The renovations going on around Godmanchester’s Mill Steps will visually improve the area and create a beautiful green space for the community. But how might it affect our local wildlife?

Photo credit: Candida Hopkinson

Many of us have benefited from being out and about in nature over lockdown, for both our physical and our mental health. And we’re so fortunate to live in an area with beautiful countryside on our doorstep.

But our relationship with nature hasn’t always been easy. The changes we’ve made to our rivers ‐ such as creating weirs, mills and sluices ‐ over the last thousand years have had a profound impact on the local fish and birds and other wildlife that rely on them for their habitat and food.

The renovation of the mill steps will go some way to putting this right. Our project partners have come together to create something that will benefit our community, our fish, birds and wildlife. Here’s how.

We’re creating a fish pass

The renovation work around the mill steps includes the creation of a fish pass. Fish passes help eels and fish migrate (travel) more freely up and downstream, helping them spawn (breed) and find food.

The Fens used to be full of eels, but their numbers have reduced drastically over the last twenty years.


Because man‐made weirs, mills and sluices have prevented them from making their annual migration to the north Atlantic to breed. The fish pass, once finished, will allow them to migrate freely, and so their numbers will increase.

A better environment for birds

And with an increase in eels and fish, comes an increase in birds, looking for their next meal!

On any walk along the banks of the Great Ouse you’re likely to see herons, kingfishers, cormorants and coots. And the 'heralds of the spring' ‐ the sand martin ‐ will be attracted to the area too next year, thanks to the creation by the Great Ouse Valley Trust of a new nesting area (or 'sand martin hotel'!).

Other wildlife to spot

The area around the river Great Ouse is rich in wildlife, with otters, deer and water voles all being spotted on river walks.

You might even spy a terrapin sunning itself on the river banks. They’re unwanted pets, released into the river, where they’ve bred, thrived and grown!

And if you’re very lucky, you might come across the Great Ouse seal. Graham Campbell, chairman of the Great Ouse Valley Trust, told us that 'once it sees you, it’s likely to follow you as you walk'. A sort of river‐based dog!

Photo credit: Candida Hopkinson

Humans and rivers

For over a thousand years, we’ve used rivers to generate electricity, move mill wheels and drive turbines. But now we’re coming together to think about how our use of the river in the past has affected our local wildlife ‐ and to do something about it, in collaboration with our project partners.

The renovation of the mill steps will create a beautiful space for our community, and a better habitat for the creatures who share our environment.

Visit the Great Ouse Valley Trust website to learn more about the sights and sounds of the Great Ouse.

Photo credit: Ian Jackson

Thanks go to Graham Campbell, Chairman of the Great Ouse Valley Trust, for sharing his knowledge and insight about all of the beautiful wildlife we can find on our doorstep in Godmanchester, and to Candida Hopkinson and Ian Jackson for providing permission to use their photographs.

You might have seen the work taking place at the Godmanchester Mill Steps recently and wondered what’s going on?

Godmanchester Mill Steps, June 2020

Well, we’re installing a Fish Pass as part of a wider project to create a beautiful green space for the community to enjoy.


So what is a fish pass?

Here are 5 quick facts to get you up to speed on what they are and how they work. And how they can help our local fish and eels. And of course, in the autumn, you’ll be able to visit the Mill Steps see a fish pass for yourself!


In a nutshell – what is a fish pass?

Fish passes help eels and fish migrate (travel) more freely up and downstream, helping them spawn (breed) and find food.

Did you know that our local Fenland eels migrate all the way to the Sargasso Sea in the North Atlantic Ocean in order to breed? They only breed once in their lifetime, and then die. As journeys go, this migration is really important as it means they can meet their life’s goals… and create a new life!

An adult eel


Why do we need fish passes?

We’ve been creating barriers in our rivers ever since the Industrial Revolution - obstacles such as mills, weirs, dams and sluices. Unfortunately, these barriers can prevent fish from migrating. And if they can’t migrate, they can't find places to spawn, feed, or avoid extremes like flooding and drought. This can have a real effect on the ecology of a region - as well as on the wellbeing of the fish.

Glass eel


How do fish passes work?

There are lots of styles of fish pass that help fish 'climb' past these obstructions on their migration routes. Of course, removing the structures and allowing rivers to be wild is the best option - but that’s not always possible!

Larinier Fish Pass

Fish passes work by letting fish and eels 'climb' barriers. They provide a gentle slope with slow water that’s deep enough to allow the fish to travel. Resting pools along the way allow the fish to recover before continuing on their journey.

Rhymer's Weir eel pass, Houghton


Are fish passes new?

Here’s the history bit – no, fish passes aren’t new! There are reports of rough fishways being created in 17th-century France. Here bundles of branches were used to make steps in steep channels that fish and eels could use, in order to bypass obstructions and migrate on their way.

Mill Steps at Godmanchester, May 2021

They’ve become more and more essential all over the world as we’ve become more industrial, and dams and other obstructions have become more widespread.


How will the fish pass at Godmanchester Mill steps help?

When complete, the Godmanchester Mill Steps fish pass will open up 100km of the Great Ouse River to the sea at Kings Lynn, allowing fish and eels to migrate freely upstream and downstream of Godmanchester. These routes were previously cut off by the town’s complex of weirs and sluices.

The careful design of this fish pass has been designed to provide the best opportunity for all species and ages ranges of fish including roach, dace, chub and eels.

As part of the project, we’re also creating a new habitat for birds, with a new naturalised rock entrance and landscape. And a beautiful green space for the community.

Project updates will be shared both here and through HDC’s social media profiles including Facebook, Twitter and Instagram.


All about eels

Eels are fascinating creatures. Critically endangered and part of a European-wide conservation effort, once common throughout the fenland landscape, numbers are now just 5% of what they were during the 1980s. They live in rivers for much of their adult lives, on average about thirty years, but sometimes much longer, before turning silver and preparing for a long and difficult journey. Migrating from a freshwater to a marine environment, the harshest of combinations. ""

Migration begins on a dark, moonless night in November. The eels make a special, 3000 mile migration to the Sargasso Sea in the North Atlantic Ocean (near the Bermuda triangle) to spawn (breed) - and then die.

In the spring, their offspring make their way back to Europe on trade currents, swimming up the coastline to find river entrances. They’ll arrive at The Wash near Kings Lynn in early spring, and by the summer these baby eels (elvers) will have made it all the way up the Great Ouse to Godmanchester.

Once here, they’ll continue their journey upstream for many more miles, negotiating obstacles and growing into bigger yellow eels – before eventually turning silver and making their own journey back to the Sargasso Sea to start the cycle again.


Barriers to their journey

But their journey from the coast up to Godmanchester isn’t easy. They’ll meet barriers along the way, such as weirs and locks, that can stop them (and fish) migrating.

And if they can’t migrate, they won’t be able to find places to spawn, feed or to avoid flooding and drought.

‘Fish passes’ can help though, by helping fish ‘climb’ past these man-made structures as they migrate.


Male or female?

Unusually, the density of the eel population dictates the sex of the animal. This means that in locations where large numbers congregate, for example below barriers to migration, males dominate. Where the population is more evenly distributed, more egg-bearing females will be present. Barriers don’t just impact migration, they also disrupt the ratio of male/female eels and in turn, the breeding cycle.


The Godmanchester Mill Fish Pass

We’re creating the Godmanchester Mill Fish Pass to allow fish to migrate freely upstream and downstream, opening up 100km of the Great Ouse previously cut off by the town’s complex of weirs and sluices.

Our new fish pass has been carefully designed to provide the best possible opportunity for all types and ages of fish to migrate easily, including roach, dace, chub and eels. And birds, invertebrates and other wildlife that rely on richer ecological diversity will be able to enjoy the new habitat and naturalised rock entrance too.

Days into the start of the project, hundreds of tiny eels were found when the mill weir structure was drained in preparation for repairing the wall. These eels would have been taking refuge in large numbers, waiting to navigate the structure - a short climb that will soon be much easier!


A place to unwind

When work is finished at the site, it will benefit the community as well as the fish! A beautiful place to take a moment, unwind, and listen to the sound of running water and birdsong.

And as we’ve learned over the last eighteen months, being in nature can help us in all sorts of ways, physical and mental.

We can’t wait to welcome residents, community groups and visitors to this new heritage site. If you’d like to learn more, follow our progress on social media.