The Secrets of the Whale Sharks of Saleh Bay: Population, Range, and Economy
The Secrets of the Whale Sharks of Saleh Bay: Population, Range, and Economy
Whale sharks (Rhincodon typus) are not merely the largest fish in the world; they are architects of marine ecosystems that play a crucial role as indicator species for the health of tropical waters. As filter feeders, their presence indicates a healthy and productive food chain. However, globally, these spotted giants are on the brink of a worrying extinction. The International Union for Conservation of Nature (IUCN) has classified whale sharks as Endangered after their global population declined by more than 50% due to threats from hunting, habitat degradation, and accidental capture in fishing nets (bycatch). Amid this bleak global conservation landscape, the waters of Saleh Bay in West Nusa Tenggara (NTB) Province, Indonesia, have emerged as a new oasis of hope. Through a scientific report titled “Preliminary Study of Whale Sharks in Saleh Bay,” released by Conservation Indonesia in collaboration with the Ministry of Marine Affairs and Fisheries (KKP) and the NTB Provincial Marine and Fisheries Agency, this semi-enclosed bay has been officially identified as one of the most important and dynamic whale shark aggregation sites in the world.
The following is a comprehensive analysis and in-depth review of all scientific aspects, research methodology, demographic structure, behavioral patterns, and the economic value of whale sharks in Saleh Bay based on data collected from 2017 to 2022.
The successful completion of this study is the result of a multi-year research commitment (2017–2022) that employed a modern, internationally recognized applied science approach. The researchers did not rely solely on random visual observations, but instead utilized the three main pillars of scientific methodology:
- AI-Based Photo-ID Method: Each whale shark has a unique pattern of white spots and lines in the area just behind the fifth gill slit and above the pectoral fin. This pattern remains unchanged throughout their lives, functioning much like a human fingerprint. Researchers take underwater photos of these vertical areas, then match them using automatic spot-pattern recognition software (such as I3S or the global Wildbook for Whale Sharks database). This method allows researchers to track whether a whale shark that appears is a new individual or a returning one.
- Satellite Tagging: To uncover the mystery of where whale sharks go when they are not visible at the surface, researchers attached Splash10-F-321 satellite tags to the dorsal fins of several selected individuals. This device records real-time data on geographic coordinates (via the Argos system), daily diving depths, and fluctuations in sea water temperature, which is then transmitted to a satellite every time a whale shark surfaces.
- Spatial Analysis and Socio-Economic Assessment: This study also mapped whale shark habitat preferences using a geographic information system (GIS) to identify areas of overlap with human activities. Additionally, in-depth interview-based surveys were conducted in coastal communities, particularly in Labuhan Jambu Village, Sumbawa, to assess both the direct and indirect economic impacts of this niche tourism activity.
2. Whale Shark Population Structure: Dominated by Male Juveniles
Over the five-year monitoring period, the research team successfully identified and recorded 108 unique whale sharks in Saleh Bay. Upon analyzing the demographic structure of these 108 individuals, the team discovered population characteristics that are highly specific and biologically intriguing:
- Absolute Dominance of Juveniles: Based on estimates of total body length, the majority of whale sharks found in Saleh Bay measure between 3 and 6 meters, with an average length of 4.5 meters. Given that whale sharks only reach sexual maturity (adulthood) when their body length reaches 8 to 9 meters (at around 25–30 years of age), this means that nearly the entire population in Saleh Bay consists of juveniles.
- Sex Ratio Imbalance: Of the total number of individuals whose sex was successfully identified visually (based on the presence of claspers or external reproductive organs in males), the population in this bay is overwhelmingly dominated by male whale sharks. Female individuals were observed very rarely.
- Ecological Function as a Nursery Ground: The dominance of these small, young males supports the scientific hypothesis that Saleh Bay is not a mating area, but rather functions as a nursery ground where they grow up. The calm physical characteristics of the bay provide natural protection for young whale sharks from large open-ocean predators (such as larger adult whale sharks or killer whales), while also serving as an ideal resting place for them before venturing into the open ocean as adults.
One of the most valuable findings of this study by Konservasi Indonesia is that whale sharks in Saleh Bay exhibit a year-round residency pattern. This phenomenon differs drastically from other aggregation sites around the world (such as Ningaloo Reef in Australia or Donsol in the Philippines), where whale sharks only visit seasonally for a few months each year.
- Symbiosis with Fishermen’s Bagan Activities: The presence of whale sharks in Saleh Bay is heavily influenced by the fixed and floating bagans used by fishermen to catch anchovies. Whale sharks have learned that around the bagan nets, especially during the critical hours just before dawn (5:00 to 9:00 a.m.), there is a very high concentration of food due to the seepage of rebon shrimp (mysid) and small fish that escape the fishermen’s nets. Whale sharks will engage in vertical feeding (sucking water vertically) directly beneath the bagan.
- High Site Fidelity: Using Photo-ID data, researchers found an exceptionally high rate of resightings. The same individuals photographed in 2017 were recorded reappearing repeatedly at the bagan site in 2020, 2021, and 2022. This demonstrates that this group of whale sharks has a strong bond or spatial memory with Saleh Bay as their long-term home range.
4. Population Size Estimation
While 108 unique individuals were physically photographed, marine science recognizes that not all whale sharks surface simultaneously. Using Mark-Recapture statistical modeling, researchers estimate the actual population dynamically utilizing Saleh Bay ranges between 120 to over 150 individuals. This solidifies Saleh Bay as the second-largest whale shark aggregation site in Indonesia, closely following Cenderawasih Bay National Park in Papua.
5. Movement Patterns and Home Range
Vertical Diving: Within the shallow bay, whale sharks spend 70% of their time in the upper 20 meters to forage. However, when venturing into the open sea, these juveniles perform extreme deep dives exceeding 1,000 meters likely searching for meso-plankton and regulating their body temperature after basking in the sun.
Horizontal Migration: While their core home range centers around Labuhan Jambu and Tarano, satellite data shows they periodically leave the bay. They travel hundreds of kilometers across the Flores Sea, Lombok Strait, Bali Sea, and southern Makassar Strait before consistently returning to Saleh Bay, proving these regional waters form a single, vital ecological corridor.
6. Community-Based Ecotourism Valuation
The year-round presence of whale sharks has proven that they are far more valuable alive than hunted. This ecotourism model operates via self-sustained conservation programs in close partnership with traditional fishermen.
Economic Surplus: This specialized tourism generates an average direct turnover of IDR 1.2 billion per year, benefiting locals through boat rentals, homestays, guiding fees, and local food stalls.
Future Projections: Optimizing a single-entry ticketing system could push local revenue to IDR 1.5 billion per year. These funds are recommended to finance community-based marine surveillance (Pokwasmas) and compensate fishermen for nets damaged by the sharks.
Uncover the full financial and conservation impact report here
6. Community-Based Ecotourism Valuation
Currently, only 23% (5,737 hectares) of primary whale shark hotspots in Saleh Bay fall under official legal protection. The remaining 77% leaves the population highly vulnerable to cumulative threats:
Marine Traffic: High risk of collisions with boat propellers from fast tourist boats or commercial fishing vessels.
Overtourism: Uncontrolled visitor spikes lead to poor behavior, such as boats crowding the sharks, camera flashes blinding their sensitive eyes, and engine noise causing acute stress.
Plastic Pollution: As massive filter feeders, whale sharks face a fatal risk of ingesting micro and macro plastics flowing from local river mouths.
8. Final Strategic Solution: Proposed Conservation Area
To mitigate these threats, Konservasi Indonesia recommends accelerating the declaration of a 69,550-hectare Whale Shark Conservation Area in Saleh Bay. This follows the ecological principle of an umbrella species. By strictly protecting the whale shark’s expansive migratory paths, all other marine biodiversity thriving beneath them manta rays, dolphins, sea turtles, dugongs, and coral reefs will automatically be shielded from destructive exploitation. The long-term survival of this paradise hinges on strict adherence to the whale shark code of conduct (maintaining 3 meters from the body, 4 meters from the tail, and strictly forbidding touching). By ensuring these sustainable standards, you actively protect Indonesia’s marine treasures. To experience these natural wonders responsibly, consider planning your journey through an eco-conscious Agensi 17Tour that is deeply committed to preserving the natural heritage of the archipelago.
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