FISHERY BULLETIN: VOL, 69. NO. 4 



(1970) and University of California, Institute 

 of Marine Resources (1971, see footnote 4). 



Larger zooplankton abundance was studied at 

 21 sites including the four stations associated 

 with Patch 1 but only at one location. Station 93, 

 where productivity was measured in Patch 2. 

 Samples were taken by vertical tows from ap- 

 proximately 100 m to the surface using paired 

 0.5 m nets having 103 fi mesh. The volume of 

 water filtered was determined by a flowmeter 

 mounted in the mouth of one of the nets. At 

 some stations wire angles of 10° to 25° developed 

 during the sampling. The numerical abundance 

 and biomass of all developmental stages of the 

 copepod Calanus chilensis Brodsky were deter- 

 mined. An estimate of the biomass of the total 

 Formalin-preserved net material divided into 

 fractions of >505 /x and <505 /i was obtained 

 as dry weight and converted to organic carbon 

 by multiplying by 0.40. For the discussion the 

 total material is considered to be zooplankton 

 although there was undoubtedly a small fraction 

 of phytoplankton and detritus associated with 

 the net sample. 



RESULTS 



UPWELLING PATCHES 



Periodic changes in position and configuration 

 of the two patches as determined from surface 

 mapping of phytoplankton pigments is shown 

 in Figures 1 and 2. Patch 1, when detected on 

 13 June, appeared relatively compact and had 

 a ma.ximum surface pigment (Chi a and "phaeo- 

 pigments") concentration of 6 to 8 /xg/liter. 

 Surrounding waters showed 1 to 2 ;ng/liter. The 

 patch was bounded on the south and west by a 

 well-defined front. Surface temperature and sa- 

 linity within the patch were 19.5° C and 35.15// 1, 

 respectively, while values reached 21.0° C and 

 35.25'/, on moving out of the patch. The levels 

 of temperature and salinity at the surface of 

 the patch were similar to those found at depths 

 of 35 to 45 m and 50 m, respectively. Surface 

 nitrate and silicate concentrations of 16 and 13 

 /LiM, respectively, were found in the patch, drop- 

 ping abruptly to about 10 and 7 ^^.u on crossing 

 the thermal front bordering the patch. A de- 



cline of surface pigment and nutrient levels was 

 observed over the period 13 to 21 June. By 

 June 17 it was apparent that this patch was dis- 

 appearing and a more extensive mapping oper- 

 ation revealed a clearly defined patch. Patch 2, 

 about 16 miles (25 km) south of Patch I (Fig- 

 ure 2). Patch 2 surface parameters included: 

 maximum pigment concentration of 6 /iig liter; 

 temperature, 19.5° C; salinity, 35.15',, ; nitrate, 

 10 jaM ; and silicate, 13 /aM. A distinct front 

 bordered the patch on the west. Somewhat cold- 

 er water (19.0° C) but with a lower pigment 

 concentration (~3 /xg/'liter) was on the eastern 

 side. A transect from east to west across Patch 

 2 passed through water with temperatures from 

 19° to 21.5° C. Variations of surface chlorophyll 

 with temperature for Patch 2 are shown dia- 

 grammatically in Figure 3. This patch was no 

 longer recognizable by 21 June. Mapping oper- 

 ations late in the cruise period revealed the 

 presence of additional patches in the area but 

 time did not allow for their study. 



WATER MOVEMENT IN AND AROUND 

 PATCHES 



Calculations of dynamic topography suggested 

 that Patch 1 occurred in a cyclonic eddy of the 

 Peru Coastal Current (Figure 4). Based on 

 the displacement of the chlorophyll pigments at 

 the surface, the patch was being shifted to the 

 west at about 23 cm/sec. Beneath the surface 

 the dynamic computations suggested a poleward 

 flow of about 15 cm sec at 50 m (Table 1, Sta- 

 tions 54, 59, and 78). Cool surface water of 

 relatively low salinity (35.15J^f) was found on 

 the nearshore side of the meander. 



The limited data available for calculation of 

 the dynamic topography around the second patch 

 (Patch 2) suggested a northward flow of surface 

 water along the western boundary of the front 

 (Figure 4). Direct measurements with a cur- 

 rent meter at Stations 99 and 101 in this patch 

 showed a flow of 18 cm/sec to the ENE at 10 m, 

 a stronger southerly flow of 30 cm/sec at 50 m 

 and little current, i.e., less than 5 cm/sec, below 

 100 m (Table 2). Beyond the temperature-sa- 

 linity front on the west of the patch, the velocity 

 of the water was about 5 cm/sec toward the ENE 



862 



