BUREAU OF FISHERIES tos 
School of Fisheries, mformation was obtained which helps to clarify 
the steps in preparation responsible for improving the nutritional 
properties of fish meal for fish feeding and which suggest legs costly 
processes of manufacture. Also, studies were made which indicate 
the possibility of materially reducing the danger of spontaneous 
heating of fish meal, a difficulty which now causes the industry creat 
inconvenience and considerable financial loss. bite 
BIOLOGICAL FISHERY INVESTIGATIONS 
INVESTIGATIONS OF COMMERCIAL FISHES 
North Atlantic fishery investigations—In the offshore fisheries of 
New England, analysis of extensive data collected during the course 
of the haddock investigation has thrown considerable light on the 
changes in the abundance of this species and has suggested a plan 
for the stabilization of yield. Years of poor survival are either years 
in which large haddock are especially abundant, offering serious com- 
petition for food, or years when the stock of adults has been so reduced 
as to furnish insufficient spawners. The most favorable level was 
approximately that which prevailed in 1922 to 1924, 1929, and 1936. 
The course of the natural cycles of abundance may be seriously inter- 
fered with if a period of intensive fishing happens to coincide with a 
period of poor survival of the young. The recent marked decline in 
the abundance of haddock, which has been evident both on Georges 
and the Nova Scotian Banks has been shown to be the result of such 
a combination of circumstances. It is indicated, therefore, that by 
holding the population at the optimum level by regulation of the fish- 
ing intensity, it would be possible to sustain the yield at a productive 
level. 
Data collected during the year on the age composition of the catch 
revealed an increasing dependence on the young or “scrod” haddock, a 
trend which is regarded as prejudicial to the interests of the fishery, 
inasmuch as these fish are growing rapidly and would be of consider- 
ably greater value if allowed at least 1 more year’s growth. 
The catch records and biological data collected during the 1937 
mackerel season, a year of extremely low production, were subjected 
to analysis during the year. The composition of the mackerel popula- 
tion differed markedly from previous years in that no year class or 
classes dominated the fishery. With the exception of the 1932 class, 
year classes following 1929 were present in better than 5 percent 
strength each. Inasmuch as a study of lightship temperature rec- 
ords revealed that water temperatures in the western part of the Gulf 
of Maine ran higher than the average for the previous 10 years, 1t 1s 
suspected that hydrographic conditions affected the distribution of 
mackerel and were an important factor in the low catch. 
The catch for the 1938 season was almost double that of 1937, but the 
early season landings for 1939 sank to a lower level than those for the 
corresponding period of 1937. Biological data show that the mack- 
erel spawned in 1937, a group that was expected to contribute much 
to the fishery, as 2-year-old fish were virtually unrepresented in 1939. 
Because pound-net fishermen inshore were reported to be making good 
catches, an investigation of the relation between the catch by seiners 
offshore and that of the pound nets was begun early in the 1959 sea- 
