480 U. S. BUREAU OF FISHEEIES 



The availability of the herring in different portions of the season 

 was carefully analyzed and tables computed showing what percent- 

 ages of the total catch is taken in each 10-day period. This knowl- 

 edge is essential, since the amount taken during such a period varies 

 materially through the season. Knowing these figures, it is possible 

 to reduce the total catch any desired percentage by means of closed 

 seasons. The extreme localization of the fishing grounds is shown 

 by an analysis of the catches for eight years (1923 to 1930, inclu- 

 sive). During this time 50.7 per cent of the total catch was taken 

 in the waters contiguous to the southern end of Evans Island, 46.6 

 per cent from other restricted localities, and 2.7 per cent from all 

 of the remainder of the immense area of Prince William Sound. 



In attempting to discover if these various areas supported inde- 

 pendent populations, it was found that the means of the number of 

 vertebrae for various year classes of herring differed significantly. 

 Comparing vertebral-count samples of the same year class only (to 

 allow for annual variations in temperature), it was found that the 

 herring populations of McClure Bay and MacLeod Harbor e^ch 

 seem to differ from the remainder of the herring of Prince William 

 Sound. 



Body-length frequencies of the herring from Prince William Sound 

 were available for seven years (1924 to 1930) and age frequencies for 

 six years (1925 to 1930). These length frequencies show clearly the 

 progression, year by year, of size modes, due to the growth of fish 

 of dominant year classes. The year classes are so unequal in abun- 

 dance that one or two year classes usually constitute the bulk of the 

 catch even though several are represented. Thus the 1926 year class, 

 which was unusually abundant, constituted 78.2 per cent of the catch 

 in 1928, 93.3 per cent in 1929, and 87.5 per cent in 1930. 



The fluctuations in the catch caused by these dominant year classes 

 are of great importance to the fishery. During the intervals when 

 no abundant year classes of young fish are present the fishery must 

 be supported by a reserve of the older age groups. Depletion of 

 these older age groups by a too intensive fishery seems to have 

 caused the variations in yield which characterize the fishery during 

 the past few years. Unless protection is adequate to insure a suffi- 

 cient quantity of older age groups at all times, the fishery can not 

 be maintained without such undesirable fluctuations. In order to 

 insure such a supply of older fish it was recommended that a 48-hour 

 weekly closed season be put into effect, and that the purse seines be 

 reduced from 180 to 150 fathoms in length. 



The field work of the herring investigation has been aided very 

 materially by the purchase of a motor vessel in July, 1931, which 

 provides comfortable living quarters and laboratory space. Using 

 this vessel, racial samples were obtained for the first time from Sagi- 

 naw Bay in Frederick Sound, Gut Bay in Chatham Strait, Point 

 Lull at the eastern entrance to Peril Strait, Point Augusta in Icy 

 Strait, and Anita Bay in Zimovia Strait. Samples of fish for ver- 

 tebral counts totaling 13,900 are now available from over 40 localities 

 in southeastern Alaska. All of the ages of these herring have been 

 read, and an analysis is now being made of the numbers of vertebrae 

 to determine their racial significance. 



