Underwater monitoring has revealed one of the largest shoals of Arctic charr ever seen in Llyn Padarn, Snowdonia.
Around 100 Arctic charr were recorded in one shoal, as part of Natural Resources Wales’ annual count to see how many Arctic charr head upstream from Llyn Padarn to spawn.
The fish were monitored at the end of last year, when charr traditionally migrate up Afon y Bala to spawn.
They usually migrate at night and return to the lake before daylight. As well as underwater cameras, NRW used a sonar acoustic device - essential to monitor the fish in the dark and in turbid water.
Over the last few years, several measures have been taken to improve the environment in Llyn Padarn and conserve the Arctic charr.
Young charr, reared in NRW’s hatchery from eggs taken from Llyn Padarn’s charr population, have been released into the lake to boost the population.
Work has also been done to improve water quality in Llyn Padarn, Wales’ only designated inland bathing water, which is now graded as excellent - the highest standard achievable.
Sian Williams, Natural Resources Wales Head of North West Wales Operations said: “Gathering evidence like this is a vital part of our work.
“I’m delighted that measures to conserve and enhance Llyn Padarn and its Arctic charr are now bearing fruit, with improved spawning runs in Afon y Bala.
“We will continue to build on this work so that wildlife continues to thrive in and around Llyn Padarn, which benefits the local community and visitors to the area. This, in turn, benefits the local economy.”
The cameras also picked up other fish in the lake including brown trout, salmon and eels.
NRW is currently analysing all the data collected by the cameras and will have further updates on the Arctic charr population later this year.
This monitoring programme is done with support from the National Slate Museum and Padarn Country Park.