Marine Life & Conservation Blogs
Love is in the air at Blue Planet Aquarium
Every year between the end of January and mid-May when the water is at its coldest and begins to warm up for summer, Blue Planet Aquarium has its annual Sand Tiger Shark mating season. During this time of year, the dynamics in the tank completely change, from what are usually slow moving and often sleeping sharks turn into fast moving Sharks who have only one thing on their mind.
In previous blogs I’ve mentioned how relaxed the Sharks are, but during this time the Sharks are at the complete opposite end of the scale, sometimes seeming oblivious to our presence, they can tend to almost “play chicken” with the divers, swimming very close, which can sometimes make us jump a little. Even with this change in behaviour however the animals are still quite easy to work with and we always respect their boundaries and rules as it is their home at the end of the day.
The changes in behaviour start around mid to late January with a huge reduction in appetite for all our Sand Tigers, they will go down to eating almost nothing throughout the mating season, we even have them spit food out after grabbing it.
The next sign usually starts with the males moving a lot faster and will duck and dive between the different levels in the tank, it can be chaotic one day and then almost nothing the next, on the opposite end the females will slow right down and tend to spend a large amount of time either on or near the bottom.
It is like this for about a month before the action really starts, the next sign is what’s known as “tracking”, this is where you will have the female of interest at the front with the alpha male close behind her, with the subordinate males trailing behind him. This happens for a couple of weeks until around March where the height of mating season starts, after a month or so of tracking and a little bit of bickering there will be an “alpha” male who will control mating in the tank. Alpha males will then protect the area where females are congregating and will then force less dominant males out by snapping their jaws at them, snapping tends to be enough to force males out, however seeing bite marks on the males is not uncommon.
When Sharks mate the males tend to bite the females around their pectoral fins or on their sides, this is done to help hold themselves in place during mating and to make it easier to mate by slowing the female down, females will often resist but will concede due to the extra weight, this could be the female testing the male’s fitness, but we honestly don’t know. The male sharks sex organs are known as Claspers, two small appendages that trail behind the Sharks pelvic fins and its these that transfer the Sperm to the female during mating, they have two so that they’re able to effectively mate no matter what side they approach the female on.
When males are finished and let go, they can sometimes leave teeth embedded in the females which will fall out after a few days and don’t affect the female long term, this does often result with toothless males during mating season, and even for a short time after it has finished, which our guests are often surprised to see gummy Sand Tigers in our exhibit. Along with having toothless males the females also become covered from nose to tail in love bites, and during rather amorous seasons the dive team will refer to the females as pin cushion Sharks due to how much they resemble pin cushions, never fear however because mere days after mating season has finished most, if not all, of the wounds on a female would have healed and results in very minor scarring or marks.
Females will mate with numerous males throughout a season, moving between different areas and mating with many alpha males who control those areas, in the case of Blue Planets main tank our males tend to gain and lose alpha status rather regularly, thus allowing them mating rights. Female Sand Tigers have two Uterus’s which can contain up to 5 pups each. After the mating season is over, females become pregnant in a rather remarkable way. Sand Tigers are known as oophagous which is where the developing embryos will feed on undeveloped eggs produced by the mother throughout her 9–12-month pregnancy.
But that’s not all, once an individual or individuals reach a certain size, they will actually turn on their sibling and begin to feed on them, this is called intrauterine cannibalism. This will continue until there is a single fully toothed pup in each uterus, however triplets have been recorded which believed to be two individuals from the same womb who were full sibling who teamed up, and one from the other womb.
This method of eating siblings is believed to be an adaptation by male Sand Tigers with whom who can father the most well-armed, active hunting embryos as described by a scientist called Damian Chapman.
Unfortunately, Blue Planet has never had a captive natural birth in our main exhibit now there could be many reasons as to why this is the case, and we have a few theories amongst the team but unfortunately, we just can’t say for certain what those are. The reasons as to why they aren’t breeding is something that been discussed for many years in aquariums across the globe as unfortunately captive breeding very limited with only a handful of recorded births worldwide.
Sand Tiger Sharks have one of the lowest reproductive rates of any Shark Species giving birth to only two pups every other year as the females take a rest year in between, on top of this Sand Tigers don’t become sexually mature until they’re between 6-7 if they’re a male, females will not become mature until they’re 9-10 this on top of the fact that the maximum lifespan recorded for a Sand Tiger in the wild is 15-17 years means that to be generous, a female may only give birth to a maximum of 16 pups throughout their lifetime. Now these natural adaptations have served them well throughout the last 450 million years but now they are a handicap.
Sand Tigers are unfortunately at threat, with some populations such as those in Europe, the Mediterranean and Eastern Australia classified as Critically Endangered. Sand Tiger Sharks were also the first Shark species to be put on the endangered species list and given full protection which was first done in Australia.
With all the odds stacking against them its now even more imperative that we learn more about these incredible animals and how to breed them effectively to create a captive population as a contingency plan in case things in the wild take a nosedive. Therefore, Zoos and Aquariums are important to the wild members of a species with housed members of the species, helping ensure their survival and as acting as ambassadors to the wild ancestors by educating our guests and the public for many years to come. Now rest assured although we haven’t yet been able to breed Sand Tiger Sharks in our main exhibit, we’re working hard to better understand and figure out how we can in the not-so-distant future.
For more about Blue Planet Aquarium visit their website by click here.
Marine Life & Conservation Blogs
Creature Feature: Goblin 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.
Written by guest contributor – Yolanda Evans.
Mysteriously slithering around the dark mesopelagic of the western Pacific, the glorious Goblin shark swims in search for their next meal. This illusive shark is one of the most unique-looking sharks to ever exist, having a long snout called a rostrum and protrusible jaws, hailing them their common name, Goblin. Their rostrum is covered with small pores called the ampullae of Lorenzini, jelly-filled pores in the snouts of many sharks that are able to pick up changes in the electro-magnetic field, for example the muscle contractions of nearby fish. However, these pores can only detect movement only a few inches in front of the shark!
In addition to their rostrum, these sharks poses and amazing ability to protrude their jaws out or their cartilaginous skull by something called slingshot feeding. This is when the jaws are shot forward, extending 8.6-9.4% of the Goblin sharks total body length. However, this fast jaw action also creates a powerful suction-known as a pharyngeal suction-forcing their prey deeper into their mouths.
While many sharks range from greys to blues to browns, this stupendous shark can be a very pale pink! However, this unusual colour is not from a pigment in their skin, but from the thinness of their skin! Their skin has such a great transparency that the oxygenated blood that flows in their capillaries-tiny blood vessels-causes what would be their grey skin, to become pink. This amazing ability might actually been an adaptation for the shark, they live 270m-1300 m deep, red light wavelengths cannot be seen, making the spectacular shark near invisible to both prey and predators!
Their scientific name, Mitsukurina owstoni, comes from the British naturalist Alan Owston who is credited with discovering the shark, and from Kakichi Mitsuriki, the Japanese scientist who identified and described the shark. While the English common name is only from their long rostrum, the direst translation into Japanese is Tengu-zame, base of the Tengu, a Japanese mythological half-man-half-bird who had red skin and a long nose, a comparison more fitting.
Despite their somewhat intimidating appearance, the Goblin shark is not an aggressive species, predating on mainly small bony fish, crustaceans, and cephalopods. Long slender teeth that protrude out from their jaws, appearing almost like blades, are perfect for clutching onto their prey. Nonetheless, the most threat they create towards humans is disrupting our internet as they are known to bite down onto submarine cables!
Like many other shark species, Goblin sharks main threat is by-catch from deep-sea longlining and deep-sea trawling. They are listed by the IUCN as least concern. Unfortunately, being relatively understudied, this may be incorrect as there is a very minimal amount of knowledge about the lives of these sharks. Leaving the question: what else is there to know about the truly incredible Goblin shark?
SCIENTIFIC NAME: Mitsukurina owstoni
MAXIMUM SIZE: Up to 3.8 meters (12.5 feet) in length
DIET: Feeds primarily on deep-sea fish, but also crustaceans and cephalopods
DISTRIBUTION: Goblin Sharks have a wide but patchy distribution, found in deep waters of the Atlantic, Indian, and Pacific Oceans.
HABITAT: Primarily found in the deep sea, typically between 200 and 1,200 meters (656 and 3,937 feet) in depth. They are occasionally seen at shallower depths, but are typically associated with steep slopes and canyons on the continental shelf and slope.
Due to their deep-sea habitat and elusive nature, they are rarely encountered and little is known about their population trends. However, they are sometimes caught as bycatch in deepwater fisheries, and there is concern over the potential impacts of deep-sea mining activities on their habitat.
Images – www.fishesofaustralia.net.au/home/species/3254 | Wikimedia Commons
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
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.
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
- 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
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