A new study published in the journal Endangered Species Research has revealed that juvenile whale sharks swim to Madagascar, a newly-identified hotspot for these huge fish, to feed. Eighty-five individual sharks were identified in a single season using photographs of their distinctive spot patterns. An isolated ‘island continent’, famed for animals and plants that exist nowhere else in the world, Madagascar’s nutrient-rich waters are also home to an incredible array of marine life attracting increasing numbers of tourists.
Whale sharks are primarily seen around the small island of Nosy Be, in northwest Madagascar. This area is a globally important hotspot for large marine species, including manta rays, sea turtles, humpback whales and even rare Omura’s whales. The study is part of the Madagascar Whale Shark Project, a collaboration initiated in 2016 by researchers from the Marine Megafauna Foundation, Florida International University, and Mada Megafauna.
Lead author and project leader Stella Diamant said: “We’ve found that whale sharks regularly visit Nosy Be between September and December. That has led to a growing ecotourism industry, as people travel to see and swim with these gigantic, harmless sharks. We’re still learning about their population structure and movement patterns, but it’s clear the area is an important hotspot for the species.”
Whale sharks are the largest fish in the world, growing up to 20 meters long. However, all of the sharks seen in Madagascar have been juveniles of less than nine meters.
“We identified 85 individual whale sharks over our first season in 2016. Some of the sharks were present across several months. They spend a lot of time in the area and seem to come here to feed,” Diamant said.
The marine biologists uploaded photographs of the sharks’ unique spot patterns to Wildbook for Whale Sharks (a global database of sightings) and compared them with data collected from known feeding areas in the Indian Ocean, including Djibouti, the Maldives, Mozambique, Seychelles and Tanzania, but found no overlap.
“Whale sharks are a globally endangered species due to overfishing, accidental catches and boat strikes. Major declines in sightings have been seen in Mozambique, where we’ve documented a 79% decline in sightings since 2005, and the Seychelles. I was hoping that some of those sharks might have shifted over to Madagascar”, said co-author Dr Simon Pierce, co-founder and principal scientist at the Marine Megafauna Foundation.
“Unfortunately, that doesn’t seem to be the case. It’s great news for Madagascar though. These sharks can be a major asset for the country. There’s already a good marine ecotourism industry developing”, he added.
As part of this study, the team attached eight satellite tags to immature whale sharks to track their movements in near real-time. They found that the sharks spent most of their time in shallow waters between 27.5-30°C around the tagging area in Nosy Be.
Half of the tagged sharks also visited a second hotspot near Pointe d’Analalava, 180 km south of Nosy Be. Five of the sharks swam over to Mayotte and the Comoros islands, and two swam right down to the southern end of Madagascar. One of those sharks then swam back to Nosy Be, a total track of 4,275 km. The sharks are slow-swimmers, travelling an average 21 km per day. Three sharks were resighted in the Nosy Be area the following season after having lost their tags.
“It was exciting to see that there is a second hotspot for the sharks in the area. We will be exploring the area later this year. Madagascar clearly provides an important seasonal habitat for these young whale sharks, so we need to ensure they are effectively protected in the country”, concluded Diamant.
Madagascar is a known location for shark fishing and finning. Whale sharks are currently afforded no formal protection except in two Marine Protected Areas located to the southwest and northeast of Nosy Be.
“Over the last decade, shark populations have declined dramatically in Madagascar due to overfishing. However, the most significant threat to this species is the incidental catch in coastal gillnets and industrial purse seiners operating offshore”, said Dr Jeremy J Kiszka, a marine biologist at Florida International University and co-scientific lead of the Madagascar Whale Shark Project.
Whale sharks are listed as ‘endangered’ on the IUCN Red List of Threatened Species since 2016 and received an Appendix I listing the UN Convention on Migratory Species in 2017. As a signatory to the Convention, Madagascar is obligated to protect the sharks and their migratory habitat in national waters.
The study was supported by Les Baleines Rand’eau, Aqua-Firma, PADI Foundation, IDEA WILD, Waterlust, the Shark Foundation, and two private trusts.
Stella Diamant, Christoph A Rohner, Jeremy J Kiszka, et al. ‘Movements and habitat use of satellite-tagged whale sharks off western Madagascar’ was published on 17 May 2018 and is available here.
For more information about Marine Megafauna Foundation please visit:
Images by www.simonjpierce.com
Breaking News: Captain charged in Conception boat fire tragedy
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.
Crossover to NAUI for FREE!
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!
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