[class Chondrichthyes subclass Elasmobranchii superorder
Selachimorpha]
Sharks are very different from other fish. When the modern fish (teleosts - bony fish) came on the scene, they rapidly pushed their predecessors toward extinction. Under severe stress some of these older fish back evolved features of their own primitive ancestors while adding some very advanced features as well. So successful were these adaptions the following era is called "The Age of Sharks" and modern fish had to struggle to survive. Photo © i0089.
Sharks have much larger brains than modern fish and a more complex social structure. They generally give live birth instead of laying eggs and many are warm blooded and very energetic. They have no bones but a skeleton of light weight cartilage, allowing them to grow very large and still float. Their scales are formed like teeth rather than the removable flakes on modern fish (thus shark is not kosher).
Many sharks are now IUCN Red Listed as VU (Vulnerable) due to slow birth rates and Chinese demand for shark fins. Finning sharks is illegal in US waters and posession of shark fins or shark fin products is now illegal in California and Hawaii, states with the largest Chinese communities.
More on Varieties of Fish (very
large page).
Spiny Dogfish - [Piked Dogfish, Mud Shark, Spurdog; Cape Shark
(market); Palombo (Sicily); Squalus acanthias]
There are many small sharks called "Dogfish", but the Spiny Dogfish has
always been the most common and perhaps the most common of all sharks. It
inhabits cooler waters worldwide and can grow to 5-1/4 feet long and 20
pounds. Numbers have declined drastically in European waters due to
overfishing, but North American populations are considered to have recovered.
This fish is often called for in Mediterranean recipes. Dogfish isn't all
that common in the Mediterranean, but no other fish are either. This fish
can inflict toxic wounds on humans.
Illustration copyright expired.
Thresher Shark - [Common Thresher; Alopias vulpinus |
Big Eye Thresher; Alopias superciliosus | Pelagic Thresher;
Alopias pelagicus]
Common Thresher is found in temperate and tropical waters worldwide and can grow to nearly 25 feet and over 760 pounds. It is a warm blooded shark, thus very energetic, and that tail is used to herd and stun prey. Thresher is fished commercially and commonly sold as frozen shark steaks. There was a major fishery in California in the 1980s but populations collapsed within a decade from overfishing. Now under strict fisheries regulation the populations are recovering, but most thresher is now caught as bycatch from other fishery operations. Due to the California experience, all three Thresher sharks are now IUCN Red Listed as VU (vulnerable). Photo by U.S. National Oceanic and Atmospheric Administration = public domain.
Big Eye Thresher and Pelagic Thresher are tropical and subtropical
fish and not warm blooded. The Big Eye, a night hunter, is found worldwide,
while the Pelagic is an Indo Pacific fish absent from the Atlantic. Both
are caught primarily as bycatch from other fishery operations.
Great White Shark - [Carcharodon carcharias]
This is one of a very few sharks where the eating can go the wrong way.
Great whites don't consider humans particularly edible, but in the surf or
murky waters they can mistake a person for something tastier. They live in
temperate and tropical waters worldwide and can grow to nearly 26 feet and
nearly 7500 pounds. This is quite large, but dwarfed by the extinct
C. megalodon which grew up to 55 feet and over 121,000 pounds (it ate
mostly whales). How closely the Great White and Megalodon are related is
currently subject to fierce scientific debate. Great White Sharks can be
used for human consumption just like any other shark - their fins are in
demand in China, their livers by the supplement industry and their hides
by fashion houses. IUCN Red Listed as VU (vulnerable).
Photo by Terry Goss distributed under license Creative Commons
Attribution-ShareAlike 3.0 Unported.
Blue Shark - [Prionace glauca]
Blue Sharks have the widest range of any animal, inhabiting all oceanic
waters between the arctic circles. .They can grow to 13 feet and 450 pounds.
This is the most widely caught shark in commercial fisheries, usually as
bycatch in other fisheries, and a major source of shark fins. They are
known to occasionally attack humans, probably mostly by mistake.
IUCN Red Listed as NT (near threatened).
Photo by U.S. National Oceanic and Atmospheric Administration =
public domain.
Tiger Shark - [Galeocerdo cuvier]
This is one of the most dangerous sharks. While a Great White may bite and
say "Yuk!", a tiger shark is more likely to actually eat a human, because
they eat just about anything, including things that are not edible. This
shark inhabits warmer waters worldwide, staying pretty close to shore, and
may even be found in river estuaries. Growing to nearly 25 feet and 1780
pounds, Tiger Shark is fished commercially for its fins, meat, hide,
cartilage and liver. IUCN Red Listed as NT (near threatened).
Photo by Albert Kok distributed under license Creative Commons
Attribution-ShareAlike 3.0 Unported.
Shark does not cook at all like other fish. Modern fish cook so quickly
and flake apart because they have none of the connective tissue land animals
have. Shark has connective tissue, distributed differently from land animals,
but connective tissue it is. Shark stays firm when cooked, so firm you may
need a knife to slice it. The texture is more like pork than like fish, and
the flavor somewhere between pork and fish. The steaks shown in the photo
are from thresher shark.
Shark Fins: Do not buy shark fins or order shark fin soup. "Finning" sharks is inhumane, very wasteful, illegal in US waters and some of the sharks used are rated "threatened". Possession of shark fins and shark fin products is now illegal in California and Hawaii, over the protests of Chinese restaurants that served shark fin soup for US $80 to over $100 per bowl. Prices from $300 to $750 per bowl have been reported from Hong Kong. The sole purpose of shark fin soup is so party hosts can show off their wealth - it isn't really outstanding in any other way.
Catching: Shark must be bled as soon as caught. Commercially caught shark is generally handled correctly, but if you catch one yourself keep this in mind. Cut off the tail, preferably still alive, and when the bleeding slows cut off the head and gut the fish immediately. Scrape the blood works and green spleen from the under side of the backbone. Rinse well and keep the body from contact with blood. Keep the head and tail so the game warden can measure your fish. Shark meat that has not been properly bled will smell of urine.
Buying: In North America shark is most commonly sold in the form of steaks, about 1-1/2 inch thick. Shark spoils rapidly so use it right away or freeze immediately, or more likely, buy it frozen. As with the related skates and rays you can tell freshness by smell. If there's a distinct smell of ammonia it's not fresh. If there's just a faint trace of ammonia, a soak in milk or water acidulated with citric acid will clear it up, but really fresh shark is better.
Skin: Shark must be skinned. The skin is completely covered with tiny teeth rather than scales, and they don't scrape off. Some cultures use shark skin as sandpaper.
Cooking: Shark is generally broiled, baked or grilled. It
is considered less desirable for steaming, boiling or frying.
Being bitten by a shark can be hazardous to your health and may result
in disability or even death. For this reason, exposure to large live sharks,
particularly in murky or turbulent water, should be limited to the extent
practical.
Photo © i0090.
The only other noted danger from sharks is that, being top predators, they tend to have a higher mercury content than prey fish. This is considered a danger mainly to the fetuses of pregnant women, though the FDA admits their recommended limits are a shot in the dark without substantial relevant scientific data. The only substantial data I know of is the Seychelles Study (1) where no effect on child development was found in a population that eats 10 times as much fish as Americans do. From this I conclude moderate shark consumption is safe.
Shark liver oil from cold water sharks has long been harvested for dietary supplements and has long been a primary source of vitamins A and D. It is also a source for alkylglycerols (also found in mother's milk and bone marrow) pristane, squalene, omega-3 fatty acids, triglycerides, glycerol ethers, and fatty alcohols. Studies of possible anti-cancer benefits are under way, but nothing conclusive so far.
Shark cartilage has been claimed to fight cancerous tumors by slowing the growth of new blood vessels needed to supply the tumor. Most studies on this have been informal and inconclusive. Better studies are under way but most have so far shown no benefit. One study reported that a liquid extract had a positive effect but solid forms did not.