PROGRESS IN BIOLOGICAL INQUIRIES, 1938 15 
frequencies furnished strong evidence that the 1923 year class was 
still present, and probably the 1928 class as well. Except for the 
1932 class, year classes following 1929 were present in better than 5 
percent strength each. None of these stood out as dominant, however, 
a real departure from conditions only a few years before. 
Field work during 1938 was conducted principally by F. E. Firth. 
This included details at Cape May and New York City in April and 
May, and at the Boston Fish Pier for the remainder of the year. 
Information on fishing effort and catch locations was obtained for 
over 1,000 trips and about 50,000 mackerel were measured for popu- 
lation composition analysis. In addition, 700 scale samples were 
taken for age reading reference. Late in June, Mr. Webster tagged 
500 mackerel at Provincetown. There were but 5 returns, all local, 
within 1 week. 
Preliminary studies of the 1938 catch show that the 1936 year class 
made large contributions to the fishery, with the combined groups of 
1934 and 1933 next in importance. Detailed analysis of these data 
will be undertaken in 1939. 
The present tendency of the seining fleet to extend both ends of 
the season may make necessary some changes in methods of deter: 
mining abundance. For furthering studies of hydrographic condi- 
tions, it appears advisable also to obtain a more representative norm 
of coastal surface water temperatures. If temperature be a real 
factor affecting the availability of mackerel, some measure of its 
significance must be found. Although some advance in the solution 
of these problems can be made with our present facilities, expansion 
is necessary in order to solve others. Direct evidence is needed of 
the fate of certain year classes which decrease in availability faster 
than others. The cause may be heavier mortality or mass changes 
in habitat through migration. A large-scale tagging program is 
needed to determine this point. Further study is needed also for an 
understanding of the relationship between the mackerel catch by 
purse seiners and pound nets in the same locality. Catch statistics 
alone are insufficient, since it 1s necessary to learn when these two 
types of gear sample the same or different populations and why. 
The aid of part-time assistants at strategic points is needed to collect 
such information. 
The mackerel problem now appears to involve more than a study 
of year-class recruitment and mortality. Events of the past 2 years 
have emphasized the need for particular knowledge of oceanic condi- 
tions affecting the mackerel fishery. In view of these facts, it is 
believed inadvisable to attempt forecasts of future abundance until 
facilities for determining these conditions are provided. 
FLOUNDER 
In 1935, the last year for which complete figures have been com- 
piled, the total North Atlantic catch of all species of flounders 
amounted to about 39,000,000 pounds, and was worth approximately 
$1,500,000. Five species compose the bulk of the catch. They are: 
(1) Lemon sole (Pseudopleuronectes dignabilis Kendall); (2) gray 
sole or witch (Glyptocephalus cynoglossus Linnaeus); (3) winter 
flounder or blackback (Pseudopleuronectes americanus Walbaum) ; 
