14 U. S. BUREAU OF FISHERIES 
lasting from about 1820 to 1885. During this time the landings 
averaged roughly 80 to 100 million pounds annually, but were subject 
to violent fluctuations. The year 1886 ushered in a period of poor 
catches, lasting until the present day. In no year during this period 
have landings Pexceeded 65,000,000 pounds, while the annual aver age 
has been nearer 40,000,000 pounds. This low level has persisted so 
long as to be considered normal. Howev er, the yearly fluctuations 
during the latter period, though less in amount, were as great in 
degree as those within the former period, 
Tnvestigations of mackerel behavior and life history have demon- 
strated that these fish range from the Middle Atlantic States to 
Canada. They school mostly over the inner portions of the conti- 
nental shelf, generally avoiding small enclosed bays and regions over 
deep water. “Analysis revealed two contingents in the population ; 
one ranging between the offing of Chesapeake Bay and the Gulf of 
Maine and the other between southern New England and the Gulf 
of St. Lawrence. Both contingents probably spend the winter in 
offshore areas near the southern portions of their range. 
Spawning occurs between April and August. Fish grow 7 to 10 
inches the first season, and attain a length ‘of 10 to 14 inches by the 
end of the second year. Thereafter, growth is slower. The maxt- 
mum life is 12 to 15 years, length about 22 inches, and weight from 
31% to 4 pounds. 
Fish from one or a few year classes usually make up a season’s 
catch, and persist as definite groups for many years. Discovery of 
this fact led to the belief that the numerical strength of these 
dominant year classes determines the success of the commercial fishery. 
On the basis of year class recruitment and mortality the investigation 
succeeded in forecasting the approximate yield for several successive 
years. In 19387, however, the mackerel catch fell about 40 percent 
below the predicted decline, indicating that some unknown factors 
were at work. 
Progress in 1938.—The current mackerel investigations, now under 
the direction of John R. Webster, have been devoted to completing 
and bringing up to date the lines ‘of investigation initiated by O. FE. 
Sette, and to ) determining the factors which caused the relative failure 
of the mackerel fishery in 1937. 
The abundance analysis for 1937 was based on more than 1.500 
catch records and 35,000 length measurements. As shown by catch 
per unit of effort, abundance fell off everywhere along the coast. 
Comnared to 1936, this decline was not much more than 30 percent 
for the area west of Nantucket Shoals, but exceeded 50 percent in 
the Gulf of Maine area. 
Study of hghtship temperature records revealed that the surface 
waters of the extreme western Gulf of Maine in 1937 ran from 
2° F. to 7° F. higher than those of the previous 10-year average. 
The shun from this norm was greatest during that portion ‘ot 
the mackerel season when the fleet operated in these waters. Since 
the offshore fishery fell so far below expectations during this period, 
it is suspected that hydrographic conditions were a factor in the 
decline. 
Composition of the whole mackerel population in 1937 apparently 
differed from that of previous years since 1925. Analysis of length- 
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