A new collaborative study, led by Dr. Sammy Andrzejaczek and Dr. David Curnick, is the first global synthesis of the vertical habitat use by elasmobranchs (sharks, skates and rays). The study compiled diving data from 989 biotelemetry tag deployments on 38 different species including a couple of mobula species.
Different species, and even within the same species, showed large variations in diving patterns. Some species were limited to quite shallow dives like the Common sawshark (Pristiophorus cirratus), Grey reef shark (Carcharhinus amblyrhynchos) and the vulnerable Munk’s pygmy devil ray (Mobula munkiana). Other species on the hand, displayed incredibly deep dives down to over 1,600m deep! These species included the Sicklefin devil ray (Mobula tarapacana), Blue shark (Prionace glauca), and Whale shark (Rhincodon typus).
Understanding how different shark and ray species use the vertical water column is important for their conservation as it helps to inform fisheries management approaches. If a species shows similar depth use across all its range, then generalised management can be used in data-deficient areas, but if there is a lot of variability within a species then conservation measures would need to be locally assessed.
A number of Manta Trust affiliate projects contributed data to this synthesis study with five of the mobula species represented. The study identified geographic and taxonomic biases in tag deployments. It is important we start to learn more about the horizontal and vertical movements of the less understood mobula species soon as seven of the nine currently recognised species are listed as endangered with extinction on the IUCN Red List.
Congratulations to all those involved in this study including but not limited to: the Zoological Society of London, Hopkins Marine Station, Bertarelli Foundation, Stanford University, and Gordon and Betty Moore Foundation.
