 |
Welcome
|
What's New! Ask
a Marine Scientist: answers to Fish questions! Choose one of the following:
ASK A SCIENTIST: ANSWERS TO QUESTIONS Chondricthyes Index to Questions SHARKSSKATES & RAYS GENERAL
Q:What is the scientific order for sharks? A: There more than one order of sharks. Sharks are found in the Class Chondrichthyes (cartilaginous fishes) and under the Subclass Elasmobranchii (sharklike fishes). Here are the orders of sharks your classified under the Subclass Elasmobranchii: Order Heterodontiformes (8 marine species): bullhead and horn sharks Order Orectolobiformes (31 marine species): collared carpet sharks, blind sharks, wobbegons, bamboo sharks, nurse sharks, zebra shark, whale shark Order Carcharhiniformes (210 species, mostly marine):catsharks, finback catsharks, false catshark, barbeled houndshark, houndsharks, weasel sharks, requiem sharks, hammerhead sharks Order Lamniformes (16 marine species): sand tiger shark, goblin shark, crocodile shark, megamouth shark, thresher sharks, basking shark, mackerel sharks, Great White shark, Mako shark Order Hexanchiformes (5 marine species): frill sharks, cow sharks Order Squaliformes (74 marine species): bramble sharks, sleeper sharks, dogfish sharks Order Squantiniformes (12 marine species): angel sharks Order Pristiophoriformes (5 marine species): sawsharks Skates and Rays are also found in the Subclass Elasmobranchii: Order Rajiiformes (456 species, marine and freshwater): sawfishes, electric rays, guitarfishes, skates, deepwater stingray, South African stingray, stingrays, round stingrays, butterfly rays, eagle rays, manta rays
A. We've looked around, but cannot find such a list on any web
page. This is not surprising, since the estimated number of shark
species in the world is about 350! Here is a good book that has
the information that you requested:
Q: What types of sharks live on the Canadian East Coast? Have there ever been reported shark attacks on the Canadian East Coast? A:
There are two sharks known to inhabit the Canadian East Coast:
Q: Which sharks are native to the Myrtle Beach area? A. There are several different species of sharks that occur along that portion of the Atlantic coast. Since many these animals are fairly motile and widely distributed, it is difficult to accurately say which of the sharks are 'native' to such a small geographical range. Here is a list of the species (some of which are accidental): 1. Sevengill shark, Notorynchus maculatus - up to 9' long, this shark is found over soft bottoms, in bays and on the open coast. These sharks are considered prime game fish due to their fighting ability; sometimes harvested commercially. 2. Nurse Shark, Ginglymostoma cirratum - up to 14' long, found inshore on shallow sand flats, channels and coral reefs. Small fishes, sea urchins and crustaceans make up most of its diet. 3. Whale Shark, Rhincodon typus - up to 60' long, this shark is found primarily on the open sea. This is the largest fish known, and it feeds primarily on small crustaceans and fishes that it filters from the water. 4. Sand Tiger, Odontaspis taurus - up tp 10' long, found on or near the bottom along inshore shallows. Occaisonally attacks people. 5. Thresher Shark, Alopias vulpinus - up to 25' long, hangs out in the open sea. Feeds on schooling fishes such as herring and anchovies, can use their tail to stun prey. 6. White Shark, Carcharodon carcharias - to 21' long, typically found in coastal surface waters. Savage predators that feed on fishes, sea otters, seals, sea lions and other marine organisms. Most dangerous shark, with the most reported attacks on humans. 7. Basking Shark, Cetorhinus maximus - to 45' long, pelagic species found on open sea. These sharks feed on plankton using their large combs of gill rakers. 8. Shortfin Mako, Isurus oxyrinchus - to 12', surface of open seas to neashore waters. Feeds primarily on schooling fishes like mackerel and herring. Potentially dangerous shark. 9. Bull Shark, Carcharhinus leucas - to 11', inshore fish that occaisonally ascends rivers for considerable distances. Several attacks on humans have been reported. 10. Blacktip Shark, Carcharhinus limbatus (also C.brevipinna) - up to 8' long, these sharks are known to swim in packs ranging in size from 6 to 12. 11. Dusky Shark, Carcharhinus obscurus - up to 12', inshore species found along the continental shelf. Feeds primarily on bottom dwelling fishes; potentially dangerous. 12. Sandbar Shark, Carcharhinus plumbeus - to 8' long, these are bottom dwellers that can be found in bays, estuaries and beaches. Feeds on a variety of molluscs, crustaceans and small fishes. 13. Tiger Shark, Galeorhinus zyopterus - up to 18' these sharks are voracious omnivores that can be found in coastal waters, but most commonly in Florida and Cuba. The stomachs of captured specimens have been found to contain anything and everything, including other sharks, fish, porpoises, turtles, dogs, tins cans and other interesting things. Dangerous to people. 14. Blue Shark, Prionace glauca - up to 13', found over shallow muddy bottoms and on the open sea. Disjunct distribution along Atlantic Coast. Feed on small schooling fishes. 15. Scalloped Hammerhead, Sphyrna lewini - up to 14', these fish are found near the surface, sometimes in estuaries. Feed on fishes and squid; sometimes known to attack people. 16. Bonnethead, Sphyrna tiburo - to 5', shallow bays, estuaries and sandy areas. Feeds on crustaceans, molluscs, and small fishes. 17. Spiny Dogfish, Squalus acanthias - to 5' (although I have seen longer ones), these fish are usually found offshore, at depth along sandy bottoms. I think that is pretty much it. There are other closely related species in each of the genera that I have listed here, which would probably bring the list of species closer to 25 or 30.
Q: Hi! I am curious to know if there are any man-eating sharks in the waters of Southeastern Florida (from West Palm Beach down to the Keys). Also, how many, if any, shark attacks on humans have been documented in that area? And what were the ocean depths of those attacks? Thank you!! A. There are lots of sharks in Southern Florida waters. That's why the centre for shark research is located at the Mote Marine Lab in Sarasota!!! Florida has the highest incidence of shark attacks, and this is largely due to the fact that there are lots of both sharks and swimmers in Florida. For stats on shark attacks and other interesting shark info, I would recommend visiting the Mote Marine Lab Shark Pages.
A. We don't have any pictures like that, but we can hopefully point you in the right direction! The dogfish shark is a popular animal for biology students to dissect. Because of this, there are many different lab manuals that have pictures of their internal organs. Here are two books, but there are many others out there. Look up books on "dogfish" in your local library. your librarian might be able to help you get these books: Gans, Carl and Parsons, Thomas 1964. A photographic atlas of shark anatomy. Academic Press, New York. Library of congress # 64-13045 Ashley, Lawrence 1950. Laboratory Anatomy of the Shark. William Brown Company, Iowa. You might also be able to find a book in a local bookstore on sharks. The "eyewitness" series published by Dorling Kindersley Ltd. has a book called "Shark" that is very good.
Q: What is the Biggest shark alive??? A:
Thanks for your question.
Q: Hi. I saw that you said that the biggest fish in the world was the whale shark. Isn't the whale shark though, a mammal. And fish lay eggs? I understand why you would say that the whale shark is the largest shark, but the largest fish? Are you sure? Thanks. I'd appreciate a reply. Bye A. The whale shark, Rhincodon typus, is infact the largest
fish in the world. Whale sharks are indeed sharks and are not related
at all to whales - they are called "whale" shark because
of their huge size. Whale sharks and all other sharks are cartilaginous
fish, meaning that their skeletal structure is made from cartilage
and not bone. All fish that share this characteristic (this includes
sharks, skates, rays, and chimaeras) are grouped in the Class Chondrichthyes
(one of the three classes of fish). Whale sharks and all other members
of this group, meet the basic criteria that qualify them as fish
such as gills, scales, fins and an aquatic existence. Unlike many
other fish however, fertilization in sharks is internal and many
sharks including whale sharks, give birth to live babies. Hope this
clears things up for you.
Q: Where are the Vestigal Gills on a Whale Shark and what are they? I'm sorry but I need an urgent answer. A: Through the course of vertebrate evolution, jaws (first seen in fish), originated through modification of the gill arch skeleton that surrounds the seven pharyngeal gill slits. (Pharyngeal gill slits are a fundamental feature of all chordates). In most sharks, the first gill slit is modified into a spiracle, a small bone attachd to the skull. In shark species that disply five gills (whale sharks included), the second gill slit is modified to form the hyoid arch, a chain of cartilage bones associated with supprting the jaws and bracing them against the skull.
Q: What do whale sharks eat? A: Whale sharks are filter feeders and feed on planktonic and larger organisms living in the water column. Their food includes krill, squid, small fish such as anchovies, sardines and mackerel.
Q: How do the hammerhead sharks male and female differ according to it's apperience and behavior? What are the prodution charicteristics of the hammerhead shark? How often do they reproduce and what is the number on off spring? Describe to me the amount of parenting that the animal gives it's young? A: Rather than just give you the answers, I'll give you a couple of really informative web sites. PBS
Sea Dwellers - good basic information, plus the rest of the
site is fun too.
Q: How big does the hammer head shark get? A: The largest Hammerhead Shark (Latin name, Sphyrna mokarran)
is recorded to be 18 feet 4 inches long; weighing 1,860 pounds.
Q: I am writing a report on tiger sharks and I need to know the following information: Habitat, Life Span, Life Cycle, Where it falls in the food chain, Reproduction, Characteristics. Your help would be greatly appreciated. Thanks. A: Tiger sharks (Galeocerdo cuvier) are classified in the Family Carcharhinidae (Requiem Sharks). Most requiem sharks are voracious predators, and the tiger shark is no exception. G. cuvier is a top predator in the food chain, feeding on an amazing variety of organisms including crustaceans (crabs and lobsters), squid, bony fishes, skates, smaller sharks, sea turtles, porpoises, marine birds, human remains and even garbage! Tiger sharks can be recognized by their short snout, very long and pointed caudal (tail) fin, and the vertical bars or stripes covering their dorsal surface (back) which give G. cuvier its common name. These are one of the largest species of sharks, commonly measuring 3.4-4.3 m (11-14 ft) in length and weighing 390-640 kg (850-1400 lb). Tiger sharks are found in all the tropical and temperate waters of the world. Off North America they are located from Cape Cod to Florida and the Gulf of Mexico, and southward from southern California. Development in G. cuvier is ovoviviparous, which means that the developing embryos are contained in eggs with thin shells which are kept in the uterus of the female. The shell disappears early in development and the young are retained inside the female until they are fully developed, feeding off a yolk sac. This is in contrast with the majority of requiem sharks which have their young attached via an umbilical cord to a placenta (viviparity). Gestation lasts just over 1 year and the pups measure 70-85 cm (27-33 in) at birth. There are usually between 35 to 55 pups per litter and maturity is reached at approximately 290 cm (114 in). For more information on sharks, head down to your local library or check out Fiona's Shark Links on the internet.
Q: dear scientist, how big can a Great White shark can get? A: The largest reliable length measurement of a Great White shark is 6 metres (19.5 feet). However, "The Guiness Book of Animal Facts and Feats" (Wood 1982) quotes the largest Great White to be 9.1 metres (29.5 feet) in length, but this record has not been verified.
Q: How big does a great white shark have to be to produce a 2 inch long, serrated tooth? A: Thanks for your great white shark question! As most scientific information is recorded in metric units I am going to convert 2 inches into centimetres (2 inches = 5.08cm). A 5cm long great white tooth would belong to a shark approximately 5 metres in length. The largest great white tooth found was 6cm long and that sharks was estimted to be 6 metres long.
Q: Why do sharks have sharp teeth? A: Great question...
Q: Please tell me some facts that you know about Megaoldon. There was also a book about Meg that i have read. How old are these sharks? older then Dinosours? What was there size? Two three buses? where did they live in the world? Are they related to The great white shark or a sandtiger shark? What was the biggest in size and teeth? A: The megatooth shark, Carcharadon megalodon, lived in during the mid-Miocene through to the late Pliocene, 16 to 1.6 million years ago. The teeth of this shark are common at most fossil-bearing sites. The length of the teeth from the base of the enamel to the tip of the tooth is around 100mm (the largest great white shark teeth are about 60mm high). The largest C. megalodon tooth found has an enamel height of 168mm. Scientific extrapolations using statistical relationships between tooth enamel height and jaw dimensions to body length and mass, of known great white sharks estimate that a megatooth shark with an enamel length of 168mm would be 16m (52ft.) long and weigh about 48,000kg (105,000 lbs.). The jaw of this shark would be 1m (3.25ft.) wide, the dorsal fin would be 1.4m (4ft.) high and its tail would be 1.75m (6ft.) high. The megatooth shark is the largest shark known to live on earth. The great white shark and sand tigers are classified in the Order Lamniformes, but are found in different families. Great white sharks are classifies in the family Lamninae (Mackeral sharks) and if the megatooth existed in today's world it would be classified in this family. The sand tiger shark is classified in the family Odontaspididae (sand tigers). For more information on the megatooth shark I suggest you check out this this section the Discovering Sharks book: Compagno, L.J.V. 1990. The evolution and diversity of sharks. In Discovering Sharks, ed. S.H. Gruber, 15-22. Highlands, NJ: American Littoral Society Spec Publ 14.
Q: I was recently scuba diving off Destin, Florida where we
sighted several large sharks. A. The fish that is commonly referred to as the Dusky shark is
known to the scientific community as Carcharhinus obscurus.
This shark is in the Family Carcharhinidae, which includes the Tiger,
Blacktip, Bull and Sandbar sharks as well. C.obscurus feeds
predominantly on bottom dwelling fishes and other small sharks,
but has been reported to occasionally attack humans.
A. This was a tough question! We finally found an estimate in: Leonard Compagno, 1984. FAO Species Catalogue Vol. 4: Sharks of the World. FAO Fisheries Synopsis No 125, Vol 4, Part 1 The Basking Shark is only one of 3 filter feeding sharks - the others are the Megamouth and the Whale Shark. Of these 3, the Basking Shark is the only one that relies entirely on the passive flow of water over the gills to filter feed. The other two species assist filter feeding by actively pumping water.Basking Sharks feed on small plankton trapped on their gill rakers with the help of mucous, including copepods, barnacle & crab larvae, and fish eggs.Assuming a cruising speed of 2 knots, a basking shark is estimated to filter 2000 tons of water every hour. This is a lot of water! The amount of plankton that it can collect in an hour is highly dependent on the amount of plankton in the water; this can be extremely variable, both in time and space. The shark may encounter a good "patch" of plankton for a while, and then not encounter much. On average, however, Whale Sharks are found with about 500 Kg (1100 pounds) of undigested plankton in their stomachs.
Q: Why is shark skin rough and what advantage does this give the shark over smooth skinned animals? A: Shark skin is rough because they have a type of scale called a placoid scale. If you look at a placoid scale close up they look like little teeth. They are shaped like triangles with the pointy end sticking up. These teeth-like scales are flat against the skin of the shark and point in the same direction. That's why if you were to feel shark skin, if you rubbed it one way it would feel rough (you are feeling the pointy ends of the scales) and if you rubbed it in the opposite direction the skin would feel smooth. Having placoid scales does not necessarily give sharks an advantage over smooth skinned animals. For example, mammals are covered with hair or fur for protection, sharks and fish have scales covering their body. Cartilagenous fish (sharks, skates, rays) do not have any bone and therefore evolved scales that are more like teeth, rather than the scales of bony fish. The tough skin would be advantagous to sharks because of their fierce mating rituals. Many female sharks have many scars on their back from where the male sharks hold her with their teeth when they are mating. By having tough skin, a sharks can heal quickly from these bites.
A: There are several examples of bony fish that hold eggs in their mouths (the yellow head jawfish, Opistognathus aurifrons is one example). After the female jawfish lays the eggs, the male holds them in his mouth until they hatch, occasionally blowing them out and sucking them back into his mouths. Other fish that are "mouth brooders" will continue to shelter the young fish in their mouths even after they hatch. We can't think of a single example where a shark does this, however, or an example of a shark "giving birth" through it's mouth!
Q: A local mexican restaruant has just recently put "shark tacos" on their menu. I am involved with the I.V. Chapter of Surfriders and one of our representatives went to discuss taking this item off the menu with the restaruants manager. He agreed to do so only if he can be presented with a reliable data from a few sources that sharks (specifically THRESHER and MAKO) have a slow reproduction rate. I have heard that these sharks do give birth to only about two pups a year, making this killing of sharks for commercial purposes a threat to their population if continued. Please send me more information on the reproduction of these sharks and possible threats these issues might have on them. A: I think it's great that you're protesting this restaurant. Sharks are an extremely overfished group of animals. There's the Asian market for shark fin, there's the new shark cartilage industry, there's sport fishing, and there's catching them for food. I think that because most people can't seem to shake the evil stigma that surrounds sharks, they think it's OK to decimate populations. For the most part, they do reproduce quite slowly. Threshers and Makos are ovoviviparous (a big word meaning they give birth to live young). Animals with this reproductive strategy tend to have less young because a lot of energy needs to go into the development of the young. Two thresher species have litters of two pups, and the third species has 4-6 pups. Short-finned makos have 8-10 pups, and long-finned makos have 2. Both sharks have variable gestation periods, depending on the surrounding ocean temperature, but it's usually between 9 and 12 months. You should be able to find out some more information on shark fisheries
on the net. AltaVista and Hotbot are both good search engines.
Q: How do you see the future of shark populations in the Pacific ocean with the extensive "finning" economy that has risen in countries such as Japan and the USA and what can I do to help as an aspiring Marine Biologist? A: The world catch of cartilaginous fishes (sharks, skates, rays and chimaeras) has been increasing since the early 1940s, and as of 1994 the total catch exceeded 730 784 tonnes. Over 19 countries have significant fisheries for cartilaginous fishes, with Indonesia as the world leader with an annual catch of over 92 000 tonnes. However, many countries do not report the species of sharks involved in fisheries and there is believed to be a high rate of discard at sea. It is estimated that up to 240 000 tonnes of cartilaginous fishes in targeted fisheries may be discarded per year, with often only the fins retained. One of the greatest concerns is the huge volume of incidental shark catches in offshore fisheries targeting other species, the true amount of which is unknown but is estimated at up to 50% of the reported take of commercial shark fisheries. Shark products currently in trade include shark meat, fins, skin, liver oil and cartilage. There are over 125 countries involved in shark fin trade and production, the most significant ones being Hong Kong, China, Singapore and Taiwan. Shark fins are among the world's most expensive fisheries products, fetching retail prices of US$40 to US$90 per kg. This represents an incentive to retain only the fin of captured sharks, discarding the rest of the fish due to its relatively low value. This is a tremendous waste which should not be tolerated, especially given the increased demand for cartilage and liver oil in recent years. Sharks are especially vulnerable to overexploitation due to their low reproductive potential. Sharks bear few young which grow and mature slowly as compared to other groups of marine fishes. Consequently, shark fisheries must be managed very conservatively, which appears to be a notoriously difficult concept in international fisheries management. Most fisheries for cartilaginous fishes are largely unregulated or unmonitored at a time when worldwide demand for shark products in increasing. The exact future of exploited shark populations is difficult to predict, however unless responsible and sustainable management is applied, targeted species and those taken in bycatch will undoubtedly decline in abundance. The impacts of this on a global scale, and in relation to the marine ecosystem as a whole, are unknown. As an aspiring marine biologist, I suggest that you become as informed as possible about the many aspects of this issue (e.g. biological, social, economic). There are some good resources on the internet and at your public or university library. Local, independent education and advocacy are crucial to the efforts of wildlife conservationists and responsible fisheries managers. For more information, see the The Pelagic Shark Research Foundation.
Q: I live in Queensland, Australia. My Mother In Law is due to visit in October, but has said that she will not go in the sea, for fear of a shark attack. I have heard that the odds of being attacked by a shark are something like 1 in 350,000. On the weekend a wetsuit was discovered off the coast of Queensland and my Mother In Law drew our attention to this. I tried to explain that Queensland was vast and that she had to be more specific. Please provide me with some tangible facts that will put this situation into perspective and that will allow my Mother In Law to swim in the sea off of the Queensland coast (Sunshine Coast region). A: There is lots of information around about sharks and the incidence of shark attacks in various parts of the world. Basically, a person is more likely to get struck by lightning than bitten by a shark. There are only about 50 shark attacks and 10 shark fatalities per year, many of which could be avoided by using common sense. Last year in Australia there was only one fatality due to an encounter with a shark. Of the many shark species that inhabit Australian waters, only a handful are even capable of an attack on people. Many people have misconceptions about sharks (especially if they have seen the movie "Jaws"). Typically, when shark attacks do occur, it is because the animal has mistaken the wetsuit-clad human as its prey (i.e. seals or sea lions). The May issue of Discover magazine has a really good article on sharks and shark behaviour. In addition, there are several web sites with valid information on sharks. The wetsuits that were found washed up on the beach are easily explained. Wetsuits left lying unattended on the beach to dry after surfing or diving are frequently lost to the tides. In fact, I almost lost one myself last summer as the tide line sneaked up on me! Surfers and SCUBA divers both use wetsuits and both activities are high risk sports. It is not uncommon to find wetsuits washed up on the beaches in areas where there is lots of surfing and diving activity. Hopefully you can convince your mother in law to go snorkelling or swimming. Otherwise, she will never experience the most beautiful 2/3 of the planet that lies underwater. It is an amazing place and it would be a shame to miss out due to an unfounded fear of big fishes.
A. The approximately 350 species of sharks in the world are carniviores, which means that they eat other animals, but not all of them pursue and attack their prey like you see in the movies. For example, two of the largest sharks in the world, the whale shark (Rhiniodon typus) and the Basking shark (Cetorhinus maximus) are both filter feeders. They swim with their large mouths open, and filter crustaceans and small fish out of the water column. They do not have the same type of sharp, pointed teeth that some other sharks have. Most of the other shark species feed on small fish in much the same way that large predatory fish such as tuna or salmon obtain their food. Sharks have received an undeserved reputation for attacking people (perhaps due to stories and movies?) Of the 350 species of sharks, only 32 have been known to attack people. In fact, shark attacks are relatively rare - more people in North America are killed each year by bees, dogs or even pigs than by sharks. Due to overfishing, many shark species are being greatly reduced in numbers - one could say that sharks have much more to fear from us than we have from them.
Q: A friend and I have a disagreement: he insists that sharks have two penises (peni?) while I am certain that they have only one penis per animal. We both agree, however, that the female Chondrichthyes has two uteruses per animal. Could you please refresh our jaded college minds and tell us if sharks have a pair, or only a single penis? Thanks. A. I guess you could say that both of you are wrong. Sharks do not have a "penis" so to speak, instead they have what is referred to as the intromittent organ, which is used to inject sperm into the female. In most sharks this organ takes the form of claspers, which are structures that are derived from the pelvic fin. The fin is bilobed, and each lobe constitutes one of the two claspers that are present. Although there are two claspers present, they are both part of the sole intromittent organ.
Q: What kind of shark migrates over 1,500 miles each day? A. There are many species of shark that make extensive movements and migrations on the order of hundreds and even thousands of kilometers. Coastal species, such as the sandbar, blacktip and dusky sharks stay near continental shelves, but may may move 1600km or more. Blue Sharks make return trips between North America and Europe, a distance that exceeds 16,000 km. However, although these sharks have large ranges, they do not make these migrations overnight. If you think about it, for a shark to go 1500 miles in one day, it would have to move at an average of 62.5 mph. Most sharks cannot maintain such high levels of activity for prolonged periods. I don't believe that there is any shark species that can migrate more than 1500 miles in one day. If there is a species that you know of, please let me know (your source of information, too).
Q: Hello, as you know my name is Robert. I know almost everything there is to know about sharks. When I grow up I want to be a marine biologest. But the one thing i don't know is what the exact number of different species of sharks there are. Do you know? A. One thing you will quickly learn if you continue studies in biology is that there is a lot of stuff we don't know. Although we have identified lots of different species on the planet, there are still many kinds of organisms that await to be discovered. For the most part, the ocean is the final frontier in many ways. It is difficult to access some of the deepest parts of the ocean, so we don't have a good grasp of what lives there. I can't answer your question about the "exact" number of shark species in the ocean. In fact, there is probably no one that can honestly give you an exact number, not even the people that have spent their entire lives studying sharks. From what we know at the present time, there are approximately 350 shark species that have been identified. New species are discovered all the time, so this number is always changing.
Q: About how many great white sharks are around today? A: Little is actually known about many shark populations throughout the world. Sharks, especially great whites, travel long distances and in areas where there are not very many people, such as the open ocean. Therefore it makes it hard to record population information on these elusive, long travellers. Recent research suggests that in the waters surrounding the United States there only under a hundred great white sharks. If you would like to learn more about great white research check out this website: http://www.ucmp.berkeley.edu/vertebrates/Doug/shark.html
Q: How do sharks eat things hole??????
Q: Which shark has the sharpest teeth? A: Sharks have the sharpest teeth around, but it is hard to say
which ONE shark has the sharpest teeth of all. Here are some candidates:
 Diversity
of Sharks - received from John in Mayfield Ky.
Q: How many different sharks are there? A: There are actually 375 different species of sharks!! Wow!!
Q: Can you give us any information about shark repellents or what sharks do not like. Thank you! A: There's some controversy about what actually works in terms
of shark repellants, but I did find a few. The first is a device
called a POD, and the way it works is that it emits an electric
current. The current is low enough that it is not harmful to the
person carrying it, but the shark is quite sensitive to low amounts
of electric current in pores in its nose. Here is a web site for
this repellant: the Natal Sharks Board.
Q: How long does a hammerhead shark live? A: There are actually 9 species of hammerhead sharks. But the one
most people refer to is the great hammerhead shark. It can live
up 20 or 25 years.
Q: What are the major reasons why Great White sharks cannot be kept in captivity? A: There is no clear-cut reason why Great Whhite sharks cannot
be kept in captivity. But there are some major theories why this
is true. Sharks need to keep water moving over their gills to keep
themselves oxygenated. When they are captured for captivity the
water flow over their gills is lessened and the sharks can die from
oxygen starvation.
Q: I like to swim in Agamemnon Channel in the Sunshine Coast of British Columbia and someone told me that there are sharks there. What types of sharks are there? Since I have heard this I am nervous about swimming there. A: There are sharks in the area but its likely just a spiny dogfish and I have never heard of those animals ever attacking people. I have been to the area you describe when I used to boat up to Desolation Sound and into Jervis Inlet and so forth. I have never had one instance in twenty years of meeting anything dangerous around Agememnon Channel. So Agamemnon channel should be safe for swimming.
Q: Are more shark attacks occuring or are they just getting more news coverage? A:
I think its a little of both in comparing why there has been so
much coverage this year on shark attacks. There has been more attacks
in the southeastern United States than normal. There has also been
much more press coverage especially relating to the young boy who
nearly lost his arm when he was attacked by a bull shark in Florida.
Q: What is the longest life span of a shark? How many years? A: I am not sure of which species has the longest lifespan but some species may live to be a hundred years old (maybe even longer). One example of the Spiny Dogfish indicates that it has a lifespan between 25-100 years.
Q; What is the stuff that is in the Hammer part of the hammer head shark? A:
Most of the stuff in the hammer part of the hammerhead shark is
cartilage. We humans have cartilage in our bodies as well too in
places like our knees.
SKATES & RAYS
Q: My Gramma lets me use her computer to learn. Can you help me understand how Rays and Skates are different please? A. Skates and rays are very closely related animals. Both are types of cartilagenous fishes in the Class Chondrichthyes. These animals are both in the Order Rajiformes, which includes the sharks, skates and rays. All of these animals share several similar anatomical structures and evolutionary histories, making them closely related. Rays typically have long slender tails that may have a sting (there are exceptions), wheras skates generally have a broader, well developed tail. Overall, these organisms are remarkably similar, and are only differentiated at the Family level of classification. Whereas rays comprise the Torpedinidae and the Dasyatidae, the skates make up the Family Rajidae. There are differences in the egg cases of these animals, the numbers of embryos present in the egg cases and differences in the developmental process as well. Visually, the animals are hard to distinguish.
Q: What is the difference of a stingeray and a manta ray?? A. Both stingrays and manta rays are classified in the Order Rajiformes, which includes sharks and skates, and in the Superorder Batoidea. Both types of rays are cartilagenous fishes, which means that these animals have a skeleton made from cartilege (like in your nose) rather than bone. Stingrays (Families Dasayatidae & Potamotrygonidae) are carnivorous animals that feed mainly on crustaceans and other invertebrates, and are usually found on the ocean bottom. These rays have a sting on their tail that is a spine modified from a placoid scale with a venom gland at its base. The spine is whipped about very effectively by the tail, and is used primarily as a defensive mechanism against larger predators. People are often stung by these animals, and the sting of many species causes considerable swelling and discomfort that can persist for several days. In contrast, the manta ray is a planktivorous animal that spends most of its time in the pelagos, feeding on tiny planktonic oransims in the water column. These animals use their large wing-like pectoral fins to fly around through the water, collecting food with scoop-like appendages on the head that direct plankton into the mouth. These rays have fine gill rakers for straining out the plankton from the water. These animals are fascinating, and a favorite among many SCUBA divers that have had the opportunity to swim with these animals.
Q: How do manta rays die? How long do manta rays live? Why don't manta rays attack swimmers? I live in Iowa, where is the closest place to see a really big manta ray? A: I couldn't find anything on how manta rays die. Considering
how big they are (up to a 7m wingspan), they probably don't have
many natural predators other than really large sharks. I also couldn't
find anything on how long they live. They are related to sharks,
and seeing as how most sharks live for a very long time, it's a
good guess that mantas live a long time too. Mantas are very peaceful
animals that feed on the tiny plants and animals that float around
in the ocean. The only time they might harm a person is if they
thrash around when they are being caught, or if they accidentally
hit a diver with one of their wings. The range of the Pacific Manta
is pretty much the whole tropical Pacific Ocean. They can be seen
in the Indian Ocean, around Japan and Hawai'i, and along South and
Central America (sometimes as far north as Southern California).
Atlantic Mantas range from South Carolina to Brazil, and are common
in Bermuda and the Gulf of Mexico. You'll have to decide which of
these is easiest for you to get to if you want to see these animals
for yourself. If you want to see some good pictures, check out Apollo
Sports.
A. Well, I'm afraid that I can't agree with you that small sting rays don't have barbs on their tails, and I can speak from personal experience on this topic. While snorkling near Jamaica a couple of years ago, I picked up a sea urchin. While doing so, I felt a slight pain in my little finger. "Hmmm" I thought, " the sea urchin didn't get me. I wonder what did?" I then saw a southern sting ray (Dasyatis americana)that must have been only 10 cm (4 inches) long, including the tail. I looked at my little finger, and saw the characteristic narrow cut caused by the sting in the tail. The cut was only about 3-4 mm long (one quarter inch). It didn't feel bad at first, but after a while, BOY did it hurt! My hand swelled up, and looked like a rubber glove for two days. After that, it got much better.
A. The pacific electric ray (Torpedo californica) is found from southern California to Northern British Columbia. As their name suggests, they are able to produce an electric current, capeable of giving a strong electric shock to any person or animal making contact with the fish at two points.The reproduction of pacific electric rays is interesting, because they give birth to live young. Technically, they are "ovoviviparous", which means that the mother fish lays eggs, but these eggs are hatched within the body of the mother, and they young swim freely out. An "oviparous" fish lays eggs, while a "viviparous" fish gives birth to live young, without any egg stage.
Q: I need to have some information on the eagle ray for a report that i am working on in school. Thank you. Oh by the way. i like your web page. my mom bookmarked it for me. thank you again. A: There are about 15 species of eagle rays in the Subfamily Myliobatinae, all of which are characterized by powerful grinding teeth which can crush even the heaviest clamshells. Eagle rays are found throughout much of the subtropical and tropical seas, swimming gracefully in mid-water with their winglike pectoral fins. One of the main differences between eagle rays and stingrays is that eagle rays have a large fleshy pad extending from their wings around to the front of the head, almost like a flabby upper lip. Sting rays, on the other hand, have a thin, flattened shelf around the front of the head. Eagle rays, like stingrays, have a well-developed venom spine attached to the upper surface of the long, thin tail. Eagle rays eat a wide variety of animals found living on or in the sand, such as lobsters, crabs, clams, worms, snails, shrimp and small fishes. Reproduction in eagle rays is ovoviviparous, meaning that the embryos are encased in thin eggs which actually hatch inside the uterus of the female. The growing rays remain inside the mother until fully developed, when they are born tail first with the wings rolled up over the body. The baby rays don't sting the mother with their spine when they are being born because it is initially quite rubbery and covered with a protective sheath which disappears quickly after birth.
A. This is quite a pretty fish that you've chosen to write a report on! The blue spotted stingray is found in the Indian and South Pacific Oceans, and is commonly seen on the coral reefs of North Queensland, Australia. Scientists know it as Dasyatis kuhlii. The young hatch out of egg cases, and are pale grey or brown, spotted with black or rusty red and white. The pattern of markings is different with each young fish. As adults, they are light-pinkish brown, with numerous large blue spots that have darker margins. Of course, since they are stingrays, they are quite flat, and lie partially buried in sand in shallow water. They have a sting in their tails that they will use if disturbed. When full grown, they are only about 25 cm (10 inches) in width. Because of the venomous sting in the tail, they do not have very many enemies, but one report from Australia that we have read states that "They are excellent eating when roasted over an open fire"! It seems that have an enemy that is common among many animals - people!
Q: What creature hunts and eats the stingray if any? A: Hammerhead sharks specialize in feeding on stingrays. The hammerhead uses the cartilagenous projections from the side of their head to pin their stingray prey down to the bottom while taking bites from stingray's disk (body). By pinning the stingray down with their head the hammerhead shark avoids being stung by the poisonous spines on the stingray's tail. I am not familiar with other stingray predators, but if you know others I would love to hear from you!
Q: Do stingrays leave their babies behind when they are born or do they take them with them and for how long will they care for them? A: Most stingrays give birth to live young. For example in the Southern Stingray the mother carries eggs inside of her but does not provide food for the young inside of her. The young hatch from the eggs while still in the mother's body. The stingray gives birth to approximately three to five, nine-inch long "pups" at the same time. Once the young stingrays are born the mother no longer cares for the young stingrays and they are in the world alone. There is one example I know of twhere baby stingrays are cared for after birth. But these baby stingrays are cared for by people. At the Vancouver Aquarium baby freshwater water stingrays are cared for by an aquarist (a person who keeps care of aquatic plants and animals at an aquarium).
|
BACK TO 
A:
Great question!