352 Shark and Company 



ods of retarded growth during winter months (dark rings). It will 

 come as no comfort to the fisherman to know that the counting of these 

 rings has indicated that some Spiny dogfish may Uve to an age of about 

 30 years. (The Spiny dogfish is one of the very few sharks whose age 

 can be even guessed at. A shark's age and life-span are two more of its 

 many mysteries. ) 



David H. Graham, of New Zealand, tells of finding fully formed 

 dogfish in a mother he caught. Graham placed them in a laboratory 

 tank, where they lived for several months and grew to lengths of about 

 13 inches. But, he said, "They lost the skin and flesh from the tip of 

 their noses through bumping into the ends of the aquarium tank, which 

 no doubt contributed to their untimely end." 



In the United States and Canada, the predaceous Uttle sharks are hated 

 by fishermen, and with reason, but they find a good market as food in 

 many areas of Europe. 



Robbed of his catch, his net ruined, and finally his hand bleeding 

 and stinging, many a fisherman has wreaked a cruel vengeance upon 

 his tormentor. The avenger breaks the dogfish's flat snout with a quick 

 upward blow, then tosses the maimed shark back into the sea. Unable to 

 dive because of its injury, the dogfish lurches along near the surface, 

 doomed to starve or fall prey to a larger fish. 



Spiny dogfish, which grow to 2 or 3 feet in length, apparently are 

 born in wintering grounds far off shore. This species is ovoviviparous, 

 and gestation lasts 18 to 22 months. While the four to six embryos in 

 the average litter are developing, a new set of eggs is growing in the 

 ovary to replace them. 



When the temperature of the water along the United States Atlantic 

 coast reaches about 43 °F. in the spring, the Spiny dogfish begin to ap- 

 pear. By the time the temperature rises to about 59°F., they either move 

 out to deeper, cooler water, or head northward, sometimes at a speed of 

 8 miles a day. Their meanderings seem to be bound by this relationship 

 to temperature, for, as northern waters drop below 43 °F., they head 

 southward again, until finally, they head for the deep, offshore water 

 where they winter. They are driven by temperature demands quite 

 similar to those of the mackerel, M^hich dogfish frequently massacre in 

 fishermen's nets. 



The Spiny dogfish is a scourge on our side of the Atlantic, heading 

 from Caribbean to subarctic waters in search of prey. As mentioned, it 

 lives off Europe also. It similarly ranges the Pacific, from San Diego to the 

 Aleutian Islands on the west coast, outward to the Hawaiian Islands, 

 beyond to Japan and northern China, southward to New Zealand, Aus- 

 tralia. 



The family Squalidae is represented in Australian and New Zealand 



