the upper posterior part of each spine. He cites 

 no case histories of injuries, however. The spines 

 presumably are used in defense and are capable 

 of inflicting a painful wound. 



Spiny dogfish frequently are confused with the 

 smooth dogfish, Mu-sfe/us canits (Mitchill), a mem- 

 ber of the family Triakidae, although examination 

 of the two species will clearly separate them. The 

 smooth dogfish, as the name implies, lacks the 

 sharp dorsal spines. It is a lighter color than the 

 spiny, although it has great ability to change color 

 to match its surroundings. Above a white sandy 

 bottom it usually is a translucent, pearly shade; 

 over a dark bottom it will have a darker color. In- 

 dividuals, in general, tend to be larger than spiny 

 dogfish; smooth dogfish are 89-137 cm. long with 

 a few attaining 152 cm. in length. Food of the 

 smooth dogfish is mostly large Crustacea, espe- 

 cially lobsters and crabs, although it also eats small 

 fish such as menhaden and tautog. It is a coastal, 

 warm water species that ranges in the Western 

 Atlantic from Uruguay and southern Brazil to 

 Cape Cod. It is one of the sharks that develops a 

 placental attachment between the embryos and the 

 mother; thus it is truly viviparous. The smooth 

 dogfish is of little concern to commercial fishermen. 



DISTRIBUTION 



Distribution of the spiny dogfish has been, until 

 recently, somewhat obscured by the question of its 

 specific identity. Many ichthyologists held that 

 there were two distinct species, S. acanfJiias in the 

 North Atlantic. Ocean and S. suckleyi in the North 

 Pacific Ocean. Bigelow and Schroeder (1948) 

 noted that although it was not entirely clear how 

 the two species were related, they had not ob- 

 viously differentiated themselves specifically dur- 

 ing the period since their ranges had become dis- 

 continuous. The prevailing opinion today is that 

 the two populations represent but a single species, 

 S. acanthiii.s, which occurs in both the Atlantic and 

 Pacific Oceans ( American Fisheries Society, 1960 ) . 

 Briefly, the distribution may be expressed as both 

 sides of the North Atlantic, chiefly in temperate 

 and subarctic latitudes, and also on both sides of 

 the North Pacific, in similar latitudes (fig. 2), with 

 close allies in corresponding latitudes in the South- 

 ern Hemisphere. The species is of minor eco- 

 nomic importance in the Southeast Atlantic, off 

 the West Coast of Africa, but fairly important in 



Mediterranean Atlantic waters.- It occurs chiefly 

 in continental, as contrasted with oceanic, waters, 

 anywhere between the surface and the bottom 

 down to 165-185 meters (Bigelow and Schroeder, 

 1948) and has been found as deep as 290 meters 

 ( see table 1 ) . 



Figure 2. — Distribution of the spiny dogfish in 

 Northern Hemisphere. 



the 



The distribution in the Northeast Atlantic is 

 described in detail by Bigelow and Schroeder 

 (1948) as follows: off France, north to Ireland, 

 Scotland, southern Scandinavia, the English 

 Channel, and the North Sea, from there eastward 

 to the Kattegat. The spiny dogfish rarely enters 

 the Baltic Sea. It is plentiful around the Orkney 

 Islands, the Faroes, and south and east of Iceland 

 (but less to the north and west), and is found off 

 Norway to the Murman coast. It is also generally 

 distributed in the Mediterranean Sea and the 

 Black Sea. 



In the Northwest Atlantic the spiny dogfish is 

 found in coastal waters from Cape Lookout, N.C., 

 northward around Nova Scotia, along both the 

 northern and southern shores of the Gulf of St. 

 Lawrence, past the Strait of Belle Isle to southeast 



2 Food and Agriculture Organization of the United Nations. 

 1957. The present status of knowledge of the living resources 

 of the marine waters of the West Coast of Africa. Fisheries 

 Division, Biology Branch. Rome. Italy, 30 pp. [Unpublished 

 processed report.] 



LIFE HISTORY OF SPINY DOGFISH 



529 



