ii CHARACTERISTICS OF VALUABLE MARINE FISHKS 53 



fishes, and have their headquarters in the tropics. The well- 

 known pilot-fish, celebrated as the companion and guide of the 

 shark, belongs to this family, as also the common scad or 

 horse mackerel. 



The John dory (Fig. 18) and the boar-fish are the British 

 members of a small family represented on the coasts of tempe- 

 rate regions. They have a thin, deep, short body, with a long 

 first dorsal fin, and narrow second dorsal and ventral. The 



FIG. 1 8. The John dory. 



mouth is curiously constructed, so that when opened it is auto- 

 matically protruded and forms a tube of some length. They are 

 very slow swimmers, accustomed to hover in the water, and 

 swim both near the bottom and in mid-water : but the dory is 

 chiefly taken by the trawl. 



The mackerel family (Fig. 19) are much more like the horse 

 mackerel than are the dory and boar-fish. They are active, 

 powerful swimmers, and many of the species are large fish living 

 in the open ocean : the latter are the tunnies. These fishes 

 usually have two dorsal fins, and behind the second dorsal and 



