Red Worms in Fish

The red worm found in the muscle and internal organs of trout and redfin in particular is a nematode worm called Eustrongyloides. The worms are 20-30 mm long and are often in clumps in the flesh. They do not affect the eating quality of the fish and the worms can be easily removed. It is spread by birds feeding on infected fish and transferring live worms.