Many well-studied elasmobranch populations have recently exhibited significant decline.
The limited data related to fisheries and sightings for many unstudied or poorly
understood populations indicate that these are also suffering. Directed fisheries and more
cryptic threats such as entanglement and vessel strike represent significant risk to
mobulid rays, arguably one of the most vulnerable elasmobranch groups. Very little
information currently exists describing the basic ecology of manta rays or quantifying
anthropogenic threats and impacts; however, recent efforts have drastically improved the
body of knowledge available for these species, including oceanographic influences on
movement, seasonal migration, and mating behaviors. Nevertheless, Red Sea mantas
remain completely enigmatic. In this thesis, Chapter 1 details results from tagging 18 reef
manta rays Manta alfredi in the eastern Red Sea using satellite and acoustic tag
technology and demonstrates that mantas occupy areas with high human traffic. The
combined satellite and acoustic techniques define both regional movements and
‘hotspots’ of habitat use where there is significant potential for manta-human interaction.
I also present opportunistic sighting data that corroborate anthropogenic impacts on this
population. Chapter 2 explores the vertical component of the nine satellite tags that were
deployed on Manta alfredi as described in the previous chapter. Seven tags returned
adequate data for analysis. Three of the seven were physically recovered yielding full
archival datasets of depth, temperature, and light levels every 10-15 seconds for over 2.6
5
million cumulative data points. Mantas frequented the upper 10 m during the day and
occupied deeper water through nocturnal periods. Individuals also exhibited deep diving
behavior as deep as 432 m, extending the known depth range of the species. An
investigation of 76 high-resolution deep dives suggests gliding is a significant behavioral
component of these dives and may provide an efficient mechanism for travel compared to
continuous horizontal swimming. This study is the first to employ satellite telemetry
techniques on Manta alfredi and is the only study directed at mobulids in the Red Sea. A
holistic understanding of these behaviors is essential for developing and implementing
appropriate management techniques, and this work is particularly timely in light of recent
international trade regulation as mantas were listed on Appendix II of the Convention on
International Trade in Endangered Species.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/296217 |
| Date | 07 1900 |
| Creators | Braun, Camrin D. |
| Contributors | Berumen, Michael L., Biological and Environmental Sciences and Engineering (BESE) Division, Jones, Burton, Kaartvedt, Stein |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | 2014-07-01, At the time of archiving, the student author of this thesis opted to temporarily restrict access to it. The full text of this thesis became available to the public after the expiration of the embargo on 2014-07-01. |
Page generated in 0.0018 seconds