Manta Ray Expeditions - A New Zealand First!

March 2023

In late February 2023, Manta Watch New Zealand (MWNZ) joined forces with Northland Dive and embarked on New Zealand’s first-ever oceanic manta ray expeditions. These expeditions utilised MWNZ’s core team’s expertise, sightings data and citizen science networks to survey multiple manta ray hot spots in the Outer Hauraki Gulf.

Each three-day expedition combined both visual open ocean surveys and exploratory SCUBA dives with the aim of locating manta ray feeding aggregations and discovering cleaning stations respectively. Both trips were highly successful, whereby oceanic manta rays were found and expedition guests enjoyed intimate interactions with feeding manta rays.

Researcher swims alongside oceanic manta ray. ©Lydia Green

MWNZ’s Founder Lydia Green and Senior Science Advisor Dr Mark Erdmann facilitated educational presentations and manta swimming activities whilst simultaneously collecting valuable data via drones and underwater cameras. Expedition guests actively contributed to the collection of biological data and identification imagery.

Swimming alongside a melanistic female oceanic manta ray. ©Marc Erdmann

A total of 4 oceanic mantas were encountered, all of which are new additions to the MWNZ national ID database. This included one 4.4m heavily pregnant melanistic female and 3 smaller chevron males. Furthermore, the team successfully deployed 3 satellite tags, 1 short-term Splash10 tag and 2 long-term MiniPat archival tags. The pregnant female was tagged with one of the long-term tags in the hope that upon retrieval this tag data will provide greater insight into this population's reproductive ecology. A key research aim for MWNZ is to determine where heavily pregnant females are giving birth and whether specific pupping grounds and nursery areas exist.

A melanistic female oceanic manta ray. ©Lydia Green

7 exploratory dives were conducted around the Hauraki Gulf on suspected cleaning stations, which consisted of pinnacles and the rocky reefs surrounding several offshore islands. Unfortunately, no manta rays were encountered at depth, however, it was an excellent opportunity for the MWNZ team to scope out these dive sites for future expeditions. The discovery of a cleaning station in the Hauraki Gulf would be an absolute game changer, enabling the team to observe new behaviours and collect data away from active feeding events that can often be quite challenging.

Oceanic manta ray somersault feeding. ©Marc Erdmann

MWNZ intend to run annual expeditions around the Hauraki Gulf coinciding with NZ’s peak manta season and mass feeding events. The team is currently planning a shoulder season expedition in NZ’s Autumn, specifically to search for oceanic manta ray nursery areas.