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Sharks the Ocean’s Greatest Mystery – Part 2

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Sharks are an incredibly significant animal in human culture of both the past and present, they are an animal that have been embodied in our culture for millennia. They are represented in formats such as books and clothing, but most notably in our TV and films, which is where a large portion of their negative reputation stems from. A popular TV representation of sharks comes from Discovery Channel’s ‘Shark Week’, and I believe sharks are possibly the only animal on our planet to have an entire week dedicated to them every year. However, despite this, we still know more collectively about the surface of the Moon and Mars, about Galaxies outside of our own, and even about animals that have been extinct for millions of years, than we do about sharks.

Sharks are our Ocean’s top predator, and they represent just how little we know about our blue planet. We have put more money into exploring outer space than we have exploring our seas and whilst many people call space the final frontier, I believe the final frontier is our Oceans. There are people that have lived in space for over a year, yet we aren’t able to stay underwater for more than a few short hours, and with each dive, scientists are discovering something new in the deep sea, giving us a better understanding of our oceans and the top predator that lives within them.

What we do not know

It is easier to talk about what we do not know and the implications of not knowing it, we still don’t know where most shark species mate or give birth, knowing this would accelerate conservation efforts for sharks in a huge way as these areas could then have realistic protections placed on them, allowing us to preserve key stages of the Sharks life cycle.

Marine Biologists have stated that the discovery of a White Shark breeding ground would be the holy grail of Ocean Science, but the only reports of White Sharks mating come from a handful of sightings from Fisherman and Sailors, so these cannot be used as an official record.

We know that Sharks mature late in the same way as us humans, it is estimated that some species are estimated to not be sexually mature until their late 30’s and 40’s, which means that these species are at extreme risk of disappearing due to fishing, as they aren’t able to replenish their numbers fast enough when put under extreme fishing pressure. There is a lot of debate over whether Sharks mature at a certain age or a certain size, for example it was estimated that White Sharks mature at four metres in length, however, in South Africa in 2017 a female White Shark was killed by Orcas, and it was determined that she was either immature or hadn’t mated, as there was the presence of a Hymen.

We are also still unsure about the impacts of human activities on Sharks and how losing Sharks, or their habitat, would affect the habitats and environments on land, environments in which we depend on for our survival.

What we do know

New Shark discoveries are made every year, and scientists are predicting that in the next 15-20 years we will be entering the golden age of ocean and shark discoveries. We already know that sharks are the oceans top predator and we have determined that they affect the very mechanics and functions of the Ocean, if we were to remove them, we would be putting the worlds ecosystems at risk of collapsing. Sharks are an integral part of the balance of the oceans, they help by controlling populations of other species, if we were to lose sharks, species such as turtles would have an increase in population, therefore leading to more seagrass being eaten, which is a prime food source for many animals. Thus, other smaller animals would not be able to feed, and their population would decrease, also the decrease of sea grass would affect us humans on earth as the oceans plant life helps to absorb carbon dioxide and create oxygen, and actually up to 75% of the oxygen we breathe is created from the oceans.

We know that some Shark species have complex social relationships that aid in their survival, although this has only been observed in a handful of species. Lemon Sharks form bonds as pups and hunt together in the shallow mangrove swamps of the Bimini Atoll, and will learn and hunt together and learn vital skills needed in their future survival. Hammerheads are possibly the most famous for social interactions as they form huge schools off places such as the Galapagos Islands and it has been observed that the more dominant females swim in the centre of the school and display for the males.

Some shark species, such as the Zebra Shark, have been known to mimic other animals. Zebra sharks are born with stripes (which fade as they get older) and they have the second longest tail (after the Thresher Shark), this helps them to mimic the highly venomous, White-Banded Sea Snake in order to trick predators into avoiding them, they have even been reported to mimic taking a breath at the surface like a sea snake would do.

It has recently been discovered that Greenland Sharks are now the longest lived Vertebrate on our Planet, they are believed to be able to exceed the age of 500, with females not reaching sexual maturity until they are around 150 years old. This was discovered by examining special proteins in their eyes that do not degrade with age. Determining age and sexual maturity are crucial for understanding and managing shark populations as knowing what age a Shark can breed will allow us to gauge what protections a species needs.

It has recently been discovered that female Whale Sharks are able to store sperm to use over a period of time, this is in order to ensure their chance of reproducing, even without recently mating. This is a huge advantage for conserving the species, as Whale Sharks are classed as an endangered species and so, with the number of whale sharks declining, this ensures the species can continue. Along with this, Whale Sharks have also been found to be pregnant with up to 300 pups, and these pups can be at different stages of development due to the staggered use of stored sperm.

Of all things we know there is one thing that is certain, a Shark, no matter the species, is unique and worth more to our world alive than dead. In the next blog we will explore the threats that Sharks face and how we can help Sharks through the tough times ahead.


Follow Donovan on Instagram at www.instagram.com/donovans_reefs

Donovan is a Divemaster who currently works as a Shark Diver at Blue Planet Aquarium based in Ellesmere Port. Donovan’s passion lies with Elasmobranch’s (Sharks & Rays) and this passion has led him to work in South Africa with White Sharks for a short period. He also believes that education through exposure is the best way to re-educate people about Sharks. Follow Donovan at www.instagram.com/donovans_reefs

Marine Life & Conservation

The BiG Scuba Podcast… with Andy Forster of Dive Project Cornwall

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Gemma and Ian chat to Andy Forster.  Andy is the Project Director at Dive Project Cornwall.  He tells us about his own passion for diving as well as how Dive Project Cornwall is going to educate and inspire many youngsters over the coming year.

Have a listen here:

Find out more at www.diveprojectcornwall.co.uk


Find more podcast episodes and information at the new www.thebigscuba.com  website and on most social platforms @thebigscuba 

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Marine Life & Conservation

Coral Spawning Predictions for Curacao and the Southern Caribbean

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The Caribbean Research and Management of Biodiversity (CARMABI) has released its 2022 annual coral spawning prediction calendar for Curacao and the south Caribbean.  This calendar plays a central role in studying the reproductive biology of Caribbean corals and guiding coral restoration efforts for the southern Dutch Caribbean islands.

Based on these predictions, researchers are able to harvest coral gametes that are reared to larvae that can be used to cultivate future coral colonies.

Coral spawning is a miraculous event where entire coral colonies, prompted by the lunar cycle, sunset time and water temperature, release gametes (eggs and sperm) simultaneously. Gametes of one species fertilize another to become fertilized embryos that settle on the ocean floor after days to weeks.

CLICK HERE FOR MORE DETAILS!

As divers, being able to witness a spawning event is a unique opportunity to enjoy the breathtaking scene as the entire reef becomes engulfed in a blizzard of future corals.

Each year, the Caribbean Research and Management of Biodiversity (CARMABI) releases a calendar to predict when each species of coral is expected to spawn. During these events, researchers from CARMABI, in collaboration with Reef Renewal Bonaire and Reef Renewal Curaçao, also collect gametes to be used to grow new corals in a laboratory setting.

Photo credit = CARMABI

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