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Opening up the Hamble to migrating fish species

By using a natural river channel to divert river flow around Botley Mill, we’re giving fish access to chalk stream habitats they’ve struggled to reach for hundreds of years.

Obstructions to fish trying to reach freshwater stretches of the UK’s waterways is one of the biggest problems affecting the ecological state of our rivers. As part of nationwide efforts to address the issue, we’ve now identified the top 30 obstructions in the southern region.

One of these was at Botley Mill in Hampshire, and we’ve recently started work on a fish pass there, using a German design not used before in the UK. The project will use a natural channel of the river to help a wide range of species access the upper reaches of the Hamble for the first time in hundreds of years. Fish that will benefit from the pass include sea trout, roach, chub, dace and lamprey.

“Mills are a common cause of obstruction, but now that many are inactive, we can divert the right level and flow of water around them – making sections of the river suitable for migrating fish,” explains James Humphrys, Area Manager from the Environment Agency. “The Botley Mill fish pass is a great example of how this can be done. It will open up roughly 15 kilometres of chalk stream habitat. This will vastly improve the fishery there and others in the area too.”