FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



247 



SPAWNING POPULATIONS 



The determination of the size of the escapement, or spawning population, of a 

 river or district is of vital importance in intelligently administering the fishery. In 

 a self-perpetuating salmon population an adequate part of the yearly run must be 

 allowed to escape the fishery and continue uninterrupted to the spawning grounds 

 in order to insure future supplies of fish. Not oniy must a proper number of fish 

 be allowed to escape in a given area or district, but each individual salmon stream, 

 and in large watersheds, each small area in the watershed, must receive a sufficient 

 escapement if adequate runs of fish are to be maintained. Under natural conditions, 

 an extremely high percentage of the fish returning to spawn proceed to the same 

 area where they emerged from the spawning gravel as fry. There is a slight degree 

 of straying, but the fact remains that if a spawning area has not been seeded, there 

 will not be a run of fish returning to that area in one or more subsequent years. Thus, 

 large river systems such as the Kvichak, Copper, Fraser, Columbia, and others, 

 must not only receive an escapement sufficient in number, but the fish must be dis- 

 tributed in the proper proportions to the various tributaries in the river system. If 

 a part of the spawning area in a given watershed be depopulated for a period of time, 

 the chief hope of restoring the productivity of that watershed to its maximum value 

 would be to restock the depleted area by the planting of eggs or fry for a period of 

 several consecutive years, an expensive undertaking which would have no positive 

 assurance of success. 



The determination of the magnitude of the escapement of Karluk River red 

 salmon is important not only in regulating the commercial fishery, but is also another 

 of the major problems involved in the biological study of this population. The 

 calculation of the total size of populations, the returns from known spawning popu- 

 lations, the mortality in fresh water, and the mortality in the ocean are based upon 

 a knowledge of the number of fish entering the river each season to spawn. 



Table 17 gives the weekly escapements of red salmon to the Karluk River for 

 the years 1921 to 1936, inclusive. The escapement records are complete except for 

 1921, 1922, 1924, and 1934. In 1921, the first year the weir was operated, it was 

 removed on September 18, as the companies fishing in the Karluk area were about 



