118 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. [28] 



erel. This is so common an occurrence that there are but few fishermen 

 who have not witnessed it." 



"Porpoises and whales may also be included in the list of enemies of 

 the mackerel. It is by no means an unusual sight on the fishing grounds 

 to see hundreds of the former rushing and leaping among schools of 

 mackerel scattering them in every direction." 



"The shark, known to fishermen as the 'mackerel shark/ is one of 

 the principal enemies of the mackerel. I have often seen them chasing 

 mackerel, and, when jigging was practiced, it was a common occurrence 

 for sharks to drive off a school from alongside of a vessel." 



Dogfish often hover around the outside of large schools of mackerel, 

 and doubtless feed on them. Great difiiculty is sometimes experienced 

 in saving fish that have been inclosed in a x)urse-seine, owing to the im- 

 mense numbers of dogfish that gather around, and in their efforts to 

 eat the mackerel, which they see through the meshes, they bite off the 

 twine, making large holes in the seine through which the inclosed fish 

 escape." 



The dogfish is doubtless a dangerous foe to the mackerel weakened 

 by the act of spawning, and remaining near the bottom. An old fisher- 

 man has described to me with great animation how greedily the dog- 

 fish devour the mackerel which have become gilled in the nets, how 

 they follow them to the surface and linger about the vessel while the 

 process of cleaning is going on, drinking the blood of the fish as it 

 flows from the scuppers. 



Among the other principal enemies of the mackerel are the bluefish, 

 tunny, and cod. The appearance of a school of bluefish in waters crowded 

 with mackerel is an almost sure signal for their disappearance. 



The young mackerel are eaten also by squids. Professor Verrill has 

 recorded the following description of the maneuvers of the squid known 

 to zoologists by the name Ommastrephes illecehrosa : 



"Messrs. S. I. Smith and Oscar Harger observed it at Provincetown, 

 Mass., among the wharves, in large numbers, July 28, engaged in cap- 

 turing and devouring the young mackerel, which were swimming about 

 in ' schools,' and at that time were about four or five inches long. In 

 attacking the mackerel they would suddenly dart backward among the 

 fish with the velocity of an arrow, and as suddenly turn obliquely to the 

 right or left and seize a fish, which was almost instantly killed by a 

 bite in the back of the neck with the sharp beaks. The bite was always 

 made in the same place, cutting out a triangular piece of flesh, and was 

 deep enough to penetrate to the spinal cord. The attacks were not 

 always successful, and were sometimes repeated a dozen times before 

 one of these active and Avary fishes could be caught. Sometimes after 

 making several unsuccessful attempts one of the squids would sud- 

 denly drop to the bottom, and, resting ujjon the sand, would change its 

 color to that of the sand so perfectly as to be olmost invisible. In this 



