Over the coming week, you may encounter a rather unusual sighting on the reserve. Not to worry though—if you do happen to spot men in boats going up and down the ditches, rest assured they are meant to be there and are carrying out an important job for us. Back in August, Anna wrote about the work we’re doing to clear our ditches for some very special wildlife as part of the Back from the Brink project. A large part of this project involves creating and maintaining habitat for the Little Whirlpool Ramshorn Snail (Anisus vorticulus) but there is another creature lurking in the ditches that is making this task rather tricky.
When the river over-tops during the winter, the water spreads across the floodplain reducing the extent of flooding elsewhere in the valley. However, in some years the flooding can be rather extreme and bring with it unwanted visitors! If you visited the reserve during the winter of 2012/2013, you may remember the view from the visitor centre resembling an ocean rather than a floodplain. It was most likely this flooding that was responsible for washing the unwanted carp into our ditches and they’ve since been making it very difficult for any other wildlife to thrive there.
This particular ditch is one of many on the reserve that has been taken over by carp. You’ll see that the water is murky and muddy with no vegetation growing—not ideal for our special snails who rely on an abundance of vegetation to survive. The carp will eat everything, including the snails, so our reserve warden team has come up with a grand plan to rid the ditches of carp, in the hope it will give the other species of wildlife a chance to reclaim their habitat. As well as the very special snail, the ditches here at Pulborough Brooks are home to some rare & protected ditch plants too such as Sharp-leaved pondweed and to a wide range of damselfly and dragonfly species.
That brings us neatly back to those men in boats you might come across. To remove the carp, they will be using a method called Electrofishing which involves passing an electrical current through the water to stun the fish. The carp won’t be hurt during this process, (nor will any of the other aquatic creatures) it simply brings them to a stop at the surface so that they can be scooped up and relocated. The work is being undertaken by licensed contractors who will check the health of the fish then relocate them to other water bodies following strict regulations. As this species of carp is an introduced species, they cannot simply be returned to the river.
If they are successful in ridding the ditches of carp, it will give the vegetation a chance to grow back and end up looking like this:
Our voluntary assistant warden has been assessing the condition of all the ditches on site and measuring the water clarity. If the water clarity is poor, this is an indication that carp are present and has helped us to prioritise which ditches to tackle this year. We’ll be continuing to monitor the condition of the ditches and this may become a regular management task following winter flooding.
It seems like an awful lot of fuss to go to for one tiny snail but plenty of other wildlife will benefit from healthy ditches too.
Helping the Little Whirlpool Ramshorn Snail ‘Back from the Brink
This tiny snail with a flattened spiral shell, who has a diameter less than 5 mm, is perhaps the rarest and most special creature on the reserve, and its presence is the reason that we have been designated as a Site of Special Scientific Interest (SSSI) and a Special Area for Conservation (SAC). In the UK it is classed as Nationally Rare and Vulnerable (IUCN) and is a European Protected Species. Pulborough Brooks reserve holds what is considered to be the second largest population in England.
The work we are doing here is part of a nationwide project 'Back from the Brink' involving a number of conservation partners and with support from the Heritage Lottery Fund.