Research Blog

Assessing the impacts of tourism on the world's largest fish Rhincodon typus at Panaon Island, Southern Leyte, Philippines (2017)

Araujo G, Vivier F, Labaja JJ, Hartley D, Ponzo A.

Shark‐based tourism is a rapidly growing industry, particularly with whale sharks, as new hotspots are identified worldwide. Understanding any impacts of tourism is essential to mini- mize any potential detrimental effects on the target species and habitat. In‐water behavioural observations of whale sharks were used to understand any impacts of tourism at a small site in Panaon Island, Southern Leyte, Philippines. A generalized linear mixed model was fitted to test anthropogenic and environmental variables, with interaction duration as the response variable, to assess any disturbance to the animals by the tourism activities. Whale sharks were observed between the months of November and June between 2013 and 2016, with highly variable seasons. In total, 527 tourist‐whale shark interactions were recorded during 359 trips identifying 104 individual whale sharks, most of which were juvenile males (85%, measuring c. 5.5 m total length). Proximity of motorized vessels and interactions in deeper waters were found to significantly shorten interactions. Short‐term behavioural changes were observed in response to human events (e.g. touching). Interactions when whale sharks were feeding were significantly longer than when they were not. Individual behavioural variability was observed. Impacts could be mitigated with small managerial changes and increased enforcement, such as limiting the number of motorized vessels and the number of people around the whale sharks. Although no long‐term impacts were recorded during this study, it is difficult to ascertain this in a long‐lived, wide‐ranging species. This knowledge gap highlights the need to build long‐term monitoring programmes, and to apply the precautionary principle for the sustainable use of this endangered species.

First records of the reef manta ray Manta alfredi in the Bohol Sea, Philippines, and its implication for conservation (2016)

Rambahiniarison J, Araujo G, Lamoste MJ, Labaja J, Snow S, Ponzo A.

We report the occurrence of the reef manta ray Manta alfredi Krefft 1868 in the Bohol Sea, Philippines, based on photographic evidence from boat-based surveys and a fishery specimen. Despite previous anecdotal reports from the diving industry and over a century of extensive targeted fisheries for mobulid rays in the Philippines, it was not until recently that the species was first confirmed in the country at the Tubbataha Reefs Natural Park, Palawan. Our results confirm the presence of M. alfredi in the Visayas region of the Philippines, extending the current range for the species from the Sulu Sea over 600 km eastwards. Its presence in a region with an active mobulid fishery has important implications for the conservation and management of M. alfredi in the country. We highlight the need to understand the distribution of M. alfredi in the region and make management recommendations based on the present study.

​Open access paper here:

Population structure, residency patterns and movements of whale sharks in Southern Leyte, Philippines: results from dedicated photo-ID and citizen science (2016)

Araujo GSnow SSo CLLabaja JMurray R, Colucci A, Ponzo A

The whale shark, Rhincodon typus, is a charismatic umbrella species whose highly mobile nature is not yet fully understood. Whale sharks roam the Philippine archipelago with two major aggregations known to occur at Donsol and at a provisioning site in Cebu. This is the first description of a previously identified aggregation occurring off Panaon Island, Southern Leyte through the use of photographic identification. In total, 93 individual whale sharks were identified, with significant male bias (58%). The mean estimated total length of individuals was 5.72 ± 1.02 m S.D., indicating a juvenile aggregation.
Partial or complete fin amputations, potentially resulting from fishing lines, boat propellers or net entanglement, were observed on 27% of animals, highlighting some of the risks human activities can have on this threatened species. Multiple parallel scars, identified as propeller impact, were observed on 45% of animals. Dedicated research seasons in 2013 and 2014 yielded very different whale shark encounters with 366 in 2013 and 12 in 2014, yet highlighted the recurrence of individuals at the study site. Complemented by data collected through citizen science, maximum likelihood methods were used to model mean residency of whale sharks at Panaon Island of 27.04 days. The modelled lagged identification rate showed that many whale sharks return to the study site over time. Whale sharks from Panaon Island were identified through photo-ID and citizen science at other sites in the Philippines, as well as a match to Taiwan, representing the first international match through photo-ID in South-east Asia with a minimum distance covered of 1600 km.
Given the highly mobile nature and recent exploitation of this species, management is recommended as a single unit regionally in South-east Asia. Additional research is needed to focus on the drivers of variation in encounters at whale shark aggregation sites.

Learning from a provisioning site: code of conduct compliance and behaviour of whale sharks in Oslob, Cebu, Philippines (2015)

Schleimer A, Araujo G, Penketh L, Heath A, McCoy E, Labaja J, Lucey A, Ponzo A.
While shark-based tourism is a rapidly growing global industry, there is ongoing controversy about the effects of provisioning on the target species. This study investigated the effect of feeding on whale sharks (Rhincodon typus) at a provisioning site in Oslob, Cebu, in terms of arrival time, avoidance and feeding behaviour using photo-identification and focal follows. Additionally, compliance to the code of conduct in place was monitored to assess tourism pressure on the whale sharks. Newly identified sharks gradually arrived earlier to the provisioning site after their initial sighting, indicating that the animals learn to associate the site with food rewards. Whale sharks with a long resighting history showed anticipatory behaviour and were recorded at the site on average 5 min after the arrival of feeder boats. Results from a generalised linear mixed model indicated that animals with a longer resighting history were less likely to show avoidance behaviour to touches or boat contact. Similarly, sequential data on feeding behaviour was modelled using a generalised estimating equations approach, which suggested that experienced whale sharks were more likely to display vertical feeding behaviour. It was proposed that the continuous source of food provides a strong incentive for the modification of behaviours, i.e., learning, through conditioning. Whale sharks are large opportunistic filter feeders in a mainly oligotrophic environment, where the ability to use novel food sources by modifying their behaviour could be of great advantage. Non-compliance to the code of conduct in terms of minimum distance to the shark (2 m) increased from 79% in 2012 to 97% in 2014, suggesting a high tourism pressure on the whale sharks in Oslob. The long-term effects of the observed behavioural modifications along with the high tourism pressure remain unknown. However, management plans are traditionally based on the precautionary principle, which aims to take preventive actions even if data on cause and effect are still inconclusive. Hence, an improved enforcement of the code of conduct coupled with a reduction in the conditioning of the whale sharks through provisioning were proposed to minimise the impacts on whale sharks in Oslob.

Check out the full paper:  
photo by Steve de Neef
Whale shark provisioning: first look
This study presents a first thorough look at the whale sharks of Oslob, Cebu. Between March 2012 and December 2013, 158 individual whale sharks were identified at Tan-awan, Oslob. Whale sharks have unique spot patterns that can be used for individual identification. 82% of animals were males, 12% females and 6% of undetermined sex. The average length of whale sharks at Tan-awan was 5.5m. This was validated by the use of laser photogrammetry, where two lasers are mounted on parallel arms, 30cm apart. This known length on a frame can be used to calculate the overall length of the sharks.
We subsequently investigated their residency patterns at Oslob based on one criterion: do they feed from the feeder boats when they visit the site? Based on this behavioural observation, 34% were defined as ‘provisioned’ and the remaining 66% were non-provisioned. We used maximum likelihood methods to model the residency patterns of these two groups, and found contrasting figures. Provisioned individuals reside at the study site more than twice that (44.9d) of non-provisioned individuals (22.4d). Whale sharks were present daily, with a min. of 2 and a maximum of 26 in a single day (mean 12.7). Using citizen science to source whale shark IDs from popular tourist destination sites, we ‘matched’ individual whale sharks across various islands of the Philippines including matches to other whale shark aggregations like Donsol (Sorsogon) and Pintuyan (So. Leyte). Extended residency periods might have an impact on the animals’ movement patterns and management should focus on mitigating these potential impacts on an endangered species.
Population structure and residency patterns of whale sharks, Rhincodon typus, at a provisioning site in Cebu, Philippines (2014)
Araujo G, Lucey A, Labaja J, So C, Snow S, Ponzo A
photos by Gonzalo Araujo | LAMAVE