Some like it hot: Repeat migration and residency of whale sharks within an extreme natural environment

PLoS One. 2017 Sep 21;12(9):e0185360. doi: 10.1371/journal.pone.0185360. eCollection 2017.

Abstract

The Arabian Gulf is the warmest sea in the world and is host to a globally significant population of the whale shark Rhincodon typus. To investigate regional whale shark behaviour and movements, 59 satellite-linked tags were deployed on whale sharks in the Al Shaheen area off Qatar from 2011-14. Four different models of tag were used throughout the study, each model able to collect differing data or quantities of data. Retention varied from one to 227 days. While all tagged sharks crossed international maritime boundaries, they typically stayed within the Arabian Gulf. Only nine sharks dispersed through the narrow Strait of Hormuz into the Gulf of Oman. Most sharks stayed close to known or suspected feeding aggregation sites over summer months, but dispersed throughout the Arabian Gulf in winter. Sharks rarely ventured into shallow areas (<40 m depth). A single, presumably pregnant female shark was the sole animal to disperse a long distance, crossing five international maritime boundaries in 37 days before the tag detached at a distance of approximately 2644 km from the tagging site, close to the Yemeni-Somali border. No clear space-use differentiation was evident between years, for sharks of different sizes, or between sexes. Whale sharks spent the most time (~66%) in temperatures of 24-30°C and in shallow waters <100 m depth (~60%). Sharks spent relatively more time in cooler (X2 = 121.692; p<0.05) and deeper (X2 = 46.402; p<0.05) water at night. Sharks rarely made dives deeper than 100 m, reflecting the bathymetric constraints of the Gulf environment. Kernel density analysis demonstrated that the tagging site at Al Shaheen was the regional hotspot for these sharks, and revealed a probable secondary aggregation site for whale sharks in nearby Saudi Arabian waters. Analysis of visual re-sightings data of tagged sharks revealed that 58% of tagged individuals were re-sighted back in Al Shaheen over the course of this study, with 40% recorded back at Al Shaheen in the year following their initial identification. Two sharks were confirmed to return to Al Shaheen in each of the five years of study.

MeSH terms

  • Animal Migration*
  • Animals
  • Behavior, Animal
  • Ecosystem
  • Female
  • Hot Temperature*
  • Male
  • Seasons
  • Sharks*
  • Spacecraft

Grants and funding

Logistics for this project were provided by the Qatar Ministry of Municipality and Environment (QMMOE) and, Maersk Oil Research and Technology Centre (MORTC). SB acted as an independent researcher throughout this study with financial support in the form of a salary from the MORTC. The journal publication fees for this manuscript were provided by the North Oil Company (NOC). The MORTC or NOC did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript and only provided financial support in the form of SB’s salary and research materials. DPR’s work on this manuscript was supported by two small grants from the Save Our Seas Foundation. Many thanks to the Save Our Seas Foundation, Al Ghurair Foods and the Emirates Diving Association, Emirates Natural History Group and, Le Meridien Al Aqah Beach Resort for providing financial support for individual satellite tags. Christoph Rohner and Simon Pierce’s contribution to this project were supported by private trusts, the Shark Foundation, Aqua-Firma, and Waterlust.