Mackerel and Tuna: the Family Scombridae

Some families of fish are defined by characteristics which the layman might fail to discern; but this family looks like a family even to the least tutored eye. All its members are powerful swimmers, with muscular and beautifully streamlined bodies. Day put it well. ‘Carnivorous and exceedingly active, their shapes are well adapted to enable them to glide rapidly through the water: while to obviate the least impediment, we even find in some depressions for the reception of the pectoral fins.’ They all perform migrations of considerable extent. They all have deeply forked or crescent-shaped tail fins; and a row of dorsal and anal finlets to the rear of the dorsal and anal fins. Their scales are small (and those of the tunas cover only part of the body, in what is called a corselet) and their coloration is like a uniform with only minor variations – blue or blue-green back, silvery sides and belly.