Shark Diversity and Order

Sharks come in many sizes and shapes and have a great deal of diversity in the over 500 plus species of living animals. Currently, science divide sharks into 9 specific orders; there are actually 13, but four orders of sharks are entirely extinct. And all sharks -big and small- fit into these categories.

1. Carcharhiniformes, otherwise known as the ground sharks or whaler sharks, include some of the most well known sharks. There are over 270 species making this order the largest of all shark orders. It includes the tiger shark, hammerhead sharks, hound shark, cat shark, shy eye shark, all of the reef sharks, and the bull shark. Some traits that differentiates these sharks from others is their lack of an inner eyelid and enlongated snouts. They average eighteen inches to twenty feet in length.

2. The order Echinorhiniforme contained only two sharks; The prickly shark and the bramble shark. These sharks are named due to the thorn like denticles covering their skin and are slow swimming sharks that dwell in the bottoms of their chosen environments

3. Lamniformes, otherwise known as the mackerel sharks, include the most famous shark- the great white. There are 15 species in this order which also includes the megamouth shark, mako shark, thresher shark, goblin shark, porbeagle shark, sand tiger shark, and basking shark. They have large jaws and give birth to live offspring. Sometimes their offspring will eat their siblings in the womb before birth. They range from 3 to 32 feet in length

4. The order Hexanchiformes, otherwise known as the six gill or cow sharks, contains only seven species and are the rarest and most primitive of all living sharks. Their defining characteristics include six or seven gill slits (all other sharks have five gill slits) and they have only one dorsal fin. This order contains the frilled shark, the cow shark, and the broadnose seven gill. They prefer cold, deep water.

5. Heterodontiforme is the name of the order that contains the bullhead sharks or horned sharks. This order only contains nine species which include the horn shark, Port Jackson shark, and the Zebra Bullhead shark. Its defining characteristic is a big head with large brows. They live off of crustaceans, mollusks, and sea urchins.

6. Squatiniformes, otherwise known as the angel sharks, are sharks that have bodies that are flattened like ray's / skates and live on the bottom of the sea and sandy places where they can easily hide. They average 4 to 6 feet in length from nose to tail end. This order includes the clouded angelfish and sand devil.

7. Orectolobiformes, also known as the carpet sharks or the wobbegongs, are defined by the ornate skin patterns that look like fancy carpets, nasel barbels as well as having a mouth in front of their eyes. Comprised of 39 species, this is the most diverse order of sharks and they come in all shapes and sizes. They range from 12" to 46 feet in length and include the nurse sharks, wobbegong, bamboo sharks, zebra shark, and the whale shark- the largest fish in the world.

8. Squaliformes, also known as the dogfish sharks,has about 126 different species and includes the world's smallest shark: the dwarf lattern shark. Species include the gulper sharks, lattern sharks, dogfish sharks, cookie-cutter shark, and the Greenland shark.

9. Order Pristiophoriformes contains the saw sharks or carpenter sharks. It's members have long, flat, toothy saw-like snouts. They average out at 5 feet long and are bottom dwellers. Their food supply varies between small fish, squid, and Crustaceans. They also give birth to live young. Members of this order include the common sawshark, Queenland sawshark, and knifetooth sawshark.







pictures from: https://en.wikipedia.org/wiki/Tiger_shark, https://en.wikipedia.org/wiki/Bramble_shark, https://oceana.org/marine-life/sharks-rays/shortfin-mako-shark, https://en.wikipedia.org/wiki/Cow_shark, https://en.wikipedia.org/wiki/Horn_shark, https://en.wikipedia.org/wiki/Angelshark, https://en.wikipedia.org/wiki/Zebra_shark, https://en.wikipedia.org/wiki/Greenland_shark, https://en.wikipedia.org/wiki/Sawshark

Outline of a Shark : The Basic Facts

A bit ago, I was privileged to spent some time with these totally cute little girls that I tend to only see at church once a week. It was a wonderful time had by all I think and I have found I am growing to love these wee ones so much. While I sometimes wish that I had more children, I have managed to find some comfort in caring for other people’s children and trying to help them with their tasks. (I do enjoy going to bed when I want though ;) During our game playing and chatting, the six year old saw a statue (maybe curio is a better word) of a shark on my bookcase- one of my treasured possessions that my sister gave me after she was married. Grimacing, she then told me that she ‘hates’ all sharks because they are always hungry and always biting people. Nothing that I could say could shake that simple foundation of that knowledge. It felt a bit sad because that seems like such a extreme and also mainly unnecessary fear. So, I picked up a few of my books- those who know me tend to know that sharks are something that I enjoy and have been trying to instill that sense of joy and wonder in my son- and we started to read about several different kinds of sharks. She decided at the end of our conversation that we should study all of them- each and every species – so we can decide who is right. A fairly mature response for anyone that age… and a little more motivation than I think I have ;) But we decided to start on the basics. So after about twenty minutes, these is what we came up with. (I have added a few of her comments in bold and parenthesis.)

We started with studying and trying to observe through picture the basic physical design. Some of the characteristics common to all sharks are gill slits on the sides of their heads and a skeleton made of cartilage and connective tissue. Sharks live in all the oceans and seas on this planet and a few species can live in freshwater rivers, although they are in the minority. All sharks have long rows of teeth that are replaced several times over their lifetime- some estimates suggest that some species grow over 10,000 teeth in their lifetime. (WOW!) Almost all sharks have eight fins and no shark has the ability to directly ‘back up’- they can turn around and go back making a u-turn if you will….but it is impossible for them to stop and swim backwards. All have skin that is covered with dermal dentacles that make their skin feel smooth from head to tail, giving them smooth and fast movement through the water. However, if you rub your hands along the skin from the tail towards the head, the skin will feel rough, like sandpaper and can even break your skin open (probably not a great idea around a shark per se ;) Most sharks need to keep moving and are unable to sleep for large periods of time without sinking and drowning; some species have developed the ability to push water past their gills when they are not actually swimming allowing them to remain stationary of settle at the ocean floor. The majority of sharks are ‘cold-blooded’ with large stomachs and short intestines. Their ability to sense smell and follow it as well to sense electromagnetic fields make them pretty excellent predators in the water. Interestingly, sharks have eyes that have the ability to change the size of their pupils (just like us) so while scientists do not understand much about their vision, that is an interesting starting point for speculation. (SO SEE, THEY CAN SEE IT’S A PERSON AND THEY DO IT ON PURPOSE!) They are also colorblind (WELL, I STILL THINK WE DON’T LOOK LIKE A SEAL) and have an average life expectancy of 20-30 years. Like us, they also take a long time to grow and mature enough to have children and they may migrate thousands of miles every year. They are thought to be quite intelligent and have been observed showing curiosity and play like behavior… which reminded me a little of dolphins. (vigorous head shaking!) Only four species have been involved in a significant number of fatal unprovoked attacks on human beings; the (in)famous great white, the oceanic white tip, the tiger, and the bull shark. Ironically, humans as a species kill on average over 100 million sharks a year for both commercial and recreation purposes. As many as one forth of known shark species are threatened with extinction and twenty five species are listed as critically endangered.

Sharks have been living in our oceans since near the beginning of creation – some estimates suggest they existed at least 400 million years ago and in many ways, they still be have and live the way they did back then. The first sharks showed great physical diversity- more than we tend to see in shark species today- and new ‘ancient’ sharks are still being discovered today as paleontologist comb through rocks and ground for fossils. With over 470 species of modern sharks in several classifications, I suspect that we will not manage to study or write about all of them. I think that’s probably reasonable and in the end I am hopeful that her fear and hatred will feel less strong towards them. But we’ll give it a good start and see where we will go from there! Any particular one that you suggest we study first? :)

pictures from: http://oceana.org/en/explore/marine-wildlife/whale-shark, http://www.aquariumofpacific.org/onlinelearningcenter/species/zebra_shark, http://www.mediabistro.com/prnewser/animal-rights-groups-help-inspire-hong-kong-shark-fin-ban_b72810

New Thoughts on a New Crisis

During the first week of December 2010, parts of the Red Sea played host to a biological murder mystery as well as to a huge amount of unwanted global publicity. As an added 'bonus', the situation almost correctly mimicked a situation in a well known horror book ('Jaws' written by Peter Benchley and published in 1974) which added to the world wide furor.

For those who have not read the novel 'Jaws', it is centered on a killer great white shark. The author Peter Benchley writes about an animal 'impelled to attack', an animal that 'exists on instinct and impulse', 'aren't very bright', and a 'maniac running around loose, killing people whenever he felt like it'. Other quotes include: "There is a creature alive today without passion... without logic... A mindless eating machine. It lives to kill." The plot of the book is fairly simple. A great white shark kills some people in the ocean off of a small seashore town in the northeastern United States. The police chief tries to close the beaches, but is overruled by the local major who is worried about the tourist industry. The beaches remain open and more people are killed by the shark. A shark expert is called to kill the shark and the shark is destroyed at the end of the book. The movie that was released in 1975 is centered around this simplified plot- leaving out the subplots for the most part.

The situation that has recently cropped up in the Red Sea is not really different. A shark- or more than one – attacked four people in two days. All four individuals survived and the local governor (Mohammed Shosha) declared the beaches closed for 48 hours. After two sharks were killed during that time, he then reopened the beaches and declared that the danger was past. True to the book, a woman standing chest deep in water was attacked and died almost immediately. Sharks sightings in this area are rare and attacks are rarer still- while five swimmers were attacked in six days recently, there have been only six reported shark attacks in the last decade in this area until now. The beaches were then closed to swimming and will be indefinitely, and hunters have been out looking for the sharks suspected. The one major twist is that these attacks appear to have been committed by members of the oceanic white-tip and the mako shark population- and add that scientist believe that one specific shark was responsible for two of the attacks- a finding that is unprecedented... well, outside of Peter Benchley's book of course. Add to that the idea that oceanic white-tip sharks are not considered seriously dangerous sharks for people and are not listed in the top killers.... and this story sounds a wee bit scary! The mako shark that attacked and caused the fatality has been caught and confirmed by checking its jaws/teeth. The oceanic white-tip is still at large.

There are lots of theories about why this 'tragedy' happened. There are thoughts that the fish supply is low causing sharks to have to look harder for food. Others have suggested that snorkelers who feed fish illegally are causing the fish to come closer to land... and bringing their predators with them. Other suggestions include the idea that illegal carcass dumping off shore could be conditioning the sharks to find food closer to the shore making humans more at risk. And other theories that are a tad less likely are climate change and possible Isreali plots- I swear I didn't make that up! The only thing that scientists seem to agree on is that these attacks are the result of humans disrupting the environmental balance in the area. My first thought upon hearing about these attacks was that the sharks are having a harder time finding food. It is also telling that the humans were a 'mistake' attack because almost all survived- they were stalked, bitten and then the shark left-recognizing that this wasn't his typical food. (that's a guess) Let's be blunt- if the shark wanted to eat the humans, they would have had no problems doing so and no one in these situations could have stopped them.

A lot of research has been done... and scientists have studied and discovered a lot more information about sharks – not just great white sharks) since the 1974 publishing of the novel that devastated beach tourist areas across the world by causing panic and vacation changes by thousands of people. We know that sharks are not animals that are looking to eat us. We know quite a few facts including

1. Sharks attack in three ways: the hit-and-run, the bump-and-bite, and the sneak attack. The sneak attack is more likely to happen during the time periods of dusk or dawn and also in murky water. The hit-and-run is the most common where a shark sees a piece of us moving (a hand or a foot perhaps) and attacks thinking it is a fish. Realizing that it made an error, the shark lets go and leaves most of the time. The bump-and-bite is the most dangerous as the shark bumps you to see what you are... and if it decides that you are food will attack wholeheartedly.

2. The three sharks that are more likely to attack humans are the bull shark, the great white shark, and the tiger shark. Each of these sharks have different behavior patterns, a different diet, and a different way for attacking prey. For instance tiger and bull sharks tend to hunt at night while great white sharks tend to hunt during daylight hours. Bull sharks are also more likely to attack in shallow water and by far are considered the most aggressive.

3. The most dangerous to humans is the great white shark which, while usually spitting out promptly its mistaken bit of human flesh, leaves huge bleeding wounds on its victims. The great whites that attack human tends to be in the 8'-12' range in length leading to speculation that they are inexperienced juveniles still figuring out how to hunt for the seals they prefer.

4. We are more dangerous to sharks and humans kill thousands for sport and food every year.

5. Some sharks travel thousands of miles and some have been known to travel 1800 miles in a six month period. Very few are thought to be territorial.

Peter Benchley himself felt some responsibility for the negative attitudes that the general public felt about sharks that he felt were created due to his book. He later in life became an ocean conservationist and in 2000, he wrote: “considering the knowledge accumulated about sharks in the last 25 years, I couldn't possibly write Jaws today ... not in good conscience anyway. Back then, it was generally accepted that great whites were anthrophagous (they ate people) by choice. Now we know that almost every attack on a human is an accident: The shark mistakes the human for its normal prey.”

What happened in the Red Sea attacks is a tragedy and frightening to think about. We as human beings man never know why the sharks attacked, and why such an infrequent thing happened so many times in one short time frame. What we can do is try to figure it out and change our behavior. For certainly, it seems very likely that no matter what the cause, human beings helped cause this tragedy. Blaming or demonizing the sharks will do nothing positive and has the potential to cause even more ecological imbalance as in our fear, we kill any shark we can catch. I hope that the families are receiving the help that they need to grieve and recover and that the victims are safe and recovering as well. But I do hope we see this as a lesson that we can attempt to learn and not as another opportunity for fear and murder. Our Heavenly Father loves us... and the sharks... and the earth. May we remember that... and that we can coexist... together.

Challenges of an Apex Predator: The Great White Shark and our Ecosystem

Yesterday, I asked the question: which is the most frightening apex predator? The choices that I brought to the discussion were a great white shark or a human being. My thoughts lean towards human beings being the more dangerous of the two groups. In this post, I want to take the time to introduce the great white shark as an unique and beautiful creation, look at the differences between great white sharks and the other shark family members, and how the great white shark interacts with his environment and its inhabitants.

The members of the shark family are different from most other animals that live in the ocean due to their lack of a bony skeleton. Instead, sharks have a cartilaginous skeleton which gives them an advantage of a lighter weight physique. They have jaws that do not attach to their cranium which allows greater range of movement, teeth that are continuously replaced with the advantage of always having a strong weapon for catching prey, and their bodies and skin are developed for easy movement and speed in water. One disadvantage to not having bones is that the shark is not able to swim backwards- only forwards or to the side. Sharks also have the disadvantage that they have problems with buoyancy- a very fatty liver helps to keep them from sinking, but most sharks need to stay in constant motion so that they do not sink, and also to breathe as they need the water to move through their mouths to their gills so that they can breathe.

Sharks have a very long history on our earth. Sharks are believed to go back hundreds of millions of years and modern shark ancestors are believed to have begun around 100 million years ago. One of the great whites well known close ancestors was C. Megalodon, a shark that is believed to have gained lengths of 100 feet (In fact the great white is C. Megalodon's only surviving close relative although this is relationship is not agreed upon by all scientists and is a subject for much debate.) The great white shark in many ways physically looks like its past ancestor -whether they have behavior in common is still debated by scientists.

The great white shark has a few traits or behaviors that are unique in comparison to its other shark cousins. The great white shark can hold its head out of the water- out of hundreds of sharks, only one other shark can do so the same. The great white shark wins hand down on the claim of being the world's largest predatory fish. Great white sharks are also different from other sharks in terms of their fins, conical nose, and distinctive coloring. It is one of less than a handful of sharks that have been documented to attack humans – not that that is a great distinction!

The great white shark is a very important and vital part of the ocean's ecosystem. As an apex predator, they feed on a large number of invertebrate and vertebrate animals - examples are sea lions, seals, other sharks, rays, whales, small cetaceans, etc... As an adaptable animal, its diet can and does change with its environment so studying the shark's feeding habits are difficult at best. Because the great white shark is the 'top dog' of the seas so to speak, its importance to the oceans and to our world cannot be overstated. If the great white shark was to become extinct, it could lead to huge increases in its prey populations which in turn will cause changes in many other animal and plant populations. And unfortunately, this shark is currently endangered and runs a real risk of extinction in the future.

So, you ask, why have I possibly bored you with all this information about a animal that at best you have never seen and know very little about? Why defend a creature that seems to have so few redeeming characteristics to the majority of the human population? A few ideas are listed above. In the last installment to this post, I hope to answer this question fully and also hope that I can instill a sense of concern if not urgency for the endangered species of the world which struggle and for the sanctity of life that I believe in.