HUNDREDS of fish across a wide variety of species have been found after a new survey conducted in a river.

The Environment Agency has conducted an electric fish survey along the River Stour near Dedham.

The National Monitoring Field Team undertakes fish surveys along all the main rivers and tributaries in East Anglia.

The surveys can take 10 to 12 hours on a very busy day.

Dan Hayter, a fisheries specialist who has worked for the Environment Agency for 20 years, explained the process.

He said: “To conduct a fish survey, we measure out a 100-metre stretch of the river and place a large stop net at the start and end of the stretch to prevent fish moving in and out during the survey.

“Four of us then get in a motorised boat and travel along the stretch with specialised electric fishing equipment.

“We usually have one person manoeuvring the boat, two people operating the handheld electrodes, stainless steel hoops on the end of a long pole, and one with a net catching the fish, moving them to a recovery, and holding container ready for us to count.

“Electric fishing involves us passing a mild electrical field through the water to temporarily immobilise the fish. This allows us to catch them.

“Electro fishing may sound a little scary, but it is harmless to the fish and is a very humane way of catching them and allowing us to carry out this vital work.

Counting - Counting is often repeated once or twice to improve accuracyWork - Counting is often repeated once or twice to improve accuracy (Image: Environment Agency)

“When conducting the survey, we start in the middle of the stretch first and then go along the sides, using the current to safely capture the fish.

“We then repeat this once or twice more to ensure we have a good capture efficiency and get accurate fish data.”

The surveys are done for several reasons, including for information about fish stocks and to discuss the health of the river.

Mr Hayter said: “When we count the fish, we note down the species and length.

“During our survey along the river Stour we caught 15 species and more than 600 fish including eel, chub, roach, bleak, dace, tench, pike, bullhead, spined loach, gudgeon, perch and flounder.

“At the end of the survey all of the fish get returned to the river and the nets are removed.

“We have 40 years of data for this stretch of river making it one of the best data sets for electric fishing in the UK.”