Search

The Alfred manta, Manta alfredi, is economically important in the Maldives due to the large number of tourists attracted to SCUBA dive and snorkel with them. It is important to understand the size of populations around main diving points and throughout the Maldives so that manta based tourism activities can be developed more successfully and the impact of tourism can be monitored. Using natural markings to identify individual manta rays, Petersen and Jolly-Seber probabilistic estimators were used to assess population size for main dive sites and the central atolls of North Male, Ari and Baa. Between 2000 and 2009, 1835 individual mantas were identified from 3373 sightings. There was a significant gender bias with a male: female ratio of 1:1.8. Only 24.7% of manta rays were re-sighted between 1 and 34 times with a maximum gap of 7 years and 11 months between sightings. Estimates for populations around main dive sites were 181–562. The estimated population of M. alfredi for North Male atoll is 537 (SE ± 53.2). Estimated atoll populations were extrapolated to obtain an estimate of Manta alfredi population for the entire Maldives of 9,677 individuals.

Despite the worldwide distribution of manta ray (Manta alfredi) in tropical and subtropical regions, there is very little published information on their biology or ecology. Knowledge of the abundance of mantas and their migration patterns is essential for conservation, and the first stage in any study is a method to identify individuals. The purpose of this paper is to present a method of visual identification of individuals of manta which can be used at any site where mantas are regularly observed. In mantas, each individual has a characteristic pattern of dark markings on the ventral side. The most important individual identifying marks are patterns of ovals in the area between the gill slits, supported by distinctive patterns of mottles and spots in the lower abdominal area (posterior to the gill slits) and areas of dark pigmentation around the head and posterior wing margins. Significant changes in ventral makings have not been observed in observation periods exceeding 5 years. Scars and miss...