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

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.

Ensemble modeling of the potential distribution of the whale shark in the Atlantic Ocean

“…Whale sharks migrate over long distances, frequently returning to their area of origin after several years (Robinson, Jaidah, et al, 2017). Thus, whale sharks may perform long-distance migrations to find highly productive feeding areas (Ramírez-Macías, Vázquez-Juárez, Galván-Magaña, & Munguía-Vega, 2007;Sequeira, Mellin, Meekan, Sims, & Bradshaw, 2013).…”

Long-Term Photo-Identification Reveals the Population Dynamics and Strong Site Fidelity of Adult Whale Sharks to the Coastal Waters of Donsol, Philippines

“…The largest of the shark species, whale sharks are highly mobile (e.g., Wilson et al, 2006;Sleeman et al, 2010;Berumen et al, 2014;Robinson et al, 2017), but form predictable seasonal aggregations in hotspots around the world, predominantly associated with the presence of food (e.g., Motta et al, 2010;Robinson et al, 2013;Rohner et al, 2015a). Some whale sharks display a degree of site fidelity on an annual and inter-annual basis (Graham and Roberts, 2007;Holmberg et al, 2008;Fox et al, 2013;Araujo et al, 2017), and this predictability makes the whale shark an ideal target species for wildlife tourism (Catlin and Jones, 2010;Rowat and Brooks, 2012).…”

Observations of stranded and swimming whale sharks Rhincodon typus in Khor Al‐Zubair, NW Arabian Gulf and Shatt Al‐Arab Estuary, Iraq

“…Accordingly, a wide variety of nektonic life is present in these two rich areas. The two small R. typus sighted at the Shatt al‐Arab Estuary were in a nearly vertical position, which is characteristic during feeding time (Motta et al ., ; Robinson et al ., ).…”

“…The stranded specimen was larger than some of the specimens tagged by Robinson et al . () in Qatari waters of the Arabian Gulf, but the two specimens sighted in the Shatt al‐Arab Estuary were much smaller than those studied by Robinson et al . (, ).…”

“…Robinson et al . () stated that within the Arabian Gulf area, sharks prefer to live in depths of 40–60 m. They also showed that R. typus can withstand surface water temperatures of c. 35°, as in the case of Qatar marine waters. No mention was given by Robinson et al .…”