PROGRESS IN BIOLOGICAL INQUIRIES, 1939 13 
appear to be correlated with the magnitude of the adult stock, with 
poor survival in years of extremely high as well as of low abun- 
dance of adults, and good survival in years of intermediate abun- 
dance. There are other apparently noncyclic variations from year 
to year which appear to be due to features of the physical environ- 
ment. 
The precipitous drop in haddock abundance during the years 
1929 to 1931 was due to the coincidence of a period of greatly in- 
creased fishing intensity and that portion of the natural cycle having 
a minimum replacement of young. Consequently, with a heavy drain 
from the commercial fishery and negligible replacements of young 
fish, the abundance of marketable haddock declined at a rapid rate. 
Following the low level reached in 1931 the abundance has recovered 
to some extent, but has failed to build up to levels comparable to 
the 1926-28 period since the commercial fishery has been so intensive 
that no considerable accumulation of market-sized haddock was 
possible. 
Information concerning the haddock populations off the Nova 
Scotian coast is much less complete, for our fleet fished this area 
only sporadically until 1938-34, and practically no fishing was done 
in the area during the years of high abundance on Georges Bank. 
Therefore, the continuous measure of abundance available for 
Georges Bank is not available for the Nova Scotian coast. 
A large amount of subsidiary biological information, discussed 
im previous annual reports, has been obtained to assist in the 
explanation and understanding of the abundance cycles. 
Progress during 1939—The investigation was continued under 
the direction of Mr. Herrington with the part-time assistance of 
H. M. Bearse and M. 8. Moses. Dr. Rounsefell continued the Maine 
tagging experiment begun in 1938. Field work was limited mainly 
to the collection of the basic data required for determining the age, 
number, and size composition of the 1939 catch, since analysis of 
abundance now is included in the groundfish studies. During the 
course of the year Mr. Bearse obtained length measurements of 
nearly 50,000 haddock and collected 3,500 haddock scale samples. 
Laboratory work was concentrated on the completion of the haddock 
abundance index from 1914 to 1937 and the compilation of a record 
of the total monthly haddock catch from the Georges Bank and Nova 
Scotian areas for the same period. Records of total monthly haddock 
catches were obtained from Bureau records for Boston, Gloucester, and 
Portland, and from records of fishing companies for New York and 
Groton. These records account for nearly the entire offshore haddock 
catch. The compilations are required to show the total fishing strain 
and for use in evaluating the effect of increased gear competition. 
Completion of the primary stage of computing the abundance index 
required special analysis to compensate for certain gaps in our data 
for 1914 to 1916. Portland landings, shown only as total haddock, were 
divided into large and scrod on the basis of hailed weights. Statis- 
tical analysis showed that this method was consistently accurate. The 
running time between port and fishing grounds, ier is required for 
our calculation of fishing effort, was obtained from the length of trip 
since data for 1917 to 1920 showed that there was a high degree of 
correlation between these two components of a trip. 
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