1. Sample poured into graduate 

 cylinder and reading noted to 

 nearest milliliter. 



2. Solution separated from plankton 

 by force-filtering solution 

 through a No. 1 Wratten disc filter 

 by means of a vacuum-pump attach- 

 ment. 



3. Filtrate poured back into gradu- 

 ate and reading noted. 



4. Volume is difference between the 

 two readings. 



For the first four cruises, however, 

 we determined volumes by fractioning and 

 centrifuging. To adjust these values to 

 conform with those obtained by filtration, 

 we ran, in duplicate, a series of plankton 

 samples of different volume ranges through 

 both methods to obtain the necessary con- 

 version factors. All plankton volumes 

 given in the tables are based on the first 

 method described. 



The volumes of water strained, as 

 tabulated, were calculated from readings 

 of the four Atlas current meters which 

 were used throughout the Alaska cruises. 

 As two meters were used with the G-III net 

 on only one cruise, the readings for all 

 quantitative hauls of this net were based 

 on readings from the rear meter. Calibra- 

 tions of the meters were obtained upon 

 completion of field work by making duplicate 

 tows in opposite directions at different 

 speeds over a 4,500-foot course in calm 

 water. The results of these calibrating 

 runs which were used in the present report 

 are as follows: 



The following tables of data and 

 their accompanying charts are tabulated 

 according to gear and cruise. G-III hauls 

 are numbered according to station. The 

 results of G-III oblique hauls during cruise 

 5-2C (table 8) are in the same order of 

 magnitude as those of horizontal tows, and 

 thus received no special treatment. 



In spite of the diversity of towing 

 techniques and gear, the distribution of 

 plankton by volume revealed a distinct 

 pattern (tables 16 and 17), with the greater 

 abundance appearing in catches made over 

 the Continental Shelf. 



In table 18 the catches of the two 

 metal nets are compared on a quantitative 

 basis. The G-III net, with its half -meter 

 opening, caught substantially more of the 

 active swimmers, but both models captured 

 inactive forms (eggs) in nearly the same 

 ratio. The table also points out the 

 abrupt decrease in plankton abundance as 

 the vessel moved seaward from waters over 

 the Continental Shelf. 



In considering the data presented in 

 this report, it should be kept in mind that 

 because of the emphasis placed on hydrog- 

 raphy during the survey, and the relatively 

 deep draft of the Alaska , few stations were 

 taken in shallow water. Limited plankton 

 collections subsequently made in shallow 

 waters from smaller vessels in the vicinity 

 of Galveston Island revealed a much higher 

 concentration of plankton, especially in 

 numbers of fish larvae, than appeared in 

 the Alaska catches from farther offshore. 

 It is probable, therefore, that intensive 

 shallow-water collecting would reveal a 

 higher potential of biological productivity 

 for the inshore area of the Gulf than may 

 be inferred from these tables. 



