Natural or Anthropogenic: Threats faced by Maldivian Manta Rays

2015

Jennifer Stark (MSc Marine Environmental Management - University of York)

Summary: This study aimed to understand the threats to manta ray populations in the Maldives to support conservation efforts. By analysing data from the Maldives Manta Conservation Programme, the researchers used photographic identification to assess injuries observed on individual reef (Manta alfredi) and oceanic (Manta birostris) manta rays. The study found that 23% of identified M. alfredi and 21% of M. birostris showed signs of permanent injury. Adult M. alfredi had more injuries than subadults or juveniles, and injuries were more likely to be of natural origin rather than anthropogenic. This analysis provides valuable information for the Maldivian government to develop management strategies for manta ray preservation.

Abstract

“Manta rays are globally listed as vulnerable, and understanding threats posed to their populations can help aid conservation measures. Manta rays in the Maldives are not directly exploited by fisheries. However, they still bear scars of injuries from both natural and anthropogenic causes. Using data from the Maldivian Manta Ray Project (MMRP) database, obtained from over 30,000 sightings in the past decade, photographic-identification was used to review details of injury observed on individual Manta alfredi and Manta birostris. Through examination of injuries sustained by these individuals, this study has determined the origin of permanent injuries in the Maldivian populations of mantas. Of the 3715 identified M. alfredi individuals in the Maldives, 23% showed signs of permanent injury, whereas 21% of the 169 known M. birostris that were injured. Adult M. alfredi had significantly more injuries than subadults or juveniles (67%, 3%, 30%, respectively: Χ2 = 66.4, df = 2, p < 0.001). Similarly, injuries were more likely to result from threats of natural (n = 471) rather than anthropogenic (n = 338) origin (Χ2 = 10.7, df = 1, p = 0.00108). By understanding the threats faced by local populations of manta rays, this analysis of the MMRP database can provide the Maldivian government with an evidence base of which to develop informed management strategies to help preserve them.”

Author Affiliations