240 FISHERY PUBLICATIONS OF THE UNITED STATES. 
information supplied. It is evident enough that these two species 
have been introduced to the Pacific coast by transporting the fry in 
railroad cars from the Atlantic side, and the fact is impressive as an 
illustration of the magnitude of the operations carried on by the 
Commission. Whatever its imperfections, it has made itself a pisci- 
cultural organisation which connects together the two greatest 
oceans of the globe. The transport of useful animals or plants from 
one continent to another across the ocean is a practice of consider- 
able antiquity ; the transportation of valuable fish from one ocean 
to another across a whole continent had never been accomplished 
before. 
But the question still remains, is there any good evidence by 
which to estimate the practical results of the piscicultural operations 
in connection with long-established fisheries? We naturally here 
examine first the case of the shad fishery on the Atlantic side, since 
we know that artificial propagation of the shad (Clupea sapidissima) 
has been more extensively and more successfully carried out by the 
Commission than that of any other fish. We look to see what the 
Commission has to say of the condition of the fishery. We know that 
the United States administration does not attempt to supply annual 
statistics of the fisheries as our own Fisheries Department does. 
The Commissioner remarks that the limited appropriation and con- 
sequent smallness of the force available for statistical inquiry pre- 
clude the possibility of an annual investigation ; and that evenif this 
were attempted it is open to question whether the variations in the 
fisheries from year to year are generally sufficiently marked, or 
whether at this time the results would be of sufficient importance to 
warrant the largely increased expenditure that would be required to 
conduct the work. He thinks that comparative statistics are more 
valuable when they relate to definite intervals of time than when 
they cover successive years. He asserts that the researches of the 
Commission furnish data for the comparison of conditions at intervals 
of three or four years, and for the determination of the influences of 
the methods and means employed upon the prosperity of the 
fisheries. 
In the Statistical Report the total produce of the shad fisheries 
in different periods is not definitely presented, but there is a very 
interesting account of the fishery in the Potomac River, of which 
the following are the most important points. In 1890, 731,453 fish 
were taken, weighing 2,571,002 Ibs., and realising to the fishermen 
$75,935, or about £15,200. In 1889, 868,900 fish were taken, 
valued at $85,378. These figures are compared with those corre- 
sponding for the end of the previous decade, namely, less than 200,000 
fish in 1878, increasing till 1880, when 600,000 was the number of 
