REPORT OF COMMISSIONERS OF INLAND FISHERIES. 49 



theory of the location of the winter home of the mackerel rests 

 entirely upon fragmentary observations and the somewhat uncer- 

 tain deductions based upon them. The problem of the course of 

 the migratory fishes has always been a peculiarly difficult one because 

 the movements of these fishes take place in such breadths and depths 

 of the ocean that only an exceedingly meagre opportunity is afforded 

 for direct observation upon them. There is, however, one possible 

 line of approach to the problem which has been applied with success 

 to the European mackerel. I refer to the methods used by Mr. 

 Walter Garstang, M. A., of the Marine Biological Laboratory at 

 Plymouth, England, in his work on the " Variation, Races, and the 

 Migrations of the Mackerel."* This is probably the most important 

 piece of scientific work ever done bearing directly upon the ques- 

 tions connected with the periodical migrations of the ocean fishes. 



A brief statement of his methods and results will suffice in this 

 place. He obtained as large a number of mackerel as possible from 

 different localities and " by the detailed study of the variations of 

 certain chosen characters in the mackerel of these different locali- 

 ties " he endeavored to determine whether or not local races exist. 

 The range of variation in these characters in the different local 

 groups of mackerel w^ere compared and the frequency with which 

 particular variations or combinations of variations occur in any one 

 local group were compared with their frequencies in all the other 

 groups. " For example, if we suppose that the number of fin rays 

 in the first dorsal fin varies between 10 and 14, the value 12 will 

 probably occur with the greatest frequency. But other possibilities 

 occur; and while 12 might be constantly the most frequent value 

 in one local group of fish, it is quite conceivable that 13 might be 

 constantly the most frequent value in samples of another group." 

 In this case, if the two groups were examined under similar condi- 

 tions and the variation determined upon a sufficient number of 

 specimens, these two groups should be regarded as two distinct races. 



* Garstang, On the Variation, Races, and Migrations of the Mackerel, Jour. Mar. Biol. As., 

 5 N. S., 1897, 235. 



