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This rare fish is a resident of just one lake, Llyn Tegid (Lake Bala) in north Wales, but its numbers are declining, prompting a rescue effort.

The species was left behind at the end of the last ice age, living in the deeper reaches of the lake for the last 10,000 years. In the last century, a combination of factors has impacted on its numbers.

Human activity is of course to blame: 20th century farming methods have created eutrophication, a suffocating algae bloom from nitrate and phosphate run-off from surrounding land, and the artificial introduction of another species, the ruffe, has provided competition.

The ruffe are thought to feed on the gwyniad's eggs and fry at breeding time.

A rescue operation has been in place for some years, organised by Environment Agency Wales. They have moved egg stocks to another suitable lake in the area.