Marine Life & Conservation Blogs
Creature Feature – Megamouth Shark
A rare and mysterious species, the Megamouth Shark Megachasma pelagios was first sighted when one had gotten entangled in a sea anchor (Oceana, 2023), and hauled up by fishermen on-board a navy ship in 1976 (Black, 2014). The Megamouth Shark is distributed worldwide in tropical to temperate latitudes, can be found in costal to open ocean (epipelagic to bathypelagic), and is a filter feeder, like that of the Whale, and Basking Shark (Oceana, 2023).
Upon its first discovery, this genus of shark generated its own taxonomy, Order Lamniformes (mackerel sharks), and belongs to the family Megachasmidae (megamouth sharks) (Oceana, 2023). Currently this shark is listed as least concern on the IUCN Red List, with the most recent assessment of species health being in 2018 (IUCN Red List, 2023). The Megamouth Shark can be found resident in countries such as Australia, Sri Lanka, Vietnam, South Africa, and China, with the current population number of sharks being unknown due to their rare sightings, and lack of research (IUCN Red List, 2023).
A large species of shark, reaching weights of up to 2700 pounds (1215kg), and approximately 16 feet in length (5m), this species has only been observed within the wild a few times, with less than 60 individual sharks having been known by scientists to of ever been captured or observed (Oceana, 2023). The smallest of the three species of filter-feeding sharks, this shark derived its name from its remarkably large, circular mouth (Oceana, 2023). From what little research has been carried out on the species, from the rare few sightings these sharks have been observed residing near to the surface, in depths of up to 15,000 feet (4600m) (Oceana, 2023).
It is believed that Megamouth sharks only come near to the surface at night, spending the majority of their lives in the dark (Oceana, 2023). They are filter feeders that swim through the ocean with their mouths open capturing food resources, such as plankton (Oceana, 2023). The inside of their mouths contain light producing organs, believed to be used for attracting pelagic crustaceans and other prey (Oceana, 2023).
With commercial fisheries pushing to deeper depths to discover new species to market as food, more and more large deep sea creatures are being discovered (Oceana, 2023). Like other species of shark, megamouths mate via internal fertilization, giving birth to a small number of live young (Oceana, 2023). The adult shark does not connect to their live young through a placenta, and instead the mother provides an unfertilized egg during gestation (Oceana, 2023). Once born, the megamouth shark immediately becomes a filter feeder (Oceana, 2023). There is a huge lack in species behavioral ecology, and richness, and so electronic tagging studies and further research is needed in order to better understand, and to conserve this species (Watanabe & Papastamatiou, 2019).
SCIENTIFIC NAME: Megachasma pelagios
FAMILY: Megachasmidae
MAXIMUM SIZE: Up to 5.5 meters (18 feet) in length
DIET: Filter feeds for plankton, but also consumes deep water fish
DISTRIBUTION: Widespread distribution in tropical and temperate waters worldwide
HABITAT: Ocean-going. Surface to deep waters – 1,000m.
CONSERVATION STATUS:
Due to its elusive nature and rare sightings, little is known about its population size or trends. It is occasionally caught as bycatch in fishing gear, but there are no known directed fisheries for this species.
Banner image – Wikimedia Commons | GordonMakryllos
References:
- Black, R. (2014) A forgotten fossil megamouth gets a name. National Geographic. Available at: https://www.nationalgeographic.com/science/article/a-forgotten-fossil-megamouth-gets-a-name. Accessed: 21st March 2023.
- IUCN Red List. (2023) Megamouth Shark. IUCN Red List. Available: https://www.iucnredlist.org/species/39338/124402302#taxonomy. Accessed: 21st March 2023.
- (2023) Megamouth Shark. Oceana. Available at: https://oceana.org/marine-life/megamouth-shark/. Accessed: 21st February 2023.
- Watanabe, YY, Papastamatiou, YP. (2019) Distribution, body size and biology of the megamouth shark Megachasma pelagios. J Fish Biol. 95: 992– 998. https://doi.org/10.1111/jfb.14007
This month’s Creature Feature has a guest writer – Jodie Moore
Blogs
The Ocean Cleanup Breaks 10,000,000 KG Barrier
The Ocean Cleanup, the global non-profit project, has removed a verified all-time total of ten million kilograms (22 million lbs.) of trash from oceans and rivers around the world – approximately the same weight as the Eiffel Tower.
To complete its mission of ridding the oceans of plastic, The Ocean Cleanup uses a dual strategy: cleaning up the Great Pacific Garbage Patch (GPGP) to remove the plastic already afloat in the oceans, while stopping the flow of plastic from the world’s most polluting rivers.
Through cleaning operations in the GPGP and in rivers in eight countries, the cumulative total of trash removed has now surpassed ten million kilograms. This milestone demonstrates the acceleration of The Ocean Cleanup’s impact, while underlining the astonishing scale of the plastic pollution problem and the need for continued support and action.
While encouraging for the mission, this milestone is only a staging point: millions more tons of plastic still pollute our oceans and The Ocean Cleanup intends to continue learning, improving and innovating to solve this global catastrophe.
This announcement comes as governments from around the world meet to continue negotiations to develop a new legally binding instrument to end plastic pollution at INC4 in Ottawa, Canada. Representatives of The Ocean Cleanup will be in attendance and the organization will be urging decision-makers to collaborate towards a comprehensive and ambitious global treaty which addresses plastic at all stages of its life cycle and in all marine environments worldwide, including in areas beyond national jurisdiction.
It is encouraging to see that the need for remediation is reflected in the various options for potential treaty provisions. It is essential that the final treaty contains clear targets for the remediation of legacy plastic pollution, and reduction of riverine plastic emissions.
Tackling plastic pollution requires innovative and impactful solutions. The treaty should therefore incentivize the innovation ecosystem by fostering innovations that make maximal use of data, technology and scientific knowledge – such as those designed and deployed by The Ocean Cleanup.
‘After many tough years of trial and error, it’s amazing to see our work is starting to pay off – and I am proud of the team who has brought us to this point.’ said Boyan Slat, Founder and CEO of The Ocean Cleanup. ‘While we still have a long way to go, our recent successes fill us with renewed confidence that the oceans can be cleaned.’
The Ocean Cleanup was founded in 2013 and captured its first plastic in 2019, with the first confirmed catch in the GPGP coming soon after the deployment of Interceptor 001 in Jakarta, Indonesia. After surpassing one million kilograms of trash removed in early 2022, the non-profit project has since progressed to the third iteration of its GPGP cleaning solution, known as System 03, and a network of Interceptors currently covering rivers in eight countries, with more deployments set for 2024.
About The Ocean Cleanup
The Ocean Cleanup is an international non-profit organization that develops and scales technologies to rid the world’s oceans of plastic. They aim to achieve this goal through a dual strategy: stemming the inflow via rivers and cleaning up the legacy plastic that has already accumulated in the ocean. For the latter, The Ocean Cleanup develops large-scale systems to efficiently concentrate the plastic for periodic removal. This plastic is tracked and traced through DNV’s chain of custody model to certify claims of origin when recycling it into new products. To curb the tide via rivers, The Ocean Cleanup has developed Interceptor™ solutions to halt and extract riverine plastic before it reaches the ocean. Founded in 2013 by Boyan Slat, The Ocean Cleanup now employs a broadly multi-disciplined team of approximately 140. The foundation is headquartered in Rotterdam, the Netherlands.
For more information, visit: theoceancleanup.com and follow @theoceancleanup on social media.
Marine Life & Conservation Blogs
Creature Feature: Dusky Shark
In this series, the Shark Trust will be sharing amazing facts about different species of sharks and what you can do to help protect them.
This month we’re taking a look at the Dusky Shark, a highly migratory species with a particularly slow growth rate and late age at maturity.
Dusky sharks are one of the largest species within the Carcharhinus genus, generally measuring 3 metres total length but able to reach up to 4.2 metres. They are grey to grey-brown on their dorsal side and their fins usually have dusky margins, with the darkest tips on the caudal fin.
Dusky Sharks can often be confused with other species of the Carcharhinus genus, particularly the Galapagos Shark (Carcharhinus galapagensis). They have very similar external morphology, so it can be easier to ID to species level by taking location into account as the two species occupy very different ecological niches – Galapagos Sharks prefer offshore seamounts and islets, whilst duskies prefer continental margins.
Hybridisation:
A 2019 study found that Dusky Sharks are hybridising with Galapagos Sharks on the Eastern Tropical Pacific (Pazmiño et al., 2019). Hybridisation is when an animal breeds with an individual of another species to produce offspring (a hybrid). Hybrids are often infertile, but this study found that the hybrids were able to produce second generation hybrids!
Long distance swimmers:
Dusky sharks are highly mobile species, undertaking long migrations to stay in warm waters throughout the winter. In the Northern Hemisphere, they head towards the poles in the summer and return southwards towards the equator in winter. The longest distance recorded was 2000 nautical miles!
Very slow to mature and reproduce:
The Dusky Shark are both targeted and caught as bycatch globally. We already know that elasmobranchs are inherently slow reproducers which means that they are heavily impacted by overfishing; it takes them so long to recover that they cannot keep up with the rate at which they are being fished. Dusky Sharks are particularly slow to reproduce – females are only ready to start breeding at roughly 20 years old, their gestation periods can last up to 22 months, and they only give birth every two to three years. This makes duskies one of the most vulnerable of all shark species.
The Dusky Shark is now listed on Appendix II of the Convention on the Conservation of Migratory Species (CMS), but further action is required to protect this important species.
Scientific Name: Carcharhinus obscurus
Family: Carcharhinidae
Maximum Size: 420cm (Total Length)
Diet: Bony fishes, cephalopods, can also eat crustaceans, and small sharks, skates and rays
Distribution: Patchy distribution in tropical and warm temperate seas; Atlantic, Indo-Pacific and Mediterranean.
Habitat: Ranges from inshore waters out to the edge of the continental shelf.
Conservation status: Endangered.
For more great shark information and conservation visit the Shark Trust Website
Images: Andy Murch
Diana A. Pazmiño, Lynne van Herderden, Colin A. Simpfendorfer, Claudia Junge, Stephen C. Donnellan, E. Mauricio Hoyos-Padilla, Clinton A.J. Duffy, Charlie Huveneers, Bronwyn M. Gillanders, Paul A. Butcher, Gregory E. Maes. (2019). Introgressive hybridisation between two widespread sharks in the east Pacific region, Molecular Phylogenetics and Evolution 136(119-127), https://doi.org/10.1016/j.ympev.2019.04.013.
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