48 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
The movements and migrations of fish are of two classes; the one 
irregular and occasional, the other regular. The irregular migrations 
are such as occur only at long intervals, sometimes altering very ma- 
terially the industrial and social conditions of maritime countries. 
Among the most notable illustrations of irregular migrations, we may 
cite the case of the bluefish, which during the past century was a well- 
known inhabitant of the eastern coast of the United States, occurring 
in great abundance and of large size. This species appears regularly 
on our eastern coast in the spring and leaves in autumn; but some 
time after the middle of the last century it disappeared entirely, ac- 
cording to the histories of the time, and was not seen during the present 
rentury until much of it had passed by, having been absent for a period 
of about fifty years. Of course it is possible that it may have occurred 
in small numbers, but not sufficient to make any impression; at any 
rate, on its reappearance in 1825 or 1830 it was entirely new to all the 
fishermen. 
‘Another case is that of the chub mackerel (Scomber pneumatophorus). 
This, twenty years ago, was extremely abundant and was taken in large 
numbers at the same time with the common mackerel; but of which © 
in later years only occasionally individuals have been captured. I 
have succeeded in securing only one or two specimens since the com- 
mencement of the operations of the United States Fish Commission, 
although every effort has been made to obtain them. 
A European member of the mackerel family is extremely capricious 
in its movements. Itis the Caranzx trachurus, or the scad, a well-known 
fish of the Mediterranean and of the European coast generally. This 
sometimes sweeps down in immense numbers upon the shores of regions 
where it was previously unknown, or where it has not been seen for 
many years; a notable instance of this occurring in 1862, when im- 
mense numbers made their appearance on the coast of Bergen and in 
the Shrange Fiord, furnishing occupation in their capture and prepara- 
tion to a large population; but scarcely was it at all known except in 
straggling specimens before or since.* 
_ The causes of these variations in distribution are entirely unknown ; 
whether the fish have been exterminated by some disease or pestilence 
(as suggested in the case of the bluefish), &c., cannot be ascertained. 
Various changes in the number of herring on the coast of Northern 
BHurope have been of a similar character. These have been more espe- 
cially important as influencing the condition of the population of Norway 
and Sweden and other northern countries. On the coast of Sweden her- 
ring were formerly in enormous abundance, sustaining a large popula- 
tion along the shores, but have disappeared for decades. Itis with the 
regular migrations of the fishes of our coast that we have at present most 
to do, and I shall proceed to consider them under several headings. 


* Baars, Des Fischerein Industrie de la Norwége, 1873; p. 158, 
