They slide below the surface with the majestic slowness of the forgotten giants, embodying the serenity of the great funds in waters which are more and more frequented. Their presence is a gift for ecosystems and a boon for the tourism economy. But under this apparent harmony, the wounds of whale sharks accumulate in silence, revealing the scars of a more brutal cohabitation than it seems.
This behavior is no coincidence. Thanks to meticulous follow -up between 2010 and 2023, the researchers were able to identify 268 individuals in these areas, more than half of which were observed several times over several years. The vast majority of them were immature males, measuring between 4 and 5 meters. This unusual concentration of young whale sharks in coastal areas seems to indicate that these habitats, rich in plankton and small fish, serve real natural nurseries.
These observations are the fruit of the work of Indonesian and international scientists, published in Frontiers in Marine Science, which used individual identification photos to trace the movements and the behavior of these marine giants. From the recurrence of meetings, it appeared that the Gulf of Cenderawasih offers exceptional stability, with an average presence of 118 days a year for each shark followed.
What the wounds of whale sharks reveal on their coastal habits
At first glance, the protected waters of this region may seem ideal for these animals. However, more than three-quarters of the studied whale sharks presented visible injuries. If some scars are superficial, others bear witness to much more serious aggressions: fins of fins, deep lacerations, skull deformations. Behind these brands rarely hide natural predators. It is above all the human structures that are the cause.
The study relayed by Scitechdaily reveals that around 80% of the injuries identified are of anthropogenic origin. Most come from the repeated contact with the threads or metal rims of the bags, but also from interactions with the tourist boats. By rubbing against platforms to access the fish benches attracted by lights, whale sharks are exposed to frequent abrasions. In some cases, collisions with the propellers of boats left clear and deep traces.
Most of these injuries affect the first dorsal fin, the most exposed area during vertical movements characteristic of their diet. The researchers even identified a juvenile whale shark whose skull has a severe deformation, probably caused by a violent shock against a human structure. This specimen, that observers saw twice in March 2020 in Kaimana, has not been reappeared since.
Adapt human practices to preserve fragile cohabitation
If the wounds of whale sharks are today visible and documented, they could be easily avoided. Scientists offer simple but crucial modifications of the bags, such as the elimination of cutting edges or strengthening the nets. These changes could significantly reduce the repeated abrasions observed on the fins and sides.
In parallel, the authorities of the protected marine areas are called upon to apply more strictly the codes of driving already in place concerning the observation of whale sharks. Reducing the number of boats present simultaneously, prohibiting too close approaches or limiting the hours of interaction would be as many measures favorable to the preservation of these animals.
Because beyond visible injuries, it is the constant pressure of poorly supervised tourism that threatens their tranquility. Satellite observations show that the most mature whale sharks, especially females, avoid these very frequented coastal areas and prefer more distant funds. The concentration of young males in the berries suggests a phenomenon of ecological segregation. Females, perhaps more sensitive to stress, would flee these too disturbed areas.
To preserve these Indonesian sanctuaries is to offer whale sharks a space to grow without clashes. But it is also to protect a fragile balance between human activities and marine life, in which the slightest negligence leaves a brand, sometimes indelible, on the backs of the giants.
