Last weekend I left the city for a day to participate in a work experience event run by the National Trust. It was the first of six days which will be spread over the next few months, offered to students studying biological science related subjects at the University of Manchester.
The sessions are held at Quarry Bank Mill, Cheshire, and are based around conservation work that takes place there – the first one was focused on the river Bollin, which runs through the estate.
In the morning we were taken to the weir to see the work being done to protect fish species – the weir is almost seventeen foot high so creates an impassable barrier for migrating fish (for example salmon) which would be trying to swim upstream to breed.
This has resulted in a loss of salmon from this section of the river, as they would no longer be able to breed there (the water further downstream is not oxygenated enough for young fish to survive).
For this reason, a fish pass was installed – this runs next to the river and enables fish to bypass the weir and swim upstream. There are two channels: the first was simply a wide tunnel (allowing fish to swim through), whereas the second one had a ‘substrate mat’ – this gives eels something to wind around so that they can also move up the river. The mat was placed on a slant in the water so no matter what the depth, any size of eel could swim through.
There was a submerged camera looking into the fish pass, enabling National Trust rangers to monitor which species pass through. The camera is activated by movement, so a lot of the time the images obtained are of debris being carried downstream. However, this year for the first time, they have footage of a salmon moving upstream. This is fantastic news as it shows that the fish pass is working, and that hopefully salmon will begin to breed in the river Bollin again.
The picture below shows the fish pass: it was a bit difficult to photograph due to the metal grill over the top, but the right hand side is for the eels (you can see the slanted substrate mat) and the left hand side is for other fish. The red light source is there to aid the camera at night – fish cannot see red light so this does not disturb them. The camera is in the wall on the far left, behind a plastic screen.
In the afternoon we walked to a different point on the river and collected data such as the river width, depth and flow rate. Monitoring these factors allows rangers to keep track of any significant changes in the river ecosystem, so that their conservation efforts can be more effective. Unfortunately I didn’t manage to get any photos of this part of the day as I left my camera in the truck (we were wading into the river so I didn’t want it to get damaged – not to mention the fact that by this point my fingers were numb!)
Hopefully this has given a little insight into the conservation of rivers – my next session with the National Trust is at the end of January so I will write another blog post about it then.