326 U.S. BUREAU OF FISHERIES 



The returns from 1931 and 1933 are similar in that most of the 

 returned cards were from the shores of New England and the Bay of 

 Fundy. In contrast, almost half of the returns from 1932 releases 

 were from across the Atlantic. Hence it appears that in 1931 and 

 1933 the surface currents were resultantly westward and northward. 

 In 1932, on the other hand, the drift was strongly to the southward 

 off the banks and thence to the eastward. 



These differences are significant because of their bearing upon 

 the destinations of fish eggs spawned in the affected areas. Their 

 continued study may throw much light on the causes for the suc- 

 cess or failure of the spawning seasons. 



We have been able to continue during the past year the arrange- 

 ments, with L. A. Walford of the Harvard Graduate School, for 

 the analysis of the collections lof eggs and larvae. The results con- 

 tinue to indicate that there is little or no transfer of haddock eggs 

 or larvae from Georges to Browns Bank or the reverse. 



MACKEREL 



A statistical review of the American mackerel fishery, which was 

 completed during the past year, is eloquent of the sharp fluc- 

 tuations in yield that have characterized this important fishery 

 throughout its history. The investigations here reported upon have 

 been designed to ascertain the causes of these remarkable fluctuations 

 and to devise such means as may be practicable to counteract their 

 ill effects. 



It has been found that the changes in abundance responsible for 

 the fluctuations in yield are caused mainly by the unequal numbers of 

 young mackerel added to the stock annually as a result of reproduc- 

 tion. For instance, the additions of young were remarkably large in 

 1923, 1930, and 1931; they were only moderate in 1921, 1928, and 

 1929; and were few or none, in all other years. As a result of the 

 remarkable production of young in 1923, the first of the " good 

 years " observed, the catch rose to a peak in 1926. However, with the 

 failure of the ensuing years the catch again declined until the 1928 

 class of young caused a recovery in 1929. Following this increase 

 there followed another decline which persisted until the highly suc- 

 cessful reproductions of 1930 and 1931 increased the commercial 

 stock to a level which in 1932 and 1933 was comparable with that 

 of 1926. 



Almost as remarkable as the inequalities in reproductive success 

 from year to year are the differences between year classes in their 

 relative rates of decline and geographical distribution during the 

 years following their first appearance in the fishery. Two general 

 types are distinguishable : a " persistent type " that affords a mod- 

 erate yield in its second year, a maximum yield in the following year, 

 and thereafter declines moderately, the decline being so gradual that 

 contributions to the commercial catch remain important for a decade 

 or more ; and a " transitory type " that furnishes its maximum yield 

 in its second year and thereafter declines so sharply that its effect is 

 felt in the commercial fishery for only 2 or 3 years. The persistent 

 type is further distinguished by its continued presence throughout 

 almost the entire fishing season in waters south of Nova Scotia but 



