3g U. S. BUREAU OF FISHERIES 



The first months of the investigation have been devoted to a pre- 

 liminary reconnaissance of the problem. The basic questions are: 

 (1) Do* the fisheries of various localities draw upon one population 

 or upon several self-perpetuating populations? (2) What intensity 

 of fishing will provide the maximum yield of fish of greatest com- 

 mercial value from each successful year-class? (3) What intensity 

 of fishing will permit survival of a spawning stock adequate to pro- 

 duce successful year-classes? 



The first question is being investigated by California, Oregon, 

 Washington, and British Columbia, by the tagging method. It has 

 already been proven that some individuals migrate long distances 

 from Southern California to Washington and vice versa. Whether 

 this represents a small percentage of mixing of the population along 

 the entire coast remains to be seen. It is planned to study this 

 aspect of the problem by discovering to what extent the yomig as 

 well as the adults occur in the north and to make comparisons of 

 morphological characters to see whether there are any distinguish- 

 ing features between northern and southern pilchards. 



Tlie second and third questions are more perplexing and their 

 answers more remote because they involve determination of age and 

 of abundance. Satisfactory techniques have not yet been developed 

 for either of these determinations. Accordingly work has started on 

 developing a technique of age determination by interpreting age 

 marks in hard structures, by observing modal progression in sizes 

 of young pilchards, and by identifying modes in frequency distribu- 

 tions of the adult population; and on developing a technique of 

 estimating abundance from catch statistics and by aerial observation 

 of schools, or by a combination of the two methods. 



Progress in the solution of these problems will be accelerated by 

 cooperation with State fishery research units which have collected 

 and kindly made available manj^ pertinent data. A series of meas- 

 urements based on samples collected from the commercial catch over 

 a period of years by the California State Fisheries Laboratory is 

 expected to be particularly useful in this connection. 



Although the discovery of techniques of age and abundance de- 

 terminations are prime essentials and will greatly advance the under- 

 standing of conservation problems, it must be pointed out that pres- 

 ervation of an adequate spawning reserve will require a quantitative 

 determination of annual egg production in all potential spawning 

 areas. This cannot be undertaken until a seagoing vessel is available 

 to make periodic surveys in cooperation with such boats as the States 

 have available for this purpose. 



GREAT LAKES FISHERY INVESTIGATIONS 



Dr. John Van Oosten, in charge 



The limited amount of field work conducted during 1937, per- 

 mitted the Great Lakes staff to continue the compilation of exten- 

 sive data collected in earlier years. In addition to the papers pub- 

 lished by staff members during the year, several other manuscripts 

 were prepared for publication. Among these was a report setting 

 forth the results of an intensive study of the whitefish fishery of 

 Lakes Huron and Michigan. This iuA'^estigation was concerned es- 



