Size and structure of a photographically identified population of manta rays Manta alfredi in southern Mozambique

Marshall, A.D., Dudgeon, C.L. and Bennett, M.B. (2011) Size and structure of a photographically identified population of manta rays Manta alfredi in southern Mozambique. Marine Biology, 158 5: 1111-1124. doi:10.1007/s00227-011-1634-6

Author Marshall, A.D.
Dudgeon, C.L.
Bennett, M.B.
Title Size and structure of a photographically identified population of manta rays Manta alfredi in southern Mozambique
Journal name Marine Biology   Check publisher's open access policy
ISSN 0025-3162
Publication date 2011-05
Sub-type Article (original research)
DOI 10.1007/s00227-011-1634-6
Volume 158
Issue 5
Start page 1111
End page 1124
Total pages 14
Place of publication Germany
Publisher Springer
Collection year 2012
Language eng
Abstract The size and structure of a photographically identified population of reef manta ray, Manta alfredi, were examined at aggregation sites over a four-year period in southern Mozambique. The use and standardisation of photo-ID techniques was examined as a minimally-intrusive means to study this species. Using these techniques, we report on the size, structure and seasonality of this population of M. alfredi. In total, 449 individuals were identified during this time period, 40.5% of which were re-sighted on at least one occasion. The longest period between re-sighting events was 1,252 days. During the study period, annual population size estimates for M. alfredi ranged from 149 to 454 individuals. The superpopulation size estimate for the entire study period was 802 individuals, the first reported for M. alfredi at a monitored aggregation site. A highly significant sex bias was evident with a female:male ratio of 3.55:1. The majority of rays (89.9% males; 49.7% females) were considered mature, with most individuals between 3.0 and 4.9 m in disc width. Manta alfredi were observed at the study sites in each month of the calendar year. The maximum number of individual rays seen per dive was 30. Large numbers of rays (20 + per dive) were seen in the months of November, December and January, which coincide with the breeding season. Natural markings were unique to individuals and did not change substantially with time, which provided further support for their use in the identification of individual M. alfredi over multiple years. Multiple re-sightings of individual M. alfredi suggest that many individuals in this population exhibit site fidelity to the examined aggregation sites. As target subsistence fishing for M. alfredi exists along the Mozambican coastline, management efforts to monitor and prevent overexploitation at these critical habitats should be a priority.
Keyword Capture-recapture Experiments
Laser photogrammetry
Sexual segregation
Marked animals
NaturalL markings
Lemon sharks
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2012 Collection
School of Biomedical Sciences Publications
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Citation counts: TR Web of Science Citation Count  Cited 29 times in Thomson Reuters Web of Science Article | Citations
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Created: Tue, 18 Oct 2011, 13:40:04 EST by Bacsweet Kaur on behalf of School of Biomedical Sciences