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Friday, June 14, 2019

Dylan and Allie’s Guide to How to Survive a Shark Attack


[Both] Hey, Dylan and Allie here!
[Allie] Summer’s arrived in the Northern Hemisphere, (okay, not officially, but it will in one week) and we thought that it’d be great to share some of our tips on how to survive a shark attack.
[Dylan] We want you to enjoy the ocean over the summer and know you’re safe and secure with some of these tips. Of course, shark attacks are extremely rare. You’re more likely to run afoul of Mayor Aldridge than get killed by a shark attack.
[Allie] Or killed by a coconut or a lightning strike.
[Dylan] Right. And as I’m sure you’ve heard; we kill a lot more sharks than sharks will ever kill of us. Humans kill millions of sharks per year, while sharks kill an average of 6 people per year worldwide.
[Allie] While both Dylan and I have a great appreciation of sharks, we do understand the fear they can instill in people. As someone who’s had several shark encounters myself, both positive and near shark attacks, I understand how someone facing a threatening shark feels.
[Dylan] So Allie thought it’d be a good idea to share some of the techniques she and others have used to prevent and survive shark attacks.

[Both] So without further comment, here’s our guide:

How to Survive a Shark Attack
By: Dylan and Allie 


How to Avoid Being Attacked

Sharks, like many wild animals, prefer to stay away from negative encounters with humans. There are many warning signs a shark will give off before attacking that if you pay attention, can alert you to a pending serious situation. One such warming is the posture of a shark. If a shark begins to arch its back, it’s annoyed and stressed out. This is a sign that you need to back away and give it space. Another is the behavior of a shark, if it circles you, it can mean one of two things. Either the shark is just curious about you, or it intends to attack and is looking for a vulnerable position where it can approach. The best way to avoid this is to keep your eye on the shark and rotate in the water to keep your gaze focused on it to where its never behind or to the side of you. If you are with someone else, stay back to back to them so that you both are protected and one of you always has a visual on the shark. Make yourself look as big and menacing as possible. If you swim away in a hurry or act scared, the shark will assume you are a prey item. Keeping calm is key to maintaining control of the situation. As you monitor the shark's behavior, stay still and calm, but if the shark begins to act aggressively, slowly make your way back to the boat or shore. If you are too far away from safety, but have anything in your hands like a pole, camera, or spear gun, place it in-between you and the shark and use it to redirect the shark away from you if it gets too close. It’s important to gently redirect it, not attack offensively, which a shark could take as a provocation to attack you. Some sharks have been known to dislike the sudden appearance of bubbles in the water. If near the surface, you can slap your arm down into the water to create a sudden column of bubbles that can deter an incoming shark.

For those of you who don’t swim in the open ocean, there are ways to avoid being attacked in inshore waters as well. First and foremost, if you are bleeding from anywhere on your body, do not enter the water. It doesn’t matter how small the amount of blood is, sharks can smell it within a one-mile radius. If you start bleeding while you’re in the water, immediately get out. As tempting as the water is to enjoy, it isn’t worth risking your life or those of others around you. If you do see a shark in the water, do not provoke it by touching it or attacking it yourself.

In general, whether you find yourself on the beach in shallow water or swimming in the open ocean, never swim alone. Sharks (and predators in general) go for the loner. If you are with others, sharks are much less likely to attack. Also, be careful about what you wear for swimwear. Anything with high contrast, bright colors like yellow, or metallic silver (swimsuit or jewelry) will attract sharks. This is because it will make you appear more like a fish. If you don’t want to be prey, don’t act like it. That includes excessive splashing. When you splash around, you mimic the death throes of a dying fish. This will attract sharks because it’s like a dinner bell ringing. If you have a dog or other pet that likes the water, keep them out of the ocean as well. Their swimming style creates a lot of unnecessary splashing.

The time in which you swim is also paramount. At night, many shark species are more active, and visibility is little to none for humans, both of which makes it extremely dangerous for us. Dusk and twilight are also not good times to swim because sharks are actively looking for food, and once again, the water clarity may not be conducive for you seeing sharks approaching.

Just like time is important, so is water quality and location. Humans can’t see well in murky water, but shark senses give them a clear view of what is in the water. They can easily ambush prey and that includes accidental attacks on humans. Stay away from the mouths of rivers as they tend to be more brackish and can have more pollution or sewage in them. Anywhere where someone is fishing is a bad place to swim. Combine all the other issues we’ve already warned you about (like excessive splashing, blood, and coloration) and you have the perfect situation for a shark invitation to dinner. Harbors aren’t a good place to swim because of murky water and boats that could run you over, (let’s be reasonable here!).

Pay attention to other animals around you. If you see typical prey items of sharks like seals, fish, or sea turtles abruptly leave the area, chances are, a shark may be present. However, do not think that the presence of a seal, fish, or dolphins mean a shark isn’t nearby or in the water. Just like lions and their prey species coexist in the Serengeti, sharks and their prey coexist in the ocean. The presence of one does not mean the absence of the other.



How To Survive An Attack

If all else fails and you find yourself in the jaws of a shark who refuses to let go, fight back. Play dead and you soon will be. Sharks don’t fall for the playing dead act. For them, it’s an invitation to keep eating. Fight back by pulling or punching the gills of the shark. For sharks, it’s the only way they can breathe and if you attack them there, they will most likely let go. If the gills are out of reach, but the eyes are not, jab them in the eye. No creature likes having their eyes attacked, (think of how bad it hurts when you accidentally jab yourself in the eye). Although some scientists have suggested punching the shark in the nose, we suggest against it. It is true that shark snouts are sensitive due to the ampullae of Lorenzini receptors they have there. But the truth is that humans are slow underwater compared to a shark and the snout of the shark is alarmingly close to their jaws. There was even a swimmer in Brazil who lost his hands because he tried punching the shark in the snout and the shark bit off his hands. We think the safest bet is to keep your body away from the shark’s razor-sharp teeth.

Whatever you do, don’t stop fighting until you’re free from the shark’s jaws. Once free, get out of the water as soon as you can. If you’re far from shore, keep an eye out for any sharks as you swim back to safety. If near others, cry out for help. Whether alone or not, keep pressure on the wound as best as possible or create a tourniquet above the wound if it’s large. Get emergency medical attention as soon as you’re out of the water to help control the bleeding until you can get to the hospital. Even if you think the bite wasn’t too bad, a shark’s mouth is full of all kinds of bacteria and you don’t want to get gangrene, so receiving medical attention is necessary.

Of course, the only 100% sure way to ensure you’ll never be attacked by a shark is to never enter any body of water outside of a swimming pool. But what fun would that be? You’d miss out on the wonder and beauty of the ocean. So just remember our tips, and you’ll have a fun and safe summer.

Author’s Note: While Dylan and Allie have had their fair share of shark encounters, neither are experts in the field of shark science. If you want to read a few modern resources on how to avoid and survive a shark attack, click any of the links below:

Friday, May 24, 2019

Research for Shark Station


Research for Shark’s Station

Introduction
While Oceania: The Underwater City took a lot of research to complete and Allie’s Return considerably less, Shark Station fell somewhere in between. I found myself returning to researching space science and in particular, how to live on a space station. I also had to learn about growing food in an isolated environment without sunlight and soil. And of course, I had to research more about some of the animals I wished to feature in the novel. In all, a week of intense research gave me enough information to write the latest adventure of Allie’s and Dylan’s. Here’s just a small portion of what I learned.

Setting: The Sirena Deep

When I set out to write this novel, I knew I didn’t want to choose the iconic Challenger Deep to place the story. It was too well known and didn’t make sense for a secret research station for Oceanians to be kept safe from Land Dwellers if it’s a place people continually strive to dive to. Instead, I decided on the second-deepest part of the ocean, but upon commencement of my research, I noticed an obvious problem. There is almost no research on the Sirena Deep. Besides the knowledge of how deep it is, little is known about what lives there. I try to be cautious in my research and use as many primary sources as I can. However, when researching the Sirena Deep, all the notes I took didn’t even take up one page of a Word document.

So, here’s what I found in bullet form:
·      Sirena Deep is 200km (124 miles) east of Challenger Deep’s location
·         The depth is 10,809m (35,462ft)
·         Microbial mats that fed on hydrogen and methane were found there
·         Sirena Deep is 144.8 km (90mi) south of Guam
·         Sirena Deep was discovered in 1997
·         The location of Sirena Deep is 12.0654° N, 144.5811° E.


To read the scant research yourself, you can click on the below links:


Mariana Trench

After realizing there was so little research on the Sirena Deep, I looked into the Mariana Trench next. To my (by now) no surprise, there wasn’t a lot about the Mariana Trench either, but it was substantially more than the Sirena Deep. The trench ranges from 6,000 to 10,000m (19,685-36,089ft) and is shaped in an arc that is 2,550km (1,584.5mi) long and 50km (31.1mi) wide. Over 200 different types of microorganisms were discovered in the mud collected by James Cameron in the Challenger Deep. Within the trench, there are several submarine volcanoes. The pressure at the bottom of the Mariana trench is 8 tons per square inch or (703kg per square m). Scientists on the HMS Challenger used sounding equipment to discover the trench in 1875. There are hydrothermal vents that emit acidic hydrogen sulfide. Bacteria eat this sulfide and are at the bottom of the food chain down there. Temperatures surrounding these vents can be up to 300°C (572°F). Animals that live at the bottom of the trench are estimated to live a long time due to the cold, some estimates go as far as 100 years or more.  Instead of photosynthesis, chemosynthesis creates the basis of the food chain.

To read more about the Mariana Trench, click on some of my research links below:


Growing Food in Space

For researching how to grow food in an environment lacking in sunlight and soil, I once again looked to NASA. I learned about how hydroponics works and was amazed by it. It was not only a viable solution for the Shark Station inhabitants, but also for people in general in both Oceania and the Above World. Hydroponics works by using a bit of soil usually placed in a soil pack, water, and an alternative light source such as an LED light. The main problem with this method of growing food is the bacteria and fungus problems it can create. A lot of specifics goes into how hydroponics works and it gets quite detailed, so if you want to learn more about it from a better resource than myself (aka NASA), click the below links.



Like with Allie’s Return, most of the rest of the research focused on the marine animals featured in the novel, which you’ve already read about in the three previous blog posts. If you missed them, you can find them at the following links: part 1, part 2, and part 3.

I hope you enjoyed reading some of my research for the novel and have been inspired to do some more of your own. If your interest has been piqued, feel free to click any of the above links to learn more. If you have any comments, you can leave them here on my blog or email me directly at elizataye@gmail.com.


Friday, May 3, 2019

Sea Creatures Part 3 – Animals of the Abyss


Introduction

We’ve reached the final blog post for sea creatures featured in Shark Station. In this post, I’ll be covering the mysterious creatures of the deep. If you’ve happened to miss the previous two parts of this special, click here for part 1 and here for part 2. Except for the barreleye fish, the other creatures in this blog post were new to me until I began researching for this novel. However, scientific research is still lacking for each species featured in this post, so I’ll apologize now for the limited information. If you’d like to read more, you can click my reference links at the bottom.   



Dumbo octopus

NOAA Okeanos Explorer [Public domain]


There are over 15 known species of Dumbo octopuses, but the one featured in Shark Station is Grimpoteuthis abyssicola. The Dumbo octopus gets its common name from the Disney movie because of its large fins that resemble ears. G. abyssicola stands out compared to other Dumbo octopuses due to the blue coloration on its mantle, with pink “ear flaps” that are actually its fins. Typically, they are between 20-30cm (7.9-11.8in) long, but the largest recorded individual weighed 5.9kg (13lbs) and was 1.8m (5.9ft) long(1). Distributed throughout the Pacific Ocean from Oregon down to New Zealand, they live between depths of 3,000-7,000m (9842.5-22,965.9ft). Their diet consists of crustaceans like amphipods, copepods, isopods and also bristle worms. They find their food either floating in the ocean or lurking around hydrothermal vents(2). As for creatures that prey on the Dumbo octopus, sharks, tuna, and marine mammals such as dolphins are their main predators(1).
                                 
The Dumbo octopus is also nicknamed the “umbrella octopus;” the reason being their various ways of movement(2). Most commonly they use their fins to “flap” through the water and their tentacles to steer(1). However, they can also expand or contract their webbed tentacles, which resembles the opening and closing of an umbrella, hence their nickname. Other forms of locomotion include forcing water through their funnel to gain a burst of speed or crawling on their tentacles(2).

Dumbo octopuses differ from other octopus in a variety of ways. For one, they lack an ink sack other octopus species use to evade predation(1). Unlike other octopuses, they don’t have to use their beak to tear into their food. They have a degenerated radula that permits them to swallow prey intact(2). Dumbo octopuses are oviparous and lay their eggs on the ocean floor. The females are able to retain sperm and allow fertilization of their eggs at any time, which suggests that there is no breeding period for this genus(1).

According to the IUCN Red List, this species is data deficient as of August 20, 2014, meaning that not enough data has been collected on them to assess whether or not their populations are at risk(3).

If you would like to see footage of a Dumbo octopus swimming courtesy of the Smithsonian Institute, click here


Snailfish

Gerringer M. E., Linley T. D., Jamieson A. J., Goetze E., Drazen J. C. [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)]


Although there are over 300 species of snailfish, the one seen in Shark Station is Pseudoliparis swirei, which is known as the Mariana snailfish. They are pinkish-white in coloration with translucent skin that allows the internal organs and muscles to be seen beneath the skin. They have small eyes and the rows of teeth increases with the size of the fish. Unlike many other species of fish, snailfish have no scales. They range from 89-235mm (3.5-9.3in) long and live at depths of 6,900-8,000m (22,637.8-26,246.7ft). As they were recently discovered, very little is known about this species(4).


To see video footage of a live snailfish, click here


Barreleye Fish

https://www.flickr.com/photos/40199468@N07/4046660963/sizes/m/


The barreleye fish (Macropinna microstoma) are peculiar-looking fish that have eyes facing upward instead of outward(5). The area where most people mistake their eyes to be are actually their olfactory organs. The eyes rest in a green fluid that fills the entire front area of the head. Their head is translucent, which allows the barreleye to see through its head to its prey lurking above. Ambush predators, they lie in wait before attacking their prey. To scan for prey, they have the ability to rotate their eyes. While they wait, their flat fins allow them to lie motionless in the water and only take off once prey has been detected. Jellyfish and other cnidarians make up their diet but it is also thought that they may eat zooplankton(5)(7). Since they have a large digestive system, it suggests that they may eat a variety of drifting animals(6).

Solitary creatures that live in the mesopelagic zone, their distribution ranges from The Bering Sea in the North, Japan to the West, and Baja California in the South. In the Pacific Ocean, they are known to live at depths of 16-1267m (52.5-4,156.8ft) and they have been caught in trawl nets as deep as 3600m (11,811ft) (7). However, they are distributed worldwide in all but the polar oceans(5).


If you'd like to see a live specimen of a barreleye fish, check out this video by Monterey Bay Aquarium Research Institute (MBARI).


This concludes the last sea creature feature for Shark Station. I hope you enjoyed reading it. From now on until the next special, the blog posts will be released every three weeks. As usual, my next blog post will be the sharing of some of the research I conducted for the novel (beyond that on the sea creatures). In the meantime, if you have any questions or comments, you can leave them here on my blog or email me at elizataye@gmail.com. I always love hearing from my readers!


References


Friday, April 19, 2019

Sea Creatures Part 2 – Animals of the Pelagic


Introduction

In Shark Station, most of the novel takes place deep beneath the waves, but there is a small portion that takes place near the surface. Due to many of the creatures encountered at the surface already being highlighted in previous blog posts (humpback whales, sperm whales, bottlenose dolphins, etc.), there will be only two animals highlighted in this post. In a way, it is poignant because the pelagic zone is so void compared to the continental shelf and coral reef regions of the sea. Regardless, I hope you enjoy learning about these two sea creatures.  


Mola mola

Flickr user: Ilse Reijs and Jan-Noud Hutten  https://www.flickr.com/photos/39891373@N07/ [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]


The silvery gray-colored ocean sunfish (Mola mola) is a unique creature of the sea. The most distinct feature is perhaps their shape. They have a flattened oval shape that contrasts with most fish species. Instead of a typical caudal fin, they have a truncated caudal fin fused to the body called a clavus that acts as a rudder to help them steer through the water(1). Elongated dorsal and anal fins are primarily used for locomotion. Their mouth is formed from two hard teeth plates that resemble a beak(2). All of these features lead to their nickname “swimming head”(1). Although their coloration is a silver to grayish-white color, they sometimes have gray spots on the posterior half of their body. Living for 8-10 years, they can grow to 2,268 kg (5,000lbs) and be up to 3m (10ft) long and 4.3 (14ft) tall(1)(3).

Distributed worldwide in temperate and tropical oceans, the ocean sunfish is often seen near the surface, but has also been recorded diving to depths and traveling long distances. It is thought that they dive deep to avoid predators. Predators of the ocean sunfish are killer whales, sea lions, and sharks(2). Ocean sunfish themselves prey upon algae, brittle stars, crustaceans, fish, jellyfish, squid, and zooplankton(1)(2). They have a mucous lining in their digestive tract to protect them from being stung by the jellyfish they eat(2).

Ocean sunfish are oviparous (meaning that they hatch from eggs). From larva to adult, they will grow 60 million times larger than the size in which they began(2). Mola molas have high fecundity. The females can produce up to 300 million eggs each breeding season; more than any other known vertebrate currently alive today. While the sunfish is still a larva, they have a tail and caudal fin, but eventually, in their second larval stage the tail absorbs and all the spines disappear. As juvenile ocean sunfish begin to grow, they can average up to almost 0.82kg (1.8lbs) a day in growth(4).

As for threats to their existence, humans in parts of Asia eat ocean sunfish and they are used in Chinese medicine(4). According to the IUCN red list, they are listed as vulnerable and their population is decreasing(3). Major threats besides human consumption are bycatch from drift nets and plastic debris such as plastic bags that they mistake for jellyfish(1).

An interesting fact about the ocean sunfish is that it’s the largest bony fish on the planet(1). They are related to pufferfish, but only exhibit spines during the second half of their larval stage(2).





Portuguese Man o’War

Rhalah [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]


Image courtesy of Islands in the Sea 2002, NOAA/OER. [Public domain]


The Portuguese man o’war (Physalia physalis) are closely related to jellyfish, but they are not a jellyfish. Instead, it is a siphonophore, which is a colony of individuals working as one(5). The siphonophore colony is made up of identical individuals that are known as zooids or clones(6). They have four separate polyps. The floating part at the top is called the pneumatophore. It is typically 30cm (12in) long and around 12.7cm (5in) wide. The tentacles are the largest part of the polyps. On average, they are 9.1m (30ft) in length but can grow as long as 50m (165ft) long with nematocysts filled with venom everywhere on the tentacles. The third polyp is the gastrozooids, which are the digestive organisms. The last one is the polyp that functions as the reproductive organ(5).

Unable to move on their own, they drift on the currents or the wind in the pelagic zone. If a threat of surface predation occurs, they can deflate their bubble on the top and submerge for a time(5). The float at the top (pneumatophore) can be a variety of colors such as blue, pink, or violet. The Portuguese man o’war is named as such due to the float resembling old-style Portuguese warships. Like warships, they will often float together, sometimes in groups of 1,000 or more. They feed on small fish and crustaceans(6). To feed, they use their feeding tentacles to stun prey and pull them up into their simple digestive tract. Due to their highly venomous nature, their only predators are sea turtles like loggerheads and the ocean sunfish (Mola mola)(7).

As for conservation, the Portuguese man o' war hasn’t been evaluated by the IUCN yet. Their populations could be thriving or declining, but as of now, scientists still do not know. Although their sting is known to be excruciatingly painful, rarely does it kill a human(1). However, if a  Portuguese man o' war does wash on shore, it can still sting you, even if its been there for weeks(2)!

I know this was the shortest creature feature yet but I hope you enjoyed it as much as the others. In two weeks, there will be another sea creature blog post—the last for Shark Station. Until then, you can check out the first sea creature feature for this novel if you missed it by clicking here. As always, if you have any questions or comments, you can leave them here on my blog or email me at elizataye@gmail.com. I always love hearing from my readers!



References



Friday, April 5, 2019

Sea Creatures Part 1 - Sharks

Sea Creatures Part 1 – Sharks

Introduction

Shark Station gets its name from the sharks that live near and around it. So, I figured they deserved their own special blog post as far as the sea creatures in Shark Station go. Each shark species featured in the novel and also those that were merely mentioned will be getting their own section in this blog post. There will be two more sea creature posts to feature the rest of the animals in the novel. Like for Allie’s Return, any animals that are repeat visitors from previous novels will not have their own feature in these posts (with the exception of the great white shark which wasn’t thoroughly highlighted before). With that said, let’s learn some more about the shark species in Shark Station starting with the most obscure to the most iconic.


Frilled Shark
saname777 from Tokyo, Japan [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]

The frilled shark (Chlamydoselachus anguineus) is a deep-sea shark ranging from the pelagic to benthic zone in depths of 120-1570m (393.7-5,150.9ft)(1)(2). Rarely are they seen at the surface, but sometimes they can be found near the continental shelf(2). They are found worldwide from subpolar to tropical latitudes, with distributions in the Atlantic and Pacific Oceans(1)(3). In the Pacific, they range from Japan to New South Wales and Australia. The females are typically larger than the males growing to a length of 2.0m (6.6ft), while the males only grow to 1.7m (5.6ft) long. Both sexes exhibit gray or darkish brown coloration on the dorsal surface with a lighter shade on the ventral side. Six gill slits lie just before the pectoral fins with the first gill slit closest to the mouth being elongated and wrapping underneath the chin(3). They swim using an eel-like motion, undulating their body through the water(1). Interestingly, their anal fins are actually longer than their dorsal fin, which differs compared to most other sharks(3).

Little is known about the frilled shark in the wild due to its rare sightings. However, they are thought to give birth to live young, which use yolk sacs for nutrition while in the womb(1). The estimated gestation period is thought to be the longest of any chordate (animal with a backbone) at up to 3 ½ years. Each pregnancy they give birth to 2-15 pups and frilled sharks are thought to live up to 25 years old (2)(3). Some distinguishing characteristics that differ from other sharks are that they have fins placed farther back on their body, creating the eel-like appearance and a mouth more towards the front of their snout than underneath it like many other shark species(1)(3). Their lateral lines are exposed to the surrounding water so the hair cells are actually “open” to the water(3).

As for their feeding ecology, frilled sharks feed mainly on squid, other cephalopods, and bony fishes, but have been known to eat other sharks as well (1)(3). Some scientists have proposed that they may be able to close their gill slits to create suction to pull in squid. Their needle-like teeth are thought to make it difficult for their prey to escape. They are capable of ingesting prey almost half of their size(3).

An interesting fact about them is that they have an expandable fold of skin along their ventral side thought to help their stomach expand for digestion. Another interesting fact is that a new subspecies was discovered in 2009 near South Africa, it was named C. Africana(3).

According to the IUCN Red List, frilled sharks are listed as least concern as of February 20, 2015(4).



Goblin Shark (Mitsukurina owstoni)
Dianne Bray / Museum Victoria [CC BY 3.0 au (https://creativecommons.org/licenses/by/3.0/au/deed.en)]

The goblin shark (Mitsukurina owstoni) is known for its expandable jaws that can extend to catch prey in a blink of an eye. However, there is still a lot to learn about this species. Only one was ever maintained in captivity and it only survived for a week (click here to see a video of it swimming in an aquarium at Tokai University in Japan)(7). In the wild, goblin sharks are found in the Atlantic, Indian, and Pacific oceans. Ranging from depths of 95m (311.7ft) to 1300m (4,265.1ft), they inhabit waters off seamounts and continental shelves(6)(7). There are some records that indicate they may be a pelagic species(7).

As for their physical appearance, goblin sharks range from a pinkish color to a grayish purple. Lining the edges of their fins is a bright blue coloration(5). They average between 3-4m (10-13ft) long. The largest caught goblin shark weighed 210kg (463lbs) and over 5.5m (18 ft) long(7). The gestation period is unknown, but the shark is thought to be ovoviviparous like many other large sharks(6). Goblin sharks lack the nictitating membranes that other shark species like the great white have(8).

From stomach contents, goblin sharks are known to eat small bony fish, cephalopods, and crab(8). Their diet consists of crustaceans, fish, and squid(5). To detect prey, they use their ampullae of Lorenzini, then capture the prey with their needle-like front-teeth and pharyngeal suction (7)(8). Their posterior teeth are shaped for crushing, which indicates that they may eat some hard-bodied organisms like crabs and shrimp(7).

As for conservation, the IUCN red list lists them as least concern since at least July 7th, 2017(9).  Threats to them include being commercially fished off of Japan, but usually only caught as by-catch elsewhere in the world(8).



Blue Shark


The blue shark (Prionace glauca) is one of the only truly pelagic shark species. They range from cold temperate waters to tropical waters and can dive as deep as 350m (1148.3ft) 15)(18). They are migratory and have been known to cross oceans. Their long pectoral fins are thought to be used to help them glide on currents as a part of energy conservation. They migrate in search of food and mates(15). The species exhibits sexual segregation, where the females tend to live at higher latitudes than the males and they only congregate to mate (16)(15). As a species, they range from 60° N to 50 ° S latitude(16). The gestation period lasts form 9-12 months and consists of a litter of pups ranging from 35-100 pups, although one litter of 135 was reported(15)(16). As adults, they can grow to 2.7-3m (9-10ft) long, although the largest reported one was 4m (13ft) long(16).

As for their diet, they are known to eat anchovies, hake, dogfish, squid, euphausiids, and mackerel, and seabirds(16).

The IUCN red list categorizes them as near threatened based on the last assessment on October 1, 2005. The major threats to their survival are longline fishing and sport fishing.



Shortfin Mako
Patrick Doll [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)] 

The shortfin mako (Isurus oxyrinchus) is a pelagic (open ocean) shark that can grow to 3.7m (12ft) long and weigh 544.3kg (1200 lbs). They can swim at 45 miles an hour, making it the fastest shark in the sea(10).  They have a countercurrent exchanger which keeps their blood warm enough to maintain a body temperature up to 0.6°C higher than the water around it, which helps them to move quickly through the water (11)(10).

Spread throughout the Pacific Ocean, the shortfin mako ranges from as far north as the Aleutian Islands to as far south as New Zealand(12). They are wide-traveling sharks. Voyages of 2,092km (1,300mi) in a month have been known to occur(11). Adult shortfin makos aren’t known to have any predators, putting them at the top of the food web in the pelagic zone but the juveniles may be eaten by other shark species and perhaps even adult makos(10). Mainly, their diet consists of tunas and billfish, but also squid, blue sharks, sea turtles, mackerels, porpoises and dolphins(11). They’ve even been known to eat swordfish, one of the other fastest fish in the sea(12).

Like the other sharks in this blog post so far, the shortfin mako is ovoviviparous. When they are captured, female makos are known to abort embryos which means little is known about their reproduction. What is known is that they have a gestation period of 15-18 months and litters consist of 8-10 pups which are born during winter(11). The coloration of the mako is an indigo to rich purple color on the dorsal side and white to silver ventral surface with an obvious line of coloration between the two(11)(12). They are thought to live somewhere between 29-32 years(12).

An interesting fact is that the scientific name for shortfin mako name means “equal tail, sharp nose”. Isurus is Greek for equal tail, oxy for sharp and rynchus for nose. There are two species of makos, the longfin and the shortfin. The way to tell the difference between a longfin mako and a shortfin are by the elongated pectoral fins and larger eyes on the longfin mako(12).

As of November 5th, 2018, they are listed as Endangered by the IUCN red list (13). Major threats to them include being fished for commercially, for recreation, and accidentally captured(10).

If you would like to see a video with blue sharks and mako sharks interacting together in the pelagic zone just like in the book, click here



Great White Shark

The great white shark (Carcharodon carcharias) is the most iconic of all shark species. They are known for their size as the largest predatory fish in the ocean(21). They can detect prey movement via the lateral line from 250m away. In quick bursts of speed, great whites can swim at 35mph, but only maintain 15mph(23)(20). Ranging from 3.6-7.62m (11-25ft) in length, they can weigh up to 2,268 kg (5,000lbs) with the females being larger than the males (22)(21). The dorsal side is a dark gray to almost black coloration with a white ventral side, they use this countershading adaptation to keep prey from detecting them.

Found in all oceans except the Arctic and Southern Oceans, they range from cold to tropical latitudes from the coast to the pelagic zone and are known to dive deep in search of food. In the eastern Pacific, they are known to migrate from Mexico to Hawaii(21). They are found from 60°N to 60°S latitude. Some sharks have been known to travel across an entire ocean.  They have been reported as far north as the Aleutian Islands to as far south as Southern Mexico(22).

It is still unknown as to where great white sharks give birth or exactly what size they are at birth. The smallest recorded great white was 1.1m (3.6ft) long and only 16kg (35lbs). An ovoviviparous species, females give birth to live young. The pups hatch within the mother in egg capsules and then the female gives birth not long afterward. The gestation period is thought to be more than a year. Litters can be anywhere from 2-10 and even as large as 17 pups. At birth, they are expected to live up to 30 years(22). As the young grow into adults, they begin seeking larger prey than the small fishes they ate as juveniles, progressing up to large marine mammals(21). Juveniles don’t start eating marine mammals until there are at least 450kg(22).

The great white diet consists of a variety of animals including fish, seals, sea lions, dolphins, sea turtles, toothed whales, and even carrion (dead meat) (19)(20). They have 300 teeth used to grab and tear meat into bite-sized chunks(19). Group hunting has been seen in great whites where they work together to kill prey and then share the kill(23). To maintain their body heat, sharks have a countercurrent exchanger to help maintain a body temperature slightly higher than that of the surrounding water. It helps them to keep their brain and muscles warmer so they can think and move effectively even in colder waters(21).

Some interesting facts about great white sharks are that their only natural predator (outside of humans) is the orca (Orcinus orca). They have been known to kill and even consume sharks including the great white. Great whites also have an “ear stone” that allows it to orient itself in the water, to basically know if they are upside down or not. Specialized eyes with retinas divided into two sections allow them to see in the daytime and low-light. Although behavioral research is ongoing, they are thought to be intelligent and scientists have seen a variety of behaviors of great whites amongst each other from aggressive to non-aggressive(23).

Great white conservation is tricky but extremely important for many reasons. They are an apex predator and they influence the health of the ocean ecosystems in which they play a part. However, no reliable data exists on their populations, but scientists do know their numbers are decreasing(20).  According to the IUCN Red List, they have been listed as vulnerable based on the last assessment on October 1, 2005. Some of the threats against them are sport fishing for their fins and teeth and also as bycatch(19).



Megalodon
Mary Parrish, Smithsonian, National Museum of Natural History [Public domain]

The Megalodon (Carcharocles megalodon), whose scientific name means big tooth, was a shark that lived millions of years ago. They are thought to have lived during the Miocene and Pliocene epoch (15.9-2.6 million years ago). Megalodon teeth have been found on every single continent instead of Antarctica(25). It lived during the Silurian period, 200 million years before the dinosaurs. Much of what we know about megalodons come from inferences based on their teeth, dermal scales, and calcified vertebrae(26). Due to the cartilaginous nature of shark skeletons, the only way to tell the size of the megalodon is by the size of its teeth. Based solely on that, it is estimated that they may have been as long as 18.3m (60 ft), while some think that they could have been as large as 24.4m (80ft) long. The largest tooth ever found was 17.8cm (7in) long, almost 3 times the length of great white teeth(25). Estimates of size put it at 45MT (50 tons)(26).  

Megalodon had 276 serrated teeth and was thought to have fed on whales and perhaps other sharks in the warm waters of the Pliocene epoch(25).

I shouldn’t have to state this, but megalodons are extinct. In fact, the most recent fossil was from 2.6 million years ago(25). The major thought behind their extinction was the warmer waters which would have made it difficult for them to survive, or as their prey adapted to colder waters, they starved because they couldn’t follow them into the colder waters(26).

This concludes the end of the sharks sea creatures blog post. In two weeks, they’ll be another sea creatures blog post, this time focusing on the animals of the pelagic zone. I hope you enjoyed reading this blog post and if you have any comments, you can leave them here on my blog or email me directly at elizataye@gmail.com.

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