FISHES OF THE GULF OF MAINE 



47 



THE SPINY DOGFISHES. FAMILY SQUALIDAE 



This group is characterized by the lack of an 

 anal fin, combined with the presence of two dorsal 

 fins, each of which is preceded by a fixed spine 

 which is long and conspicuous in some, but so 

 short in others that its presence can be detected 

 only by touch. The teeth are alike in the two 

 jaws in some, unli ke in others. 



Spiny dogfish Squalus acanthias Linnaeus 1758 



Dogfish; Piked dogfish; Grayfish 



Bigelow and Schroeder, 1948, p. 455. 

 Garman, 1913, pi. 14, figs. 1-4. 



Description. — Any little gray or brownish shark, 

 with a large sharp spine lying along the front 

 margin of each dorsal fin, caught within the Gulf, 

 or on the shoaler parts of the offshore fishing 

 banks, is practically sure to be this "dog," of 

 which there are thousands in the Gulf to every 

 one shark of any other kind. One of its relatives, 

 the black dogfish (p. 51), is a regular inhabitant 

 of the deeper slopes of the offshore Banks that 

 front the Gulf, where we also trawled more than 

 50 specimens of another relative Etmopterus 

 princeps Collett 1904 during the summer of 1952. 

 But there is no danger of confusing the common 

 spiny -dog with either of these, for they are velvety 

 black in color, the rear margins of their tail fins 

 are indented near the tip, which is not the case in 



the spiny-dog, and each of their teeth, at least in 

 the upper jaw (lower jaw as well in the black dog- 

 fish) has 3 to 5 sharp points, but only one point 

 in the spiny dog. 



This is a slender little shark, with flattened 

 head and snout tapering to a blunt tip. Its first 

 dorsal fin stands between pectorals and pelvics; 

 its second dorsal fin is about two-thirds as large 

 as the first; its pectorals form nearly an equilateral 

 triangle; and its pelvics are well forward of its 

 second dorsal fin. The dorsal fin spines lie close 

 along the front margins of the two dorsals, the 

 first not more tha.i one-half as long, and the second 

 nearly as long as the front margin of their respec- 

 tive fin, and they are very sharp. The spiny-dog 

 has no anal fin, a lack separating it from all 

 smooth-finned sharks known from the Gulf of 

 Maine, except for the Greenland shark (p. 53), 

 Dalatias (p. 55), and the bramble shark (p. 56). 

 There is a low fold of skin on either side of the 

 root of the tail back of the second dorsal fin, so 

 small, however, that there is no danger of confusing 

 it with the caudal keels of the mackerel-shark 

 tribe. The teeth are small, their sharp points 

 bent toward the outer corners of the mouth so 

 that they form a nearly continuous cutting edge 

 along each jaw. 



Color. — The upper surface is slate colored usu- 

 ally, sometimes tinged brown, with a row of small 



Figure 17. — Spiny dogfish (Squalus acanthias), female, 27 Inches long; after Garman. A, upper and lower teeth, mid- 

 point of mouth marked by the dotted line, about 3 times natural size. From Bigelow and Schroeder. Drawing 

 by E. N. Fischer. 



