.5lb; 2x 23lb; 8x 24lb; 10x 25lb; 10x 25lb; 2x 25.5lb; 3x 36lb; 1x 26.5lb; 1x 27lb; 2x 28lb; 29lb; 31lb; 34lb; 35lb; 36lb; 36.5lb; 38lb.

Total that yr - 460 fish to 6545.5lb

Even tho' DJ Voss may have a point and that there has been a recent improvement in the situation nothing can take away from the long term trend. The only way we can begin to address this and see a return to former times is by a complete understanding of the factors involved.

It is true that when a species is under stress it produces more copies of itself
and - undoubtedly - food supply has a part to play but I suspect these are of secondary importance. Fish, like humans, are pre-programmed in the first days of life what size they are destined to be. I believe it is the conditions they find themselves in at this critical stage of development that determine final size.

We should remember that as recently as 1970's sea-trout were considered a larger fish than salmon in places like Maree. The decline in size of these fish is more marked than the salmon.


Slander gets nobody anywhere.