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River Wandle fish survey is electrifying

Hundreds of eels were given a health check by our fisheries staff during a two-week operation assessing population on the River Wandle.

Around eight members of our sampling and monitoring team took part in the survey at 12 sites along the river’s south London stretch earlier this month.

Electro-fishing techniques were used to temporarily stun the 671 European eels, making them possible to catch and measure. Information was also taken from other fish caught in the survey, including a sample of their scales, which reveals their age and how well they grow in the River Wandle.

Eel populations are in decline across the whole of Europe and although the survey found a lot of eels living in the Wandle, it probably represents a fraction of the population that would have lived there before the Industrial Revolution.

The river has not been thoroughly surveyed like this for some time so this investigation gave staff more detail on the state of the river and highlighted any issues. The same stretch is due to be examined in two years, which will reveal if numbers have gone up or down.

Tanya Houston, an environment officer, said: “This was an extremely useful exercise to have carried out as it is important to see how the eel population is faring, whilst getting extra information on the other fish in the river. It will tell us a lot about how the eels are using the River Wandle in their life cycle.”

Other fish species including chub, barbel, roach, gudgeon, dace and perch were also caught. This highlighted to the local community the type and range of biodiversity available on their doorstep and the wealth of fish species that live in the river. The eels and fish were returned to the river once the operation finished.

The work is partly funded by income from rod licence sales and part of a larger monitoring effort for fish and eels in the Thames Region