A RECENT population study of whale sharks in southern Cebu town of Oslob stresses the importance of the area in the conservation of the species.
The research noted that whale sharks in Oslob likely account for 24 percent of the 650 individual sharks identified in the “Wildbook for Whale Sharks” in the Philippines.
The paper, published on the peer-reviewed academic journal www.peerj.com, also highlights the need for further studies to be able to come up with proper management and more effective protection of the species.
Researchers, who are also working with the Large Marine Vertebrates (Lamave) Research Institute Philippines, said that 158 whale sharks were sighted and identified in Barangay Tan-awan, Oslob from March 2012 to December 2013. Of the total, 47 percent or more than 70 have propeller scars caused by small outrigger boats and commercial fishing vessels.
Propeller scars were observed on 51 percent of fed sharks.
The local and international researchers also found signs showing possible changes in the migratory behavior of the whale sharks, as indicated by the length of time that provisioned or fed sharks stay in the area.
Out the 158 sharks, 54 individual whale sharks were fed. They are also the same ones seen more often at the Barangay Tan-awan whale shark tourism interaction area.
The study noted that some of the whale sharks sighted in Oslob were also observed in other areas in Cebu (Moalboal and Malapascua) and in Southern Leyte, Panglao in Bohol and Donsol in Sorsogon.
The researchers pointed out that the percentage of individual sharks with propeller cuts in Oslob is higher compared to that of a whale shark population in Isla Holbox in Mexico, which only has 25 percent.
“Given the high occurrence of propeller scars, propeller guards were highly recommended for operators visiting the study area. Unfortunately none have been implemented yet,” the researchers said.
Risk
Several wildlife conservationists have disapproved of feeding whale sharks, which are supposed to be wary of humans as a defensive behavior.
“The migratory nature of the whale sharks highlights the potential risk that the behavior change induced by the provisioning poses to such migratory nature,” the study states.
“The results of the present study show a significant difference in residency patterns between provisioned and non-provisioned individuals suggesting behavioral modification. This aggregation site is different to any other whale shark site previously identified and described because of the nature of the interaction, where the animals are attracted to the area with food,” the researchers said.
The study also found that 54 individual sharks were found 50 percent during the survey days, which highlighted the potential conditioning the provisioning activities can have on the whale sharks.
Food
Researchers also noted that there is an increase in number of individual sharks coming to the interaction site, showing that other whale sharks have learned how to feed from the feeder boats.
Of the 54 sharks that are fed by tour guides, 49 are males and five are females. Researchers said that based on their size, the sharks in Oslob are young. The biggest is nine meters in length.
While the population of whale sharks visiting Oslob follows a similar structure in terms of size and sex distribution to other populations around the globe, the residency of whale sharks in the southern Cebu town is “considerably higher.”
Researchers concluded that the short- and long-term impacts of prolonged residency in one area for a highly migratory species like the whale shark needs further investigation. They added that there is need to study the environmental impact of the provisioning activities on the area.
They also added that a management plan for the whale sharks must be made to ensure that the provisioning activities in Oslob will be limited to acceptable change.
The researchers also admit that their findings cannot be used to conclude that sharks in Oslob have altered behaviors.