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Marine Life & Conservation Blogs

Creature Feature: Whale Shark

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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.

On 30th August it’s International Whale Shark Day! So to celebrate this month’s creature feature is all about the largest fish in the ocean… the Whale Shark!

The biggest shark in the ocean. The biggest fish in the ocean. The Whale Shark lives up to its name. Reaching a whopping 18m in length (potentially more). This is a legendary and beautiful shark.

They are unmistakable. Apart from their size, these filter-feeders have a beautiful patterning on their back. They have a checkerboard of white or yellowish spots on a grey, blue or brown back. It is often compared to a starry sky. In fact. In Madagascar they are known as “marokintana” for “many stars”.

Each Whale Shark’s pattern is unique. Amazingly, software used to identify star clusters from images of space has been adapted to identify individual Whale Sharks!

These sharks are highly migratory. Including journeys of 13,000km (made one way only) over 37 months. Which falls short of the most migratory shark, the Blue Shark. Tagging has revealed that there are regular ‘aggregation sites’. Here, Whale Sharks come together in huge numbers. Several hundred Whale Sharks may come together. To feed at annual, seasonal or lunar fish and invertebrate spawning events. The huge numbers of plankton at these events are consumed by suction. Whale Sharks can hang vertically and feed by sucking and gulping in water which is filtered through gill rakers.

Despite everything we know about them. And tagging studies. We still don’t know where Whale Shark’s pupping or nursery grounds are! We do know they are viviparous, giving birth to live young. Giving birth to up to 300 young.

Although they are protected by international agreements such as CITES and CMS. Unfortunately, Whale Sharks are endangered. They’ve been overfished in many areas for meat. Currently, the tourism industry for this species is booming. If you’re lucky enough to be able to go and see Whale Sharks – then why take a look at our guide for ecotourism.

Finally, if you want to support this majestic creature why not adopt a Whale Shark?

SCIENTIFIC NAME: Rhincodon typus

FAMILY:  Rhincodontidae

MAXIMUM SIZE: 17m – 21m

DIET: Plankton

DISTRIBUTION: Circumglobal, all tropical and warm seas except the Mediterranean

HABITAT: Open ocean to close inshore off beaches

CONSERVATION STATUS:


Banner Image – © Paul Cowell | Shutterstock

In-text 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

Celebrating the biggest fish in the sea: International Whale Shark Day 2022

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On August 30, the world is showing the biggest shark that lives in our oceans some big, BIG love. Because believe it or not, the biggest fish in the sea needs all the love they can get! Sure they are a shark – but they are the closest thing to a vegetarian that exists in the shark world.  Filter feeders, they eat plankton. While their mouths are 4 feet wide, their throats are the size of a quarter. And before you begin to worry about their 3000+ teeth, you should probably know they are only the size of the head of a match.

It’s hard to believe given the fact they can grow up to 40 feet in length and weigh up to 20 tons, but they are very elusive and proficient in the art of underwater camouflage. In fact, Jacques Cousteau only saw three in his lifetime!

Photo: Simon J Pierce

They are found in all temperate and tropical oceans around the world except for the Mediterranean Sea, and can migrate thousands of miles between feeding areas. They spend most of their lives near the surface, but have been known to dive to depths of almost 2,000m.

These gentle giants are magical – with a unique dot pattern that is specific to each individual whale shark.  Their populations are so low that there is a genetic similarity among all whale sharks worldwide.  Whale sharks play an extremely important role keeping the oceans healthy while also creating sustainable income for local communities through tourism. However, like many other shark species, whale sharks are classified as Endangered on the IUCN Red List of Endangered Species, with declining populations worldwide.  With massive migratory areas that make them difficult to protect, the fact they are often bycatch or targeted for their meat + fins, and as filter feeders that they often consume micro-plastics, whale sharks need all the help they can get.

Photo: Rodrigo Friscione

Here’s everything you need to know about these incredible fish – including how to meet them, how to protect them, and how to celebrate them every day!

Whale Shark Fun Facts:

  • Name: Rhincodon typus
  • Size: 18- 40 feet
  • Weight: up to 20 tons (equivalent to 3 African Elephants, a full school bus or 12,000+ bricks!)
  • Physical features: mouths are 5 feet wide with 3,000 teeth, eyes are as big as golf balls
  • Life Span: estimated 60-100 years
  • IUCN Red List Status: Endangered

1) Love Tropical Waters Both Deep and Shallow

The preferred environments of whale sharks are tropical and temperate waters and all over the world, including both deep and shallow coastal waters and lagoons of coral atolls.

A marine biologist named Eric Hoffmayer recorded the deepest dive yet: in 2008, he monitored a shark in the Gulf of Mexico that descended 6,324 feet. Sharks lack a swim bladder that keeps other fish buoyant, so one idea is that whale sharks free-fall toward the seafloor to rest.

Whale sharks especially love the Philippines. In 2016, the 1000th whale shark was identified in Philippine waters, making the Philippines the third largest known aggregation of whale sharks in the world and the biggest in South East Asia.

2) Endurance Swimmers Who Are Global Travelers

Whale sharks are one of the most migratory species and can travel around 40 miles per day! They tend to prefer different geographic locations at various times of year based largely on water temperature, food supplies and breeding opportunities. Genetic studies show that whale sharks across the globe are closely related which suggests that mating is one of the reasons for such long travels.

It is believed that pregnant females will migrate long distances to be able to give birth near remote islands where baby sharks will be out of reach of common predators.

But they are also slow swimmers (for sharks) usually moving at no more than 3 mph. Their swimming pattern is different than most sharks in that instead of using just the caudal fin for primary propulsion, they use the full posterior two-thirds of their body length.

The record for whale shark migration was 12,000 miles by a whale shark named Anne in 2011. She was tracked making the mammoth migration from near Panama in the southeastern Pacific, to an area close to the Philippines in the Indo-Pacific. Other tracked whale sharks have traveled:

  • Over 8,000 miles from the Gulf of CA, Mexico to Tonga
  • 3,107 miles to the coast of Thailand

Photo: Julie Andersen

3) They Enjoy Alone Time

Whale sharks are usually solitary creatures but come together for months in large aggregations to feed in plankton-dense waters. After feeding, they drift off in random directions, completely disappearing during winter and spring.

4) They Practice Vegetarianism

Whale sharks can eat plankton up to 45 pounds of plankton each day (which is equivalent to  121 cheeseburgers per day). But they also eat shrimp, sardines, anchovies, mackerels, squid, tuna, and albacore. and fish eggs. According to The Nature Conservatory, whale sharks will wait as long as 14 hours for fish to spawn on reefs and then they will swoop in and eat the eggs.

But they also largely have a vegetarian diet, especially when other prey is scarce. Scientists discovered that whale sharks get more than half their nutrients from plants and algae.

5) Each Baby Whale Shark is a Miracle!

Whale sharks are ovoviviparous, meaning they produce eggs that hatch inside the mother’s uterus.  Litters can be up to 300 pups but not all pups are birthed at the same time. That is almost twice as many as any other shark species.

But only one pregnant whale shark has ever been studied and, interestingly, many of these embryos were at different stages of development. Scientists observed that some were still in their egg cases whilst others had emerged but were still in the uterus. This may signify that females are able to store a male’s sperm, selectively fertilizing their eggs over a prolonged period.

Juvenile whale sharks, as docile and vulnerable as their elders, often become prey for other sharks and orcas, so while a female may birth more than 300 pups at a time, survival rates are devastatingly low; females giving birth to multiple litters at different times could increase their survival rate which could be why they have their very own, built-in sperm banks.

Making the birth of a whale shark even more miraculous is the fact that each whale shark’s pattern is as unique as a human fingerprint!

Think You Know Whale Sharks? Click here for a fun way to test your whale shark IQ!

Header Photo: Whale shark in Oslob by Shawn Heinrichs

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Marine Life & Conservation

Of grazers, browsers, scrapers and a miracle plant called Vetiver

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Guest article by Greet Meulepas who lives in Mauritius…

About 25% of reef fishes are herbivores, grazing on algae that would otherwise smother the corals.

In ‘Reef Fish Behavior’, a wonderful book written by Ned Deloach and Paul Humann, published in1999 the writers state “If left ungrazed, the competitively superior algae would quickly smother existing corals and blanket reef rock, leaving nowhere for coral larvae to settle and establish new colonies.” They also state that due to “continued overfishing and nutrient-rich run-off from coastal development and agriculture algae continue to dominate the reefs in many areas”. These facts were known 22 years ago and still hold today. Yet these days it is easy to blame climate change as the sole culprit for the disappearance of the reefs. Truth is that reefs are even more susceptible to temperature rises because they are already stressed due to overfishing and pollution.

Reef fishes need the reefs for shelter and food, but the reef needs reef fishes in order to survive too. Without the fishes the delicate balance of the reef ecosystem is lost. Certain fish species in particular are crucial for reef survival. Parrotfishes should be “legally protected from fisheries, strictly enforcing fishing restrictions and educating the public on the ecological importance and economic benefits of wild parrotfish”, according to a 2014 IUCN report. Parrotfishes are known as scrapers. Their beaks are powerful tools to scrape fast-growing turf algae from the corals. Doing so they scrape clean and even bite off pieces of coral and in this way provide clean substrate for coral planulae to settle.

Grazers like surgeonfishes are herbivores that keep the growth of turf algae in check by grazing the reef substrate. Grazers limit the growth of macro algae, that would otherwise outcompete the corals for space and light on the reef.

Macro-algae are also known to limit the potential for coral planulae to settle on to the reef. Not only are they prevented to grow by grazers, they are also eaten by browsers should they have survived the grazers.

So without browsers, grazers and scrapers the reef would fast be overtaken by algae as we see happening in many areas surrounding Mauritius and elsewhere in the world.

Luckily, the solution is known. It is two-fold and easy enough to implement.

First of all, like the IUCN suggests, there needs to come a ban on fishing parrotfish and other crucial herbivorous reef fish species.  Those who oppose this should think about the fact that without a reef there won’t be any reef fishes anyway. So either act now or pay the terrible price in the near future.

Protection of reef fishes can be done by specific bans to fish certain species or by protecting entire regions by implementing no-take zones and thus protect the entire reef ecosystem of that area.

This solution will not have the desired effect in a timely manner if we do not add to it the second part of the plan: tackle pollution caused by nutrient-rich run-off from coastal development and agriculture. Obviously the logical thing to do is to stop using these polluting chemicals. In addition, Nature offers us a beautiful extra solution, if we only dare to open our eyes to see the beauty in its simplicity: the miracle plant called Vetiver.

This plant, a grass closely related to lemongrass, is so beneficial in many ways that it has been called the miracle plant. Its uses are known for more than 4 decades yet this knowledge has never  spread beyond a receptive few.

For if people knew and really saw what Vetiver could mean, all coastal areas all around the world would have surely been planted full with vetiver by now. I can only imagine that the simplicity of the plan turns people sceptic.

Here it is: Vetiver has meters long roots that purify water by trapping and absorbing toxicities, while at the same time the plant stabilises the soil and is thus an excellent weapon against erosion. On top of that Vetiver increases soil fertility and can be used in wetland restoration, agricultural improvement, erosion and sediment control, agrochemical pollution and climate change mitigation. Vetiver has been successfully used to rehabilitate coral reefs in Vanuatu, the Philippines and Guam, will be used to help save the Great Barrier Reef and I am hoping we can add Mauritius to that list in the near future.

So, dear reader, I invite you to submerge yourself in the wonderful world of Vetiver and plant this wonder in your garden, plantation, farm, hotel gardens, surrounding golf courses…. and help the beautiful coral reefs to survive!

Find out more at: www.vetiver.org

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