Abstract
Manta rays (Genus Manta) are economically important for fisheries and tourism in Indonesia. These species have been listed by the International Union for the Conservation of Nature Red List as Vulnerable to extinction; therefore, human exploitation of manta rays must be regulated. A better understanding of the habitat use and movement patterns of manta rays in Indonesia is needed in order to employ effective conservation measures. To gain better insight into the movements of Manta alfredi we used ‘Manta Matcher’, an online database with an integrated automated matching algorithm, to compare photographs from 2,604 encounters of M. alfredi collected by recreational divers and dive operators throughout Indonesia over a nine-year period. This photographic comparison revealed that manta rays migrated between regional sanctuaries such as Nusa Penida, the Gili Islands, and the Komodo National Park (up to 450 km straight-line distance). The areas between these sanctuaries are heavily fished and trafficked by ships, and when manta rays travel through these regions they risk being fished and injured by ship strikes. These long-range manta ray movements suggest connectivity between M. alfredi populations in neighboring islands and raise concerns about the future management of regional populations. It is recommended that a national conservation strategy be developed to protect the remaining populations in the country.
Highlights
Manta rays are large pelagic filter-feeding, elasmobranchs that are economically important for both tourism [1] and fisheries throughout many parts of their range [2,3]
Manta rays are classified as Vulnerable to extinction according to the International Union for Conservation of Nature (IUCN) Red List [4,5] due to their slow growth rates, low fecundity [6] and globally rising pressure from fisheries [3,7]
Identified Individuals A total of 820 -individual M. alfredi were identified from 2,604 sightings within the Nusa Penida (NP), WM & K and Raja Ampat (RA) regions of Indonesia between 2006 and February 2014 (Figure 1)
Summary
Manta rays (genus Manta) are large pelagic filter-feeding, elasmobranchs that are economically important for both tourism [1] and fisheries throughout many parts of their range [2,3]. Manta rays aggregate at many locations within the Indonesian archipelago [3,7,8]. Indonesia has the fourth highest number of known tourism sites for viewing manta rays worldwide and rates as one of the top countries in the world for manta ray watching tourism [1]. Manta ray tourism in Indonesia is valued at over $15 million USD per year [1]. Indonesia has some of the most aggressive targeted fisheries for manta rays [2,3,9,10]. Fisheries most negatively impact the sizes of manta ray populations [1,3]. The reduced number of manta rays will likely negatively impact the burgeoning manta ray tourism industry [1]
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