Mark Deakos, Ph.D.
- Monitor population sizes and trends with photo-ID.
- Describe the genetic stock structure of Hawaii’s manta ray populations.
- Describe age-related growth by combining photo-ID and photogrammetry on known-aged manta rays.
- Identify and describe critical habitats with acoustic tracking.
Project Start Date:
The Hawaii Association for Marine Education and Research (HAMER) is a not for profit organization dedicated to protecting Hawaii’s marine resources. Through its Manta Ray Ambassador Program, efforts are ongoing to better understand and protect manta ray populations in Hawaii through bona fide research and effective education. Project goals include monitoring the status and habitat needs of manta rays in the Hawaiian archipelago and mitigating against anthropogenic threats that can negatively impact these fragile populations.
Why this is Important:
Each year, thousands of tourists flock to the Big Island of Hawaii to dive with manta rays generating millions of dollars in revenue for this small community. In addition to their economic value, manta rays captivate the hearts and minds of people all over the world, raising awareness about our rapidly depleting ocean resources. This makes manta rays great ambassadors for our oceans. When manta ray populations are small, with distinct, island-associated breeding stocks as they appear to be in Hawaii, their slow growth, late maturity, and low fecundity make them extremely vulnerable to even small impacts on their populations. Without a clear understanding of their behavior and biology, these populations could rapidly become depleted. Although protected by law against being captured or killed in Hawaii, anthropogenic threats such as habitat loss, entanglement in fishing or mooring lines, boat strikes, and human disturbance can pose a constant threat. The more we understand about how manta rays live and how they use our oceans, the more effective we can be at protecting them for future generations to enjoy. Raising awareness about these majestic and graceful giants is critical to their survival.
Kona’s iconic manta rays have been greeting divers off the West coast of the Big Island for over 30 years. But 100 km to the northwest resides a population of about 350 manta rays in waters off the island of Maui. Thus far, the Maui population appears to be distinct from those in Kona and has been the main focus of our research since 2005. Using research techniques such as photo-identification, paired-laser photogrammetry, acoustic tracking, and behavioral analysis, we have increased our understanding of the population and reproductive ecology of reef-associated manta rays. To better understand how unique Hawaii’s manta rays are, comparative research is being carried out with populations at Palmyra Atoll (1000 km south of Hawaii), and the Marianas (6000 km west of Hawaii).
- Continue to monitor the population size and trend of Hawaii’s manta ray populations.
- Through genetics, describe the inter-island connectivity between neighbouring island populations.
- Explore and identify important feeding, cleaning, mating, and pupping habitats for manta rays throughout Hawaii.
- Describe the social dynamics of reef-associated manta rays.
- Develop an age-related growth curve for reef-associated manta rays.
- Mitigate against the loss of critical manta ray habitat from coastal development through education and policy changes.
- Mitigate against manta ray entanglement in fishing gear by identifying high risk areas and educating fishermen.
- Mitigate against harassment from swim-with manta ray programs through education and the implementation of codes of conduct.
- A doctoral dissertation describing the ecology and social behaviour of manta rays in Maui.
- Paper describing how paired-laser photogrammetry can be used as an effective tool to measure free-ranging manta rays.
- Paper describing the population structure and size of Maui’s manta ray population with a quantification of natural and anthropogenic threats.
- Paper describing the reproductive ecology of Maui’s manta rays including seasonal patterns, pregnancy rates, size at sexual maturity, and mating strategies.
- In collaboration with Manta Pacific Research Foundation, establishment of a law protecting manta rays in Hawaii from being captured or killed.
Partners & Sponsors:
Without the generous, collaborative support from our partners we would not be able to effectively carry out our work. We are very grateful to these organisations for their support.