Please Explain: Sharks

Friday, September 25, 2009

There are some 440 species of sharks, and the fish have been swimming in the oceans for 420 million years, before dinosaurs existed. On today's Please Explain we'll find out about sharks, from hammerheads to great whites, and look at how they are becoming threatened. We're joined by Melanie L. J. Stiassny, Axelrod Research Curator of Fishes, Department of Ichthyology, American Museum of Natural History; and John Maisey Curator and Axelrod Research Chair, Division of Paleontology, American Museum of Natural History.


John Maisey

Comments [19]

JeffM from Rhode Island

I agree with Coco (comment 14), Dr. Stiassny has a lovely radio voice and is both scientists did an excellent job explaining these misunderstood creatures.

Sep. 25 2009 03:23 PM

In response to the lady who called in about shark nets in Durban S Africa. I also remember them and I was told that they did not go down to the ocean floor as the Sharks would not come in that far down. I also remember that there were shark attacs up and down the East coast of S Africa but that Port Elizabeth didn't have the problem as they had a lot of Porpoises which kept the sharks away. I don't know how factual all this was but I have a picture of my wife & I standing next to a sign at a beach near Margate (an east coast town)saying that "Bathing is illegal on this beach as there are no shark nets"

Sep. 25 2009 02:08 PM
Martin Lubin from Jackson Heights

I've read that fishes don't form a clade--i.e., that there is not a single ancestor whose descendants include all fishes and only fishes. What animal was the last common ancestor, and what are its non-fish descendants?

Sep. 25 2009 02:06 PM
William from Manhattan

Yes - wonderful guests and show. BTW, about that last question on the Devonian - the movie "Ponyo" has some wonderful animation imagining the ancient Devonian sea, with big sharks and those fish with the big bony plates on their heads.

Sep. 25 2009 02:04 PM
Steve from Morristown

I have seen people swim with Tiger Sharks which are baited and left tethered underwater to struggle against the "hook". The shark is sufficiently exhausted so that by the next morning when the shark is released it swims off at a very slow rate and this allows people to swim "with" the shark. I wouldnt do it, not so much because of the risk but more to the point, it stress the shark and sounds cruel. Dont know if the same is being done with Great Whites - I would be shocked.

Sep. 25 2009 02:01 PM
Coco from Shelter Island, NY

Excellent show. Dr. Stiassny makes it easy to understand why we should not demonize sharks! And she has a lovely radio voice.

Sep. 25 2009 01:59 PM
Ted Roper from Murray Hill, NJ

There are shark repellents that do work

I know the inventor.

Sep. 25 2009 01:57 PM
Steve from Morristown

Sharks are resistant to cancer, what sort of research is being conducted on that front and what is overfishing doing to the shark populations and our ability to learn from these very resilient creatures?

Sep. 25 2009 01:56 PM
Nando from Bayside

Do sharks show signs of empathy?

Sep. 25 2009 01:54 PM
Ken from Soho

Sharks AREN'T FISH - fish have scales and bones, while sharks have cartilage instead.

Sep. 25 2009 01:53 PM
Liz from Washington Heights

On 4th of July weekend, we saw a small (2 ft.) shark wash up on shore. A gentleman threw it back into the ocean. We were concerned b/c on Dirty Jobs they slid an Artic shark back into the ocean. Should this small shark been slid back into the water?

Sep. 25 2009 01:53 PM
thomas from manhattan

I'm going to south africa this christmas to visit my family and my brother suggested swimming with great whites. Is this as dangerous as just jumping into shark infested waters alone or is there a certain level of safety?

Sep. 25 2009 01:52 PM
zen from south salem

Could you ask you guest to remind "sport fisherman" that even though they may be releasing the shark after hooking it, the shark suffers great stress during the process, and without a skeletal structure they can suffer dammage when pulled up out of the water for photo ops.

Sep. 25 2009 01:48 PM
Benigno Veraz from Washington Heights

I thought that sharks, still considered vertebrates, and their relatives, preceded the rest of animals with backbones instead of the other way around. Please, explain. Thank you.

Sep. 25 2009 01:47 PM
Dax from Monmouth County NJ

Hi I'm 8 years old and reading lots of books on sharks. Where do most sharks live in the world? and do they migrate?

Sep. 25 2009 01:45 PM
Adriana from New York

Excellent show: thanks!

Sep. 25 2009 01:36 PM
Adam Cherson from NYC

Has anyone ever tested those electric shark repelling devices for surfers. Do they work or do they attract them even more?

Sep. 25 2009 01:35 PM
zen from south salem

So glad you are educating people about these very important creatures. People fail to realize how crucial this top predator is to the oceans eco system.
I just spent last week on a boat at Isla Guadalupe viewing many white sharks, and what wonderful creatures they are. Even made eye contact with them and physical contact to. In seeing them you realize very quickly that if they wanted to eat people they could, there would be no attacks only missing persons. We are deffinitely not of interest as a food source to them and should not fear them.

Sep. 25 2009 01:29 PM
PL Hayes from Aberystwyth

Do sharks have an instinct for compassion? ;-)

Sep. 25 2009 01:04 PM

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