As summer slips away and autumn begins the countdown to winter, things are still a stirring and moving in the River Tees as the flow of the river continues to encourage fish migration. Spend some time at the Tees Barrage and you may well be treated to the spectacle of a prime adult salmon leaping out of the water, striving to cross the barrage gate and continue its journey upstream to spawn. Some fish make it up the fish pass which runs along the side of the barrage and can be counted but unknown numbers also use the navigation lock and the white water rafting course.

Research is ongoing, looking at ways of enabling the fish to cross the barrage quickly and so avoid the seals which can be spotted catching and eating the mature fish. The seals are highly intelligent and adaptable predators and it’s no surprise that some have learnt to exploit the opportunities provided by the barrage but scientists are keen to redress the balance and continue to support the recovery of the Tees as a salmon and sea trout river.

This year, sonar equipment has been used by the Environment Agency to investigate the size of fish using Flood Gate 1 as previous tagging studies revealed that this was the main route for migratory fish. In addition, the navigation lock was also monitored as staff and visitors often report large fish moving through. A new gate clamp designed by Canal and River Trust staff at the barrage was also trialled this year, holding the lock gates sufficiently open to enable fish to move upstream but not wide enough for the seals to follow. An Acoustic Deterrent Device (ADD) was also used in the navigation lock to see how effective it is in a more confined space compared with the main river. This won’t drive the seals away permanently but it is hoped makes the experience of being in the lock uncomfortable enough for the seals to let the fish move quickly through.

In addition to the work being carried out at the barrage, a new River Tees Rediscovered project, Fish for Tees, has begun, hosted by the Tees Rivers Trust and employing a former Canal and River Trust volunteer at the barrage, Zoe Fraser, as the delivery officer. The next 2 years will see Zoe set up monitoring programmes with volunteers to look at how artificial barriers affect the migration of elvers in the spring, the eel being another very important part of the aquatic food chain and one which has seen a huge decline on a European scale. We’ll soon have more information about this exciting project on the website and it will feature in the next newsletter too.