56 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



ing combinations of the conditions in its environment. It is impos- 

 sible at present to speak more definitely on this subject, and the time 

 is probably considerably remote when our knowledge of specific 

 conditions in the vast and comparatively inaccessible spaces of the 

 ocean is such as to enable us to predict the movements of schools of 

 the mackerel and the times of their abundance and scarcity. 



IV. Reproduction. — The first investigation of the breeding habits 

 of the mackerel was made in 1865 off the coast of Norway by the 

 Norwegian scientist, Professor Sars. He found that the mackerel 

 spawns in coastal waters and that the eggs are buoyant. His 

 observations have later been confirmed and extended by other 

 naturalists, both European and American. At Plymouth, England, 

 where the eggs and young have been carefully studied by Cunning- 

 ham, spawning fish are taken from 14 to 50 or more miles from the 

 coast while the temperature was about 54° F. and the water density, 

 1.0269. The breeding season varies in different localities, being 

 considerably later towards the north than at the south. In America 

 the mackerel spawn in May in southern New England; in ^lay and 

 June in Massachusetts Bay, and in June and early July in the Gulf 

 of St. Lawrence. Spent fish have been taken off of the Virginia coast 

 in April. In Europe the spawning season is in March and April in 

 the Gulf of Marseilles, in May and June off the southwest coast of 

 Ireland, from the end of May to the end of July on the southwest 

 coast of England, and during the first half of July along the Norwe- 

 gian coast. 



The fish of the first spring schools are very poor and of compara.- 

 tively little value as food. Ripe males will take the hook, but ripe 

 and spawning females can be captured only in nets. 



The eggs are spherical and transparent; the yolk is simple, but 

 with a large oil globule which distinguishes it from the cod's egg. 

 The diameter of the egg is about one-twentieth of an inch. At a 

 temperature of 68° F. the incubation period is about six days. The 

 number of eggs in a medium sized female has been estimated at a 

 little less than half a million. 



