Following a nice collaboration with Andrew Chin and Jodie Rummer from James Cook University (Australia), we recently published an article documenting a range of diverse wounds and injuries on the blacktip reef shark (Carcharhinus melanopterus) and demonstrating how quickly sharks were able to heal and recover from these injuries. This healing ability has different implications and application to understanding of shark’s ecology.
We first documented the rapid healing of this species following an internal tagging procedure involving a small incision in the belly of the shark to implant the transmitter. This not only shows that sharks are healing quickly but also that they are robust to this tagging procedure which is important to know as a scientist when you work with free-living animal.
The same kinds of incisions/open-wounds are present in neonate sharks from viviparous species such as the blacktip reef shark. Just after birth, an open umbilical scar is visible but it quickly close and heals. It is then important to assess the speed of healing in ecology as it can inform the approximate date of birth when the juvenile is caught in its nursery. Small umbilical wounds in neonates decreased in surface area by 71% in less than a week and were barely detectable after 24 days.
The same rate of healing is helpful when females are bitten by males during mating. Indeed, as it is really rare to observe shark copulation, we can indirectly infer when mating occurred using the fresh bite wounds on female’s body. Inferring the speed of healing of these wounds can therefore tell us exactly when mating occurred.
Blacktip reef sharks can also have other sources of injuries. For example, larger sharks or other conspecifics can bite them during agonistic/dominance behaviour or predation attempt by larger predators, and healing quickly is therefore important.
Anthropogenic activities can injure sharks (e.g. boat propellers). We report here an unbelievable healing case of a shark surviving a serious deep wound that might have been inflicted by a boat propeller in Moorea lagoon. I less than a month the wound closed completely.
Finally, we reported two cases of survival after fin removal due to targeted shark-finning in which the basal wound of fin removal healed well and the sharks were observed alive a while after injury, swimming without their dorsal fin. However, even if they survive for un unknown time, the removal of the dorsal fin may greatly affect their daily life and in turn their fitness (and most of finned sharks may not survive).
In summary, this study suggests that elasmobranchs may be resilient to injuries, showing rapid healing from minor wounds and long-term survival from even major mechanical injuries. These are positive findings for elasmobranch conservation, especially considering that up to a quarter of all shark and ray species worldwide are threatened with extinction. Despite this incredible ability, we encourage minimal handling time and stress when releasing sharks after fishing or by-catch, which could include cutting a line near the hook instead of repeatedly attempting to remove the hook. Anglers should also be made aware that sharks can recover from mechanical injury; therefore, sharks should be released even if the animal sustains injuries during the capture process.
The paper is Open Access and available at:
Chin A, Mourier J, Rummer J (2015) Blacktip reef sharks (Carcharhinus melanopterus) show high capacity for wound healing and recovery following injury. Conservation Physiology 3(1): cov062