ABSTRACT 



This portion of a comprehensive study on the Atlantic mackerel (Scomber scombrus) 

 treats of the early life history from spawning up to about the time the schooling habit develops, 

 with emphasis on the quantitative aspects. 



Spawning takes place along the Atlantic coast, mostly 10 to 30 miles from shore, from 

 Chesapeake Bay to Newfoundland, with perhaps Yio of the volume between the Chesapeake 

 Capes and Cape Cod; Mo in the southern half of the Gulf of St. Lawrence, and negligible 

 amounts elsewhere. Embryological development at the temperature usually encountered 

 occupies about 1 week. The pelagic eggs are confined to a surface stratum 15-25 meters 

 thick. Hatching at 3 mm. of length, larvae grow to 10 mm. in about 26 days, and to 50 mm. 

 in an additional 40 days, by which length they approximate the typical form for adult 

 mackerel, and assume the schooling habit. 



In 1932, it is estimated, 64,000 billion eggs were produced south of Cape Cod by a 

 spawning population estimated at 100 million individuals. That year dominant north- 

 easterly winds (which were abnormally strong) drifted one concentration of larvae, originat- 

 ing off northern New Jersey, and another concentration, originating off southern New Jersey, 

 in a southwesterly direction, to localities abreast of Delaware Bay and Chesapeake Capes, 

 respectively. A reversal of dominant winds, consequently of drift, returned both groups to 

 northern New Jersey, by the 9-mm. stage of growth. 



Mortality during most of the developmental period was 10 to 14 percent per day, but 

 was as high as 30 to 45 percent per day during the 8- to 10-millimeter period when fin develop- 

 ment we s rapid. Survival from spawning of the eggs to the end of the planktonic phase of 

 life (50 mm.) was in the order of 1 to 10 fish per million eggs spawned. This rale of survival 

 is an abnormally low one since the fish from this spawning season were abnormally scarce 

 in the adult populations of subsequent years. The low survival rate is ascribed to the 

 abnormal amount of southerly drift, coupled with a general scarcity of plankton in the 

 spring of 1932. 



