Salmon superhighways mapped to explore how wind farms affect Highland fish

Scotland’s ‘salmon superhighways’ are being mapped by scientists to see if the surge in wind farms will affect the endangered Highland fish.

Threatened with extinction, the UK’s salmon populations have fallen 50% since 2006 due to climate change, habitat loss, water quality, and plummeting prey.

Now, University of Essex researchers will see if newly developed wind farms will interact with Atlantic salmon migration paths.

They have used these routes for generations, leaving Scotland when young, heading north to the Norwegian Sea and returning to their home river to spawn.

It is thought offshore developments may impact the food web by providing a haven for predators and prey, alter electromagnetic fields which may disrupt homing ability, and construction noise could also change behaviour.

Targeting tributaries from across the East Coast, the Essex team has sampled water samples and 400 salmon from 80 sites to find genetic and chemical ‘fingerprints’ that can tell each river apart.

This is vital as the fish could pass through 37 windfarms currently being developed or already operational off the east coast of Scotland.

Pioneering techniques

World-leading salmon expert and UKRI Future Leaders Fellow Dr Anna Sturrock is leading the project after pioneering techniques to monitor salmon movements in California.

There, Dr Sturrock, from the School of Life Sciences, studied chemical markers in their otoliths, bone-like structures in fish heads that assist in balance and hearing, and in their eye lenses.

These structures are unique because they grow throughout life and incorporate markers from the surrounding water and food, forming a lifetime chronology of movement and diet.

Because these fish are too small to tag, researchers will sample young fish at sea – including right on the footprint of proposed windfarms – and figuring out where they are from.

'Power to make positive change'

Dr Sturrock said: “Probing the earliest growth rings in these tissues allows us to 'look back in time' and find out which areas and migration routes are busiest and most important to salmon, and thus where and when targeted protection would be most valuable.

“We often lack information about the movement behaviours of young fish because they are too small to tag, but this is often where we have the most power to make positive changes, as their nursery areas are often concentrated in rivers and estuaries where human impacts are most extensive.

“Tracking fish origin and lifetime movements using natural tags in ‘archival tissues’ such as otoliths and eye lenses allow us to make informed decisions about which habitats and migration pathways are most important to protect.”

The School of Life Sciences researchers will use techniques similar to forensics and archaeology to identify which rivers, such as the Spey, Tweed, and Tay, sea-caught salmon were born in.

The researchers have partnered with wind farm operators Kincardine Offshore Windfarm Ltd, The Scottish Government, the Atlantic Salmon Trust and many fisheries trusts and boards.

'Innovative project'

José Polimón Olabarrieta, General Manager at Kincardine Offshore Windfarm Ltd, said: “KOWL are pleased to co-fund this important and innovative project, which will greatly enhance scientific understanding of how migrating salmon interact with offshore windfarms in the North Sea.”

Salmon are an integral part of the European ecosystem and a vital part of the nation’s economy and cultural heritage.

Country sports – such as salmon fishing – are worth more than £350million to Scotland, with avid anglers and fly fishers part of that boon.

Carrying the research forward, PhD Researcher Michael Bevins Cameron has been collecting salmon and water samples to build the ‘salmon library’ that underpins the project.

Now he will spend months dissecting and analysing tiny salmon eyes and ears in the lab.

He said: “Our initial data based on the tissue chemistry of adult fish that were sampled after they died post-spawning looks really promising, with large differences in eye lens isotopes and otolith element concentrations between rivers.

“We will be testing this further, but this is likely the result of variation in the rivers - with geographic variation in rock types and age, and local food webs making an impact.”

The project will run until 2027.