Monitoring is an important part of our work. It helps us to gauge river and habitat health and to discover what species are inhabiting areas of our catchment. It also helps us to determine whether the river’s health is improving.
Following our fish passage schemes at Hoghton Bottoms, Oakenshaw, and Lower Darwen we’re using radio tracking studies to monitor the movement of fish up the fish passes we have created. The weirs which we carried out work on were known to be posing a barrier to fish migration, with our studies prior to work being carried out showing that few, if any, fish were migrating upstream of these barriers.
Although monitoring is still ongoing we already have some positive results. At Lower Darwen 16 of the 20 trout that were tagged have moved upstream through the fish pass, with 3 of 16 having moved successfully up Hoghton Bottoms fish pass.
At Oakenshaw, which was completed last year, 3 of 19 tagged trout have moved upstream. Additionally, a juvenile salmon, also known as a parr, has been found upstream. This indicates that the fish pass had been used last year.
What is radio tracking?
There are many methods of monitoring fish. In the case of these sites manual tracking was agreed to be the best option for tracking based on location, accessibility, and stream size.
The fish used in the study were first captured via electrofishing and then tagged with radio transmitters. Each transmitter was set at a different frequency range and pulse rate which helps to identify individual fish. The fish were then tracked on foot from the bankside using a receiver.