266 THE VARIATION, RACES AND MIGRATIONS OF THE MACKEREL. 



The conclusion, therefore, seems to me to be inevitable that the 

 mackerel which frequent the south and west coasts of Ireland are 

 not a single stock of fish which visit both coasts indifferently, but 

 are separable into two stocks, one of which inhabits the waters off 

 the west coast, the other those off the south coast. 



I find some support for this conclusion in Mr. Green's statement 

 that he has met with no evidence to show that mackerel in approaching 

 the Irish coast " travel along it, either to north or south. From Cork 

 to Donegal, which are the extreme limits of the fishery on the Irish 

 coast, they appear at the same time." (Bull. U.S. Fish Com., xiii. 

 1893, p. 358.) 



There is, of course, no impassable barrier between the two stocks 

 of fish. Mixture must undoubtedly take place at the imaginary border- 

 line between the southern and western areas, and in the spawning 

 season a variable number of the floating eggs from one stock must 

 be carried by currents into the area of the other ; but it must be 

 remembered that my samples are derived from localities relatively far 

 apart, viz., Kinsale and off the mouth of the Shannon, and that while 

 the west coast fish are only subject to mixture with the closely related 

 south coast fish, those which are found in the eastern waters of the 

 south coast are also liable to mixture with the mackerel of the English 

 Channel. It is probably significant, therefore, that the differences 

 between the Kinsale and Kerry fish consist in an approximation of 

 the former fish, and not of the latter, towards those of the Channel in 

 regard to the present character. 



I may draw attention to the fact that this intermediate condition 

 of the Kinsale fish is not confined to the present character. If 

 reference is made again to Table B, it will be seen that the mean 

 number of transverse bars is distinctly lower for Kinsale (27"15) than 

 for Kerry (27'27), and consequently approximates towards the mean 

 value for the Channel, which is the lowest of all (26'79). In this 

 character, however, the Kinsale fish maintain a closer resemblance to 

 the Kerry fish than to those of the Channel. Similar results have 

 also been yielded by the first dorsal fin, as will be described later 

 on (p. 275). 



From a comparison of all three tables (B, C, and D) it would appear 

 to be probable that the mixture which actually accounts for the inter- 

 mediate condition of the Kinsale fish is rather with the Brest and 

 Scilly fish than with those of the Channel in its narrower sense. Such 

 a conclusion would harmonise well with the known range in the 

 position of the fishing quarters during the spring season. 



To conclude this chapter, I give a more condensed statement of the 

 results for the four principal regions. 



