318 REPORT OF THE SECRETARY OF THE INTERIOR 
in abundance of these stocks from year to year, and discovering how 
large a catch may be made each year without impairing the future 
productiveness of the stock. For approximately 10 years such a 
study has been under way for the haddock, which supplies a larger 
yield than any other New England food fish. It has been demon- 
strated that in the Georges Bank area, which accounts for the major 
part of the catch, fluctuations in the abundance of commercial-sized 
haddock follow regular cycles, which are related to similar cycles in 
the number of young that survive to commercial size. When years of 
intensive exploitation of the stock happen to coincide with years of 
poor survival of the young, a sharp decline in haddock abundance 
may be expected. Extensive data collected and analyzed by the 
staff have provided an index of the size of the haddock stocks on 
Georges Bank for the period from 1914 to 1937. Because of changes 
in the size and composition of the fleet and the adoption of new 
gear which in itself increased the effectiveness of fishing operations 
by at least 29 percent, the catch records alone are no indication of 
the abundance of haddock, but must be subjected to elaborate sta- 
tistical analysis before the size of the available stocks may be 
ascertained. 
Mackerel landings on the Atlantic coast in 1939 were considerably 
smaller than in 1938, although the early months of the 1940 season 
were marked by a slight upward trend. There has been, moreover, 
a steady decline in the number of purse-seine vessels engaged in 
mackerel fishing, with the 1940 fleet the smallest in many years. 
Investigation of the mackerel fishery has brought to hght many 
significant facts related to the distribution, spawning habits, growth 
rate, and migrations of the species. While progress has also been 
made toward determining measures of abundance and _ predicting 
changes in the availability and abundance of the mackerel, final 
solution of these problems awaits offshore investigations from the 
newly acquired fishery research vessel Albatross IIT. 
The various species of groundfish, including the haddock, cod, 
pollock, rosefish, cusk, hake, and several species of flounders, form _ 
the basis of the most important New England fisheries. Fluctuations 
in the total yield of these fishes have been noticed in past years, 
but until a biological study of groundfish was begun in 1938 the 
causes and extent of these fluctuations were unknown. Indices of 
abundance are now being constructed for each species. When these 
indices are completed and the requisite knowledge of the life his- 
tory becomes available for each species, it will be possible to suggest 
means of maintaining the population at that level which will yield the 
largest sustained annual catch. 
