286 THE YAIUATION, RACES AND MIGRATIONS OF THE MACKEREL. 



observations is taken into account, that the data accumulated for North 

 Sea and Plymouth fish should coincide so closely as they do, and differ 

 to so considerable an extent from the data determined for the fish from 

 Kerry. 



Nevertheless, although certain differences between the Irish fish 

 and those from the Channel and North Sea must, I think, be conceded, 

 it would be a serious error to conclude that the division between these 

 two races of mackerel is hard and fast. I have shown that the Kinsale 

 fish are distinctly intermediate in character between the fish from 

 the west coast of Ireland and those of the Channel in regard to the 

 following features: — (1) number of transverse bars, (2) spottiness, and 

 (3) number of first dorsal finrays. I have also shown that the 

 mackerel caught off Brest and Scilly, though closely related to the 

 Channel fish as a whole, also betray a certain approximation towards 

 the Irish, especially the Kinsale, values in regard to the same characters ; 

 and, although the number of fish representing this region is relatively 

 small, I see no reason for doubting that the consensus of evidence 

 on this point is of some significance. These two intermediate cases, 

 therefore, prevent the establishment of any rigid line of separation 

 between the Irish and the Channel races ; but they at the same time 

 confirm in a most emphatic manner the one paramount conclusion 

 of the whole inquiry, viz., that the mackerel which frequent British 

 waters are not exactly alike in all localities, hut possess certain average 

 peculiarities which distinguish one local race from another. These 

 2}eculiarities are greatest between the races of localities ivhich are 

 geographicallg remote, and least between those which occupy areas that 

 are geographically contiguous. Bctiveen the mackerel of the North Sea 

 and English Channel there are no differences at all; but the Irish race 

 is distinctly divisible into tivo stocks, one of which is restricted to the 

 west coast, the other to the south. A considerable amount of mixture 

 takes place between the southern Irish stock and the fish lohich frequent 

 the mouth of the English Channel. The western Irish stock represents 

 more closely than any other race the primitive type of mackerel, from which 

 all, whether British or American, have been derived. 



XV. The Migrations of the Mackerel. 



The establishment of geographical or local races of the mackerel 

 settles a number of disputed points concerning the migrations of this 

 fish. The theory of long migrations must be altogether given up. The 

 mackerel certainly does not cross the Atlantic ; the marked difference 

 between American and European samples shows that at the present 

 period of the earth's history there is no mixture between the two races. 



