Trauma linked to fishing nets and accidental capture of conger eel
The conger eel (Conger conger) is a hardy marine eel, often caught accidentally in fishing nets, traps or lines intended for other species. This accidental capture, also called bycatch, frequently causes physical injuries. These injuries ra...
What is it?
The conger eel (Conger conger) is a hardy marine eel, often caught accidentally in fishing nets, traps or lines intended for other species.
This accidental capture, also called bycatch, frequently causes physical injuries.
These injuries range from simple scratches to deep lesions that can compromise the survival of the animal, especially if it is released after capture.
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:
The signs depend on the severity of the trauma.
We often observe wounds or tears in the skin, sometimes deep, on the body or head.
The skin's protective mucus can be stripped away in places, leaving the animal more susceptible to infection.
The fins, particularly the continuous dorsal fin characteristic of the conger eel, may be damaged or torn.
Local swelling sometimes appears around the injured area.
The animal may swim abnormally, spinning around or remaining motionless at the bottom.
A state of despondency and general fatigue is common after a stressful capture, especially if the animal has been kept out of water for a long time or in a tight net.
In serious cases, internal injuries invisible from the outside can occur, particularly in the event of crushing in a net or rising too quickly from great depths.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Trauma comes directly from contact with fishing equipment.
The mesh can compress or cut the skin, especially if the conger eel struggles to free itself.
Hooks, when swallowed or stuck in the mouth, cause oral or digestive injuries.
Handling by humans, especially without precaution, can aggravate skin lesions by removing the protective mucus.
Prolonged stay out of water dries the skin and gills, increasing stress and the risk of complications.
Rapid ascent from great depths can also cause internal damage linked to the pressure difference, although the conger eel is less sensitive to this phenomenon than some fish with swim bladders.
Conger eels fished in rocky areas or in bottom nets are particularly exposed, because this is their natural habitat.
A high catch density in the net increases the risk of injuries from friction between individuals.
Prolonged capture time before release or recovery increases the severity of lesions.
Young conger eels and already weakened individuals tolerate the stress of capture less well.
Hot or poorly oxygenated water at the time of capture aggravates the animal's exhaustion.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
An aquatic animal veterinarian or marine biologist examines the animal, observing the condition of the skin, fins and swimming behavior.
The exam looks for signs of secondary infection, such as marked redness, increasing swelling, or unusual deposits on the wound.
In a healthcare center setting, an assessment of the general condition, including gill breathing and reactivity, makes it possible to judge the severity of the trauma.
Treatment
Treatment is primarily based on rest in a stable, well-oxygenated aquatic environment.
Superficial wounds are sometimes treated locally with antiseptic products adapted to the aquatic environment.
In the event of a suspected secondary bacterial infection, systemic antibiotic treatment may be considered by a veterinarian.
Pain and stress management may include local or general anesthetics during treatment, carried out only by a trained professional.
No self-medication should be attempted by an individual on an injured marine animal.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
To limit trauma, rapid and gentle handling is essential if the animal must be released.
Avoiding prolonged contact outside of water reduces stress and skin drying.
The use of suitable tools, such as fine-mesh, non-abrasive landing nets, limits skin injuries.
In a fisheries management context, reducing net dragging time and limiting bycatch are measures recommended by marine fisheries management organizations.
In captivity or in a care center, well-oxygenated water and sufficient space limit injuries related to stress or impacts against walls.
Possible complications
The main complications are secondary bacterial or fungal infections that develop on damaged skin lacking its protective mucus.
Extensive mucus loss can disrupt the animal's water and mineral balance.
Deep lesions affecting the muscles or internal organs can lead to the death of the animal, sometimes delayed after release into the water.
Significant stress can also weaken the immune system, making the animal more vulnerable to other illnesses in the days following capture.
When to see a veterinarian
Presence of a deep or bleeding wound
Swelling that increases rapidly around an injury
Abnormal swimming, animal that stays at the bottom or turns on itself
Lack of reaction or great lethargy after a capture
Signs of infection such as an unusual deposit or strong odor on a wound
Prognosis
The prognosis directly depends on the severity of the injuries and the speed of treatment.
A superficial lesion treated quickly in good water conditions often evolves favorably.
Deep wounds, internal injuries or prolonged handling out of water significantly worsen the prognosis.
The survival rate after release of an accidentally captured conger eel remains variable and strongly depends on the conditions of capture and release.
Frequently asked questions
Can a conger eel injured by a net survive if released into the sea?
It depends on the severity of the injury. A superficial lesion often leaves a fair chance of survival. A deep injury or prolonged stay out of water greatly reduces the chances of survival after re-entering the water.
Why is the skin of the conger eel so fragile after capture?
Like many fish, conger eels have a protective layer of mucus on their skin. This mucus limits infections and helps with skin respiration. It is easily damaged by contact with threads or careless handling.
Should you disinfect a wound on a conger eel found injured yourself?
It is best not to apply anything yourself without professional advice. Certain products unsuitable for the aquatic environment can aggravate the injury. A marine wildlife care center or specialist veterinarian should be contacted if possible.
Do capture trauma only concern professional fishing?
No, recreational fishing can also cause this type of injury, particularly when conger eel are accidentally captured while fishing for other species with a line or net.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 18 August 2026
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