Whale Sharks are the largest fish on Earth and highly endangered. A new study in the Bird’s Head Seascape off West Papua shows: 62% of the animals recorded there bear injuries, mostly caused by humans. Collisions with bagans (traditional lift-net platforms) and boats are particularly common, while growing whale shark tourism poses additional risks. The good news: simple modifications to fishing gear and boat equipment could prevent much of the damage.
What the researchers found
Between 2010 and 2023, an international team documented whale sharks in Cenderawasih Bay, Kaimana (including Triton Bay), Raja Ampat, and Fakfak, a network of 26 marine protected areas. Using photo-ID (unique spot patterns), 268 individuals were identified. 98% of sightings occurred in Cenderawasih Bay and Kaimana. More than half (52.6%) were resighted, with one young male even spotted 34 times in three years. Around 90% of the animals were male, mostly juvenile whale sharks measuring four to five metres in length.
Of 206 documented animals with injuries or scars, 80.6% could be attributed to humans, while 58.3% showed traces of natural causes (multiple attributions possible). Severe injuries such as deep cuts, amputations, or blunt trauma from human activity occurred in 17.7%. More common were non-life-threatening abrasions, such as those caused by rubbing against net edges, outriggers, or boat hulls when whale sharks suck baitfish from bagans.
“Scars and injuries are mostly due to collisions with bagans and tourist boats,” says study leader Dr. Edy Setyawan (Elasmobranch Institute Indonesia). “Natural causes play a much smaller role.”
Divers freed whale shark from tangled rope! The scars on it were deep 😥!
by inTheDepthsBelow
Why so many young males – and where are the females?
Sightings were almost exclusively concentrated near bagans, where whale sharks feed on baitfish such as anchovies, herring, or sprats, gliding horizontally or in a vertical “head-up” position. Adult animals, especially females, are more frequently found near deep-sea structures like canyons and seamounts and use the open ocean, while juvenile males prefer coastal, plankton-rich areas.
“Adult whale sharks – especially females – often use the deep sea and follow different prey like krill and schooling fish,” explains co-author Mochamad Iqbal Herwata Putra (Konservasi Indonesia).
Simple solutions with great impact
Since most encounters occur at bagans and tourism is growing, researchers expect more injuries without countermeasures. Small, immediately implementable interventions are proposed: removing sharp edges from outriggers and net frames, modifying nets and platforms, and establishing clear rules for tourist boats in protected areas. This would significantly reduce scarring and secure the whale shark as a long-term resource for communities and authorities.
“With minor modifications to bagans – such as removing sharp edges – we can significantly reduce the scarring rate,” says Dr. Mark Erdmann (Re:wild).
Since whale sharks reach sexual maturity late (up to 30 years), populations recover slowly. Preventive measures against avoidable injuries and tourism that protects the “gentle giants” rather than endangering them are all the more important.
