Wildly fluctuating temperatures not seen before are making life even harder for Salmon……
We generally think of Salmon as a freshwater fish that goes out to sea to feed in Arctic waters. But it is equally true to think of the salmon as an Arctic sea-fish that comes south to breed. What we see in the Tweed is just one part of the life history of the salmon, which is a biathlon – one competition to win in streams and rivers, a second completion to survive and grow at sea. We can help the salmon in its first competition, mainly by not making it even more difficult with the things we do in rivers, streams and catchments, but there is nothing we can really do to help it out at sea. We do, however, always have to be aware what is going on out there if we are to understand the ups and downs of salmon and not think that these are only due to factors in its more visible freshwater phase.
There are two different types of influences that the sea can have on salmon populations:
- Temperature effects on the proportions of Grilse and Salmon. Colder temperatures give more Grilse, warmer, more Salmon. These often alternate in a roughly fifty year cycle, the North Atlantic Multi-decadal Oscillation (AMO). The effects of these temperature changes can be seen in salmon catches over the last 250 years and produce nothing that we have not seen before.
- The effect of climate change – which is affecting the Artic more than anywhere else – and which we have not seen before. This month there have been temperatures 20C higher than average in Greenland, melting the surface of the sea-ice . We know that Tweed multi-sea-winter salmon go to West Greenland from genetic work which has identified fish from “South and East Scotland” as the largest single proportion of the European salmon that feed there (American salmon also go there).
Whist parts of the Arctic are hotter than ever before, parts of the North Atlantic have had record cold temperatures. The causes of this are a matter of dispute, but the fact remains that our salmon have been experiencing both record warm and cold temperatures at different places in their migration route in recent years, which, at the very least, will not be making their lives any easier and could well be making considerable difficulties for both them and the animals they feed on.