U. S. BUREAU OF FISHERIES. 



activities, vast numbers of eggs would be sent to market in the fish 

 and become a total loss. In the case of certain species, notably but 

 not exclusively the salmons of the Pacific coast, where commercial 

 fishing does not extend to or is not permitted on the spawning 

 areas, employees of the bureau capture the spawning fish either in 

 seines or in traps and artificially incubate in its hatcheries the eggs 

 thus obtained. The object of this work is to bring about a higher 

 percentage of fertility in the eggs than is possible in natural repro- 

 duction and to afford the eggs and the resulting young fish protection 

 from their natural enemies. Eggs in appreciable numbers are also 

 obtained from domesticated fish, which are maintained in ponds at 

 fish-cultural stations from year to year under more or less artificial 

 conditions. 



A decrease of approximately 121,000,000 in the aggregate egg 

 collections occurred this season as compared with last year, as is indi- 

 cated by the accompanying table, and the same causes that were 

 operative to the detriment of the work then were again in evidence. 

 However, in any line of enterprise where results are dependent to a 

 large extent upon weather conditions, as is the case in all of our egg- 

 collecting fields, a comparison of one season's work with that of 

 another will indicate a considerable fluctuation in total results, and 

 it is only by comparing the results over a period of years that the 

 actual trend of the work may be traced with any degree of accuracy. 



The most noticeable variations in the egg collections of 1921 as 

 compared with 1920 are increased collections of eggs of chum salmon, 

 Cisco, rainbow trout, blackspotled trout, whitefish, pike perch, yellow 

 perch, striped bass, carp, haddock, and glut herring, and decreased 

 collections of eggs of the chinook, silver, sockeye, humpback, and 

 steelhead salmon, landlocked salmon, lake and brook trout, shad, 

 buffalofish, cod, pollock, and other species of less importance. It is 

 to be noted that while a decrease occurred in the number of eggs 

 collected during 1921, as compared with the previous year, there was 

 an increase of approximately 179,000.000 in the aggregate output of 

 the stations in eggs, fry, and fingerlings. This apparent dis- 

 crepancy in figures is accounted for by the better quality of the eggs 

 handled during the year and the higher percentage of fi-y produced; 

 also to an increase in the numbers of eggs fertilized and planted on 

 the spawning grounds. 



Comparison of Ego Collections, 1920 and 1921. 



