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Study shows krill is important food source for Mobulid Rays

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8 years ago

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A new study by scientists at the Marine Megafauna Foundation (MMF), Large Marine Vertebrates Research Institute Philippines (LAMAVE), the University of Queensland, and Scripps Institution of Oceanography was published in Royal Society Open Science last week, providing novel insights into the food sources of four mobulid ray species found in the Bohol Sea, Philippines.

Mobulids have slow growth and reproductive rates, making them vulnerable to overexploitation. Targeted and incidental fishing continue to cause population declines in various locations worldwide, and, as a result, Manta birostris and Mobula tarapacana have been listed as ‘vulnerable’ on the IUCN Red List of Threatened Species, and Mobula japanica and Mobula thurstoni as ‘near threatened’.

Dietary studies can inform fisheries and help reduce by-catch through the identification of critical feeding areas, where the occurrence of mobulid rays and targeted fishes overlap. For direct, short-term assessment of diet through stomach contents analyses, access to dead specimens is required, which can be challenging for rare or internationally protected species such as mobulids.

For this study, scientists were granted access to a targeted mobulid fishery which operates out of Jagna, Bohol in the Philippines from November to May. Stomach contents of all examined mobulid species were dominated by the krill Euphausia diomedeae (91% of stomachs contained the species), suggesting that this zooplankton species is abundant during this period. The larger mobulids also contained small mesopelagic fishes in their stomachs in addition to krill.

“Our results show that krill can be an important food source for large filter feeders living in tropical seas with surface waters that are low in plankton at the surface during the day. Krill migrates vertically, staying deep during the day and shallow, including at the surface, at night when the mobulids were caught”, commented Dr Chris Rohner, principal scientist at the Marine Megafauna Foundation. “Some mobulids had empty stomachs, while others had just finished a huge meal, which shows that tropical mobulids have a boom-and-bust strategy, feeding in dense prey patches when they are available and then undergo a period of starvation until they find the next prey patch.”

Stomach content studies provide a direct, but short-term snapshot of a species’ diet, while biochemical analyses can provide an indirect, but longer-term view. In 2016, manta ray scientists at the Marine Megafauna Foundation in collaboration with Proyecto Mantas Ecuador published a study using non-lethal muscle tissue sampling and stable isotope analysis, which revealed that Manta birostris found in the waters off Isla de la Plata, Ecuador, largely feed on prey originating from the mesopelagic zone (200 to 1,000 meters below the ocean surface) rather than on surface zooplankton. The new study from the Philippines now provides direct evidence to the theory that large planktivores in the tropics and subtropics heavily feed on mesopelagic migrating prey.

Photo: Gonzalo Araujo, LAMAVE

The Marine Megafauna Foundation was created in 2009 to research, protect and conserve the populations of threatened marine megafauna around the world. ‘Megafauna’ are large marine species such as sharks, rays, marine mammals and sea turtles – marinemegafauna.org

Large Marine Vertebrates Research Institute Philippines (LAMAVE) is the largest independent non-stock non-governmental organization dedicated to the conservation of marine megafauna and their habitats in the Philippines. LAMAVE strive for conservation through scientific research, policy and education -
 lamave.org

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BTM Travel: Your Gateway to Unforgettable Dive Adventures

Published

2 days ago

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December 4, 2024

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dive travel

Who We Are

BTM Travel is a boutique dive travel agency based in Munich, Germany, led by a passionate team of seasoned diving professionals.

  • Marcel Wilpernig, our founder, has explored nearly every corner of the underwater world and brings over a decade of experience in the diving industry.
  • Tim De Deygere, our product manager, made the bold leap from a successful law career to follow his true passion—diving.
  • Simona Hlavova is the backbone of BTM Travel, ensuring smooth operations with her expertise in administration and sales.

While a significant portion of our clientele comes from Germany, our reach extends globally—from Bangladesh to California. BTM Travel is closely connected to Behind the Mask, an underwater videography network that inspires us to bring divers to the world’s most breathtaking ocean destinations.

dive travel

What We Do

BTM Travel specializes in group diving adventures and tailored big animal experiences:

  • Group Travel: We organize intimate trips to premier dive spots, led by expert photographers or wildlife guides for an unforgettable adventure. The vibe? Laid-back and adrenaline-filled.
  • Tailor-Made Trips: For seasoned divers, we craft bespoke itineraries, offering insider tips on where to go, when to go, and what to expect. Our expertise ensures realistic expectations and unforgettable experiences.

Our focus lies on big animal diving, delivering the thrill of encounters with marine giants. While we love macro and reef diving, we know our true strength lies in providing high-octane experiences for adventurers.

What Makes Us Different

We take a fresh look at traditional diving industry practices, challenging outdated habits to better serve modern-day customers.

  • Authenticity First: We only recommend destinations we trust, avoiding overselling places that don’t offer great value or quality.
  • Heartfelt Advice: Our honest approach resonates with clients, building lasting relationships and unforgettable journeys.

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Our Mission

Helping divers explore the places we love is not just our job—it’s our passion. Our goal is to remain small, authentic, and dedicated to delivering exceptional dive travel experiences.

Find Out More

For more information about itineraries, destinations, and bespoke dive adventures, contact BTM Travel:

Email: marcel@behind-the-mask.com

Call: +49 (0) 176 55771225

Website: www.behind-the-mask.com/group-trips

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Dive into Adventure: Limited Space Available for January Socorro Liveaboard Trip with Oyster Diving

Published

3 days ago

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December 3, 2024

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socorro

Socorro Giant Mantas, Sharks and Dolphins – 8-16th January 2025

Oyster Diving is offering an unforgettable opportunity to experience one of the world’s most extraordinary dive destinations – Socorro Island. With only one male space left for this January’s liveaboard adventure, divers are invited to join an exclusive trip to explore the waters of Socorro, renowned for its remarkable marine life and incredible dive experiences.

Unmatched Diving in Socorro

Socorro is home to a unique population of giant oceanic mantas that actively seek interaction with divers and snorkelers, making it one of the best places in the world to encounter these majestic creatures. But the adventure doesn’t stop there – the waters surrounding Socorro are also teeming with marine life, including schooling hammerheads and silky sharks, over 10 other species of sharks, playful bottlenose dolphins that love to interact with divers, large schools of pelagic fish, and, during the season, humpback whales.

Luxury Aboard the Nautilus Belle Amie

Diving in such an extraordinary location is made even more special by the Nautilus Belle Amie. Launched in 2015, this modern, spacious liveaboard yacht is designed with divers in mind, ensuring comfort and luxury throughout the trip. The boat offers various suite options, including twin rooms and superior double suites, all with the ambiance of a boutique hotel. Divers will spend 8 days aboard the Belle Amie, with all meals, guided dives, and soft drinks included.

Pricing and Availability

This exclusive Socorro liveaboard trip is available for the following prices:

  • Twin Room (2 people sharing a Stateroom): £3360 per person
  • Superior Double Suite (2 people sharing): £3860 per person

Both prices include Socorro Island fees. A port fee of $35 is payable upon arrival.

Additional Costs:

  • Return economy flights: Approx. £1,000 – £1,300 per person (prices confirmed prior to booking)
  • One night hotel B&B accommodation before the liveaboard: Approx. £100 per person

Book Now

With only one spot left, this opportunity to explore Socorro’s spectacular underwater world is sure to fill up fast. Interested divers are encouraged to get in touch with Oyster Diving Holidays to secure their place today.

For more information and bookings, please contact:

Oyster Diving Holidays
Phone: 0800 699 0243
Email: info@oysterdiving.com

Don’t miss your chance to dive with mantas, sharks, dolphins, and humpbacks in one of the world’s most pristine marine environments!

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