176 AMERICAN FISHES. 



size varies from year to year, sometimes very few barrels which can be 

 rated as No. I's being found in our waters. A No. i Mackerel, accord- 

 ing to the Massachusetts inspection laws, measures thirteen inches from 

 the tip of the snout to the crotch or fork of the caudal fin. The average 

 length from year to year for the whole coast is probably not far from 

 twelve inches in length, and a weight of twelve to sixteen ounces. 



The gannet is one of the most destructive enemies of the Mackerel. 

 These birds are often seen so heavily weighted with these fish that they 

 are unable to rise on the approach of the vessel until they have disgorged 

 from two to four good-sized Mackerel. 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 leading among schools of Mack- 

 erel, 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 difficulty is sometimes experienced in 

 saving fish that have been inclosed in a purse-seine, owing to the immense 

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

 Mackerel, which they see through the meshes, bite off the twine, making 

 large holes in the seine through which the inclosed fish escape. 



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

 and the 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 by squids also. Prof. Verrill has recorded 

 the following account of the maneuvers of the squid known to zoologists 

 by the name OmmastrcpJics illecebrosus : 



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

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

 ing and devouring the young Mackerel, which were swimming about in 

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

 ing the Mackerel they would suddenly dart backward among the fish with 

 the velocity of an arrow and suddenly turn obliquely to the right or left 



