18 



UNUTILIZED FISHES. 



ESTIMATE OF DESTRl'C'TIVENESS. 



The foregoing figures show that the food of the sand shark consists 

 almost entirely of fish. Xo lobster, crab, or other crustacean was 

 found in any of the stomachs, which fact is at variance with the 

 report of Verrill and Smith, who state that the sand shark feeds 

 extensively on these forms. My observations accord more closely 

 with Dr. Linton's. It should be taken into account, however, that 

 the sharks examined were taken from unnatural surroundings, 

 namely, the traps, where they were held in close quarters with most 

 of the species of fish found within them. But, taking the data as 

 collected, and estimating the number of sand sharks in the vicinity 

 where these were taken (Buzzards Bay and Vineyard Sound) at only 

 25,000, and allowing to each sand shark four fish per week, a most 

 conservative estimate, the numbers eaten by sand sharks in one month 

 would be as follows : 



Estimate of Fish Destroyed Each Month by 25,000 Sand Sharks in Buzzards 



Bay and Vineyard Sound. 



The sand shark is to be characterized as a fish wdiich is destructive 

 to fishes of food or other commercial value, although not nearly so 

 destructive as the horned dogfish, which will be considered next. 



THE HORNED DOGFISH. 



GENERAL APPEARANCE AND HABITS. 



In general appearance the horned dogfish (Squalus acanthias) very 

 much resembles the smooth dogfish. It has the same slender, elon- 

 gate body covered with numerous sharp tubercles (placoid scales), 

 the ventrally placed mouth and nostrils, and the characteristic spira- 

 cles. The color is slaty above, with a line of whitish spots extending 

 along either side of the back. The under portions fade out almost 

 to white. The horned dogfish is to be distinguished from the smooth 

 dogfish by its small sharp teeth and a rather high dorsal spine in 

 front of each of the two dorsal fins. In length the adults vary from 

 2 to 3 feet and in weight from 5 to 15 pounds. They are strong, 

 active swimmers, and roam about the shoals and deeper waters in 

 great schools, pursuing their prey like a pack of wolves. The name 



