Anchor Worms In Fish: Causes, Signs & Treatment

Anchor worms in fish are a type of parasitic worms having anchor type structure. The causative agent is Lernaea sp. They attach themselves to the fish’s flesh with a sharp, anchoring head.

Anchor worms attach themselves to the fish’s body with their large, hooked claws and feed on the fish’s blood.

Signs that a fish may have redness, inflammation, and lesions on the skin. These parasites are easy to identify, and you can treat them with a variety of methods.

They are responsible for millions of dollars in losses to the aquaculture industry every year.

Here the article will provide a deep brief on the causes, symptoms, prevention, and treatment.

Fish Infested with Crustacean Lernaea Anchor Worm
Pictures of anchor worms on fish

What is Anchor Worm

Anchor worm is a parasite having anchor type structure on the posterior side of the body. This anchor type structure and anchoring nature into the fish skin called them “Anchor Worm”.

The larnaea species, called “anchorworms,” are crustaceans that typically infect freshwater fish and cause bodily distress and mortality. The diseases is known as lernaeasis.

Around 110 genera of lernaeids have been noted. Among them, Lernaea cyprinacea is more commonly identified and observed in the culture system.

These parasites belong to the crustacean subphylum (Phylum-Arthropoda) and Copepoda sub class.

So where does anchor worm comes from? Copepods are a type of crustacean that mostly lives in water. They are found in freshwater environments.

Where Do Anchor Worms Attach?

They can attach themselves anywhere on your cultured or pet fish including skin, fins (dorsal, pectoral, pelvic and tail) and gills.

They attach the gill tissues to the gill arch bone and gill filaments leading to mechanical damage and negative physiological effects.

Affected fish face further malnutrition and secondary infections through their attachment sites as well as low growth problems.

Taxonomic Tree of Lernaea

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Subphylum: Crustacea
  • Class: Maxillopoda
  • Subclass: Copepoda
  • Order: Caligoida
  • Family: Lernaeidae
  • Genus: Lernaea
  • Species: cyprinacea
Picture of A Typical Anchor Worm Lernaea cyprinacea

Geographical Distribution

These parasites are most commonly found in tropical and sub-tropical regions, but can also be found in temperate climates. They tend to cause problems in summer when water temperatures are warmer.

Species Affected

Major hosts (fish) of Lernaeid are,

  • Major carps (Indian & Chinese),
  • Minor barbs
  • Catfish and
  • Perches

Body Features (Morphology or Characteristics) of a Typical Lernaea

What does an anchor worm look like? They are typically gray or white in color and can grow up to two inches long.

Female worms are one of nature’s most bizarre creatures having pair of sacs when female mature into adult.

They have a slender body having an attachment organ in their posterior end.

They burrow into the flesh of a fish and transform into an unsegmented, wormlike form, usually with a portion hanging from the fish’s body; they can be as long as 1 cm.

Anchor worms can be identified by their long, white body and brown head. They range in size from 2 to 6 inches in length.

Anchor worm lernaea image

Most copepods have a long body but they can also have a short body.

It is a long, white worm with a small head and a large tail that attaches itself to the flesh of the fish with a sharp-pointed head.

These parasites use their sharp mouthparts to pierce the skin of their host fish and feed on the blood and tissues.

Life Cycle of Lernaea (Anchor Worm)

Source: Researchgat

The life cycle of Lernaea includes several stages:


Female Lernaea lays eggs, which are typically attached to the fins or scales of the host fish. The eggs are oval-shaped and are usually about 0.5 mm in diameter.


After hatching, the first larval stage is the free-living nauplius (singular; nauplii). This stage is characterized by a single eye, three pairs of appendages, and a small tail.


The next stage is the copepodid, which is similar in shape to the adult but smaller. This stage typically has five pairs of appendages and a long tail.

They develop through five different copepodid stages in about four days before molting into their first parasitic stage and attaching to fish or amphibians, often on gills.

Cyclopoid Adult

The final stage is the cyclopoid adult, which is characterized by a distinctive head and thorax, a large body, and five pairs of appendages.

Adult females are typically larger than adult males. Male adult die after reproduction and female attached to the fish skin.

The lernaea development is also known as Cyclopoid copepod, where they they do not go through metamorphosis as many other crustaceans do.

Causes Anchor Worm in Fish

There are several factors that can contribute to anchor worm infestations in fish:

Water Temperature

Anchor worms thrive in warm water, so infestations are more likely to occur in the summer months. These worms thrive in warm water and are less prevalent in cooler climates.

Fish Density

Anchor worms are more likely to spread in crowded conditions, such as in overstocked ponds or aquariums. High stocking density deteriorate the water conditions accelerate the abundance of these types of parasites.

Poor Water Quality

Anchor worms can take advantage of weakened or stressed fish, so poor water quality (e.g. high levels of pollution, low oxygen levels) can make fish more susceptible to infection.

The worms burrow into the affected area on a fish’s body which is often caused by contact with muddy or dirty water as this provides them nourishment.

Immune Suppression

certain medications, changes in pH and other stressors can suppress the fish’s immune system, leaving them vulnerable to anchor worm infestations.

Additionally, certain types of fish are more susceptible to anchor worm infestation than others.

Introduction of infected fish

Anchor worms can also be introduced to a pond or tank through infected fish, which can then spread the parasites to other fish in the system.

Presence of Suitable Intermediate Host

The presence of suitable intermediate hosts accelerate their life cycle. They prefer to parasitize fish, and sometimes infest amphibians and reptiles.

Signs and Symptoms of Anchor Worm in Fish

Anchor worms are small and thin creatures that attach themselves to the flesh of fish using their strong hooks. They can be identified with the naked eye.

Anchor worm attached in dorsal fin base

A visible pale thread-like organism protruding from the fish’s skin.

Anchor worms attached in pelvic fin base

They do this by burrowing through it, creating lesions that can allow secondary bacterial and viral infections that lead to severe infestations.

-Significant skin damage to their host, leading to infection, tissue death, and even death.

-Redness, inflammation, and lesions on the skin.

Excessive lethargy, and loss of appetite.

-Scratching or rubbing abnormally against objects in the aquarium or pond.

In severe cases, they can actually cause gill damage that causes death in some infestations.

Diagnosis of Anchor Worms

Diagnose Anchor Worms in Microscope

They can be difficult to diagnose, as they often look like small pieces of string or thread.

The best way to tell if your fish has an anchor worm is by looking for the worm’s “head” on the fish’s body.

If you see a small, brown spot on your fish that looks like a head, then there is a good chance that your fish has an anchor worm.

How To Prevent Anchor Worm in Fish

-To prevent an infestation, it is important to practice good hygiene when handling bait or live fish and to properly clean and disinfect any equipment that comes into contact with water.

-Keep your aquarium and pond clean and free of debris. This will help reduce the number of parasites in the water.

-Use a good quality water filter to remove any parasites from the water.

-Anglers should take care to properly clean their gear after each outing.

-Quarantine any new fish before adding them to your aquarium or pond. This will help protect your other fish from potential infection.

Anchor Worm Treatment

There are several things that can be used to kill or remove them from fish.

Picking off

Lernaea are a common nuisance for both freshwater and saltwater anglers. How do you remove anchor worms?

Fortunately, there are several methods that can be used to pick off them.

-One way to remove an anchor worm is to use a hook or pliers. Hook the worm near the head and pull it off. If using pliers, grip the worm as close to the head as possible and twist until it comes off.

-Another method is to use a sharp knife or razor blade. Cut the worm near the head and pull it off. Be careful not to cut yourself in the process.

-One can hold the fish in their hand and remove them with a pair of tweezers. However, it is important not to break off the tail or head while removing them because if that happens then they will be left embedded in fish skin.

-To pick off anchor worms, pinch off the worm head and pull the body in opposite direction.

Change the Poor Water

The first thing you need to do when dealing with a fish disease or infection is changing the water. By doing so, your aquarium will be in good condition for healing and not have any toxic water conditions that would otherwise harm them even more.

Salt Treatment

Put the infested fish into your water at 1-2 tablespoons which may help prevent secondary infections if they happen to come up later on down the line too.

Another option is to make your own treatment using Epsom salt and garlic cloves. To do this, dissolve 1 cup of Epsom salt in 1 gallon of water.

Cut up 2-3 cloves of garlic and add them to the solution. Soak your fish in the solution for 10-15 minutes, then rinse them off with fresh water.

Potassium Permanganate Treatment

Potassium permanganate is usually considered the best treatment and works in aquariums or fish ponds.

Potassium permanganate is a strong oxidizing agent that is used to treat anchor worms.

It works by killing the parasites that are attached to the fish. Potassium permanganate can be added to the aquarium water or it can be used as a dip.

It is important to follow the instructions carefully when using potassium permanganate, as it can be toxic if not used correctly.

Anchor Worms in Saltwater (Marine Fishes)

They are a common occurrence in saltwater, and can often be seen clinging to fish skin sucking their blood.

They can also cause harm to other marine life by attaching themselves to gills or fins.

Anchor Worm in Freshwater Fish Pond & Their Treatment

According to the University of Florida, there are a few ways to get rid of pond fish anchor worms. Farmer can physically remove the worms by hand.

This can be done by using a fine net or simply reaching in and grabbing them. Another option is to treat the water with an approved chemical insecticide.

One popular method is to use a commercial pond treatment. These treatments are available at most pet stores and come in both liquid and powder forms.

Be sure to read the directions carefully and follow them closely.

Anchor Worms in Aquarium Fishes

Anchor Worms in Aquarium Fishes

While these worms can occur naturally in aquatic ecosystems, But how did anchor worms get in my fish tank?

-They can introduced into a fish tank by way of infected bait or live fish. Once introduced, they can quickly become established and cause significant harm to the fish population.

-In most cases, they are introduced into a fish tank when a new fish is added to the tank.

-They can also be spread through contaminated water or food.

There are a number of ways to remove them from an aquarium, including manual removal and the use of chemical treatments.

Frequently Asked Questions

Do anchor worms fall off?

If you remove an anchor worm from a fish’s skin yourself, the worm will die. Others maintain that the anchor worm will eventually detach itself from the host’s flesh and fall off on its own.

How many days do anchor worms live without a host?

Anchor worms can live without a host for up to 10-12 days but will die within 2-3 days if they do not find a host.

Are anchor worms infect (harmful) for human?

Can humans get anchor worms from fish? Although anchor worms are not known to specifically target humans as a host, they are still capable of infecting us. There is no evidence that they can infect humans.

They are not harmful as worms may die when cooked for eating, if remain in fish body.

Can anchor worms kill fish?

While they may not always kill their host, they can reduce growth somewhat. This can be a major issue for commercial fisheries, as smaller fish yield less profit.


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