of 1 .5, 3.0, and 4.5 knots, as estimated by a taffrail log, 

 and were repeated in succession throughout the 30-hr 

 period. Haul positions, local time, and other data for 

 this series are listed in Table 1. Samples were pre- 

 served at sea with sodium acetate-buffered formal- 

 dehyde of about 3.7%. This report is largely restricted 

 to the amphipods from the 60 cm, 0.333-mm mesh net. 



RESULTS 



Problems such as malfunctions of the flowmeter, net 

 damage, and uncertainty of towing speeds (as mea- 

 sured by the taffrail log) place limitations on the data 

 from six of the hauls (numbers 2, 8, 12, 13, 14, 18) as 

 noted in Table 1 . Also, the varying actual depths of the 

 hauls limit the validity of direct comparisons among 

 them. However, general trends in numbers and diurnal 

 occurrence of some species are evident. 



Table 2 lists the species identified. The higher taxa 

 follow the classification of Bowman and Gruner 

 (1974). Fourteen species were present in the samples, 

 in 10 genera and 8 families. Two of these were Gam- 

 marideans and the rest of the suborder Hyperiidea. 



Table 3 summarizes by haul, the numbers collected 

 of each species, their relative abundance, estimated 

 number per 1,000 m^ of water, and their overall rela- 

 tive abundance and rate of occurrence. Numbers were 

 clearly dominated by Parathemisto pacifica, which 

 formed 87.2% of all amphipods collected. Primno 



macropa comprised 10.1% of the total and was the 

 only species besides Parathemisto pacifica present in 

 all hauls. Cyphocaris challengeri formed 1.6% of all 

 amphipods taken but, except for one specimen, was 

 present only in the night hauls. Hyperia medusariim 

 was present in 14 (82%) of the hauls but accounted for 

 less than 1% of the total numbers. 



The diurnal variation in estimated numbers per 

 1.000 m^ of water strained is shown in Figure 2. Ex- 

 cept for Parathemisto pacifica, maximum combined 

 numbers of the other species occurred at night, just 

 before 0100 on 9 June. Peak numbers of P. pacifica 

 occurred at 1000 on 9 June, but numbers otherwise 

 varied from haul to haul, with no diurnal trend evident. 

 Numbers of C . challengeri. and to a lesser extent 

 Primno macropa and H. medusarum, increased at 

 night. This was presumably due to vertical migration, 

 but daytime avoidance of the net is also a possibiUty. 



Figure 3 depicts the diurnal variations in relative 

 abundance and total number of species per haul. The 

 relative abundance was strongly dominated by 

 Parathemisto pacifica throughout the study period, al- 

 though it fell to 68% during the two hauls between 

 midnight and 0100. At that time maximum relative 

 abundance of Primno macropa (27.4%) and C. chal- 

 lengeri (13.5%) were observed. The maximum number 

 of species per haul (8) occurred at 0200. 



The drogue travelled about 6 miles during the sam- 

 pling (Fig. 1), and surface conditions suggest that it 



Table 1. — Location and dates of plankton hauls' and associated sampling data for station no. 6 of 

 RV George B. Kelez. Cruise K71.3, June 1971. 



'Zooplankton collected with 60 cm bongo net of 0.333-mm mesh. 

 ^Value estimated; towing time uncertain. 

 'Value estimated; based on ship's speed. 

 ■•Net damaged during tow. 



