PROGRESS IN BIOLOGICAL INQUIRIES, 1935 389 



mackerel investigation. In addition to the field work at the fisli 

 pier, two trawling trips were made on the Atlantis to obtain material 

 for the study of the abundance, distribution, and growth of 1-, 2-, and 

 3-year-old haddock wliich, being below marketable size, cannot be 

 obtained from the commercial catch. 



Georges Bank and adjacent areas. — As stated in the 1934 annual 

 report, the success of the fishery on Georges Bank during any year, 

 that is, the return for a given unit of fishing effort, is primarily 

 dependent on two factors: (1) The rate at which the commercial 

 stock declines as the result of catch and natural mortality. (2) The 

 contribution to the connnercial stock from the young haddock 

 spawned 3 years earlier. There can be no sustained improvement in 

 the catch except through the growth to commercial size of a large 

 group of young haddock. Mass migrations do not appear to be an 

 important factor; at least, they have not been since our detailed ob- 

 servations began. 



A feature of the last 4 years has been the appearance of 3 fair 

 year classes in the commercial catch on Georges Bank. These classes 

 were spawned in 1929, 1931, and 1932. Of these, the 1929 class was 

 the best and served to increase the fishermen's catch considerably in 

 1932. The 1931 and 1932 classes were less successful, and under a 

 fishing intensity such as prevailed on Georges in 1927-33, hardly 

 would have maintained the level of the fishery in 1934 and 1935. 

 However, during these years a large portion of the fishing fleet was 

 diverted to the Nova Scotian banks as a result of poor fishing on 

 Georges and improved catches elsewhere. Hence, the fishing inten- 

 sity on Georges decreased to less than half that of 1933 and earlier. 

 With this lessened strain, the Georges haddock stock has increased for 

 2 successive years, the first 8 months of 1935 providing an average 

 daily trawler catch about 30 percent better than the same period in 

 1933. 



The moderate improvement in the fishery on Georges during the. 

 past 2 years has been encouraging, although the present population 

 is far below the level prevailing in the years prior to 1930 ; and partial 

 recovery occurred only with a greatly reduced fishing intensity. 



The trend of the Georges Bank haddock fishery in 1936 depends 

 on two elements now but qualitatively known. First, the abundance 

 of the 1933 class which reaches commercial size in the winter of 

 1935-36. Second, the distribution of the trawling fleet, i e., the 

 amount of fishing effort that will be expended on this bank in 1936. 

 The first element — abundance of the 1933 class — cannot be evaluated 

 until later in the year when it has been possible to analyze data from 

 the winter fishery. However, cursory examination of incomplete 

 records indicates that it may approximately equal the classes of 1931 

 and 1932. The second element — distribution of fishing effort — could 

 be estimated if the relative abundance of fish on Georges and Nova 

 Scotian banks were known. This too can be but roughly estimated 

 until the results of the winter fishery can be analyzed. In view of a 

 probable decrease in the catch per day on the Nova Scotian banks 

 and an increase on Georges, one may expect a larger percentage of 

 fisliing effort to be concentrated on Georges Bank in 1936. This 

 increased strain will, to some extent, counteract the expected increase 



