Our most recent event has been on the subject of electrofishing ā€“ not something that the average enthusiast can do, due to the cost of the equipment, need for licensing, and fairly obvious safety precautions. Fortunately we had Dr Kevin Nash, from the Environment Agency, to explain to us how it worked, and to take us for a field session (or should that be river session?).

The morning was spent at the Frodsham Community Centre learning about the fish that can be found in British waters, with lots of information about their ecology and identification. We also covered the problem of alien species, which is a very real issue for British waters, with several species being established as accidental introductions and from the aquaculture trade. Then after lunch a convoy of cars made its way down to the Gowy near Mickle Trafford.

The equipment consists of a battery-powered backpack which generates a high voltage in the water around the probe. Fish swim towards the probe and then lose co-ordination and float to the surface where they can be netted. The operators have to be fully insulated in dry suits or they may come floating to the surface themselves! We all had to stay well clear of the water while the equipment was in use.

Batman and Robin make their way upstream

The catch for the day was fairly modest; a dace, a bullhead, and two eels.

The Bullhead

The Dace

The age of fish can be estimated from the scales, in a similar manner to counting tree rings. Katherine demonstrated how a scale was pulled out from the fish (which grows a new one) before releasing it.

A scale (inset) being sampled from the dace

The eels were very slippery customers! Attempt to handle them resulted in huge amounts of mucus being secreted which dripped through the net. Ours were about 40 cm and 15 cm long, measuring them accurately being almost impossible. They can slide backwards and forwards and resisted all attempts to put them on a measuring board.

An Eel

Many thanks to Katherine and Kevin for organising this event for us and giving us an insight into fish biology and the work of the Environment Agency.