Some farmed salmon from the Bay of Fundy are turning up in rivers in New Brunswick and Maine, concerning both conservation groups and the industry.
It's not clear from which salmon operations they came.
Jonathan Carr of the Atlantic Salmon Federation said the latest market-sized fish turned up in the Magaguadavic River Friday morning.
That makes more than a dozen escapees found in the past week.
Carr said while that seems like a small amount, it generally indicates otherwise.
"Under one per cent of those that escape from net pens actually make it to rivers. So this escape could've been in the thousands, or even 10- to 20,000, we just don't know," he said.
Nell Halse with Cooke Aquaculture said divers have been double-checking company pens, but the fish don't appear to have come from their farms.
She said her company has a vested interest in not letting fish escape.
"We don't want to lose our inventory, like any farmer would," said Halse.
Both sides say they need to work together to improve river monitoring and salmon conservation.
A report from the federal government released a week ago paints a dire future for wild stock in the Bay of Fundy.
It said the fish are suffering from interbreeding with escaped domestic salmon, and, in some rivers, there's little likelihood of rescuing the species.