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:
Teresa Cope 'an extraordinarily dedicated public servant' who wasn't pushed out of job, says Manx Care chair
Wendy Reid discusses circumstances around CEO's departure
Ramsey Minor Injuries Unit to reopen next week
Manx Care says urgent treatment and diagnostic support will return to Ramsey Cottage Hospital
Local pharmacist believes gap to GP's is "narrowing"
However, he says in-store professionals wont replace a doctor
Young farmer hopes to shine light on mental health
Thomase Cleator says isolation can have a big impact, especially amid ongoing industry challenges
Manx Care: Hospital pressures beginning to ease after OPEL 4 escalation
Elective procedures continue as services move back to OPEL 3 following "exceptional demand"