THE :\IACKEREL OR TUNNY FAMILY 313 



Five or six finlets behind the second dorsal and the ventral. 

 Scales minute, almost undistinguishable on the sides and belly. 

 A single row of sharp teeth in the jaws, and others on the tongue 

 and roof of the mouth. A slight keel at the base of each lobe 

 of the tail, but none in the centre of the root of the tail. Eyes 

 with transparent upright fixed lids in front and behind. A 

 number of wavy black bands pass down from the mid-dorsal line : 

 between them the colour is deep green : the sides and belly are 

 brilliantly silver}- with iridescent reflections. The shape of the 

 body is somewhat slender, sharp at both ends, somewhat narrow 

 from side to side. 



Varieties are seen in w^iich there are small black spots or 

 irregular scribbled lines, instead of the usual wavy bands. 



Habitat. — From the south of Norway to the Canary Isles, 

 and throughout the Mediterranean. In the British Isles, most 

 abundant in the Channel and northward to Norfolk, but they 

 occur also to some extent along the east coast of Britain to the 

 Orkneys : also in the Irish Sea, and on the south and south-west 

 coasts of Ireland. 



Food. — The mackerel is able to live on minute surface 

 creatures, especially Crustacea, when small fish are not available. 

 It appears to feed at these times like herring or pilchard, strain- 

 ing the swarms of small creatures through the gill rakers, which 

 are as well developed as in the herring family. Thus at Ply- 

 mouth in May I found only the minute Crustacea called copepods 

 in some stomachs, in some a quantit)' of the green slimy vege- 

 table matter, which was then abundant in the sea, and amongst it 

 copepods and buo}'ant fish eggs. In August I found small sprats, 

 and in a considerable number examined in November, only small 

 pilchards between 3 and 4 inches long. The mackerel enter 

 Plymouth Sound and such ba}-s to feed on the young sprats in 

 July and August. 



Breeding. — The number of eggs in a single female has been 

 calculated to be from 430,000 to 540,000 in specimens 18 to 

 20 ounces in weight. 



Sars first described the buoyant eggs of the mackerel in 1865. 

 I studied them at the Ph'mouth Laboratory in 1888. In the 

 latter neighbourhood spawning takes place from the end of May 

 to the latter part of July, and the period seems to be distinctly 

 limited within these times. The spawning fish are found from 



