Last week, as part of a major survey of coarse fish in the mid Severn (from Shrewsbury to Worcester), we used a special piece of monitoring kit we borrowed from our friends in the South East region of the Environment Agency.
It’s called an electrofishing boom boat and has been specifically designed to sample larger rivers. Catching fish in a big river presents lots of problems. It’s too deep and wide to net effectively, too big and deep for normal hand held electrofishing gear, and debris, obstructions and depth changes make sonar equipment unreliable. The boom boat is effective as it greatly increases the effective size of the electric capture field. The two large multiple rings arrangements on the front of the boat with metal prongs dipping into the water are the anodes and electricity passes between them and the cathodes (metal plates situated under the boat). This electric field then attracts fish towards the anodes and then immobilises them. The fish are caught by two people with nets on either side of the boat, and placed into an aerated storage tank on board the boat.
Last week we fished between the County Showground and English Bridge in Shrewsbury. At various locations along this section fish caught were unloaded to colleagues on the bank.
The team on the bank identify and count the fish, measure their tail fork length and take samples of scales which are sent for analysis. This tells us how old the fish are and how quickly they are growing. They are then released back into the water.
We caught good numbers and a wide selection of fish including some large pike and perch, a shoal of roach, dace, chub, ruffe, gudgeon, European eel and juvenile Atlantic salmon as well as plenty of bullheads and minnows. A large adult Atlantic salmon was also seen but not caught.
The results from this investigation will be combined with match catch data from anglers and fry surveys to get a better appreciation of the fish population of this important fishery. We hope to produce a report on our findings later this year.