Sharks

It's the Discovery Channel's shark week; arguably one of the best weeks on TV! To coincide with this, I thought I would do a shark post. I had wished to do this a few weeks ago when some of us here in Barbados had our very own shark week but thought I would let things simmer down and do more of a factual post so Sharks 101 coming right up!

Sharks, believed to be older than dinosaurs are fish that rely on gills to breathe while underwater. Most sharks must swim continuously in order to maintain a steady flow of water over their gills, allowing them to breathe. However, some species such as the nurse shark can actively pump water over their gills while resting on the sea floor. 

Sharks inhabit all of the World's oceans from coastal, inshore waters to the open oceans with some species being found in freshwater lakes and rivers. There are approximately 500 shark species known with many of them having rough tooth-like skin that feels like sandpaper when touched. Some shark species are oviparous, meaning that they lay eggs while others are viviparous and give birth to live young and have a placenta. The young are born fully formed and as soon as they pop out, they must fend for themselves.  When a shark loses a tooth,  another moves forward from the rows of backup teeth. A shark may use over 20,000 teeth during its life with teeth in some species being replaced every 8-15 days as a result of heavy use as an efficient weapon. As predators, sharks also have acute senses and make good use of smell which aid them in finding prey. They have a large oil filled liver which helps them maintain buoyancy but is also extracted for uses such as Vitamin A for humans.

These cartilaginous fishes play a valuable role in maintaining balance in an ecosystem. They are apex predators sitting (or rather swimming) at the top of the food chain. When sharks are removed, their interaction with other species is disrupted and some populations are no longer kept in check. 

Due to being a long-lived species that takes many years to mature and having only a few young at a time, sharks are vulnerable to overfishing for their meat, liver oil, fins and skin. Due to this slow rate reproduction and growth, these species cannot sustain heavy fishing pressure.  However, humans are not the only enemies of sharks. Killer whales, parasites and other sharks are also responsible for eating sharks. 

Populations are declining globally, many of this attributed to the shark fin trade where an estimated 100 million sharks are killed per year. Many fins are cut off and the sharks are thrown back into the water and die as a result of drowning, bleeding or being eaten by others.

Image via phys.org

There is still a lot of talk  that sharks are the deadliest predator but this is false! Yes, it is true that people have more regular encounters with the things mentioned in this video but it is still interesting. Take a look:Things deadlier than sharks.

So now that we have covered some of the basics on sharks, let's talk about Barbados. There are many shark species in and around our waters including the nurse shark, reef species such as the smoothskin (silky shark), black tips, tiger sharks, hammerhead sharks with sightings of bull sharks occurring as well. With that being said, the chances of the average Bajan having an amazing shark encounter are slim. The local population is not known and thus it is hard to even give an estimate of the number of sharks in our waters. This would be further complicated by some species being migratory. However, there does seem to be an increase in the population, perhaps as a result of increased turtle populations (however no bite marks have been found on the turtles monitored) or due to increased species feeding under and off of the seaweed. 

So next time you see a shark or hear of one being caught, let me know so that we can start to get an idea of numbers together and proceed from there.

Happy Shark Week!