also known as: salmon fluke, salmon leech
Gyrodactylus are a group of monogenean (i.e. 1-host) trematode parasites of fish, most often found on skin, occasionally gills. They are similar to Dactylogyrus, except their anterior (head) end does not have eyespots, but does have prominent hooks for anchoring to the skin. They have direct fish-to-fish life cycles. Adult worms do not lay eggs, rather they give birth to live offspring, with up to three generations of offspring present in an adult worm at the same time, which may be visible within the body of adults. Transmission requires direct fish-to-fish contact. In Europe, Gyrodactylus salaris can cause significant losses of native fish.