Salmon and sea trout tagged on River Tweed to track migration

The first year of an important European fish migration project has just been completed.

By The Newsroom
Thursday, 6th January 2011, 8:11 am

Staff from the Tweed Foundation and the Environment Agency in the north east have been involved, tracking the movement of fish and taking genetic samples from fish in numerous rivers opening onto the North Sea.

The Living North Sea project is seeking to promote free fish migration and track fish from individual rivers through their lifecycle.

Biologists from the Tweed Foundation acoustic tagged a total of 76 sea trout smolts (juvenile fish), 14 salmon smolts, and just over 100 adult fish.

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These tags emit individual signals which are picked up on specialist ‘listening stations’ placed along riverbanks to track the movement of the fish. This enables Foundation staff to monitor the migration of fish both up and down the rivers.

Nick Yonge, director of the Tweed Foundation told the Berwickshire News that the Foundation’s side of the project concentrated on the movement of smolts downstream and then the adult fish up river when they return from the sea.

Mr Yonge said: “We hope we are going to learn an awful lot about migration in the river and what happens when the fish go out to sea.”

Tracking the fish both up and down the Tweed and its tributaries will enable Tweed Foundation staff to see if fish encounter any delays on their migration, such as at caulds, as well as charting the success rate of migration, and possibly establish the reasons why fish fail to make it to the sea.

If this research is successful, then improvements could be made to man-made obstacles in rivers which slow the migration of fish or make it easier for predators to catch them.

Mr Yonge said: “Caulds look as if they may be a problem, but if there is problems identified then it gives us the opportunity to do something about them.”

However, he added that the past year had seen low water levels which may have exacerbated problems from migrating fish.

“When they are migrating, if fish are delayed that increases the opportunity for predation,” said Mr Yonge.

“If there are very large numbers of smolts then predation is not a problem, but if a particular component of the stock is weak, in our case spring stock, then any predation is very bad news.”

The number of fish migrating from the sea to fresh water to spawn has fallen, and the project aims to halt this decline.

Mr Yonge said: “We know that survival at sea is reducing,therefore every smolt going to sea is important, and we need to put excess smolts to sea to ensure we have enough adult fish coming back into the river to spawn again.”

The project involves 15 different partners from seven different countries, including the Association of Rivers Trusts, the Norwegian Institute for Nature Research and the Dutch Angling Association.

Mr Yonge said that although the project is for three years, the Tweed Foundation only has funding to carry out its study for two years, with the help of Durham University and a PhD student.

As part of the project, fisheries staff from the Environment Agency in the north east have collected samples from sea trout from a number of rivers including the Coquet, Wear, Tyne, Tees and Ure.

Phil Rippon, Environment Agency project manager for the north east, said: “Our work is part of a bigger genetics project which involves taking samples from sea trout stocks throughout the North Sea area, from countries such as Norway, Sweden, Denmark, and Scotland.

“It is believed that sea trout stocks in different rivers are genetically different and it should be possible to track individual river stocks throughout their lifecycles once a genetic fingerprint for that stock is established.

“The aim is to collect samples from both juvenile sea trout in the rivers and adult sea trout caught at sea so that we can discover more about the migratory routes of this important species.

“The information will help us to identify where individual river stocks migrate to in the North Sea, whether sea trout stray back to different rivers and where there are pressures on individual river stocks.

He added: “The link between rivers, estuaries and the North Sea is vital and we can use this information to see whether there are any problems in our own areas.

“Next year we hope to progress with our surveys by sampling adult fish around the north east coast.”

Genetic information has been sent to Danish experts, who will analyse the data.