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.
Diving with Frogfish in Costa Rica: A Hidden Gem Underwater
In the vast and vibrant underwater world of Costa Rica, there’s a peculiar creature that often goes unnoticed but holds a special place in the hearts of divers: the frogfish. This enigmatic and somewhat odd-looking species is a master of camouflage and a marvel of marine life. Diving with frogfish in Costa Rica is not just a dive; it’s an adventurous treasure hunt that rewards the patient and observant with unforgettable encounters. Let’s dive into the world of frogfish and discover what makes these creatures so fascinating and where you can find them in Costa Rica.
The Mystique of Frogfish
Frogfish belong to the family Antennariidae, a group of marine fish known for their incredible ability to blend into their surroundings. They can be found in a variety of colors, including yellow, pink, red, green, black, and white, and they often have unique spots and textures that mimic the coral and sponges around them. This camouflage isn’t just for show; it’s a critical survival tactic that helps them ambush prey and avoid predators.
One of the most remarkable features of the frogfish is its modified dorsal fin, which has evolved into a luring appendage called an esca. The frogfish uses this esca to mimic prey, such as small fish or crustaceans, enticing unsuspecting victims close enough to be engulfed by its surprisingly large mouth in a fraction of a second. This method of hunting is a fascinating spectacle that few divers forget once witnessed.
Where to Find Frogfish in Costa Rica
Costa Rica’s Pacific coast is dotted with dive sites that offer the chance to encounter these intriguing creatures. Bat Islands (Islas Murciélagos), Catalina Islands (Islas Catalinas), and the area around the Gulf of Papagayo are renowned for their rich marine life, including frogfish. These sites vary in depth and conditions, catering to both novice and experienced divers.
The key to spotting frogfish is to dive with a knowledgeable guide who can point out these master camouflagers hiding in plain sight. They’re often found perched on rocky outcroppings, nestled within coral, or even hiding among debris, perfectly mimicking their surroundings.
Diving Tips for Spotting Frogfish
Go Slow: The secret to spotting frogfish is to move slowly and scan carefully. Their camouflage is so effective that they can be right in front of you without being noticed.
Look for Details: Pay attention to the small details. A slightly different texture or an out-of-place color can be the clue you need.
Dive with Local Experts: Local dive guides have an eagle eye for spotting wildlife, including frogfish. Their expertise can significantly increase your chances of an encounter.
Practice Buoyancy Control: Good buoyancy control is essential not just for safety and coral preservation but also for getting a closer look without disturbing these delicate creatures.
Be Patient: Patience is key. Frogfish aren’t known for their speed, and sometimes staying in one spot and observing can yield the best sightings.
Conservation and Respect
While the excitement of spotting a frogfish can be thrilling, it’s crucial to approach all marine life with respect and care. Maintain a safe distance, resist the urge to touch or provoke, and take only photos, leaving behind nothing but bubbles. Remember, the health of the reef and its inhabitants ensures future divers can enjoy these incredible encounters as much as you do.
Join the Adventure
Diving with frogfish in Costa Rica is just one of the many underwater adventures that await in this biodiverse paradise. Whether you’re a seasoned diver or taking your first plunge, the waters here offer an unparalleled experience filled with wonders at every turn. Beyond the thrill of the hunt for frogfish, you’ll be treated to a world teeming with incredible marine life, majestic rays, playful dolphins, and so much more.
So, gear up, dive in, and let the mysteries of Costa Rica’s underwater realm unfold before your eyes. With every dive, you’re not just exploring the ocean; you’re embarking on an adventure that highlights the beauty, complexity, and fragility of our marine ecosystems. And who knows? Your next dive might just be the one where you come face-to-face with the elusive and captivating frogfish. Join us at Rocket Frog Divers for the dive of a lifetime, where the marvels of the ocean are waiting to be discovered.
About the Author: Jonathan Rowe
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Creature Feature: Swell Sharks
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 taking a look at some truly swell sharks, the Swell Sharks!
Swell Sharks are a group of catsharks belonging to the family Scyliorhinidae. Their most unique feature is probably their threat response: they are able to expand their bodies to twice their normal size by swallowing water! This wedges them into their hiding spot, making it more difficult for predators to bite them from inside.
There are 18 different species of swell shark. In this article, we will focus on two of them, the Swell Shark (Cephaloscyllium ventriosum) and the Australian Swell Shark (Cephaloscyllium laticeps).
The Swell Shark (Cephaloscyllium ventriosum)
In 2019, scientists discovered the molecules responsible for a special ability of the swell shark – their biofluorescence. In the dark, special amino acids in their skin reflect the moonlight, appearing bright green in the darkness. This has been found to be species specific, and sex specific, and therefore this unique adaptation may function to help sharks species recognise each other or even potential mates. It may also play a role in camouflage.
Australian Swellshark, Cephaloscyllium laticeps
The Australian Swellshark is also sometimes known as the Draughtboard Shark due to its colouration: It has 11 brown ‘saddles’ that alternate with blotches on its flanks, forming a pattern resembling that of a checkerboard.
Like many other species of Swell Shark, the Australian Swellshark is oviparous. This means that the adult swell shark lays an eggcase with the embryo inside. Depending on the species, the shark may lay two at a time. These eggcases contain a developing embryo and a yolk. Before hatching, the embryo can feed on this yolk for sustenance as it grows. Once fully developed, the embryo hatches out as a fully formed miniature version of the adult shark.
Australian Swell Sharks have a particularly interesting eggcase: cream-coloured and flask shaped, this eggcase has 19-27 transverse ridges (lined horizontally across the eggcase). As with most catsharks, there are long curly tendrils on either end too.
Although the Swell Shark is listed as Least Concern globally on the IUCN Red List of Threatened Species, some species of are listed as Critically Endangered. Take, for instance, the Whitefin Swellshark, endemic to southeastern Australia. Much of its habitat overlaps with areas of intensive fishing effort – as such, although not a target species, they were and still are frequently caught as bycatch. According to the IUCN, populations have reduced by >80% over the past three generations,
Scientific Name: Cephaloscyllium ventriosum
Maximum Size: 110cm
Diet: Small crustaceans, cephalopods and fish
Distribution: Eastern Pacific, most commonly found at 5m to 40m depth.
Habitat: Usually found in rocky areas of kelp beds.
Conservation Status: They’re not typically targeted for food as their meat is generally considered to be of poor quality. They are however, often caught as bycatch in gillnets and trawls.
IUCN Red List Status: Least Concern
For more great shark information and conservation visit the Shark Trust Website
biofluorescence (Sparks, J. S.; Schelly, R. C.; Smith, W. L.; Davis, M. P.; Tchernov, D.; Pieribone, V. A.; Gruber, D. F., CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons)
laticeps (Mark Norman / Museum Victoria, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons)
Eggcase 1 ‘Cephaolscyllium ventriosum’ (vagabondvince310, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons)
Eggcase 2 ‘Cephaloscyllium laticeps eggcase’ (Museum Victoria, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons)
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