2 10 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
now be safely left in the basins till they have grown stronger. When 
several months old the young fish is already vigorous ; it knows how to 
flee from danger ; it is, therefore, better able than younger fish to escape 
numerous accidents and causes of destruction. Eivers may, therefore, 
be stocked with much greater prospect of success ; and it may safely 
be asserted that 3,000 or 4,000 young fish, ten to twelve months old, 
are infinitely more valuable for stocking a river than 10,000 or 15,000 
very young fish, which, not being strong enough to bear the change 
from the basin to the river, often perish in large numbers when placed 
in the river, where they become an easy prey to older fish living in the 
same waters. 
This opinion is at this day shared by the vast majority of piscicult- 
urists in Great Britain. Nearly everywhere in England and Scotland 
it is considered that the best young trout for stocking rivers are those 
which are about a year old, and which for this reason are called “year- 
lings.” 1 
These young fish are strong enough to seek their food, and conse- 
quently to avoid the principal cause of mortality in young fish, viz, 
inanition ; they can easily be transported, and will bear a change of 
water without difficulty. These young fish cost, it is true, considera- 
bly more than others, but as the final expense is much less, and the 
result is much more prompt and certain, there is an absolute advantage 
in using them for stocking rivers. 
There is only one point in the system which leaves something to be 
desired : If one operates on that large scale which is required for stock- 
ing an entire river, it involves considerable labor to assure the feeding 
of the young fish with artificial food. As the animal is, so to speak, 
made during its early age, and as during this period its assimilating 
organs acquire their strength and their power of absorption, a young 
fish which is insufficiently fed not only grows very slowly, but will never 
become a fine fish. It has been ascertained long since that if, of young 
fish of one and the same hatching, one portion is immediately placed in 
the river, whilst the other portion is kept in basins and fed with ex- 
treme care, the first will, after a short while, be twice as large as the 
second, because they have food which is better adapted to their needs; 
only, the losses among those which have been kept in basins will not 
be as large (unless the circumstances are particularly unfavorable), 
whilst the ranks of those which have been placed in the river have 
often been thinned to such an extent as to leave hardly any. They 
have fallen a prey to water-rats, perch, pike, and even to older trout. 
Thanks to the system of raising employed by Messrs. Lugrin and du 
1 This term is really applied to fish which in many cases are from 10 to 14 months 
old. Practically speaking, the age of a fish is counted from the date when it begins 
to eat, and not from the date when it was born. Thus, a trout of 1887 is a fish which 
commenced to eat in February or March, 1887, although it may possibly have been 
born about the end of the year 1886, and not in the beginning of 1887. 
