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Marine Life & Conservation Blogs

Creature Feature: Oceanic Manta Ray

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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 our Creature Feature is from guest writer – Yolanda Evans. 17-year old Yolanda has been passionate about sharks all her life, and this month she explores the world of the Oceanic Manta Ray…

The graceful Oceanic Manta Ray dances their way through the blue waters with a wingspan of 7 metres which can reach a maximum of 9 metres, making them the biggest ray in the world. These manta’s have a circumglobal distribution and are found in temperate, tropical, and subtropical. They have a deep black dorsal side with a white T marking on their back and the ventral side is white with black freckles. However, they can be easily confused with Reef Manta’s, but the two main differentiating features (despite their size) is that the white markings on the Reef Manata make a Y shape and there are no freckles on their underside.

Recognisable by the two mouth parts known as the cephalic lobes: extensions of their massive pectoral fins that are used for feeding, helping the ray scoop mouthfuls of plankton. They must eat 20-30 kg of plankton a day, which is only about 2% of their total body weight.

Oceanic Manta’s can have up to 4000 tiny teeth but they don’t use these for feeding, they use them for when they are mating as the males have to hold themselves onto the females! The cephalic lobes can either be flexed out-seen when they are feeding, or curled up for spiral swimming and doing underwater flips!

Having the largest brain to body ratio of any cold-blooded fish, it is thought that they are able to pass the mirror test, showing that they have self-awareness! They are also capable of creating mental maps using smells and environmental barings, helping on their migrations. 

Gatherings of these manta’s are rare, but when they come together it is an elegant marine ballet! A group of manta’s, known as a squadron, typically gather for two main reasons: mating and feeding. Manta’s will do somersaults in areas rich in prey to maximise their intake of prey. They will also participate in chain-feeding, this is when each manta follows the other in a circle to create a whirlpool which traps their prey inside! 

Cleaning and maintenance is very important to these fish as they will undergo special migrations to coral reefs where Cleaner fish come and groom off parasites and dead skin. These cleaning stations are so important to these rays that they will go back to the same spot for many years!

Out of all elasmobranchs the Giant Manta has one of the slowest reproduction rates, only producing one pup every two to three years and can be pregnant for 12-13 months! However, due to commercial fishing and bycatch, they cannot keep up with the extortionate rate that their populations are decreasing by. This has led to the Oceanic Manta Ray to be listed as endangered by the IUCN. Manta’s are targeted for their gill rakers by traditional medicines that can reach up to $400 USD per kg. 

Not only are Oceanic Manta’s threatened by fishing, but also by pollution in the oceans. Microplastics and heavy metals accumulate in their tissues. This can unfortunately lead to serious illnesses like cancers.

SCIENTIFIC NAME: Mobula birostris

FAMILY:  Mobulidae

MAXIMUM WINGSPAN: 8.8m

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:

Images: Frogfish Photography

For more amazing facts about sharks and what you can do to help the Shark Trust protect them visit the Shark Trust website by clicking here.

The Shark Trust is the leading UK-based shark conservation charity. The team works globally to safeguard the future of sharks, and their close cousins, the skates and rays. Engaging with a global network of scientists, policymakers, conservation professionals, businesses and supporters, to further shark conservation. Established in 1997 to provide a voice for UK sharks, the Shark Trust has an ever-growing number of passionate supporters. And together we're creating positive change for sharks around the world. Want to join us and help protect sharks around the world? Click here! www.sharktrust.org

Marine Life & Conservation Blogs

Creature Feature: Undulate Ray

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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 looking at the Undulate Ray. Easily identified by its beautiful, ornate pattern, the Undulate Ray gets its name from the undulating patterns of lines and spots on its dorsal side.

This skate is usually found on sandy or muddy sea floors, down to about 200 m deep, although it is more commonly found shallower. They can grow up to 90 cm total length. Depending on the size of the individual, their diet can range from shrimps to crabs.

Although sometimes called the Undulate Ray, this is actually a species of skate, meaning that, as all true skates do, they lay eggs. The eggs are contained in keratin eggcases – the same material that our hair and nails are made up of! These eggcases are also commonly called mermaid’s purses and can be found washed up on beaches all around the UK. If you find one, be sure to take a picture and upload your find to the Great Eggcase Hunt – the Shark Trust’s flagship citizen science project.

It is worth noting that on the south coasts, these eggcases can be confused with those of the Spotted Ray, especially as they look very similar and the ranges overlap, so we sometimes informally refer to them as ‘Spundulates’.

Scientific Name: Raja undulata

Family: Rajidae

Maximum Size: 90cm (total length)

Diet: shrimps and crabs

Distribution: found around the eastern Atlantic and in the Mediterranean Sea.

Habitat: shelf waters down to 200m deep.

Conservation Status : As a commercially exploited species, the Undulate Ray is a recovering species in some areas. The good thing is that they have some of the most comprehensive management measures of almost any elasmobranch species, with both minimum and maximum landing sizes as well as a closed season. Additionally, targeting is entirely prohibited in some areas. They are also often caught as bycatch in various fisheries – in some areas they can be landed whilst in others they must be discarded.

IUCN Red List Status: Endangered

For more great shark information and conservation visit the Shark Trust Website


Image Credits: Banner – Sheila Openshaw; Illustration – Marc Dando

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Guarding Against Coral Invaders

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Protecting (Dutch) Caribbean Reefs from Unomia stolonifera

Recent reports highlight the concerning spread of the invasive soft coral, Unomia stolonifera, currently devastating Venezuela’s marine ecosystems and detected in Cuba. With the potential threat of its expansion to the (Dutch) Caribbean islands, urgent action and awareness are essential to safeguard marine biodiversity and local economies from possible catastrophic consequences.

Invasive species are animals or plants from another region of the world that don’t belong in their new environment. These species can have major ecological effects by decimating native flora or fauna. They can also cause large economic losses and impact human health. Invasive species also pose a significant threat to marine ecosystems worldwide, including the Dutch Caribbean. Among these invaders is the octocoral species Unomia stolonifera or “Pulsing Xenia”, originally from the Indo-Pacific. With its rapid growth and lack of natural predators, this species can outcompete native species and disrupt fragile marine habitats such as seagrass beds and coral reefs.

Background

The invasive soft coral U. stolonifera was first identified in 2014, off the coast of Venezuela. It is believed to have been introduced via the illegal aquarium trade.  Since this species can reproduce sexually and asexually (or fragment), even small pieces can regenerate to spread.  Once introduced it quickly took over shallow reefs and hard substrate at depths of 0-50 meters, outcompeting local corals and seagrass for space.  Follow on surveys found that this coral species exhibited average percentage cover as high as 80%, vastly outcompeting native corals. In highly colonized areas, fish are disappearing due to loss of habitats.

In 2022, during a survey conducted in Cuba by the University of Havana, an unknown octocoral was discovered which was later identified as the invasive Unomia stolonifera. It is suspected that the coral larvae arrived in ballast water from fossil fuel ships originating from Venezuela, as nearby sites adjacent to Venezuelan ports have been heavily affected by the invasion.

How to help

Prevention through continuous monitoring, particularly in high-risk areas such as marine harbors and oil facilities, is paramount. Early detection plays a pivotal role in mitigating the threat posed by Unomia stolonifera.

The public’s involvement and awareness are also vital. Local communities, recreational divers, tourists, and all stakeholders are urged to participate in early detection efforts by reporting sightings (photo, location and date) of this invasive coral to their respective Protected Area Management Organization (PMO’s)- the Fundacion Parke Nacional Aruba (FPNA)STINAPA BonaireCARMABI Curaçao Saba Conservation Foundation (SCF)Nature Foundation St. Maarten (NFSXM) and St. Eustatius National Parks (STENAPA). If an invaded area is confirmed, follow the recommendations by the local PMO’s.

Keys to Success

Despite the challenges, early detection is key to mitigating the threat posed by Unomia stolonifera. With continued vigilance, research, and community engagement, there is hope for containing this potential issue before it becomes a major threat.

About the DCNA

The Dutch Caribbean Nature Alliance (DCNA) supports (science) communication and outreach in the Dutch Caribbean region by making nature related (scientific) information more widely available through amongst others the Dutch Caribbean Biodiversity Database, DCNA’s news platform BioNews and through the press. This article contains the results from several scientific studies but the studies themselves are not DCNA studies. No rights can be derived from the content. DCNA is not liable for the content and the in(direct) impacts resulting from publishing this article.

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