THE MACKEREL OR TUNNY FAMILY 



The fishes of this family have two dorsal fins, the first spiny 

 the second soft ; and one ventral fin placed under the second 

 dorsal. Behind each of these two is a row of small finlets. The 

 pelvic fins are directly below the pectoral. The tail fin is deeply 

 forked. The mouth is large and the jaws strong, but the teeth 

 are small and sharp. The scales are small and without spines, 

 in the tunnies confined to distinctly defined areas on the front 

 part of the body, forming a corselet. The gill-openings are wide. 

 The sides of the tail are sometimes keeled. In some of the tun- 

 nies the pectoral fins when closed fit into depressions of the skin, 

 and thus lie level with the surrounding surface. 



These fishes are e.x'tremely active, migratory, and predaceous. 

 They swim in shoals and seize their prey with great voracity, 

 and hunt merely by sight. They pursue other surface and mid- 

 water fishes, and snap at an}'thing moving through the water, 

 especially if it is silvery like a small surface fish. The different 

 kinds are of very different sizes, from the mackerel not exceeding 

 1 8 inches long and 2h lbs. in weight to the huge tunny some- 

 times reaching nearl)' lo cwt. These fishes are not confined 

 to the neighbourhood of the coasts, although the mackerel is 

 a coast fish, the tunnies ranging through the open oceans. 

 They belong to the tropical and temperate zones, none of them 

 occurring in the Arctic or Antarctic Ocean. 



The following are the species found in British waters, with 

 the chief peculiarities wdiich distinguish them from one another. 



I. Species of small size in which the two dorsal fins are widely 

 separated ; the corselet is not distinctly defined ; and there is no 

 keel in the middle of the side of the root of the tail. 



