A fish farmer is suing the Environment Agency for £2 million, claiming it allowed otters to swallow up his business.
Entrepreneur Brian Dobson, 60, went bust after otters ate thousands of fish brought in to build up the business, a court heard.
He was given planning permission to set up Waen Wen Fishery in the village of Tregarth, near Bangor, Gwynedd, in 1999.
Six lakes were dug to accommodate up to 20,000 carp and a partial harvest in late 2005 proved the scheme was coming along well.
Three years later he went to remove more fish to raise money to pay his mortgage only to discover all that was left were bones stripped bare.
He claims the Environmental Agency (EA) ruined his business by encouraging otters to breed in the nearby River Cegin.
Mr Dobson also claims the EA constructed otter holts to encourage an increase in the river's otter population.
An expert on otters dismissed that view today, claiming that the EA's actions had no effect on otter numbers.
But Mr Dobson is suing the EA accusing it of breaching its duty of care by failing to warn him of what it was doing.