Satellite tracking of juvenile whale sharks in the Sulu and Bohol Seas, Philippines.

Gonzalo Araujo,Simon J Pierce,Christoph A Rohner,Jessica Labaja,Segundo J Conales,Sally J Snow,Ryan Murray,Alessandro Ponzo

doi:10.7717/peerj.5231

Gonzalo Araujo, Simon J Pierce + Show 6 more

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https://doi.org/10.7717/peerj.5231

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Abstract

The whale shark Rhincodon typus was uplisted to ‘Endangered’ in the 2016 IUCN Red List due to >50% population decline, largely caused by continued exploitation in the Indo-Pacific. Though the Philippines protected the whale shark in 1998, concerns remain due to continued take in regional waters. In light of this, understanding the movements of whale sharks in the Philippines, one of the most important hotspots for the species, is vital. We tagged 17 juvenile whale sharks with towed SPOT5 tags from three general areas in the Sulu and Bohol Seas: Panaon Island in Southern Leyte, northern Mindanao, and Tubbataha Reefs Natural Park (TRNP). The sharks all remained in Philippine waters for the duration of tracking (6–126 days, mean 64). Individuals travelled 86–2,580 km (mean 887 km) at a mean horizontal speed of 15.5 ± 13.0 SD km day−1. Whale sharks tagged in Panaon Island and Mindanao remained close to shore but still spent significant time off the shelf (>200 m). Sharks tagged at TRNP spent most of their time offshore in the Sulu Sea. Three of twelve whale sharks tagged in the Bohol Sea moved through to the Sulu Sea, whilst two others moved east through the Surigao Strait to the eastern coast of Leyte. One individual tagged at TRNP moved to northern Palawan, and subsequently to the eastern coast of Mindanao in the Pacific Ocean. Based on inferred relationships with temperature histograms, whale sharks performed most deep dives (>200 m) during the night, in contrast to results from whale sharks elsewhere. While all sharks stayed in national waters, our results highlight the high mobility of juvenile whale sharks and demonstrate their connectivity across the Sulu and Bohol Seas, highlighting the importance of the area for this endangered species.

Highlights

The whale shark Rhincodon typus is the world’s largest fish
Few data are available from this region, though whale shark hunters once operated from Talisayan in Misamis Oriental and in Salay, where ∼100 individuals were landed per year in the 1990’s (Alava et al, 2002), and where Eckert et al (2002) tagged two whale sharks in 1997. Both tagging sites are within the Bohol Sea, a rich ecosystem that reaches >2,000 m depth and hosts 19 species of cetaceans (Ponzo et al, 2011), marine turtles (Quimpo, 2013; Araujo et al, 2016), five species of mobulid rays (Rambahiniarison et al, 2016), and in which whale shark movements have been confirmed through photo-ID (Araujo et al, 2014; Araujo et al, 2017a). (c: ‘‘TRNP’’) Tubbataha Reefs Natural Park (TRNP) has been an offshore no-take marine protected area (MPA) since 1988 and a UNESCO World Heritage Site since 1993
The Sulu and Bohol Seas are an important habitat for whale sharks, with over 500 individuals identified to date in this region (Wildbook for Whale Sharks, February 2018) and where >700 individuals were harvested between 1991 and 1997 (Alava et al, 2002)

Summary

Introduction

The whale shark Rhincodon typus is the world’s largest fish. Most coastal aggregations are dominated by juvenile male sharks (Norman et al, 2017), Cochran et al (2016) reported the first known juvenile 1:1 male to female aggregation in the Red Sea. Recent observations from the. How to cite this article Araujo et al (2018), Satellite tracking of juvenile whale sharks in the Sulu and Bohol Seas, Philippines. Qatar, St Helena and Baja California (Hearn et al, 2016; Robinson et al, 2017; Clingham et al, 2016; Ramírez-Macías et al, 2017) have highlighted that adult sharks are likely to have more pelagic habitat preferences than juveniles

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