Trauma linked to fishing nets and accidental captures
The tiger shark (Galeocerdo cuvier) is a large pelagic and coastal species that can be accidentally caught in fishing nets, longlines or traps. We speak of “accidental capture” or “bycatch” when an animal not targeted by fishing finds itsel...
What is it?
The tiger shark (Galeocerdo cuvier) is a large pelagic and coastal species that can be accidentally caught in fishing nets, longlines or traps. We speak of “accidental capture” or “bycatch” when an animal not targeted by fishing finds itself trapped in fishing gear. \n\nThis situation often leads to significant physical injuries: lacerations of the skin, deep cuts caused by lines or mesh, hooks stuck in the mouth or throat, and sometimes internal injuries linked to prolonged immobilization underwater. \n\nIt is not an infectious disease but an accidental trauma, the severity of which depends on the time spent trapped, the type of fishing gear and the speed of release into the water.
Key point
Prolonged capture or fin mutilation can be fatal 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:
The signs observed depend on the severity and age of the trauma. \n\nOpen wounds or lacerations can be observed on the skin, sometimes deep to the muscle, often located around the fins, tail or head. \n\nCircular or linear marks corresponding to the imprint of the mesh of the net or the line can remain visible for several weeks, or even leave permanent scars. \n\nA hook can get stuck in the jaw, throat or esophagus, causing difficulty eating. \n\nAn animal caught in a net for a long time may show abnormal swimming, muscular exhaustion, disturbed breathing (the tiger shark needs to swim to circulate water over its gills) and pale mucous membranes in the event of shock or significant blood loss. \n\nIn the most serious cases, we may find a severed fin or partial mutilation (removal of the fins for example), which seriously compromises the animal's swimming abilities.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The cause is purely mechanical and accidental: prolonged contact with fishing gear (gillnet, seine, longline, trawl, trap) not intended for this species. \n\nInjuries come from the friction of the mesh or line on the skin, the traction exerted by the animal to free itself, the presence of a swallowed or planted hook, or even rough handling during release into the water by fishermen.
The risk is higher in areas of high coastal or offshore fishing activity, particularly near migratory passage areas of the species. \n\nDrifting gillnets and bottom or surface longlines are particularly concerned. \n\nThe presence of bait or fishing waste also attracts the tiger shark, known for its opportunistic behavior and curiosity about food, which increases its exposure to fishing gear. \n\nJuveniles and females during the breeding season, which frequent shallow coastal areas, are also more exposed.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The evaluation of an injured tiger shark is most often done in the field, by a marine professional, a marine biologist or a veterinarian specializing in aquatic wildlife, rarely in a traditional clinic given the size of the species. \n\nThe examination focuses on the extent and depth of the skin lesions, the presence of a retained hook, the animal's state of vigilance and swimming, as well as signs of shock (color of mucous membranes, behavior). \n\nAs part of a scientific program or a specialized center (rare for this large species), a more in-depth assessment may include prolonged observation in a tank.
Treatment
There is no standard drug treatment for this wild species in the wild. \n\nTreatment consists above all of physical actions: careful removal of the hook or line when possible without excessive stress for the animal, rapid return to the water. \n\nIn rare cases of treatment in a specialized structure (aquarium, marine wildlife care center), wound care (cleaning, antiseptics) and anti-infectious therapeutic families may be considered by a specialized veterinary team, but this remains exceptional for this large pelagic species.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is essentially based on fisheries management measures: use of devices reducing accidental catches (exclusion devices, modification of the type of hook), limitation of the immersion time of nets, training of fishermen in good practices for rapid and gentle release into the water. \n\nRaising awareness among marine professionals about the identification of the species and the actions to take in the event of accidental capture (cutting the line near the hook rather than pulling on the animal, avoiding removing it from the water) greatly limits the severity of injuries. \n\nCompliance with fishing regulations and protected areas also helps reduce the species' exposure.
Possible complications
Possible complications include secondary infection of wounds, significant hemorrhage, loss of mobility in the event of a severed fin, exhaustion which can lead to drowning (the tiger shark must swim to breathe), or even death by shock if the capture was long and brutal. \n\nA mutilation of the fins (finning) makes the survival of the animal almost impossible.
When to see a veterinarian
An accidentally captured tiger shark must be reported quickly to the maritime authorities or to a competent scientific structure.
The animal has a deep wound or visible hemorrhage.
The animal's swimming appears abnormal, weak or disorganized after release into the water.
A fishhook remains visible or palpable in the mouth or throat.
The animal remains motionless or appears in shock after capture.
A fin is severed or missing.
Prognosis
The prognosis directly depends on the duration of capture, the type of injury and the speed of release into the water. \n\nA brief capture followed by a quick and gentle return to water often allows survival without major after-effects, with progressive healing of superficial lacerations over a few weeks. \n\nProlonged capture, mutilation of the fins or a marked state of shock clearly darken the prognosis, with a risk of delayed mortality in the days following release into the water.
Frequently asked questions
Can a tiger shark caught in a net survive if released quickly?
Yes, if the capture was brief and the animal is returned to the water quickly and without rough handling, the chances of survival are good, even with superficial injuries.
What to do if you find a hook stuck in the mouth of a tiger shark?
It is best to cut the line as close to the hook as possible rather than pulling on it, and report the catch to the appropriate maritime authorities. Complete removal should only be attempted by an experienced person.
Are mesh scars permanent?
Superficial marks often fade over time, but deep lesions can leave permanent scars or permanently affect the mobility of the affected fin.
Does accidental capture threaten the tiger shark population?
Bycatch contributes to pressure on shark populations, a species already vulnerable in several regions, justifying international efforts to reduce incidental catches.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 24 September 2026
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