PHL waters ‘incredibly important’ for juvenile whale sharks–study
For juvenile whale sharks—or at least to a few which scientists were able to observe—the Sulu and Bohol Seas and the waters in between are important feeding grounds.
A globally endangered species, the behavior of whale sharks, locally called butanding, largely remains a mystery.
Scientists studying their behavior continue to work to demystify these gentle giants, even as governments have recently agreed to step up the effort to protect and conserve them.
The Philippines is known to promote whale shark interaction as a tourist attraction, particularly in Donsol in Sorsogon and Oslob in Cebu, where the largest congregation of whale sharks have been observed in the past.
The authors of the study, entitled “Satellite tracking of juvenile whale sharks in the Sulu and Bohol Seas, Philippines,” include Gonzalo Araujo, Sally Snow, the executive directors of the Large Marine Vertebrates Research Institute Philippines (Lamave) and Chris Rohner and Simon Pierce of the Marine Megafauna Foundation (MMF).
Satellite-tag study
Last month scientists from Lamave, MMF and Tubbataha Mangement Office announced the result of a scientific study on satellite-tagging whale sharks in the Philippines.
Lamave is the largest independent nonprofit, nongovernment organization solely dedicated to the conservation of marine megafauna and their habitats in the Philippines.
The study, published in the journal PeerJ, was the most complete tracking study of whale sharks in the Philippines to date, with satellite tags deployed on individuals in multiple sites.
The study has contributed to what is currently known about whale sharks in the Philippines and Southeast Asia. It shows that the Philippines is an incredibly important area for juvenile whale sharks.
But the proponents of the study said more research is needed to understand the location and movements of adult whale sharks.
Whale shark hot spot
An important hot spot for whale sharks, the Philippines hosts the third-largest known population of whale sharks.
While the species has been protected in the Philippines since 1998, globally it was uplisted in 2016 to “endangered to extinction” in the International Union for Conservation of Nature Red List of Threatened Species.
The reason: population decline of more than 50 percent largely caused by continued exploitation in the Indo-Pacific area, the proponents of the paper said in a July 24 statement to the press.
In Southeast Asia concerns remain due to continued fishing in regional waters.
The proponents of the study believe that understanding the movements of whale sharks in the Philippines is vital if we are to identify conservation priorities for the species.
Spot5 satellite tags
In the study, 17 whale sharks were tagged with Wildlife Computers Spot5, or the French Satellite Pour l’Observation de la Terre (Satellite for the Observation of Earth) tags in three different locations in the Philippines: Panaon Island (Southern Leyte), Northern Mindanao (Misamis Oriental and Surigao del Norte) and Tubbataha Reefs Natural Park (Palawan). Tagging took place between April 2015 and April 2016.
All tagged whale sharks were juveniles, ranging in size between 4.5 meters to 7 meters; 73 percent of them were male.
“By attaching Spot5 satellite tags to the sharks, the team was able to follow the movements of juvenile whale sharks in near real time. The tags work by communicating with passing Argos [Advanced Research and Global Observation Satellite], transmitting a location when the wet/dry sensor is triggered when a tagged whale shark breaks the surface,” the study said.
Transmission tags were tethered to a whale shark by a 1.8-meter line.
Tracking results
The tracks from the tags revealed that all whale sharks stayed within the Philippines over the tracking period, emphasizing the importance of the archipelago for the species, the study revealed.
The longest track observed was from a whale shark originally tagged in Tubbataha Reefs Natural Park, which appeared to swim through the Sulu and Bohol Seas and into the Pacific, a journey accumulating over 2,500 km in length.
“While whale sharks are not known for their speed, results revealed that one individual whale shark was averaging 47 km a day, further emphasizing the species’ mobile tendencies,” the study added.
Araujo, the lead author of the paper, explained: “This research highlights the high mobility of whale sharks, even juveniles, and the need for broader-scale management and conservation plans for this endangered species.”
Conservation priorities
So far, dedicated research by Lamave and citizen scientists has identified over 600 whale sharks in the Sulu and Bohol Seas, yet the proximity of this population to fisheries in the broader region (South China Sea) means it is vital to monitor this population as a whole to understand if this population is in recovery or continuing to decline.
“Identifying threats and mitigation strategies is a conservation priority for the species. Lamave continues to study whale sharks in five key areas in the Philippines, working with local and national governments, as well as collaborating organizations to develop conservation strategies for this iconic species,” he said.
Further study needed
In an e-mailed response to the BusinessMirror, Snow, one of the study proponents, said further study of the behavior of whale sharks is needed.
They admitted that because the study was for a limited time only with the tags having attached for a short period, they cannot say for sure whether the observed whale sharks would stay in Philippine waters.
However, they suggested that since the Philippines is an important feeding area for whale sharks, with rich upwellings of food, the juvenile sharks found near the coast often aggregate to feed and the sharks’ movements may be between feeding sites.
Unknown behavior
The normal behavior of a whale shark remains unknown because of the limited study conducted about them. Studies should cover the entire life cycle of the species if to be able to really know what is a “normal behavior” of the species, the study proponents said.
They said it is also inconclusive to say that feeding the observed areas is part of their so-called normal behavior of the species
“Scientists are still trying to answer many questions about whale sharks, including where they reproduce, where they give birth and how far they travel,” they said in the press statement.
Crossing borders
However, different studies have shown that some whale sharks have swum between international borders, while others have found that some have stayed within one region.
However, this information was limited to the time the sharks are tagged and only gave the scientists an insight into their behavior during that time of six months, and not for their entire life.
“For this reason, we can’t really call it ‘normal behavior’ as we are still investigating what normal behavior is,” they said.
In search for food
They added, however, that whale sharks may be making large-scale movements in search for food, or in the case of the adults, they could also be moving to different areas to reproduce.
Scientists are still investigating the answer to the questions on the behavior of this mysterious species.
As the study only recorded the movements of some individuals for a limited period, the proponents of the study could not ascertain how long the whale sharks stay in the Philippines.
Besides, they said a lack of baseline data for comparison prevents them from making a conclusion.
“What we found out was that the juvenile whale sharks we tagged for this study, stayed within Philippine waters. So at least for these individuals at this stage of their life, the Philippine waters are important,” they said.
What makes the Philippine waters unique?
The Philippines lies at the heart of the Coral Triangle, the global center of marine biodiversity. It is an incredibly important area for marine life and hosts a huge number of species, including the whale shark.
‘Butanding’ conservation leader
Since whale sharks have been protected in the Philippines since 1998, the proponents of the study believe that the Philippines is already a leader in whale shark conservation.
“The biggest threat lies outside Philippine boundaries where whale sharks are not protected. The findings from this study contributed to what we already knew about the butanding here and helped us create effective conservation strategies for the species, by identifying key hotspots or movement corridors,” they said.
Further research, they reiterated, is needed to investigate if whale sharks move outside the country’s boundaries. Such information will be a key to creating better international protection.
More protection needed
As the whale shark is protected, the best way people can ensure they contribute to the shark’s protection is by supporting sustainable whale shark-tourism initiatives, which have strict guidelines and interact with the sharks in the natural environment.
Another way is by keeping the oceans clean by reducing plastic use and engaging in cleanup activities, adding that marine life needs healthy oceans.
More important, to help protect the whale shark, various stakeholders should report any whale shark stranding or incidents with fishing gear to the Department of Environment and Natural Resources, and concerned local government units “so teams can ensure the safe return of the animal to the sea.”
source: https://businessmirror.com.ph/phl-waters-incredibly-important-for-juvenile-whale-sharks-study/
By freedivinguae