State/National/WorldFish Rap

Why Lie? Fish Can Contract Lice.

As kids, many of us had the incredibly annoying experience of acquiring head lice. But did you know that lice are found in the fur and feathers of almost every mammal and bird species? For humans, they live in hair or clothes. But what about animals without fur or feathers? Can naked, bald fish get lice? The answer is both yes and no. Yes, fish do get lice, but they are very different from the lice you might have had in third grade.


Your childhood lice were insects, but the lice found in the ocean are not. Like crabs and lobster, oceanic lice are crustaceans. Argulus, or fish louse, is a small lobster-like animal that lodges on the skin of Cypriniformes fish, like koi or goldfish. Fish louse can be observed with the naked eye. The fish that have been infected will get red spots and will start behaving differently, like rubbing against stones and jumping above the water. Argulus can be a major threat to fish health. Heavy infestations of this parasite can cause significant morbidity and mortality. 


If you happen to have a koi pond in your backyard, it is wise to put diseased fish in quarantine outside the pond to prevent a plague. It is, of course, better to prevent fish louse by inspecting newly introduced fish to find out if they have been infected. In rare cases, birds might introduce Argulus to a pond. It is therefore advised to observe fish regularly.

To improve the health of the fish, it is crucial to feed fish during the summer months on good quality feed— feed containing many essential nutrients, vitamins, and minerals. Healthy fish can resist attacks of fish louse more easily.


According to, sea lice are not harmful to humans, but the lesions caused by even a minor infestation can make fish, such as salmon, unmarketable. Unfortunately for the industry, sea lice have been around for years and have adapted well to living on marketed fish such as salmon.


Fish can also contract tongue-eating lice. It’s what science fiction is made of: a parasite that eats and replaces the tongue of its host.—Cymothoa exigua. These parasites are isopod crustaceans as well, related to the pill bugs (or roly-polies) you can find in your yard. As an isopod, they have a segmented exoskeleton. They seem to be selective of the species of fish they parasitize for unknown reasons. To date, they have only been found in eight species of fish, including Atlantic croaker, spotted seatrout, and a few species of snapper. The louse seems not to cause any other damage to the host fish. However, once it replaces the tongue, it feeds on the host’s blood and mucus or the fish’s prey. If a fish has multiple lice, it can cause the fish to become malnourished.


If your pond or aquarium fish contract lice, there are treatment options. But if you catch one in fresh or salt water and see it, release the fish and always follow proper hand washing methods to prevent the parasite from spreading and keep yourself healthy. 

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