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Spiny Dogfish

 

 

Spiny Dogfish Shark

 

 

  • SPINY DOGFISH SHARK

Scientific name...............Squalus Acanthias

Family name...................Squalidae

Other common names..........Piked dogfish, Whitespotted spurdog

 

  • GENERAL DESCRIPTION

The Spiny dogfish is also known as the piked dogfish or whitespotted spurdog. It is identified by a large spiracle behind each large eye, the presence of spines on the two dorsal fins, and the lack of an anal fin. This shark is a slender dogfish, narrow head, relatively long, pointed snout and no medial barbel on anterior nasal flaps. Pectoral fins with shallowly concave posterior margins and narrowly rounded rear tips. First dorsal fin low, origin usually behind or sometimes over pectoral free rear tips, first dorsal spine slender and very short with origin well behind pectoral free rear tips. The spines of the spiny dogfish are formed from material much like that of our teeth. Growth zones marked on the spines enable us to determine the age of the shark. Some have been found that are 25 to30 years old.

 

  • SIZE

The maximum length these sharks can grow is 4 feet, highly variable regionally. Males mature at ( 24.5 to 39.3 inches ) and females mature at ( 25.9 to 47.2 inches ). Pups are born at ( 7.3 to 12.9 inches ).

 

  • TEETH

The smooth edged short and oblique teeth are similar in both the upper and lower jaws.

 

  • COLOR

Spiny dogfish sharks are gray to bluish-gray to a brownish color on above, and lighter to white below, often with white spots on the sides. Pectoral fins with light posterior margins in adults, dorsal fin tips and edges dusky or plain in adults, with black apices and white posterior margins and free rear tips in young, no conspicuous black blotches on fins.

 

  • FEEDING HABITS

Their diet includes small fishes, such as cod, herring, menhaden, and haddock, as well as invertebrates such as krill, squid, scallops, and crustaceans. Can capture and dismember prey larger than itself. The spiny dogfish uses its spines defensively when it curls itself around in a bow to strike an enemy. It is very probable that the spines are slightly poisonous.

 

  • BEHAVIOUR

Mainly demersal, apparently also epipelagic, sometimes solitary or schooling with other small sharks, often forming immense dense feeding aggregations on rich feeding grounds. Segregates by size and sex into packs or schools of small juveniles ( both sexes ), mature males , larger immature females, or large mature females ( often Pregnant ). Mixed adults schools occasionally reported. They are slow swimmers but undertakes long-distant seasonal migrations north-south or deep-shallow as water temperature changes, prefers 45-59 F ( 7-15C ).

 

  • HABITAT

They are found almost world-wide, except tropics northern and southern hemisphere populations and limited genetic mixing between some stocks with overlapping range and feeding grounds but different migration patterns. Spiny dogfish are cold-water sharks, preferring temperatures from ( 45-59F ). They are caught in waters down to about 2,600 feet deep, but not exclusively in deep water. They form extremely large schools, routinely frequenting the shallow and coastal waters of higher latitudes in spring and fall, and migrating into deep waters during cooler winter months. Often on soft sediments in enclosed and open bays and estuaries, where most nursery grounds occur.

 

  • REPRODUCTION

These sharks are ovoviviparous, with a litter size of ( 1 to 32 ), although varies regionally and larger females have more and larger pups. Gestation period varies regionally, from 18 to 24 months, to only 12 months in the Black Sea ( where largest females, pups and litters occur.

 

  • SHARK ATTACKS

Not dangerous to man except through lacerations from the mildly toxic dorsal spines.

 

  • POPULATION REPORT

Common, but stocks are nearly depleted in many areas. ( Endangered northeast Atlantic, Vulnerable northwest Atlantic ). Extremely well studied. Possibly once the most abundant shark and the most important commercial species, utilized for meat ( high value in Europe ), liver oil and fins and supporting large target trawl and line fisheries comparable to those for bony fishes. Its slow growth, late maturity, longevity and low reproductive capacity make it highly vulnerable to overfishing, particularly since aggregations of large pregnant females are usually targeted. Few fisheries are managed, some stocks are now very seriously depleted or collapsed and catches declining steeply. Also of commercial fisheries significance because large numbers may damage fishing gear and affect catches of other species. Targeted by sports anglers in some regions, displayed in public aquaria, and important for scientific research and teaching.

 
     

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