First Insights Into the Horizontal Movements of Whale Sharks (Rhincodon typus) in the Northern Arabian Sea

Lucy M Arrowsmith,Farukhkha Husenkha Bloch,Charan Kumar Paidi,Rahul Kaul,Mark G Meekan,Charitha B Pattiaratchi,Sajan John,Ana M M Sequeira,Binod Chandra Choudhury

doi:10.3389/fmars.2021.682730

Lucy M Arrowsmith, Farukhkha Husenkha Bloch + Show 7 more

Open Access

https://doi.org/10.3389/fmars.2021.682730

Copy DOI

Abstract

Whale sharks off the western coast of India have suffered high levels of fishing pressure in the past, and today continue to be caught in small-scale fisheries as by-catch. Additionally, coastlines in this region host very large and growing human populations that are undergoing rapid development. This exacerbates ongoing anthropogenic threats to this species such as pollution, habitat loss, and ship traffic. For these reasons, there is an urgent need for data on movement patterns of whale sharks in this region of the Indian Ocean. Here, we address this issue by providing the first data on the horizontal movements of whale sharks tagged in the northern Arabian Sea off the western coast of the Indian state of Gujarat. From 2011 to 2017, eight individuals, ranging from 5.4 to 8 m were tagged and monitored using satellite telemetry. Tag retention varied from 1 to 137 days, with the sharks traveling distances of 34 – ∼2,230 km. Six of the eight individuals remained close to their tagging locations, although two sharks displayed wide ranging movements into the Arabian Sea, following frontal zones between water masses of different sea surface temperatures. We explore the relationship between the movement patterns of these whale sharks and the physical and biological processes of the region.

Highlights

The whale shark (Rhincodon typus, Smith 1828) is found in shallow and open ocean locations throughout the world’s tropical and subtropical environments, with known aggregations occurring from the Gulf of Mexico (Hueter et al, 2013) to Ningaloo Reef, Western Australia (Norman et al, 2016)
Our tagging resulted in tracks of different durations, with most lasting
The path of this longer track was consistent with suggestions that whale sharks tend to occupy water masses with temperatures in the range of 24–29◦C and are associated with frontal zones (Sequeira et al, 2012; Ryan et al, 2017)

Summary

Introduction

The whale shark (Rhincodon typus, Smith 1828) is found in shallow and open ocean locations throughout the world’s tropical and subtropical environments, with known aggregations occurring from the Gulf of Mexico (Hueter et al, 2013) to Ningaloo Reef, Western Australia (Norman et al, 2016). The migratory behavior of whale sharks, in combination with their slow growth rates (Meekan et al, 2020) and K-selected life history, make populations highly vulnerable to anthropogenic pressures, such as ship strikes (Speed et al, 2008; Lester et al, 2020), bycatch and targeted fishing (Capietto et al, 2014) and pollution (Boldrocchi et al, 2020). These threats are of particular concern as the species is classified as “Endangered” on the IUCN Red List (Pearce and Norman, 2016). This has motivated satellite tagging programs that seek to identify movement patterns and assist in identifying areas of potential threats to the species (Reynolds et al, 2017; Robinson et al, 2017; Araujo et al, 2018; Rohner et al, 2020) in order to target effective conservation planning (Sequeira et al, 2019)

Methods

Results

Conclusion