Shark!

Shark Tidbits

The first shark on Earth: The first known sharks appear in the fossil record some 350 million years ago.
Shark evolution: Sharks evolved from placoderms - a group of primitive jawed fishes. For the past 70 million years, they have changed very little.
Number of species: Today, there are 344 known species of sharks.
Shark habitat: The oceans and seas in which sharks live cover 71 percent of the earth's entire surface, an area of some 361 million square miles.

Average life span of a shark: 20-30 years
Longest living shark species: Piked Dogfish, 70-100 years
Birth: The various species of sharks give birth to their young in 3 different ways:
1. Like most mammals, many sharks carry their young in their oviducts for several months during gestation and feed them through their offspring's umbilical cord.
2. Some shark species lay eggs.
3. Other shark females produce eggs and carry them internally until the young "hatch."
Gestation period: from 9 months to as long as 22 months
Number of offspring: varies from one to up to 100, as observed in the tiger shark

Teeth: Over the span of a few years a shark may grow, use and discard tens of thousands of teeth.
Tail Fins: All sharks have tails which are asymmetric -- the upper lobe portion is larger than the lower lobe.
The difference between a shark and other fish: Sharks are cartilaginous, their skeletons made of cartilage and not bone. Their skin is covered with denticles, not scales, and they have five gill slits per side, not one per side like all bony fish.
Sixth sense?: Sharks have the greatest sensitivity of any known marine animal to electric fields surrounding animals. This extreme sensitivity to electromagnetism enables them to detect crabs buried underneath the ocean floor.

Lowest note a shark can hear: 10 Hertz (or 1.5 octaves below the lowest key on the piano). The lowest note a human can hear is 25 Hertz, so we miss out on some of the very low frequencies which sharks can detect.
Highest note a shark can hear: 800 Hertz (or G above High C on the piano) - so humans can hear many high sounds that sharks cannot.

Worldwide shark attack rate: Less than 100 a year, and only 25 to 30 fatalities. This is low, given the number of people who spend time in the ocean.

Largest Shark: The whale shark (Rhiniodon typus) is the largest fish in the world, measuring in at 40 feet long.
Smallest Shark: The dwarf shark (Squaliolus laticaudus) is easily the smallest shark. At maturity they reach an average length of 6 inches.
Greatest threat to sharks: humans
Average swimming speed of a shark: 00.7 mph
Fastest clocked speed: 20 mph (mako shark) for a few seconds
Youngest shark to bite a human: A marine biologist, while probing a pregnant sandtiger's uterus, was bitten by an unborn pup.
The strongest shark bite: The greatest force of a shark bite ever recorded measured in at 132 pounds of force between the jaws of a dusky shark (Carcharhinus obscurus).
Largest egg in the world: That of a whale shark. One found in the Gulf of Mexico measured 12 x 5.5 x 3.2 inches.
Most travelled shark: blue shark -- 3740 miles (from New York to Brazil)
Least travelled shark: nurse shark -- territorial
Fresh Water Shark?: The bull shark (Carcharhinus leucas) is the only shark known to frequent fresh water rivers.

Longest time span between tagging and recapture of a shark: two sandbar sharks were tagged in the same week in 1965 and were recovered within the same week 19.7 years later, 1000 miles from the tagging site and only 160 miles apart.
What to do if you find a tagged shark: retrieve the tag (assuming the shark has either been captured or is dead) and record the date and the place of capture. Note any other information you can obtain, like weight, measurements, and sex. Send the tag and information to one of these two addresses:

Gamefish Tagging Programme
New South Wales Department of Agriculture Fisheries
Research Institute
P.O. Box 21
Cronulla 2230, AUSTRALIA

Co-operative Shark Tagging Program
National Marine Fisheries Service
Narragansett, RI 02882
USA