44 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



fishes which have not attracted so much attention. There is, of 

 course, little doubt as to the general significance of these move- 

 ments themselves in the hfe history of the mackerel, but the course 

 and extent of these migrations involve many questions which are 

 still open to debate. 



The mackerel first approach the coast in spring or early summer 

 for the purpose of spawning. The shore waters are more favorable 

 for this on account of the obvious advantage to the newly hatched 

 young near the coast, where an abundance of the more minute sur- 

 face organisms are present. The females, during the breeding sea- 

 son, do not feed and can not be taken with a hook. The first migra- 

 tion towards the coast must, then, be looked upon as, to a large 

 extent, independent of the food supply, and therefore what 8ars 

 called a " spawning migration." But the presence of the mackerel 

 in shore waters during summer and autumn, after spawning has 

 taken place, is for the purpose of feeding on the young of other 

 fishes which abound in those waters during the latter part of the 

 season. The latter movements of the mackerel are therefore " feed- 

 ing migrations."* 



Notwithstanding the fact that the final causes of the migrations 

 are to be found in the feeding and reproductive processes, the move- 

 ments of the schools are largely influenced by various physical factors, 

 the most important of which is probably the temperature of the sea 

 water. According to Goode, the appearance of the mackerel takes 

 place off the American coast when the average harbor temperature 

 is not below 45° F. The temperature in the open sea at this time 

 is somewhat lower, probably as low as 40° or even less.f On the 

 European coast, according to Allen, J the mackerel first appear off 

 the southwest of the coast of Ireland when the surface temperature 

 is about 50° F. ; off the Mediterranean coast of the south of France, 

 when the temperature approaches 60° F. This may indicate the 

 existence of three separate races of mackerel which have become 



* Allen, Jour. Mar. Biol. As., 1897, 25. 

 t Report, U. S. Fish Com., 1881, 99. 

 t Loc. cit., 25. 



