Keith Lockwood, Fisheries Biologist
- Oxford, MD
- Total Reports: 39
- View all reports by Keith Lockwood →
Posted on March 6, 2012 | Permalink
Inquiry on Parasitic Worm in Yellow Perch
Location: Tidal and Nontidal Waters
Mike Hohm recently sent in the picture below of some strange red worms he found in a yellow perch he was cleaning. The red worms in the picture are called Philometra worms that are a common parasitic nematode worm in fish. A small larval stage of the worm is released into the water by infected fish and this small larval stage is eaten by tiny copepods (a small invertebrate) which act as an intermediate host. The copepods are then eaten by fish and the larval stage of the worm is released into the digestive system of the fish. Once in the fish the larvae migrate to target organs and molt into adults where they can become encysted in the viscera (guts) or muscle of the fish. They may grow as long as 2” in length and often move out of the cysts when the fish is dead and can be found free in the body cavity or flesh when the fish is being cleaned by a fisherman. The life cycle of these worms is not well documented but they are a common parasite in freshwater and estuarine fish such as striped bass, perch and other species such as minnows. They can not infect humans and as with all parasites cooking kills them.