6 “ U. S. BUREAU OF FISHERIES. 
For many years investigations have been directed particularly 
at the Pacific salmon, and the facts of life histories which are easiest 
to secure have been acquired, but yet we are far from having pos- 
session of the full knowledge necessary to direct propagation most 
efficiently, or to determine correctly the restrictive measures which 
may be enforced with least interference with the proper utilization 
of the fishes. The problems before us now are those requiring the 
closest and most persistent study, and yielding solution only slowly 
and by small stages. : 
IMMATURE SALMON IN THE OCEAN. 
The investigations of salmon in Pacific Coast States have been 
conducted by Willis H. Rich, special assistant. The study of salmon 
taken by troll and purse seine in the open ocean has practically been 
completed. A preliminary report was prepared and, by authority 
of this Bureau, was published by the California Fish and Game 
Commission. ‘The conclusions reached may be briefly summarized. 
The fish taken in the ocean off the mouth of the Columbia River 
contain, in the spring and early summer, approximately 70 per cent 
of individuals which will not become sexually mature for one or two 
years, but by the middle of August this condition has changed so 
that nearly 90 per cent are fish which will soon enter the river for the 
purpose of spawning. The rate at which this change takes place 
and the time at which it occurs have not yet been determined, but 
will be taken up in a later report. A comparatively small per- 
centage of the fish found just within the mouth of the Columbia 
River are immature. It should be mentioned in this connection that 
it is only occasionally, when unusual tidal conditions obtain, that any 
immature fish are taken inside the mouth of the stream. 
The fish taken by troll in Monterey Bay in June contain a con- 
siderable proportion of immature individuals. The data obtained 
in 1918 are most reliable and indicate that only about 40 per cent 
of the fish taken would have spawned during the same year. The 
data for 1915 indicate that 75 per cent were mature, but selection 
may well have taken place in making this collection which consisted 
of egg samples only. 
The fish taken near Drakes Bay and Fort Bragg in July and 
August, 1918, contain approximately 30 per cent of immature fish. 
It is of interest to note that this is an approach to the conditions 
found off the mouth of the Columbia River in August and suggests 
that the composition of all the schools found near the coast changes 
materially during the summer season. 
It is understood that the preliminary report was used to advan- 
tage in the recent movement restricting the operations of both troll- 
ers and purse seiners off the coasts of Oregon and Washington. Ad- 
ditional data will be embodied in a later report. 
Incidental to the work with the fish taken in the ocean considerable 
data have been collected which will apply to the report dealing with 
the general life history of the chinook salmon. Progress has been 
made in the identification of races, and additional evidence from the 
scales of returned marked fish has confirmed the work done last year 
on the significance of the various types of nuclear growth. 
