Almost 80% of Whale Sharks in Popular Marine Tourism Spot Show Human-Induced Scars

Whale sharks, the majestic giants of the oceans and the largest living fish species, face a precarious future. Classified as endangered on the IUCN Red List of Threatened Species, these gentle behemoths have experienced a worrying decline in their populations over the past seven decades. Studies indicate a global decrease exceeding 50%, with the Indo-Pacific region suffering losses of up to 63%. This alarming downturn is compounded by the species’ late sexual maturity—taking roughly 30 years—which severely limits their capacity for rapid population recovery in the face of multiple threats such as targeted hunting, habitat degradation, and accidental capture in fishing gear.

A groundbreaking international research initiative focusing on the Bird’s Head Seascape in Indonesian West Papua—a biodiversity hotspot known for its vast marine protected areas and rich megafaunal assemblages—has unveiled a troubling pattern. Researchers found that approximately 62% of observed whale sharks bore visible scars and injuries, predominantly linked to human activities. This high incidence underscores the urgent need for focused conservation interventions aimed at mitigating preventable harms caused by fishing operations and increasing ecotourism pressure.

In this comprehensive longitudinal study spanning 13 years from 2010 to 2023, researchers meticulously documented whale shark presence across several critical sites, including Cenderawasih Bay, Kaimana, Raja Ampat, and Fakfak. Utilizing a robust photo-identification methodology, enabled by the uniquely patterned white spot and stripe arrays on each whale shark, scientists compiled a detailed catalog of 268 individual sharks. These differentiable markings enabled precise tracking of movements, residency patterns, and health status over time, contributing invaluable data for the species’ demographic understanding.

The investigative team employed a multifaceted observational approach, collecting GPS locations, recording temporal sighting data, and noting both biological parameters—such as sex, maturity, and size—and ethological aspects like behavior and visible injuries. Their results revealed a striking spatial fidelity: 98% of whale shark encounters occurred in Cenderawasih Bay and Kaimana. Sightings were predominantly proximal to “bagans,” traditional Indonesian fishing platforms with lift nets, where juvenile whale sharks, mostly males between four and five meters in length, congregated to feed on baitfish species including anchovies, herrings, and sprats. Notably, this feeding behavior often led to direct interactions, such as rubbing against fishing nets, contributing to the observed injuries.

An intriguing aspect of the study involved long-term individual monitoring. Over half of the identified whale sharks were re-encountered multiple times, some over an eleven-year span. One particular young male stood out with 34 documented sightings across three years, exemplifying the importance of site fidelity and longevity in this population. The prevalence of injuries was also meticulously analyzed: among 206 sharks displaying scars or wounds, 80.6% had anthropogenic injury markers, with serious traumas like amputations and lacerations comprising 17.7% of cases. Conversely, natural injuries resulting from predator attacks or environmental interactions were less frequent, affecting a smaller subset of individuals.

The nature of the injuries paints a compelling picture of human-wildlife conflict in marine ecosystems. Most scars resulted from minor abrasions attributable to contact with bagans and whale shark-watching boats, revealing unintended consequences of traditional fishing and emergent tourism. Despite the seemingly superficial nature of many injuries, the cumulative effect raises concerns about the long-term health and survival capabilities of this vulnerable population. Furthermore, the prospect of escalating whale shark tourism, if unmanaged, portends increased risks absent regulatory frameworks tailored to species protection.

While juvenile male whale sharks were the primary subjects within the coastal and netted areas, a conspicuous void exists regarding adult females and sexually mature individuals. This demographic skew aligns with global insights noting that mature whale sharks, especially females, tend to inhabit offshore deep-ocean habitats where prey such as krill and schooling fish are more abundant. Satellite telemetry tracking corroborates this spatial segregation, revealing adults’ tendencies to frequent seafloor features like canyons and seamounts. Understanding this sexual and maturational habitat partitioning is critical for holistic species management and conservation strategies.

Local stakeholders and scientists alike recognize the ecological and economic value embedded in the region’s whale shark populations. These animals, through responsible whale shark tourism, represent an untapped asset offering sustainable income streams for communities and governments. However, the sustainability of this potential hinges on balancing human activities with the biological needs of whale sharks. The study’s authors advocate strongly for interventions focused on modifying current fishing infrastructure, including the safe redesign of bagans to eliminate sharp edges that exacerbate physical harm to the sharks.

Conservationists recommend straightforward yet impactful measures such as removing abrasive components on boat outriggers and net frames connected to bagans. These adjustments could substantially mitigate scarring and injury rates, preserving the animals’ health and enhancing their survival prospects. The research team is actively engaging with marine protected area management authorities to implement such changes, stressing a collaborative, science-driven approach that integrates traditional livelihoods with modern conservation imperatives.

This research not only extends scientific understanding of whale shark population dynamics and residency patterns in the Bird’s Head Seascape but also underscores the critical nexus between human maritime practices and marine megafauna welfare. As anthropogenic pressures intensify globally, this case study offers a vital example of how targeted monitoring, community involvement, and adaptive management can converge to safeguard endangered species while sustaining economic and cultural activities.

In conclusion, the conservation prospects for whale sharks in the Indonesian region remain cautiously optimistic, contingent upon timely and effective intervention. Through innovative tracking, detailed behavioral studies, and pragmatic infrastructure reforms, there lies an opportunity to stem the tide of decline for these enigmatic giants. The research highlights a pressing mandate for marine policy makers, local communities, and global stakeholders to harmonize human enterprise with ocean stewardship, ensuring that whale sharks continue to thrive for generations to come.

News Publication Date: 28-Aug-2025

Web References:
https://www.iucnredlist.org

References:
DOI: 10.3389/fmars.2025.1607027