GROWTH AND DEGREE OF MATURITY OF CHINOOK 
SALMON IN THE OCEAN 
By WILLIS H. RICH, Ph. D. 
Assistant in charge of scientific inquiry, United States Bureau of Fisheries 
CONTENTS 
Page 
Introduction 15 
Methods 18 
Determination of age 18 
Determination of relative maturity 20 
Correlation between size of eggs and size of fish 27 
Fish taken in the Columbia River and in the ocean off the mouth of the river 28 
Relative maturity of chinook salmon taken in the ocean 29 
Age of immature fish 39 
Percentages of immature fish at different times 40 
Percentages of fish more than one year from maturity 42 
Abundance of the various age groups 43 
Growth 48 
Fish taken in Monterey Bay 63 
Size 63 
Percentages of the various age groups 64 
Relative maturity 66 
Fish from Drakes Bay and Fort Bragg 67 
Summary and conclusions 69 
Supplementary tables 75 
Bibliography 89 
INTRODUCTION 
I'iie rapid increase in the amount of trolling and purse seining for salmon which 
has taken place along the Pacific coast during the past few years has directed atten- 
tion toward this phase of the salmon industry. The general consensus of opinion of 
those interested in conservation is to the effect that these methods of taking salmon 
are, under certain circumstances at least, destructive and undesirable. The fishing 
on Swiftsure Bank, off the coast of Washington, was reported on a number of years 
ago by Dr. C. H. Gilbert (1915), who found that the silver salmon (cohoes) taken 
by purse seines on the bank, "especially in the first part of the season, are far from 
having attained their full growth, although maturity is but a few months distant." 
Of the spring salmon (the chinook) he makes the following statement : 
The spring salmon is taken in large numbers and furnishes a somewhat inferior product, with 
soft flesh, little oil, and poor color. Several thousand young of this species are captured during 
the season, 2-year-olds about a foot long with white, soft flesh — a total waste. The numbers of 
these are relatively small, as the great majority of the salmon on the bank are in their last season, 
but the loss is nevertheless serious and deplorable. 
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