THE VARIATION, llACES AND MIGRATIONS OF THE MACKEREL. 287 



Moreover, in view of the difference between Irish and Channel fish, it 

 can no longer be maintained that the mackerel of these regions wander 

 far in winter from their summer haunts. Each race of fish must 

 possess its own winter habitat, and this must be situated close to the 

 region where the fish make tlieir first appearance in the spring. Indeed, 

 the only migrations which can, for the most part, be conceded, are 

 migrations from shallow to deeper water off the same coasts. The one 

 exception to this rule concerns the North Sea fish. The racial identity 

 of these fish with those of the Channel proper furnishes a conclusive 

 proof of the accuracy of the view that the North Sea fish are derived 

 from the English Channel in the spring, and return to it in the 

 autumn, thus ensuring a complete mixture between the two groups 

 during the winter period. By North Sea fish, however, are meant merely 

 the fish which are taken off the east coast of England from Yarmouth 

 southwards. How far to the northwards the spring migration extends 

 must be settled by further investigation. 



The relation between the autumn and spring fish of any locality is 

 also elucidated by the same results. No racial differences between 

 autumn and spring fish have been revealed by my inquiries for any 

 locality which has been represented by samples taken at both periods ; 

 and the existence of differences between the fish of different localities 

 renders it practically certain that each locality is frequented by one 

 race only, viz., the race peculiar to the locality. So far as the Irish fish 

 are concerned, the minor racial differences established between the fish 

 of Kinsale and Kerry prevent a special pronouncement upon this 

 matter on the present occasion, since the Kerry fish were exclusively 

 spring fish, and the Kinsale fish almost entirely autumn fish. The 

 evidence, so far as it goes, points to the conclusion that on the Irish 

 coast the small autumn mackerel are young fish which will to a large 

 extent form part of the breeding shoals in the following spring. 



This matter, however, is being further investigated, and the same 

 material will furnish a means of testing the accuracy of the conclusions 

 which have here been submitted concerning the characters of the local 

 races. 



In conclusion, I may draw attention to the relation of the local races 

 to the conformation of the sea-bed, which appears to me to be of con- 

 siderable importance in any attempt to delimit the area normally 

 frequented by each race. If reference is made to a properly contoured 

 chart — e.g., the charts of the fishing grounds in Cunningham's Market- 

 able Fishes of the British Islands (Macmillan, 1896) — it will be seen 

 that the mouth of the English Channel coincides with the 50-fathom 

 line, that the same line bounds a large plateau of ground off the south 

 coast of Ireland, but that off the west coast of Ireland it runs close 



