Movement ecology and foraging behaviours of oceanic manta rays Mobula birostris in the coastal waters of Aotearoa, New Zealand

Understanding the movements and associated behaviours of animals is critical for informed management decisions. This is particularly important for species such as the Endangered oceanic manta ray (Mobula birostris), which has a conservative life history and is therefore vulnerable to population disturbances. Twelve oceanic manta rays were tracked for 9–84 days using high-resolution SPLASH10F-321A/E Fastloc GPS tags during their seasonal presence in northeastern Aotearoa, New Zealand, which indicated broad variation in fine-scale (100 m to 10 km) movements in Tīkapa Moana—Te Moananui-ā-Toi—the Hauraki Gulf and the nearby shelf. While in this region, the tagged oceanic manta rays spent most of their time in surface waters <5 m, with occasional dives up to 365 m. Generalized additive mixed-effect models indicate that movement patterns associated with daytime foraging in the region are linked to northerly winds but inhibited by high wind speeds (10+ ms−1). Dives deeper than 5 m were more frequent at night, and during gibbous moon phases. A key challenge of this study is the lack of knowledge about oceanic manta ray prey composition and distribution: gathering and incorporating this information into modelling is necessary to better understand the movement ecology and behaviours of manta rays at the southernmost part of their range.