Bronze Whaler – Carcharhinus brachyurus
Family – Carcharhinidae
Geographic location / distribution
Habitat: Bronze whalers are coastal-pelagic species, preferring inshore and offshore temperate waters.
They range from close inshore in the surf zone to far offshore, from the sea surface to 400m in depth.
Populations of bronze whalers in both hemispheres have seasonal migrations that are in response to the changes in water temperature and other factors like food availability, reproductive events, sex and age.
Maturity and Sizes
Bonze whalers are born at a size of 60cm / 23.6 inches; females reach maturity from 2,4m / 7.8feet and will reach a maximum size over 3m / 9.8feet.
Physical description and identifying characters
The snout is moderately long and narrowly rounded, with small anterior nasal flaps
The first dorsal fin with bluntly pointed apex and short free rear tip is much larger than second dorsal or anal fins. The first dorsal fin originates over or behind free rear tip of pectorals. The second dorsal fin has short free tip and originates over or slightly behind the anal fin. The inter-dorsal ridge is usually absent with the pectoral fins long, falcate and narrow-tipped. The striking colour of bronzy or olive grey above, white below; with no conspicuous marks on any of the fins; with a moderately prominent white band on each flank.
Small, silver and scale less with a trunk-like snout – there is no denying that St Joseph sharks are unusual-looking fish. Their bodies are soft, their heads are large and they only have a single gill opening on each side.
Their unusually long snout is an advanced sensory organ that St Joseph sharks use to detect prey. They also have a venomous spine protruding from their dorsal fin that is used for self-defence.
A “real life” chimaera, the reason they are so weird is that they branched off from other members of the Chondrichthyes (cartilaginous fishes) family about 400 million years ago.
Elasmobranchii (the subclass that contains sharks and rays) evolved the distinct characteristics we associate with cartilaginous fishes, but the Holocephali class took a different evolutionary path.
They are a member of the subclass Holocephali, commonly known as chimaeras – the only member of this group commonly found in South African waters. In Greek mythology, a chimaera was a beast composed of the parts of different animals, many of which you may have heard of – minotaur’s gryphons and Cerberus.
Unlike these mythical creatures, the St Joseph shark is as close to a real-life chimaera as we can get – a combination of traits commonly associated with sharks and those associated with bony, ray-finned fish. You can think of a St Joseph shark as being halfway between a typical fish and a typical shark.
Here are some of the key differences:
Elasmobranchs have multiple gill openings, but Holocephali like St Joseph sharks only have one on each side – a trait they share with bony fish.
In addition to having only one set of gills, these are covered by operculum’s structures only seen in bony fish. Their upper jaw is fused with their skull, whereas the upper jaw moves freely in true sharks.
Like other sharks, St Joseph sharks have external claspers that are used for reproduction. However, they also have three tentacle-like structures, two that can be extended from the pelvis and the other from their heads, to help clasp the female. Unlike sharks, their teeth are not replaceable and they only have three pairs of large grinding teeth that must last their entire lives. They have separate genital and anal openings.
Other members of Holocephali are just as weird as the St Joseph shark – falling into the genera of ratfishes, rabbitfishes and elephant fishes.
Helicopter Shark is a composition of two photographs that gives the impression that a Great white shark is leaping out of the water attacking military personnel climbing a suspended ladder attached to a Special Forces UH-60 Black Hawk helicopter. The photo was widely circulated via an email in 2001, along with a claim that it had been chosen as “National Geographic Photo of the Year”. The email in question was usually written in the following form: “and you think you are having a bad day at work”
The photo is similar to an incident in the 1966 film Batman where a shark attacks Batman on a ladder from a helicopter. This raised suspicions that the photo in question was a hoax. National Geographic publicly disavowed the photo. The hoax has been discussed in various texts, including a marketing book to teach lessons about influence and a book on teaching critical thinking.
The final edited photo was created by combining a photograph of a HH-60G Pave Hawk helicopter taken by Lance Cheung for the United States Air Force (USAF), and a photo taken by South African photographer Chris Fallows from our very own Apex Shark Expeditions. While the helicopter photo was in fact taken in front of the Golden Gate Bridge, the photo of the shark was ironically taken in False Bay, South Africa.
Below are the original images.
The tiger shark gets its name from the characteristic vertical bars that cover the sides of its body. Though these bars fade slightly as individuals reach adulthood, they are very noticeable in juveniles and at least party visible throughout the lifetime. Reaching lengths of at least 18 feet (5.5 m) and 2000 pounds (nearly a metric tonne), the tiger shark is the fourth largest shark and second largest predatory shark, behind only the Great White.
Tiger sharks are aggressive predators, famous for eating just about anything they find or are able to capture. They have been known to eat many different fishes and invertebrates, seabirds, sea turtles, some marine mammals, stingrays and other rays, smaller sharks, sea snakes, and scavenged dead animals, among other things. Several tiger sharks have been known to eat garbage, including metal, plastic, wood, fishing gear, and other trash. Though they are generalist predators, in some areas, tiger sharks likely specialize on certain highly available prey. For example, in Hawaii, tiger sharks are known to regularly attack and eat green turtles and Hawaiian monk seals near the nesting beaches for those two species. Scientists often observe individuals with missing flippers that have been bitten off by a Tiger. At other island groups, tiger sharks are known to congregate near seabird rookeries during the times when young birds are learning to fly (and often end up on the sea surface). Finally, tiger sharks have been known to bite people, and their rather large size leads to occasional fatalities, particularly in areas where large numbers of people use the ocean, recreationally.
Tiger sharks mate via internal fertilization and give live birth to as many as 80 or small young. Though they give live birth, tiger sharks do not connect to their young through a placenta, like in most mammals. Instead, embryos develop inside individual eggs until they hatch. Only then does the mother give birth to live juveniles. After they are born, young tiger sharks are already natural predators, and they eat coastal fishes and invertebrates. Adult tiger sharks have no natural predators, though juveniles may be eaten by other sharks, including adult tiger sharks. For this and other reasons, juveniles and adults live in slightly different habitats. Adults prefer the open coast and high-energy coral reefs, while juveniles are typically found in estuaries and protected bays. This division of habitat use may offer some protection to the juveniles from cannibalistic adults.
Though the tiger shark is thought to be a predominately coastal species, its geographic distribution includes all tropical and temperate waters around the world, so some individuals must migrate between island groups. Experts consider tiger sharks to be ‘near threatened’ with extinction, noting the reduction in their numbers from targeted and accidental catch in fisheries. Their reputation as a species that bites people (though very rarely) makes them a target of population control efforts in some places, a practice that is not supported by scientists anywhere that it occurs.
Tiger sharks can grow up to 18 feet (5.5 m) long and 2,000 pounds (900 kg), making it one of the largest shark species.
Tiger sharks are named for the distinctive, grey vertical stripes or spots covering the sides of their bodies.
Tiger sharks are known for eating almost anything, including other sharks, fish, seabirds, dolphins, sea turtles, rays and crustaceans. They have also been found with many non-food items in their stomachs, including metal objects, plastics, burlap sacks and other refuse.
Female tiger sharks have anywhere from 10 to 82 embryos and give birth to an average of 30 to 35 pups per litter.
Tiger sharks live in shallow, coastal waters, but have been seen 1,150 feet (350 m) deep.
Recognizable by the distinct yellow hue of its skin, the lemon shark occupies coral keys and mangrove forests along the Atlantic Ocean and parts of the Pacific. This shark’s stocky build and other physical features make it a powerful predator underwater, but it is also a common target of commercial fishers looking to sell and trade the shark’s fins and meat.
The lemon shark’s yellow skin colour provides perfect camouflage against sandy in-shore areas where it often forages for food. This, along with the shark’s flattened head and short snout, makes the lemon shark a skilful predator of bony fish, crustaceans and stingrays. Occasionally, this species will also be observed eating seabirds or smaller sharks. An adult lemon shark may grow to be 10 feet long, making it one of the larger species of sharks in our oceans. The lemon shark’s retina is also equipped with a specialized horizontal band, or “visual streak,” that allows the shark to see fine detail and colour when underwater. Though lemon sharks prefer shallow coastal waters, some individuals have been observed entering fresh water or undergoing migrations through the open ocean. Still, lemon sharks prefer a defined home range and may congregate in groups of up to 20 individuals to feed together at dawn and dusk. During the day, lemon sharks can be observed “resting” on the seabed, waiting for small fish to clean off parasites from their body, however this behaviour takes up more energy than swimming as the shark must continually pump water over its gills to breathe.
The lemon shark is viviparous, meaning it gives birth to live young rather than eggs. Embryos develop inside the mother for up to 12 months until the female seeks shelter in a shallow nursery during spring or summer to give birth. A litter of lemon sharks may be as large as 17 pups. Pups remain in the nursery for several years, sheltered from larger predators, and feed on nutrients from nearby mangroves. Lemon sharks reach sexual maturity at around 6 years of age and may live for up to 27 years.
The lemon shark is targeted by commercial and recreational fisheries throughout its range and is listed as Near Threatened by the IUCN Red List. The shark’s fins and meat are highly sought after to be sold on international markets. The thickness of the lemon shark’s skin also makes it ideal for the production of leather.
A 410-million-year-old fossil , the fish, known as Minjinia turgenensis, had a skeleton made of bone, as opposed to the cartilage that sharks are largely comprised of now, save for their teeth. Experts discovered the fossilized skull in the Mongolian mountains.
Conventional wisdom says that a bony inner skeleton was a unique innovation of the lineage that split from the ancestor of sharks more than 400 million years ago, but here is clear evidence of bony inner skeleton in a cousin of both sharks and, ultimately, us.”
It’s possible that M. turgenensis could have been larger than Great whites, with some members of the placoderm (jawed fish) species reaching 30 feet or more in length. Although M. turgenensis is believed to have been significantly smaller than modern-day whale sharks or Great whites at approximately 1 foot long, it has made an enormous impact, suggesting that sharks once had bone and then lost it, researchers said.
In addition to having a skeleton comprised of bone, it had bony plates over its head and shoulders that acted as shields, “extensive armor” as it swam the ancient seas.
“If sharks had bony skeletons and lost it, it could be an evolutionary adaptation,” Brazeau added. “Sharks don’t have swim bladders, which evolved later in bony fish, but a lighter skeleton would have helped them be more mobile in the water and swim at different depths.
Is a Dunkleosteus a shark?
Dunkleosteus was the fifth most dangerous sea predator in Sea Monsters.
The Dunkleosteus existed in the late Devonian period and the prehistoric levels takes place 355 million years ago. They were already extinct during that time. Even its echolocation sprite resembles a shark. It grew to 10 metres (33 feet), and was the top predator of its time and one of the top predators of the Paleozoic era.
Dunkelosteus belongs to the Placodermi, a family of armour-plated fish. It was an arthodire – one of the more advanced members of the placoderm fish.
Dunkelosteus was probably the largest member of the placoderms, and the largest animal up to that time, which would stay that way until the evolution of the dinosaurs. The Placodermi first started appearing in the Silurian, and all of them were extinct by the late Devonian. There are no modern descendants.
Dunkleosteus had one of the most powerful bites of any fish, well ahead of all modern-day sharks, including the Great white shark.
Dunkleosteus could concentrate a force of up to 8,000 pounds (3,628 kg) per square inch at the tip of its mouth, effectively placing Dunkleosteus in the league of Tyrannosaurus rex and modern crocodiles as having the most powerful known bite. Dunkleosteus could also open its mouth in one-fiftieth of a second, which would have caused a powerful suction that pulled the prey into its mouth, a food-capture technique reinvented by many of the most advanced teleost fishes today. Due to its
heavily armoured nature, Dunkleosteus was likely a relatively slow (albeit powerful) swimmer.
A dunkleosteus was actually bigger than a killer whale.
By Devonian standards, Dunkleosteus was one of the most highly evolved animals. It was one of the earliest jawed fishes. Instead of actual teeth, Dunkleosteus possessed two long, bony blades that were extensions of its jaw that could slice through flesh and snap and crush bones and almost anything else. These plates also sharpened themselves every time the fish closed its mouth.
It was a vicious, gluttonous hunter, and probably ate whatever hapless creature it could overpower. The discovery of Dunkleosteus armor with unhealed bite marks strongly suggest that they cannibalized each other when the opportunity arose. Frequently, fossils of Dunkleosteus are found with boluses of fish bones, semi-digested and partially eaten remains of other fish. As a result, the fossil record indicates that it may have routinely regurgitated prey bones rather than digesting them.
Cladoselache did not prey on Dunkleosteus, it was the other way around. It is commonly thought, and commonly said that placoderms, such as Dunkleosteus, were outcompeted by the smaller, swifter fishes, such as the early shark Cladoselache. However, this assessment fails to take into account that predatory placoderms would have inhabited different ecological niches than the early sharks during the Devonian period. As such, claiming that Cladoselache was a more efficient predatory fish than Dunkleosteus because the former was apparently faster than the latter would be akin to saying that the orca is a superior marine predator than the swordfish because orcas have teeth. Dunkleosteus may have also been one of the first animals to internalize egg fertilization, and thus sexually reproduce in the manner that most mammals do today.
Although Placoderms only existed for 50 million years, their mark on the fossil record is quite visible. They were a pioneer in the later scenes of the Paleozoic, and were vital to the success of the vertebrates. The Placoderms died out in the late Devonian for reasons that are still not well understood.
The impression of a Nurse shark has always been a very slow and sleepy shark that spends its time just lazily sitting on the ocean floor while pumping water through its gills in order to breathe. They prefer warm shallow waters and of course their home range puts them in the western Atlantic and eastern Pacific oceans. Their favourite spot was of course, on the sea floor. Here they sat not moving a muscle. Although normal size is around 7.5 feet they can get up to 10 feet in length and can weigh as much as 260 pounds. They have very strong jaws which they use to crush their prey such as shellfish. But they also feed on fish, shrimp and squid. Their jaws are filled with thousands of tiny serrated teeth but despite this they are not aggressive towards humans at all unless unintentionally disturbed. These teeth during summer months are replaced every 10 to 20 days. They are nocturnal hunters and hunt for prey near to sand and even in the sand. Incredibly they are also known to be able to walk on the sea floor using their pectoral fins.
Nurse sharks may appear lazy but they have an amazing adaption that allows them to pass water over their gills to obtain oxygen by not moving as most other sharks need to do. This is called Buccal pumping and it works by using oral muscles to literally suck water in through their mouth and then move it over its gills. This vacuum skill also assists them in hunting as they suck up their prey when they make a successful catch. There are many fascinating attributes and adaptions to them.