Anglers in Guernsey have been asked to limit the number of fish they eat from St Saviour’s reservoir, after a chemical was detected in the water.
Environmental Health said the chemical was known as PFOS, and was a component of fire-fighting foam.
It stressed that while anglers were unlikely to be eating enough fish to cause concern, it suggested limiting intake to 26 fish per year.
It said that drinking water from the facility remained safe for consumption.
Fishing at St Saviour’s is limited to members of the Guernsey Trout Society.
The society’s records showed that since 2002 anglers each took away eight fish per year.
As well as warning against eating large amounts of trout, the Environment Health unit advised against eating any carp from the reservoir.
Environmental Health said the diversion of pollution from Guernsey Airport away from the reservoir in future would reduce the levels of PFOS in the water.