98 REPORT OF THE SECRETARY OF COMMERCE 
terior waters for the purpose of developing scientifically sound meth- 
ods of hatchery procedure, of formulating stocking policies compatible 
with the productive capacities of the waters stocked, and of improv- 
ing environmental conditions in streams by investigating methods of 
eliminating pollution hazards; and (3) development of more effective 
methods of shellfish culture through control of natural enemies and 
improvement of the market quality of oysters. 
INVESTIGATIONS OF COMMERCIAL FISHES 
North and Middle Atlantic fishery investigations—W ith the con- 
tinued rise in fish prices and the increasing activity in the fishing 
business, New England fishery landings were the largest in their re- 
cent history. It should nevertheless be noted that the yield of several 
staple species, such as mackerel, haddock, and cod, declined. The 
larger total production was the result of increases in the landings of 
rosefish (a species hitherto little exploited) from 17 million to 66.6 
million pounds for the calendar year 1936, and in vessel-caught whit- 
ing from less than 2 million to nearly 18 million pounds. 
Observations on the condition of the haddock fishery have been 
continued to the full extent that limitations of personnel and equip- 
ment permit. A continued improvement from the low level of 1930-31 
was noted in the fishery on Georges Bank, which remains, however, 
far below the 1925-29 level. On the Nova Scotian banks the average 
productivity was less than during the preceding year, owing to the 
scarcity of haddock spawned since 1929. As a result of the long- 
period program of study inaugurated in 1930 it has been learned 
that the haddock populations on the New England and Nova Scotian 
banks are subject to wide fluctuations in abundance not only from 
year to year but to an even greater extent over periods of years. The 
direct cause of such fluctuations is the varying survival of the young. 
The combination of an intensive fishery and a succession of poor 
spawning years may reduce the population to disastrously low levels, 
as happened between 1927 and 1931. It is further evident that the 
haddock populations of the various Nova Scotian banks differ mark- 
edly from each other and from that of Georges in their variations in 
abundance; each therefore requiring individual observation if effective 
measures for the management of the fishery are to be prescribed. 
Direct observations over widely scattered areas of the fishing grounds 
to assess the abundance and distribution of young haddock below com- 
mercial size are highly desirable, but are not practicable with present 
facilities. Up to the present time the fluctuations and trends in the 
haddock fishery have been considered mainly in qualitative terms. 
As a result of findings and recommendations of the Bureau, the 
majority of the New England operators of large and medium otter 
trawlers voted to begin the use of larger meshed otter trawls early 
in 1937 and to continue such use for a trial period of 6 months. Such 
savings gear is considered the most effective and practical measure 
to decrease the destruction and capture of undersize haddock. 
Continuation during the year of research on the natural history 
and fluctuations in abundance of mackerel provided more definite in- 
formation on the seasonal movements of these fish; the location of 
important spawning grounds; the rate of growth during larval, juve- 
nile, and adult existence; fluctuations in survival rate of the young; 
