Spiny dogfish Facts
Spiny dogfish Facts
Comman names:Spurdog, Piked Dogfish, Dogfish, Blue Dog, Darwen Salmon, Rock Salmon, Spring Dogfish, Victorian Spotted Dogfish, White-Spotted Dogfish.
1. They are called dogfish because they hunt and travel in packs like wild dogs.
2. Only fish that have skeletons made entirely of cartilage. Most fish have a swim bladder-sharks do not. They are heavier than the water they displace. If it stops moving, it sinks. If these are in deep water, they are crushed.
3. Concentration of salts is higher than that of surrounding sea water-so no need for sharks to drink. Fertilization is internal. Pups hatch internally in uterus after 2 years.
4. The number of pups in a little varies from 2 in some species to 60 in others. Some sharks are oviparous, laying large eggs enclosed in shells-anchored to seaweed. Size of sharks 6 inches-50 feet (Whale shark-inoffensive..eat planktonic animals).
5. Has poisonous spines one in front of each dorsal fin.3 1/2 feet - 15 pounds. Feed on fish, squid, jelly fish, algae. Will devour plant and animals! Abundant species-disruptive to fishermen.
6. Fins of this species are used as sandpaper for fine sanding of wood materials.When in Europe, if you order "Fish & Chips", you will probably be eating spiny dogfish. Watch out for those two dorsal spines, they are mildly venomous.
7. This long-lived species is also the most studied of all the sharks no doubt due in part to their use as a dissection subject in the classrooms.
8. Spiney dogfish shark mate in winter. Females are ovoviviparous (produce eggs that hatch within the body) and have a gestation period of 18-24 months, the longest of any vertebrate. They generally have from 1 to 20 pups, with an average of about 6-7, with each being 18-30 cm. (9-12") in length.It is known the these sharks (Spiny Dogfish) tend to school by size when smaller and by sex when they mature. Females of the species mature in about 10 years at length of 70-100 centimeters (27-40"). Males mature in 11 years at a size of 60-72 centimeters (24-28"). Life expectancy 25-100 years.
9. The Spiny Dogfish Shark is the world's most abundant shark, occurring worldwide in temperate and sub-arctic ocean waters. They prefer water temperatures from a low of around 7-8 degrees Centigrade (45-46 Fahrenheit) to a high of 12-15 degrees Centigrade (54-59 Fahrenheit).
10. They occur in oceans and coastal zones but rarely enter the upper reaches of estuaries. They never occur in fresh water.Spiney dogfish shark are powerful, voracious predators that feed primarily on bony fishes.
11. Spiny dogfish are gray to slate brown with a pale or white belly. They can be differentiated from other small sharks by a row of small white dots running along their sides.
12. In size, adult females can reach lengths of 3 1/2 feet and weigh around 8 pounds, while males are normally smaller in size. Despite their small size, spiny dogfish are aggressive and have a reputation of relentlessly pursuing their prey.
13. The name “dogfish” stems from their habit of feeding in packs-sometimes numbering in the hundreds or thousands. Gathered together, they sweep an area, eating the fishes in front of them. They’ll eat almost anything they can get their strong jaws and teeth on. Newborn dogfish will even attack fishes two to three times their size.
14. All sharks have unique skin. It’s covered with toothlike scales called denticles-unique to sharks and very similar to the teeth of all vertebrates-which make the skin rough and abrasive. In fact, shark skin was once dried and then used as sandpaper to polish wood. Today, shark skin is still cured and, after the denticles are removed, used as leather.
15. This shark probably has the longest gestation (pregnancy) period of any vertebrate i.e 22 to 24 months.
16. Spiny dogfish sharks are long-distance travelers. One spiny dogfish tagged and released from Washington State showed up off the coast of Japan -a 5,000-mile journey.
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