BIOLOGY OP THE ATLANTIC MACKEREL 



187 



That it did not do (1) or (2) is proved by the relative scarcity of larvae of appro- 

 priate sizes at stations of the Chesapeake section and the outer station of the Winter- 

 quarter section; though the few caught at Chesapeake II, III, and Winterquarter III 

 indicate a slight tendency for southward and outward streaming. That (3) was the 

 major result is shown by the "snubbing" of the southern center in its southward travel 

 and by the increase in numbers of larvae in the southern center relative to the number 



Figure 15— Drift of the 2 centers of distribution of the S group compared with wind movements, as recorded at Winterquarter 



Lightship. 



in the northern center, 17 as if indeed the water and its burden of larvae did pile up in 

 the vicinity of Winterquarter I. This piling up very likely was in the nature of a 

 thickening of the surface stratum of light water offset by a depression of the lower 

 layers of heavier water rather than an outright raising of the water level. Of course, 

 the depressing of the subsurface stratum would set up a subsurface flow to restore 

 equilibrium. This flow would not transport the main body of larvae, since they were 



17 It is not supposed that the entire increase in relative number at the southern center was due to the mechanism being discussed. 

 Part of it could have been due to random fluctuations of sampling. 



