Marine Life & Conservation Blogs
Sharks the Ocean’s Greatest Mystery – Part 2
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
In our last blog we talked about why the Shark Trust had been in The Bahamas in December. With the underwater part of the expedition focused on getting 360 footage for a new immersive shark experience, OneOcean360: A Shark Story, that will be launched later this year. Now, let’s tell you a little bit more about the diving we did, along some more surprising shark sightings!
The Shark Trust 3-island expedition, which was fully funded and supported by the Bahamas Ministry of Tourism, started in Nassau. And we were booked to do 2 days of diving with Stuart Cove’s Dive Bahamas. We packed in as much diving as possible, leaving as soon as the boat was loaded and returning as the sun was setting, covering 7 dive sites over the 2 days, with a mix of reef and wrecks to ensure we got as much varied footage as possible.
Pumpkin Patch saw us hang out with a very chilled turtle while Caribbean Reef Sharks swam along the drop off beside us. We visited a “wreck” structure built for the filming of a James Bond film that was now covered in bright corals and home to a multitude of reef fish. Steel Forest saw us diver some “proper” wrecks that have been sunk alongside each other. Glass fish swirled under overhangs and larger fish hung motionless in the wheelhouse. Southern Sting rays lay buried in the sandy seabed alongside. Our final dive of the day, as the sun started to set, Ridges, combined a reef and wreck where we caught a fleeting glimpse of a Bull Shark as we ascended the line. It was a great diving day that gave us the perfect introduction to the underwater world of The Bahamas.
Our second day was going to focus on getting close up footage of Caribbean Reef Sharks on both wrecks and reef. The Ray of Hope and Big Crabs wrecks are perfect for this. With our guide placing bait boxes inside the wrecks to attract the sharks, and with our cameras setup on the wreck structure, we could back away and let the sharks do their thing without us disturbing them or being in the 360 filming frame. With clear water and plenty of sharks, the footage we came away with in pretty striking.
Next stop: Bimini. Great Hammerhead Sharks are the number one attraction here. And we were able to join Neal Watsons Bimini Scuba for a 2-tank dive with these magnificent sharks, along with the Nurse Sharks that like to join in with the experience. But we were also able to snorkel with juvenile Lemon Sharks in the Mangroves, see Bull Sharks and spotted eagle rays from a submarine experience and from the dock side. Our second day of diving saw us dive the SS Sapona wreck and then experience the Caribbean Reef Sharks on the reef. Bimini really does allow you to pack in a load of shark and ray experiences in a short space of time.
Finally, we headed to Grand Bahama. Whilst much of our time was spent above the water meeting people working to conserve different marine habitats (watch this space for more information on this) – we did manage to squeeze in a couple of dives on the reefs here and were delighted to see both Caribbean Reef Shark and Southern Stingrays on both. Our final shark and ray experience saw us take a tour to Sandy Cay with Keith Cooper. We were able to get footage of stingrays, lemon and blacktip reef sharks on the seagrass and over the sandy seabed. Sometimes just in ankle deep water.
If you are heading to the Go Diving Show – then you will be able to see a short 360 film, using our VR headsets, that shows many of these experiences. Please come and say hello to the Shark Trust team on the Diverse Travel stand (340). We will also be on The Bahamas stand twice a day to chat to people about our experiences on the islands. And Diverse travel will have special offers on travel to The Bahamas should you want to follow in our fin-kicks.
To find out more about the work of he Shark Trust and how you can support us, visit out website www.sharktrust.org
Op-ed by Beth Brady, PhD, Senior Science and Conservation Associate, Save the Manatee® Club
Recent news articles and broadcasts have claimed that manatees are not native to Florida or only arrived on Florida’s west coast in the 1950s. These claims, based on limited anthropological records, point to where manatees were historically exploited by humans and assume that a lack of evidence means manatees were absent from certain areas. However, absence of evidence is not evidence of absence—it’s like looking for stars in the daytime; just because you can’t see them doesn’t mean they’re not there. Moreover, genetic and fossil evidence indicate manatees have been present in Florida for the last 12,000 years.
The Florida Fish and Wildlife Conservation Commission (FWC), which manages Florida manatee populations, has created a manatee timeline highlighting key dates and notable information about manatee presence in Florida (https://myfwc.com/education/wildlife/manatee/timeline/). Historical records suggest that manatees have been observed in Florida as far back as the 1500s, with some details presented by the Florida Fish and Wildlife timeline aligning with evidence presented in the publication.
Manatee species, such as the African manatee and the Antillean manatee, continue to be poached by humans (Marsh et al., 2022). As a result, these species are difficult to observe in the wild and may adapt by foraging at night to avoid human encounters (Rycyk et al., 2021). This behavior could help explain why historical Florida manatee populations that were hunted by humans are absent from middens and rarely mentioned in historical accounts.
Further, the publication only briefly touches on the paleontological record and genetic evidence, which indicate that manatees have existed in Florida for a much longer period. Fossil and genetic evidence reveal a rich history of manatees in Florida. Manatees belong to the order Sirenia, which includes the Amazonian, African, and West Indian manatee species. While Sirenian fossils have been found globally, only Florida and the Caribbean contain specimens from every epoch over the past 50 million years (Reep and Bonde, 2006). The modern manatee, as we know it, emerged in the Caribbean about 2 million years ago (Domning, 1982).
The evolution of manatees during the Pleistocene epoch provides valuable insights into how environmental changes shaped their distribution and genetic diversity. During the Pleistocene epoch (2.59 million to 11,700 years ago), there were roughly 20 cycles of long glacial periods (40,000–100,000 years) followed by shorter interglacial periods lasting around 20,000 years. At the start of these warmer periods, Caribbean manatees migrated northward with the warming waters (Reep and Bonde, 2006). Water currents and thermal barriers isolated these manatees from populations in Mexico and the Caribbean, leading to genetic divergence. Fossil evidence indicates that Trichechus manatus bakerorum lived in Florida and North Carolina about 125,000 years ago but did not survive the last glacial period, which began 100,000 to 85,000 years ago (Domning, 2005). This subspecies was eventually replaced by modern Florida manatees.
This evolutionary theory is further supported by genetic evidence. Research indicates that Florida manatees trace their evolutionary origins to Caribbean ancestors that migrated northward over the past 12,000 years (Garcia-Rodriguez et al., 1998). A 2012 study by Tucker et al. reinforces this theory, showing higher genetic diversity in manatees on Florida’s west coast compared to those on the east. Over time, core populations migrated northward, with some groups moving south and east along the Florida coastline before heading north along the Atlantic. This migration pattern left the west coast population with greater genetic diversity, while the east coast population retained only a smaller subset. These findings suggest that the founding population of Florida manatees—arriving approximately 12,000 years ago—originated along Florida’s southwestern coast, which became the center of the state’s manatee population (Reep and Bonde, 2006). The process of vicariance further supports this hypothesis; as geographic and ecological barriers emerged, they likely isolated the Florida manatee populations from their Caribbean ancestors. This isolation likely limited migration back and forth between regions, fostering the establishment of local populations in southwestern Florida.
Manatees are not only a cherished symbol of Florida’s natural heritage but also a species with deep evolutionary and historical ties to the region. In sum, despite recent claims questioning their nativity, extensive fossil and genetic evidence confirms that manatees have been present in Florida’s waters for thousands of years, with ancestors dating back over 12,000 years. We agree with the authors of the published article that protecting these iconic creatures and their habitats is essential to preserving Florida’s unique ecological identity for future generations
Beth Brady is the Senior Science and Conservation Associate at Save the Manatee Club whose work focuses on manatee biology and conservation. She has her PhD from Florida Atlantic University and her Master’s in Marine Science from Nova Southeastern University.
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