BUREAU OF FISHERIES 117 



late the fisheries accordingly. These observations consist in counts of 

 the spawning migrants so that the total egg production may be esti- 

 mated, followed later in the season by counts of the migrating young. 

 From these figures the fresh water mortality is computed. The total 

 ocean mortality is determined by comparing the number of seaward- 

 migrants with the numbers returning 2 years later. Because the sur- 

 vival of eggs has been shown to be affected by the exti-eme seasonal 

 variations in rainfall and temperature, a meteorological record has 

 been kept during the year at the experimental stream at Little Port 

 Walter to secure accurate data on weather conditions. 



Studies of the coho salmon in Puget Sound are concerned with 

 methods of rebuilding the runs which were formerly so important in 

 this area. Studies have been carried on over a period of several years 

 to determine the age at which hatchery reared fry may be released 

 most advantageously. Results show conclusively that long periods of 

 rearing bring much larger returns of adult fish. These studies are 

 being continued and exact costs of rearing and handling are being 

 computed. 



The extensive tagging work of previous years of the Alaska herring 

 was continued, with the result that the migratory habits of practically 

 every commercially important population has been established. The 

 electronic tag detector was again operated successfully for the re- 

 covery of tagged fish. 



Herring in the Cape Ommaney area, from which the bulk of the 

 catch in southeastern Alaska is made, have shown a marked decline in 

 abundance during recent years. This decline is the result of a combi- 

 nation of factors — intensive fishing, migrations, and failure of spawn- 

 ing in 1932, 1933, and 1934. Continued observ^ations on each of these 

 conditions being essential to proper management of the fisliery, tag- 

 ging studies were supplemented by the collection of catch statistics 

 a,nd data on the size and age composition of the catch. 



PacifiG filchard mvestigations. — The phenomenal increase in the 

 landings of tlie Pacific pilchard fishery to a level three times as great 

 as the total landings of all other kinds of fish in the Pacific Coast 

 States has given rise to public concern over the ability of the resource 

 to provide catches of this size without undergoing depletion. In 

 response to this demand, the Bureau of Fisheries w'as provided with 

 funds by Congress at the beginning of the fiscal year to investigate 

 the condition of the resource. 



Major attention is being given to the question of determining the 

 intensity of fishing w^hich will provide the maximum yield of fish of 

 greatest commercial value, and, at the same time, leave an adequate 

 spawning stock. Since accurate methods of determining age and 

 estimating abundance are fundamental to the solution of these prob- 

 lems, the early months of the investigation have been devoted chiefly 

 to developing a satisfactory technique of age determination and a 

 method of estimating abundance from catch statistics or by aerial 

 observation of schools. Preservation of an adequate spawning re- 

 serve, however, depends on an annual census of egg production which 

 cannot be undertaken without a seagoing vessel. 



Great Lakes fshenes investigations. — Because of the severe deple- 

 tion of the Great Lakes fisheries, now generally recognized, problems 

 of fishery research in this area are concerned chiefly with obtaining 



