BIGELOW: COAST WATER EXPLORATION OF 1913. 327 



Were the macroplankton of the Gulf uniformly distributed at all 

 depths from surface to bottom, this table would sufficiently establish 

 the relative richness of different regions in plankton, and hence in food 

 for the pelagic fishes. But unfortunately such is not the case (p. 290) ; 

 hence to get a fair idea of the regional density of the plankton the less 

 exact evidence of the ordinary tow nets must be used to check the 

 results of the quantitative hauls. 



Volumes of horizontal hauls. 



The depth is the level at which the major part of the haul was 

 made. 



This table shows that at every station where the hauls were made at 

 two intermediate depths, the deeper invariably yielded the smaller 

 volume of plankton. At first sight this difference might be laid to the 

 use of different nets, the mouth area of the Helgoland net, which was 

 usually used for the deeper haul, being only about 50% of that of 

 the four foot net (the same grade of silk was used in both). But at 

 Station 10092, where the nets were reversed, the catch of the Hel- 

 goland net was three times as great as that of the four foot net. 

 And even allowing for the different sizes of the nets, the shallow haul 

 is still considerably the richest at six of the eight stations. Appar- 

 ently the plankton was usually densest in the upper layers, and decidedly 

 impoverished below, say, forty fathoms. On the other hand the sur- 

 face water was usually barren, except at Stations 10092, 10093, 10096, 

 10097, 10100, and 10103, but the surface hauls are not directly com- 



