UNUTILIZED FISHES. 



15 



Estimate of Fish Destroyed Each Year by Every 100,000 Dogfish in 



Buzzards Bay-. 



FEEDING HABITS. 



The unnatural conditions surrounding the fishes in the traps 

 involve the above results in a considerable degree of error. For more 

 nearly accurate calculation it is necessary to consider, in addition to 

 the above factors, what the dogfish had met with during its short 

 experience in captivity and also what is its normal habit of feeding. 

 In the traps it was generally crowded into close quarters with men- 

 haden, squids, puffers, scups, bonitos, squeteagues, and other fishes. 

 Any food taken in the trap had to come from this list, and that food 

 was taken in the trap is very evident upon a glance at the above 

 table. On the other hand, the crustaceans (except the spider crab) 

 and the molluscs were rarely, if ever, taken in the traps, so that such 

 of these as were found in the dogfish were most likely taken in their 

 natural haunts. 



The study of a number of live dogfish kept in the shark pool of 

 the Woods Hole station shed considerable light on their habits of 

 feeding. This pool is about 100 feet long by 25 feet wide, with a 

 depth of the water varying from about 4 to 7^ feet, according to the 

 tide. Except when the tide was quite high, it was an easy matter to 

 see the bottom and the fishes swimming about. 



The usual habit of the dogfishes was to swim close to the bottom, 

 searching for food over every square inch of the ground. If a rock 

 crab or spider oral) were thrown into the pool, they soon found it. 

 They would turn over on their sides to seize it, and then dart rapidly 

 off, shaking it much as a terrier would shake a rat. After swal- 

 lowing the crab, the dogfish kept up its active swimming, often 

 returning to the place where the food had been found, just as if 

 hoping more might be discovered there. The experiment of throwing 

 in food was repeated several times, always with the same result. A 

 tame loon, which was kept in the pool for a week or two, was often 



