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Tourists key to future of rare manta nursery

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Scientists from the Marine Megafauna Foundation and Murdoch University are reporting a large number of juvenile manta rays in the waters of Nusa Penida, a small island 18km southeast of Bali, suggesting the area may be a nursery for this threatened species.

Reef mantas (Mobula alfredi), which grow up to 5m, tend to reside and feed in shallow, coastal habitats. They also visit ‘cleaning stations’ on coral reefs to have parasites or dead skin picked off by small fish. In Nusa Penida, they are present year-round making the Marine Protected Area (MPA) a snorkeling and diving hotspot.

One of the popular dive sites (Manta Bay) described in this new study is predominantly frequented by juvenile males looking for food. Some are as small as 1.5m in disc width on first sighting, providing strong evidence that the site forms part of a nursery habitat and foraging ground for the local reef manta population. Most individuals have been seen repeatedly across multiple years.

Image: Simon Pierce (www.simonpierce.com)

Where manta rays are born and grow up still baffles us. Our research in Indonesia suggests there might be a reef manta nursery in the Nusa Penida area and possibly also in the famous Raja Ampat archipelago”, said lead author Elitza Germanov. “It’s really important for us to know where these nurseries are. They provide a safe space for young, vulnerable manta rays to grow and develop away from the reach of predators.”

Interestingly, mature males and females seem to prefer Manta Point, a second dive site a mere 12 km away. Here, the manta rays are mostly observed visiting cleaning stations and engaging in social activity as well as courtship display during the mating season (peaking in May).

Nusa Penida attracts more than 200,000 tourists each year. Of the 11 main dive spots in these waters, Manta Bay and Manta Point are frequented most by tourism operators, putting the local manta ray population under increasing pressure. While manta rays are protected in Indonesia2, there are currently few regulations in place to manage the growing tourism industry. The number of boats allowed to enter manta ray habitats is not limited and codes of conduct for manta ray interactions are voluntary. The average annual number of boats present at the two manta ray sites has increased by 60% since 2012 and tourism is highest during the mating season.

Germanov commented: “Large diving groups and boat engine noise can cause chronic stress to these vulnerable animals. Tourists may disrupt the foraging, cleaning and mating behavior of manta rays if they get too close, which can have serious implications for their growth and fitness.”

Limiting the number of tourism vessels allowed at one time and making codes of conduct for diving and snorkeling with manta rays mandatory are proposed as a way to minimize the impact from tourism. Seasonal closure of Manta Point could also be considered to protect the manta rays from disturbance during the mating period.

Artisanal fishing poses a further threat to the local population. During the study, 14% of manta rays were either trailing hooks and lines or had injuries and even amputations from fishing gear cutting through their skin and cartilage skeleton. While all fishing activities are officially prohibited in both Manta Bay and Manta Point, the whole west coast of Nusa Penida could be closed off as a precautionary measure.

Dr Andrea Marshall, principal scientist and co-founder of the Marine Megafauna Foundation said: “This is clearly an important habitat for reef mantas. In fact, the resighting rates in the Nusa Penida MPA are higher than anywhere else in the world.

“The two aggregation sites are very close to each other but used for different purposes. We still don’t know much about when and how the mantas move between the feeding, cleaning and mating grounds. Putting the pieces of this puzzle together will help us figure out how to protect these slow-growing animals.

For more information about the work of the Marine Megafauna Foundation visit their website by clicking here.

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Breaking News: Captain charged in Conception boat fire tragedy

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According to reports in the international press today, it has been announced that the Captain of the dive boat Conception, which was completely destroyed by fire last year, resulting in the tragic loss of 34 passengers and crew, has been charged with 34 counts of seaman’s manslaughter. 

The Captain Jerry Nehl Boylan was among five crew members to escape the blaze on board Conception, a dive boat operated by Truth Aquatics, which took place in the early hours of 2 September 2019 whilst the boat was moored offshore, close to Santa Cruz Island off the coast of California.

The BBC reports that Mr Boylan has not publicly commented on the charges, and is expected to surrender to the authorities at a later date. According to the BBC, each charge of seaman’s manslaughter carries up to 10 years in federal prison.

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Crossover to NAUI for FREE!

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As a boost to help the diving industry, NAUI are still offering a FREE Instructor cross-over course together with five free certifications to all Instructors. This can include Open Water, Advance, Rescue, Nitrox and various other specialities and can be mixed and matched so all five do not necessarily need to be for the same certification.

NAUI have also frozen the membership fees for 2021 for instructors crossing over or restarting.

NAUI’s Southern UK Rep Simon Lodge says: “Throughout this year, the diving industry has severely suffered so as a result, to help kickstart the diving industry NAUI will not be charging membership fees 2020/2021 to any new instructors.” 

Founded in 1960, NAUI Worldwide is one of the scuba industry’s largest not-for-profit agencies whose purpose is to enable people to enjoy underwater activities as safely as possible by providing the highest quality practical education, and to actively promote the preservation and protection of the world’s underwater environments. As a pioneer in diving education, NAUI has developed many of the programs and concepts accepted throughout the diving industry. NAUI: A Higher Standard!

For more details please contact Simon Lodge (Southern UK Rep) on simon@europe.naui.org or Craig Warner (Northern UK Rep) on cwarner@europe.naui.org.

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Sharks Bay Umbi Diving Village is a Bedouin-owned resort with stunning views and a lovely private beach. It is ideal for divers as everything is onsite including the resort's jetty, dive centre and house reef. The warm hospitality makes for a diving holiday like no other. There is an excellent seafood restaurent and beach bar onsite, and with the enormous diversity of the Sharm El Sheikh dive sites and the surrounding areas of the South Sinai, there really is something for every level of diver to enjoy.

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