'Fish farm impact needs studying'
Record numbers of sockeye salmon returned to spawning grounds in Canada's Fraser River last month - the highest in a century.
The arrival of the 34 million fish followed a year when just one million made the journey - the lowest in decades - prompting questions about why fish stocks were declining.
Biologist and environmental activist Alexandra Morton explains why she believes salmon farms on the migration route have a negative effect on wild salmon.
Watch Susan Watts' film from British Columbia on Newsnight on Tuesday 26 October 2010 at 2230 BST on BBC Two.