10 Things You Didn't Know About Sharks
1. They come in a range of shapes and sizes
Dwarf lantern shark
The dwarf lanternshark is thought to be the smallest species growing up to approximately 20 cm in length. Not much is known about this species as so far it has only been found in 200-400m of water off of Colombia and Venezuela.
Whale shark (c: Oceana.org)
The largest shark is the whale shark which can grow up to 9m (some have been recorded at over 12m). Just like the large whales, the whale shark also feeds on the smallest creatures in the ocean - plankton! It can be found in the open waters of tropical and sub-temperate oceans. There are even reports of these sharks in the Summer of the Northern North Island.
2. They have no bones
Sharks are a type of fish known as elasmobranchs. This means that instead of bones, their skeleton is made up of cartilage which is the same as what your ears are made of.
3. They can detect electricity
Sharks use their ability to detect electrical currents to pick up on the small movements made by their prey, this is called electroreception. The sensors, known as ampullae of Lorenzini are small pores on the snout and other areas of the body.
4. You can hypnotise them
Sharks, if flipped upside down, go into a trance-like state similar to that of being hypnotised. This is called tonic immobility. New Zealand coastal orca use this to their advantage when hunting sharks and rays (who also have tonic immobility).
A New Zealand orca parading a successful shark hunt
5. Some feed on the flesh of living whales
Cookie-cutter sharks live in tropical and temperate open ocean waters. They feed by latching on to whales (and other large animals) and scooping out a circular chunk of skin and blubber, the result is a cookie-cutter shaped hole in the whale which eventually heals over time.
When we are on safari, we often see some of the Bryde's whales with fresh and/or healed cookie cutter scars. This can help us gauge if particular individuals have recently spent time away from the Hauraki Gulf in deeper waters.
6. They are one of the oldest living animals on the planet
Sharks have been around for approximately 450 million years, well before the first dinosaurs who only appeared 230 million years ago! The hammerhead group is the youngest and first appeared on scene 195 million years ago.
A smooth hammerhead shark cruising the Hauraki Gulf Marine Park
7. Sharks are amongst the most threatened animals
Unfortunately, sharks are considered to be 'Threatened' by the IUCN with many species classified as 'Vulnerable', 'Endangered' or 'Critically Endangered'. They are threatened for many reasons including fishing pressure where they are either caught as bycatch or are targeted for their use in medicine and as a delicacy in different areas of the world.
8. They are super important for the world's oceans
Sharks are key to keeping everybody else in the ocean in check. As an apex predator, they help to regulate the lower levels of the food chain by limiting other species distribution, predating on the weak, ill and vulnerable and on various different prey types
Without sharks, the rest of the food chain and the ecosystem would be altered leading to other species being affected either positively or negatively. In fact, it has been shown that areas with sharks have a great number of different species living within it.
Sharks like this bronze whaler shark, help to regulate the ocean's ecosystems
9. Shark 'attacks' are rare
The majority of shark attacks are a case of mistaken identity and generally, if the shark bites, it is only once before it realises its mistake.
Worldwide, there are approximately four fatalities caused by these mistakes each year. On the other hand, it is estimated that approximately 100 million sharks are killed per year through human activity.
10. You can see them in the Hauraki Gulf Marine Park
We encounter sharks in the Hauraki Gulf Marine Park right next to Auckland City. They are mostly seen during the summer when adults come into the shallower, coastal areas to give birth to their pups. Once the pups are born, there's no parental care so the adults generally head back out again soon after whilst pups may stay around to feed and grow.
A hammerhead shark glides past passengers on the Dolphin Explorer