New Genetic Study Finds Reef Manta Rays Stay Close To Home

Manta rays are truly remarkable creatures, with unique physical features that set them apart from other rays. Their coloration is especially captivating, displaying two distinct patterns. The first pattern, known as the chevron, features a mostly black back and a striking white belly. The second pattern, the black color type, showcases nearly all black sides. With their large diamond-shaped bodies, elongated wing-like pectoral fins, gill slits on their undersides, eyes on the sides of their bodies, and wide mouths, it’s impossible to mistake the manta ray for any other animal!

As one of the largest ray species, mantas primarily rely on tiny plankton as their main source of food. Interestingly, they have two intriguing structures called cephalic lobes in front of their mouths, which help channel water into their mouths while feeding. Manta rays truly are extraordinary creatures, easily distinguishable from other rays due to their unique physical features.

Manta rays have a wide distribution around the world, inhabiting tropical, subtropical, and temperate waters. However, their specific habitats vary depending on the species. Giant manta rays (Manta birostris) are often found in offshore and oceanic waters, as well as productive coastal areas like estuaries, inlets, bays, and intercoastal waterways. Reef mantas (Manta alfredi), on the other hand, primarily reside in productive coastal environments, particularly reefs and atolls. Differentiating between these two species involves examining their preferred habitats and coloration patterns. Manta rays typically have pale grey “chevron” shapes on their backs, forming a “Y” shape in reef mantas and a more defined “T” shape in giant mantas. Giant mantas also have a distinguishable lump at the base of their tail, which is absent in reef mantas. Additionally, each manta ray has unique spots on its underbelly for identification purposes. In reef mantas, these spots can be found anywhere on their underside, while in giant mantas, the spots are mainly limited to the belly.

Recent genetic evidence has distinguished reef and giant manta rays as separate species. Belonging to the family Mobulidae, their impressive size and captivating beauty make them popular tourist attractions. Unfortunately, their popularity also exposes them to threats from the exploitation of their gill rakers, putting their survival at risk. In addition to overfishing and habitat degradation, manta rays’ slow reproductive rate makes them vulnerable to population declines.

A collaborative team of scientists conducted a groundbreaking genetic study to understand the genetic distinctions between reef manta rays in Hawaiʻi Island and Maui Nui. The study revealed that there are separate island-specific populations of manta rays, each consisting of only a few hundred individuals. The limited migration between these populations and the tendency of female reef mantas to reproduce near their birthplace have resulted in strong genetic isolation. The small breeding populations on Hawaiʻi Island and Maui Nui make the manta rays particularly susceptible to individual losses. It’s crucial to protect these isolated and vulnerable populations to ensure their survival.

To address these findings, the researchers are actively monitoring the small, island-specific manta ray populations and plan to expand their study to understand gene flow within these groups. A statewide survey is also underway to gather comprehensive data about manta rays across all the islands in Hawaiʻi. Involving the community in conservation efforts, researchers encourage people to report sightings of manta rays on any island to the Hawaiʻi Association for Marine Education and Research and the Manta Pacific Research Foundation. These reports can provide valuable information for ongoing research and help safeguard these precious ocean giants for future generations.