Members of the public are being asked to look out for poachers over Christmas.
Autumn rains force stocks of salmon and trout into the rivers to spawn, and they become easy targets for criminals with nets.
Hoteliers and restaurateurs are being urged not to accept any fish offered for sale, and to report any encounters with poachers to the police.
Manx River Improvement Association spokesman Brian Craig (pictured) says poaching is aganist the law, and is seriously damaging rivers stocks:
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