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Giant manta rays found to be predators of the deep ocean

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A new scientific study by the Marine Megafauna Foundation (MMF), the University of Queensland (UQ) and Proyecto Mantas Ecuador has been published in Royal Society Open Science today, providing novel insights into the food sources of giant manta rays found in the eastern equatorial Pacific.

The giant manta ray (Manta birostris) is a filter-feeding and highly migratory marine species found in tropical and temperate waters worldwide. The large majority of existing information about the species’ diet is based on observational data limited to feeding activities at the sea surface during daylight at well-known aggregation sites.

This new study focused on Isla de la Plata, an island off Ecuador, which seasonally hosts the largest known aggregation of giant manta rays in the world. Manta ray muscle and surface zooplankton were examined through stable isotope analysis, and revealed that the species’ dietary intake largely comes from the mesopelagic zone (200 to 1,000 meters below the ocean surface) rather than from surface zooplankton as previously thought.

MMF’s manta ray researcher Katherine Burgess, who authored this study as part of her PhD project at the University of Queensland, commented: “Manta rays are one of the most iconic marine animals, yet we still know very little about their feeding habits. The study reports much-needed information on the diet of this elusive species.”

katherine-burgess-taking-a-tissue-sample-of-a-giant-manta-ray-in-ecuador-copyright-andrea-marshall

Katherine Burgess taking a tissue sample of a giant manta ray in Ecuador. Copyright: Andrea Marshall

“We studied the giant manta rays’ diet using biochemical tests, such as stable isotope analysis, which work on the ‘you are what you eat’ paradigm. These tests can determine what animals have been eating by examining a piece of tissue from a muscle biopsy from a free-swimming animal,” she added.

Professor Anthony Richardson, a scientist with UQ’s School of Mathematics and Physics and the CSIRO’s Oceans and Atmosphere Flagship, said: “The research found an average 27 per cent of the giant manta rays’ diet comes from surface zooplankton and 73 per cent from mesopelagic sources including fish from 200m to 1,000m below the ocean surface.”

“The deep ocean is the next frontier for open ocean fisheries, and we are only just realizing the potential reliance on this zone by threatened marine megafauna,” he added.

Giant mantas are known to dive to depths of over 1,000 meters making it difficult to study their feeding ecology. To determine the diet of a fish, researchers normally examine its stomach contents. However, this is usually a distressing or lethal procedure and would not be appropriate considering global manta ray populations have been in drastic decline due to anthropogenic threats such as targeted fishing or bycatch, pollution and habitat destruction.

Both species of Manta – the giant manta ray (Manta birostris) and reef manta ray (Manta alfredi) – are listed as ‘vulnerable to extinction’ on the IUCN Red List of Threatened Species. To date, manta rays are formally protected in Ecuador, Peru, New Zealand, the USA (Florida, Hawaii and Flower Garden Banks), Guam, Maldives, Yap, Indonesia, the Philippines and Mexico only. Filling the knowledge gaps on manta ray feeding ecology is crucial for the identification of critical habitats and aggregation sites, which are vital for developing effective conservation measures for these species.

marinemegafauna.org

science.uq.edu.au

mantasecuador.org

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Mares & SSI launch new promotion

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SSI expands financial support to SSI Members worldwide. 

2020 has been an unusual and challenging year for the entire world, especially the diving and travel industry!  To weather the crisis, SSI immediately jumped into action to help Training Centers and Professionals around the world.  

In response to COVID-19, SSI launched the No Water, No Problem Campaign, put Final Exams online, and held hundreds of Webinars to train Professionals on how to use distance learning to teach the dry Specialties online. The FREE SCIENCE OF DIVING promotion resulted in SSI Training Centers worldwide register over 50,000 FREE DIGITAL KITS, funding more than $3.5 MILLION IN RETAIL VALUE. Additionally, SSI introduced an aggressive DOUBLE PRO REWARDS incentive to help SSI Professionals compensate 2020 Renewal Fees and reduce those for 2021. Currently, the WE WANT YOU Crossover promotion aims to fill the industry need for instructors and strengthen the entire SSI Professional community.

Now, in conjunction with Mares, SSI is launching the GO DIVING – PROTECT YOURSELF. OWN EQUIPMENT Promotion, which includes a FREE SSI EQUIPMENT TECHNIQUES DIGITAL KIT. This new campaign strives to motivate divers worldwide to go diving and buy equipment. Look for more information on this next retail support campaign within the next few days.

“These are just a few examples of how we have supported and are continuing to support our Training Centers, Professionals, and divers worldwide. To provide even more economic security and help in business recovery, WE WILL NOT INCREASE PRICES FOR 2021. While travel was restricted and some key resort areas completely locked down, SSI mainly focused on supporting domestic markets with retail-driven incentives. Now, in this next re-opening phase, we need to shift gear and assist resort markets that have no local diving community and are 100% dependent on the traveling diver. Therefore, SSI will grant certain special conditions and delayed payment options to specific resort markets which have been locked down for longer than six months or suffered from closed borders,” stated Guido Waetzig, SSI CEO.

Guido Waetzig, SSI CEO, explains further, “To financially support these needed investments which directly benefit SSI Members and to protect the health of our valuable members and staff, we will forego all 2021 Trade Shows over the next 12 months. Despite international uncertainty, every time we experience one of these events, the entire SSI Network emerges stronger and more resilient. Be assured, SSI is your trustful partner within the Diving Industry!”

For more information about SSI visit their website by clicking here.

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Photo Gallery: Shark Diving in The Bahamas

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In our Gallery feature, we let the photos tell the story… Each Gallery showcases a selection of outstanding images on a chosen theme, taken by our Underwater Photography Editor Nick and Deputy Editor Caroline of Frogfish Photography. This time they look at Shark Diving in The Bahamas.


The Bahamas offers some of the very finest shark diving experiences in the world. The islands have protected sharks in their waters creating one of the first Shark Sanctuaries in the world. Several species of shark can be seen and photographed, with each island offering a different type of shark diving, making this destination the perfect place for a multi-island, multi-shark trip of a lifetime.

Great Hammerhead Shark diving in Bimini

Bull Sharks in Bimini

Tiger Shark off Grand Bahama

Oceanic Whitetip Shark off Cat Island

Nurse Shark off Abaco

Caribbean Reef Sharks off New Providence

Lemon Sharks off Grand Bahama

For more images from The Bahamas and around the world, visit the Frogfish Photography website by clicking here.

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