Date of Award

Winter 12-3-2019

Document Type

Thesis: Open Access

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Brent S. Stewart, Ph.D., J.D

Committee Member

Pamela K.Yochem, D.V.M., Ph.D.

Committee Member

Andrew Nosal, Ph.D.

Committee Member

Zhi-Yong Yin, Ph.D.

Abstract

Though whale sharks (Rhincodon typus) are the largest fish in the ocean there is little known about the species’ life history. Juvenile males are often observed at a number of locations world-wide but adult females, adult males, and neonates are rarely seen. Consequently, important issues like where whale sharks mate and give birth are unknown. Similarly, what geographic and vertical habitats whale sharks use to forage in are similarly poorly known. Seventeen juvenile whale sharks (10 female, 7 male) were outfitted with satellite tags off Ningaloo Reef, Western Australia between 2003 and 2009, and subsequently monitored for 1920 days cumulatively. I analyzed the data acquired from those tags to characterize the sharks’ vertical, thermal, and geographic habitats in the eastern Indian Ocean, and to determine if any differences between females and males in their behaviors might help to explain differences in sightings of them. I found that all sharks moved continually, vertically and geographically, throughout the period that they were monitored. Sea Surface and water column water temperature did not appear to have any causative effects on their movements. Similarly, there were no positive correlations between the movements of sharks and surface phytoplankton productivity. There was substantial variability among sharks in their behaviors. Although there was no significant difference in diving patterns during the day and at night, for all sharks pooled together, males did spend more time at greater depths during the day and at night than did females. I did not find any other significant differences between movements or diving patterns of females versus males. Moreover, the apparent (though not statistically significant) divergence in tracks as well as subtle differences between some females and males where they spent most of their time suggests that additional studies of a larger number of sharks might clarify habitat use and perhaps reveal where female of all ages, neonates, and adult males spend most of their lives and why they are rarely seen.

Available for download on Sunday, January 30, 2022

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