PROGRESS IN BIOLOGICAL INQUIRIES, 1926 647 
The quantitative results of rearing sockeyes to the yearling stage have been 
shown best by three later experiments, in which rewards were paid for records 
of recoveries. The reported returns from these experiments represent 1.4, 2.5, 
and 4.8 per cent of the number liberated. The last two percentages represent 
only the 4-year-olds, which were recovered during the past season; additional 
returns from these experiments are to be expected in 1927. 
The returns have been expressed in relation to the number of yearlings liber- 
ated, because the data of the mortality in the hatchery are not sufficiently 
accurate (in most cases, at least) to be of value. In one case, comparatively 
accurate records of the entire history of the fish are available. In round num- 
bers, the history is as follows: Starting with 100,000 eggs, 50,000 yearlings 
remained at the time of marking in February of the second year; 2,400 adults 
were caught in the commercial fishery when they returned in their fourth year; 
and an additional 100 4-year-olds passed through the commercial fishery and 
returned to the hatchery at which they had been liberated. From this 100 
fish, 150,000 eggs were taken. The cycle ends, then, with a stock of eggs one- 
balf greater than the number with which it started. The total number of 
adults recovered represents 21%4 per cent of the number of eggs required to 
produce them. 
A return of 2% per cent may, at first thought, seem very small, but the im- 
pression is quite different when the fact is taken into consideration that each 
female sockeye produces two or three thousand eggs. The return in this ex- 
periment was at least 30 fish to each parent fish. Hatchery operations that 
provide a return to the commercial fishery of 30 fish from each parent and a 
spawning escapement sufficient to double the stock in two generations must be 
considered as successful. 
The artificial propagation concerned in this particular experiment has been 
underrated in several ways. The quoted returns represent only the 4-year-olds, 
The 5-year-olds will return next season. The spawners did not all return to 
the place of likeration; only those that did have been considered here. It must 
be pointed out, however, that this experiment has been more successful than 
any other in producing returns. Similar practices may or may not produce 
equal returns. 
Possibly the most valuable contributions to be added to our knowledge by 
these experiments are in regard to the habits, instincts, and racial peculiarities 
of the fish. One of the racial peculiarities is that of storing fat in the flesh. 
Chemical analyses of canned salmon have shown that the blueback of the 
Columbia stores a greater quantity of fat than does any other representative of 
the species, the flesh being about 16 per cent fat. In Alaska this species has 
from 5 per cent to 10 per cent of fat, the average being 7 per cent, or less 
than half that of the Columbia River blueback. The question in regard to the 
imported sockeyes was: Is the quantity of fat stored determined by heredity 
or by environment? The former has been found to be the case. The imported 
sockeyes, although presumably living under the same conditions as the native 
bluebacks, still store much less oil than do the bluebacks. Samples of a second 
generation of sockeyes in the Columbia are now available. The samples have 
not been analyzed as yet, but from general observation the fat content does 
not seem to have been changed by the longer residence in the Columbia. Inter- 
est in this character lies in the fact that the value of the canned product 
varies directly with the quantity of fat. The imported fish, therefore, are 
greatly inferior to the native bluebacks. 
Among the instincts of salmon the homing instinct has been of most concern. 
The fact that salmon return to spawn in the river system from which they 
entered the ocean is substantiated by a wealth of data from other sources. It 
will be sufficient merely to mention here that no fish marked on the Columbia 
has been recovered in any other river system. We shall be concerned here 
with a more exacting analysis of the homing instinct—the return to a par- 
ticular tributary. The sockeye-marking experiments are not especially satis- 
factory for this consideration, because they involve transplanted fish and 
because the tributaries in which the fingerlings were liberated have not offered 
favorable conditions for the return of the adult fish. Nevertheless, there has 
been a distinct tendency on the part of the fish to return to the place of 
liberation. What straying has occurred has been mainly to the tributaries in 
the vicinity of the one in which the fingerlings were liberated. In one experi- 
ment, however, none of the adult fish returned to the place of liberation. 
This instance is of much interest to practical fish culturists. The hatchery 
at which the fish were reared was constructed primarily for the propagation 
