Knowing your rudd from your roach

Our lucky Pollution Patrol volunteers were treated to a FIN-tastic day with our local Environment Agency team, learning all about fish.

It may come as a surprise to some people, but the Hogsmill, Wandle and Beverley Brook all contain a variety of different fish species. Common species across all three rivers include chub, dace, roach, barbel, stickleback and European eels.

But how do you tell the different between these species? For some, it is easier than others. The European eel is quite distinctive compared to the others for example. But as to the rest, it’s a bit more difficult.

Tom Cousins, a local EA Fisheries Officer, started the day for us with a presentation on the different fish species and the key identifying features.

The diagram below shows the external morphology of an average fish, and the features that help us distinguish one species from another.

For example: Roach and Rudd

These two fish are quite similar in appearance, both large-bodied with reddish fins. So how can we tell them apart? The answer is by looking at the mouth.

The roach is a bottom feeder, and its mouth points downwards, with the upper lip over-hanging the bottom lip – whereas a rudd feeds from the surface, and therefore the bottom lip overhangs the top lip.

The presentation from the Environment Agency is available below for you to download, with many more tricks and tips for ID.

Fish ID Presentation

As part of the training day, we also got to witness the Environment Agency’s electrofishing survey at Morden Hall Park on the River Wandle in South London.

It was amazing to learn about the fish in the classroom, and then come outside and see some in the flesh. Each fish caught was measured, and scale samples from some were taken in order to age the fish.

Once they had been recorded and had recovered, they were returned safely back to the Wandle. 

Many thanks to Morden Hall Park for hosting us and to the Environment Agency for running the event!

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