Parasitism by copepods and parasitic crustaceans in shortfin mako sharks
The shortfin mako shark, like most sharks and rays, can harbour small parasitic crustaceans called copepods on its skin, gills, or fins, as well as other related crustaceans. These organisms attach firmly to the shark's body surface to feed...
What is it?
The shortfin mako shark, like most sharks and rays, can harbour small parasitic crustaceans called copepods on its skin, gills, or fins, as well as other related crustaceans. These organisms attach firmly to the shark's body surface to feed on mucus, skin, or blood. In the wild, a light infestation is common and usually causes no serious harm. In captivity, however — whether in an aquarium or holding tank — an infestation can build up rapidly in the absence of natural control mechanisms, and may become a genuine health problem for the animal.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Signs are often subtle at first. Small whitish, yellowish, or translucent dots or filaments attached to the skin, fins, or near the gills may be visible to the naked eye depending on the copepod species size. The shark may rub against the tank walls, floor, or objects in an attempt to rid itself of parasites, causing irritation, redness, or small wounds. Jerky, hesitant, or unusual swimming patterns are sometimes noticed. With heavy infestation on the gills, the animal may appear lethargic, breathe more labouredly, and lose weight progressively if appetite declines. Skin lesions can become secondarily infected and heal poorly.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Infestation results from attachment of parasitic copepods — for example species from the families Pandaridae, Kroyeriidae, or Eudactylinidae, which are well documented in sharks — or other small crustaceans to the shortfin mako shark's skin, fins, eyes, or gills. These parasites exploit the host for feeding and reproduction, anchoring themselves using structures adapted for firm attachment to the typically rough skin of sharks.
Confinement in a tank or aquarium promotes parasite multiplication because free-living larvae can easily reinfect the same animal or contaminate other fish present. High stress levels, poor water quality, immunity weakened by transport, or pre-existing wounds increase the shark's vulnerability. Introduction of a new animal or untreated water into a tank may also introduce parasites. In the wild, close contact with other heavily parasitized sharks may promote transmission.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is based on direct observation of parasites attached to the skin, fins, or gills, often performed by a veterinarian specializing in aquatic animals or by trained aquarium staff. Sampling of the parasites allows precise identification under the microscope. A more thorough examination of the gills may be necessary if respiratory compromise is suspected, along with assessment of the animal's overall condition.
Treatment
Management relies on antiparasitic treatments suited to aquatic environments, under strict veterinary supervision, as many substances toxic to crustaceans can also affect the shark or its environment. Treatment of the tank water may be combined with individual treatment of the animal. Local care of skin lesions and monitoring for possible secondary infections are part of overall management.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
In captivity, systematic quarantine of any new animal before introduction into a shared tank helps limit the arrival of parasites. Regular visual inspection of the skin and gills helps detect any abnormality early. Maintaining good water quality, effective filtration, and stress management (sufficient space, limited handling) reduces the risk of severe infestation. Periodic veterinary check-ups of animals in professional aquatic facilities are recommended.
Possible complications
Severe infestation can lead to extensive skin lesions, secondary bacterial or fungal infections, gill damage that impairs breathing, general weakness, and weight loss. In an already compromised animal, these complications can threaten survival, particularly in captivity where escape or avoidance of infested areas is impossible.
When to see a veterinarian
Presence of abnormal spots or filaments visible on the skin or fins.
Repeated rubbing against tank walls or floor.
Unusual swimming, hesitant movement, or behavioral changes.
Skin lesions, redness, or wounds that do not heal.
Signs of fatigue, loss of appetite, or progressive weight loss.
Breathing that appears more labored than usual.
Prognosis
The prognosis is generally good if infestation is detected early and treated promptly, especially in a controlled environment such as a professional aquarium. In case of severe infestation with significant gill involvement or infectious complications, the prognosis becomes more guarded, particularly in an already weakened animal.
Frequently asked questions
Are parasitic copepods of the shortfin mako shark dangerous to humans?
No, these parasites are specific to fish and sharks. They pose no risk of transmission to humans.
Should a wild mako shark carrying a few parasites be treated?
In nature, a light parasitic load is common and generally well tolerated. Treatment is considered only in case of problematic infestation, particularly in captivity.
How can these parasites be recognized with the naked eye?
They often appear as small dots, filaments, or whitish to yellowish structures attached to the skin, fins, or near the gills, but their precise identification requires specialized examination.
Is the mako shark particularly susceptible to this type of parasitism?
Like most pelagic sharks, it can harbor several copepod species specific to elasmobranchs, though this is not unique to this species alone.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 24 August 2026
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