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Seals on the Tees

Spotting a seal isn’t one of the first things you might expect to do on your local river. But if you live close to the Tees, it’s a day out to look forward to. Waterfront spoke to senior ecologist, Jonny Hart-Woods, to find out why seals are now so easy to spot from the Tees Barrage.

Grey seal lying in shallow water

“People who grew up around here will tell you the river was dead, the pollution was so bad,” says Jonny painting a picture of the ‘smoggy' Stockton and Middlesbrough riverside of the past. “But now the Tees Barrage is a wonderful place to see seals and other wildlife. We've got cormorants, otters, common terns. There's Portrack Marshes nature reserve on the north bank and Maze Park reserve on the south. It's one of my favourite places to see wildlife on the whole canal and river network.”

Reviving the river

The revival of the river began with the building of the Tees Barrage in 1995. As well as protecting the Tees valley from flooding and contributing to the regeneration of the area, the barrier has also helped revive eco-systems above and below it.

Above the barrage, Jonny explains: “The Tees is now recognised as one of the best coarse fishing rivers in the North of England. As well as pike, bream and grayling, salmon and sea trout travel upriver to spawn in the freshwater each summer.”

The arrival of seals, otters and cormorants to feed on these fish, signifies a vast improvement in water quality in this fast-recovering river. They simply wouldn't be there without a healthy, diverse food chain to support them. No wonder Tees Barrage Park recently won a Green Flag award.

People posing and holding flag

Helping salmon outsmart the seals

Below the barrage, the migrating salmon and sea trout present an opportunity for the local grey and common seal population. “The barrage is a sharp barrier for salmon and sea trout to cross, so we do all we can to get these migrating fish through,” explains Jonny. “There are already two bespoke fish passes built into the barrier. We know they also go upriver through our navigation lock. So we've also got plans to add ‘cat flaps' to the lock gates to help more fish pass through in future.”

Yet the barrier still provides feeding opportunities for clever seals. They now ‘goal hang' waiting for sea trout and salmon to arrive, especially in high spring and summer. Much as we love seeing the seals, Jonny says the fish must come first – especially with numbers in the estuary dropping, as climate change warms the North Sea and moves feeding grounds towards the Arctic.

There have been many attempts to deter the seals from gathering in this ‘salmon six-yard box'. “One idea was to use sonar signals to scare the seals away,” says Jonny, but sadly this proved counterproductive. “For the highly intelligent, adaptable and ingenious seals, it proved more of a ‘dinner gong' telling them salmon were close by than a warning shot telling them to stay away.”

Seal with a fish

Volunteer to spot a seal like ‘Scarface'

For now, it looks as if the seals are here to stay. If you would like to become a seal spotter, Jonny and his team are always looking for volunteers for their Annual Seal Survey, which will start as soon as restrictions ease. By analysing 623 photographs of seals using facial recognition technology the team has identified at least 26 individual seals, like ‘Scarface', a mature grey seal, as regular visitors. With so many seals visiting at any given time, you are sure to spot some yourself. Why not get involved?

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Last Edited: 18 January 2021

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