52 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



complete mixture between mackerel of the two regions during the 

 winter. The North Sea fish, then, must migrate through the Channel ; 

 only by that way is the warm, deep water accessible to them in the 

 winter. Here, then, is a case in which racial identity coincides with 

 the geographical conditions which are such that the winter habitat 

 and the course of the migrations of the fishes of the two localities 

 cannot be separate. These facts all point strongly to the conclusion 

 that the racial distinctness of the fishes of these different localities 

 indicates the geographical .distinctness of the winter habitats, of 

 their spawning grounds, and of their courses of migration, and 

 further, that the length of their migrations can scarcely be of greater 

 extent than from shallow to deep water off the same coast. 



Similar investigations of the American mackerel have been under- 

 taken by the United States Fish Commission. Their work led to the 

 following conclusions : 



"1. The existence of a marked racial distinction between American 

 and British mackerel, as indicated by the studies of Garstang is 

 strongly confirmed. 



" 2. The evidence thus far accumulated fails to disclose the 

 existence on the American coast of distinct bodies of mackerel, 

 characterized by color or structural features, such as are found on 

 the shores of the British Isles. The examination of further material 

 from extreme southern and northern localities is desirable, however, 

 before the question can be considered settled."* 



This discussion of the migrations of the common mackerel may be 

 summarized as follows : The spawning season of the mackerel occurs 

 later in the season in the schools appearing further north; this is 

 probably clue to the arrival on the coast of new schools which have 

 moved in from deeper water not far away : the capture of mackerel in 

 nets near the shore before they have appeared at the surface fur- 

 ther out, the presence of slightly digested mackerel in the stomachs of 

 codfish taken in the w^inter, the capture of mackerel in trawls in winter, 



♦Report, U. S. Fish Com., 1900, 127. 



