160 FISHES OF AUSTRALIA. 



THE MACKEREL FAMILY. 



( Family : Scorn bridtc . ) 



FROM 50 to 60 species of this family are known from various 

 parts of the world, about 8 of which are to be found in 

 Australian waters. These fishes are amongst the swiftest 

 inhabitants of the sea. Elegant in form (and often in 

 colour) their beautiful spindle-shaped bodies are able to 

 gracefully cleave the waters with but little muscular exer- 

 tion. Typical "submarines," they are able to make their way 

 in the water, in any direction, and at any angle, with a 

 speed that is surprising. If a typical Mackerel be closely 

 examined, it will be at once apparent that the fish has been 

 "built for speed." The skin is smooth and slippery, the 

 snout is pointed and somewhat conical in shape, and the 

 body tapers away rapidly to the shaft of the tail, from 

 which the comparatively-large, forked caudal fin spreads 

 out. Upon examining the back we find that there is a 

 groove which enables the first dorsal fin to lie right down 

 out of sight and that the second dorsal and anal fins are 

 partly sheathed and arranged in such a way that there is 

 little resistance to the water. Even the pectoral and ventral 

 fins also, fit into shallow depressions in the body; so that 

 when the fish is travelling at a high rate of speed, a clean, 

 smooth, non-resistant surface is presented, this allowing the 

 fish to literally "slide" through the water; so that with a 

 minimum of effort a very high rate of speed is attainable. 

 Upon the tail in certain Mackerels there is a kind of leathery 

 keel developed on each side, followed by two other smaller 

 ones one above it and one below it on the somewhat- 

 flattened root of the caudal fin itself; while in others only 

 the latter are developed. The purpose of these is to assist 

 in giving a little stability to what would otherwise be a 

 "very cranky craft" when the balancing fins are laid back. 

 Of course, when the fish is only travelling at a low rate or 

 moving about within a small area the pectoral, ventral, 

 dorsal and anal fins are continually in use. I should also 

 have mentioned that the little "finlets" which follow after 



