The discovery was made by marine biology PhD candidate Joshua Stewartand colleagues from the National Oceanic and Atmospheric Association’s (NOAA) Office of National Marine Sanctuaries at NOAA’s Flower Garden Banks National Marine Sanctuary.
Stewart, who is also an executive director at the Manta Trust, made the discovery while conducting research on the reef’s manta ray population. He first encountered a juvenile manta at the site in 2016 – a rare encounter in seven years of manta research dominated by adult sightings – and asked marine sanctuary staff if juveniles were regularly seen in the area.
To ascertain juvenile frequency in the area, Stewart and sanctuary staff analysed 25 years of dive logs and photo ID data. Adult mantas can grow to have a wingspan of up to 23 feet; the average wingspan of the mantas at Flower Garden Banks was 7.38 feet. Incredibly, 95% of them were determined to be juveniles.
“This discovery is a major advancement in our understanding of the species and the importance of different habitats throughout their lives,” said Stewart. “The juvenile life stage for oceanic mantas has been a bit of a black box for us, since we’re so rarely able to observe them. Identifying this area as a nursery highlights its importance for conservation and management, but it also gives us the opportunity to focus on the juveniles and learn about them.”
Oceanic mantas are large, plankton-eating rays that live in the open ocean, typically found in subtropical and tropical waters. Baby mantas are almost entirely absent from studied manta populations, making the discovery of a juvenile nursery especially exciting.
Stewart and colleagues write about their discovery in the journal Marine Biology: “Important juvenile manta ray habitat at Flower Garden Banks National Marine Sanctuary in the northwestern Gulf of Mexico.”