38 REPORT OF COMMISSIONERS OF IXLAXD FISHERIES, 



out spines. It is entirely covered with a considerable quantity 

 of slime, which still further smooths off the surface of the skin by 

 filling in its lesser inequalities. 



All these modifications of the external structure of the body of 

 the fish reduce to a minimum the resistance to its rapid motion 

 through the water. It is strong and muscular; the vertebrie are rela- 

 tively small and numerous, an arrangement which is conducive to 

 flexibility of the body. The Spanish Mackerel thus possesses a 

 combination of qualities which makes it one of the swiftest and 

 most powerful swimmers of the sea. The same applies equally well 

 to the Bonito, and all the fishes of this family possess the above 

 described characters with greater or less modification. They are 

 thus, perhaps, the best adapted of any fishes for an active and 

 predacious existence in the Dpen waters of the ocean. 



The external structure of the fishes of the ^Mackerel family is 

 distinguished by the following characteristics: The body is elon- 

 gate, spindle shaped, and slightly .compressed. The head is cone 

 shaped, and pointed in front; the mouth is large, the jaws strong, 

 the teeth sharp and, in most of the species, small. The gill open- 

 ings are very wide. They have two fins on the back, the first one 

 spiny and depressable in a groove; the second is made up of soft 

 rays. Directly under the latter, on the ventral side, is placed the 

 ventral fin. Behind each of these two is placed a row of small fin- 

 lets. The pelvic fins are placed directly below the pectoral fins. 

 The tail fin is strong, broadly forked, and adapted for rapid motion. 

 Most of the species have a median longitudinal keel just in front of 

 the tail fin. The scales are usually minute and without spines, but 

 in some of the species they are somewhat enlarged and confined to a 

 distinctly defined area on the front part of the body so as to form a 

 corslet. The lateral line is present and is usually very wavy in its 

 course. In size the different species vary much; the Chub Mackerel 

 is scarcely over 14 inches in length, while the Horse Mackerel some- 

 times reaches a length of 10 feet or more and weighs up to 1,500 

 pounds. 



