The occurrence of mobulid rays at St Helena Island, Cardno seamount and Bonaparte seamount in the South Atlantic and its significance for conservation

Alistair D.M. Dove,Samantha Cherrett,Annalea Beard,Leeann Henry

doi:10.1186/s41200-021-00214-8

Alistair D.M. Dove, Samantha Cherrett

Open Access

https://doi.org/10.1186/s41200-021-00214-8

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Abstract

Data from 369 sightings of mobulid rays from St Helena Island, Cardno and Bonaparte seamounts in the South Atlantic are summarised. 50 % (183) of sightings were observed from a boat, 48 % (176) of sightings were encountered in water, of which 95 % (168) were whilst actively scuba diving. 2 % (10) of mobulid ray sightings were observed from land. Sightings data indicate that the Chilean devil ray Mobula tarapacana (Philippi, 1892) is a frequent visitor to St Helena and is present all year. We document the first photographic evidence of the presence of oceanic manta, Mobula birostris (Walbaum, 1792) at St Helena. Two solitary individuals were photographed off the north coast of St Helena in June 2018. These sightings confirm previous unverified reports on the species occurrence and extend the known distribution range of M. birostris in the open South Atlantic Ocean to 16°S.

Highlights

St Helena is an isolated volcanic island in the South Atlantic, 1200 miles from southern Africa and 1800 miles from South America
369 sightings of mobulid rays were documented between April 1999 and April 2019. 363 sightings were of M. tarapacana consisting of solitary individuals (67 %, n = 244) and schools of up to 14 (33 %, n = 119)
Four sightings were of unidentified mobulid species and two sightings were of oceanic mantas M. birostris

Summary

Introduction

St Helena is an isolated volcanic island in the South Atlantic, 1200 miles from southern Africa and 1800 miles from South America. Mobula tarapacana and M. birostris have a circumglobal distribution, occurring in tropical, subtropical and warm temperate waters. Both species are currently classified as threatened under the IUCN red list (Pardo et al 2017; Marshall et al 2011). M. tarapacana were first mentioned occurring at St Helena by Wirtz et al (2014), this species has only recently has been formally confirmed (Brown et al 2019), despite anecdotal records of mobulids occurring as early as 1987 (Edwards et al 1987; Edwards 1993; Edwards 1990).The closest records of M. birostris to St Helena are 1930 km north west at

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