Fish population monitoring
This winter we are having a comprehensive review of the fish populations in all the main water bodies on the project with particular focus on the Eel sizes and numbers.
Following the very dry conditions and large numbers of little egret this summer, I had feared that our fish populations would be very low, particularly with regard to small fish. This however doesn't appear to be the case and good numbers of Rudd and Perch have been caught across a large range of sizes in the lake.
The Eels trapped do not give such good news. I already knew we had some very large eels in the project when adjusting water controllers, however there appear to be very few small eels in the project at all. This is not unexpected however as we do not abstract water from the river and therefore it is unlikely that elvers will find their way into the project.
Small eels are the primary food source for Bittern, one of our key species here at Kingfishers Bridge. we have made an arrangement with the Environment agency to monitor our eel populations and remove any mature eels to the River Cam where they have the opportunity to leave fresh-water and breed. In return we shall release elvers into the project and monitor their numbers and growth rates over the coming years. If we can promote mature eels to 'silver-up' (the process by which a mature eel's physiology changes to allow them to enter salt water) whilst in the project, or they can be shown to actively leave the project then an eel pass may be constructed to remove the need for trapping and relocation.
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Reserves Manager at the Kingfishers Bridge wetland creation project in Cambridgeshire.