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Abundance, home range, and movement patterns of manta rays (Manta alfredi, M. birostris) in Hawaiʻi

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Item Summary

Title:Abundance, home range, and movement patterns of manta rays (Manta alfredi, M. birostris) in Hawaiʻi
Authors:Clark, Timothy B.
Keywords:Manta alfredi
Manta birostris
home range
movement patterns
acoustic telemetry
Date Issued:Dec 2010
Publisher:[Honolulu] : [University of Hawaii at Manoa], [December 2010]
Abstract:Sightings data identified two species of mantas using the Kona Coast of the island of Hawaiʻi between 1992 and 2007. The more common species, Manta alfredi, is thought to be a coastal, island associated species due to the 76% resight rate of 105 individuals identified along the coast, versus a 7% resight rate of the 29 pelagic M. birostris. A negative binomial model identified significant effects of site, season, plankton abundance, and tidal phase on manta abundance at two sites. The high occurrence of mantas attracts over 10,000 visitors per year, providing over $4 million annually to Hawaiʻi's economy.
Nine mantas (M. alfredi) were actively tracked using acoustic telemetry to investigate their fine scale movement patterns. Individuals remained within six km of shore, and showed high fidelity to nearshore feeding and cleaning sties. Home range analysis identified a diel cycle between offshore waters, a nearshore cleaning station, a diurnal foraging area, and a nocturnal foraging area. Cycles in productivity likely drive the diel cycle in manta site use.
Long-term movement patterns were investigated using passive acoustic telemetry to track the movements of 5 mantas (M. alfredi) on Maui and 26 on Hawaiʻi. The presence of mantas was monitored at 2 sites on Maui and 33 on Hawaiʻi. No mantas were identified crossing the 47 km wide channel between islands, despite one of the Maui sites being the only known area where mating behavior is regularly observed. Mantas were resident along the coast for up to 1 ½ years, and showed high fidelity to foraging and cleaning areas.
These studies provide the first documentation of two manta species in Hawaiʻi. No study to date has provided as detailed a look at both the fine scale and long term movements of this species. Short term and long term fidelity to specific sites along the coast indicate that efforts to conserve the species would require large marine reserves spanning tens of km and would need to include specific foraging and cleaning sites. Cleaning stations are of special concern as they appear to be a limited resource where the potential for disturbance is high.
Description:Ph.D. University of Hawaii at Manoa 2010.
Includes bibliographical references.
Appears in Collections: Ph.D. - Zoology

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