Predation on horsehair worms (Phylum nematomorpha)

Field observations revealed cases of predation on horsehair worms by brown trout (Salmo trutta) in Maryland and Minnesota a rock bass (Ambloplites rup estris) in Kentucky, and a crayfish in Wisconsin. Some fish contained more than one worm and may have consumed reproductive aggregations. In laborator y feeding trials with Gordius robustus, most individuals of several fish sp ecies either ignored the horsehair worms or rejected them after taking them into their mouths briefly, but a green sunfish (Lepomis cyanellus) consume d both individual worms and a compact ball of 18 worms. A literature review yielded cases of predation on horsehair worms by at least 12 fish species. Horsehair worms usually were only a trace component of the diet, but some individual fish had eaten multiple worms.