2019 in the International Year of the Salmon and provides us with an opportunity to highlight some important studies that are taking place to help ensure the survival of the iconic Atlantic Salmon, which is in sharp decline in major Scottish Rivers, including the Tweed.
There has been a very significant and worrying drop in the number of Salmon returning to Tweed over the last four seasons. This is of huge concern both for the conservation of the Atlantic Salmon and for the Borders rural economy, which relies heavily on visiting anglers for its income.
This drop in returning Salmon is due to many factors – most of which are taking place out at sea. What fisheries managers can do is to ensure that as many smolts as possible – the ‘final product’ of the Salmon’s river phase and, as such, irreplaceable – are able to successfully migrate down the river and out to sea. Through many years of careful monitoring and management in the river, the Tweed fisheries management bodies of River Tweed Commission and Tweed Foundation know that conditions in the Tweed have not altered and that our juvenile fish habitat is extremely good and very productive.
A dietary analysis study of piscivorous (fish-eating) birds is starting this month on four rivers, including Tweed, and is being led by Marine Scotland with the support of Scottish Natural Heritage, the licensing body to look at one factor that impacts on the Salmon’s survival.
The study aims to identify the components of the birds’ diet. This work was last undertaken in the 1990s when, on Tweed, the main component of the birds’ diet was Eel. The Eel population has declined dramatically in the intervening years and so this work needs to be done to establish what the birds are currently feeding on.
The study will involve taking a very small number of birds (Goosander and Cormorant) from the system over the next 12 months for dietary analysis. Marine Scotland and Scottish Natural Heritage have provided Tweed with a licence to take the minimum number of birds required to enable a satisfactory sample to be gathered.
Tweed has seen an increasing population of Cormorant over the last 5 years or so, with numbers highest during the autumn and winter months. This is taking its toll on the survival of young fish and is one of many factors that is contributing to the current decline in adult Salmon returning to our river. Scaring techniques are being employed to help move the Cormorants back out to sea, their ‘natural’ habitat, so that the fish have a better chance of survival in the river.
During the Spring, fish-eating birds impact on the smolt run – the ‘final product’ of the river – but they also damage juvenile fish stocks during the autumn and winter months – predating not only on Salmon, but on Tweed’s Trout and Grayling stocks as well, which are an integral part of the angling economy on the river.
It is important that fisheries managers understand all the factors that may impact on fish stocks. Those that have the potential to prevent juvenile Salmon from surviving to the migration stage and getting safely out to sea are of major concern, because at that stage the fish are irreplaceable. This diet analysis study is welcomed and will help rivers to better understand the interaction between birds and fish, and will assist the Scottish Government in making informed decisions when balancing the requirements of the different protected species.