The video describes how the run times of the types of Tweed Salmon have changed over the centuries. The information comes from a long term study that was made by the Tweed Foundation using historic Tweed Salmon catches, mostly from the netting stations. It shows that the kind of changes that we are currently seeing in Salmon runs have occurred in the past and postulates that they may be part of a very long term, periodic cycle. The video is an updated version of a talk given to the River Tweed Commission by Dr Ronald Campbell on 5th December 2016.

While this clearly relates to Tweed salmon and grilse, similar trends can be seen in the Tay, Spey and Dee salmon runs. Here in Ayrshire, we don’t have the historic data to allow such comparisons to be made but if its is happening on the east coast, then it is highly likely that it happens on the west too. It seems clear that there are wide fluctuations between grilse and salmon and indeed there appears to be cycles extending to over 50 years and therefore we should consider this when making assessments of our salmon stocks at all times. Essentially, determining a base line for our stocks should not mean expectations are set too high (or too low) but without the historic data that the Tweed and other large east coast rivers have, it is impossible to be precise and perhaps we should be guided by common trends highlighted within their data.

Of course there are other factors that impact salmon populations on the west coast such as Aquaculture and it is perhaps these that are tipping the balance against wild salmon in rivers up and down the country.

This is a very interesting 1/2 hour film and certainly worth watching.

https://www.youtube.com/watch?v=5DjuyMzxpt4

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One Response to A Theory about salmon declines on the Tweed (and around Scotland?)

  1. Martin says:

    The problem of trying to draw conclusions, or extrapolate into the future, without long term statistical information. How far back do records go for Ayrshire rivers?

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