FISHERY BULLETIN: VOL. 69. NO. 4 



column sampled for the "net" zooplankton was 

 examined at Station 77. Expressed as a per- 

 centage of the average ciiiate organic carbon 

 concentration within the euphotic zone, the ver- 

 tical distribution was 30 to 50 m, 14%; 55 to 

 75 m, T'r ; and 80 to 100 m, 6%. Chlorophyll 

 levels over the same depth intervals were 20%, 

 8%, and 1% of the euphotic zone average. Cii- 

 iate organic carbon estimate for the 100-m col- 

 umn was more than 20 ^,r of that of the total 

 103-/X net sample. 



The numbers of small shelled sarcodinan pro- 

 tozoa, i.e., Foraminifera and Radiolaria, were 

 relatively low. Numbers counted in the samples 

 integrated over the euphotic zone were too small 

 to provide a good estimate but suggested less 

 than 10 foraminiferans and radiolarians/liter. 

 At the surface, the average abundance of Sar- 

 codina for the 12 stations was low — 5.3 organ- 

 isms/liter or 0.032 jjig C/liter. 



The metazoan microzooplankters, principally 

 juvenile copepods, were also few in numbers. 

 Less than one metazoan/liter was found, on the 

 average, in + 35 sample from the surface. Aver- 

 age numbers in the unconcentrated samples over 

 the euphotic zone were higher (up to 40/liter) 

 but the very few counted puts wide confidence 

 limits on the figure. The size of the "average" 

 individual copepod, both naupliar and post-nau- 

 pliar, was significantly greater than seen pre- 

 viously (Beers and Stewart, 1970) and this sug- 

 gests the relative absence, at least at this time 

 of year, of the smaller species and their devel- 

 opmental stages compared with nutrient-rich 

 coastal areas off California. 



LARGER ( + 103 /x) ZOOPLANKTON 



Standing stock zooplankton at five stations 

 where productivity was measured (Station 59, 

 ()8, 77, 87, and 93) averaged 2.4 mgC/m' over the 

 upper 100 m and showed less than a twofold 

 diff'erence between sites (Table 5). For the 

 twenty-one 103-/x net samples collected, average 

 zooplankton organic carbon was calculated to be 

 4.9 mg/m^. Zooi)Iankters small enough to pass 

 505 fi mesh were 30% of the total at the "pro- 

 ductivity" sites and 2b'^r overall. Calamis chil- 

 ensis (NVI-adults) constituted approximately 



Table 5. — The standing stock biomass, as dry weight, 

 of the 103 fj, net zooplankton samples, 100 m to surface 

 tows. 



25% of total net organic carbon at the produc- 

 tivity sites. At other stations its estimated 

 abundance as a percentage of the total ranged 

 from <4% to more than 100%. It appeared 

 as though the Calunus population associated with 

 Patch 1 was staying with the patch and growing 

 as evidenced by following a cohort of NV and 

 NVI individuals into CI at Day 3 (June 15) 

 and CII at Day 6 (June 18) (see University of 

 California, Institute of Marine Resources, 1971; 

 footnote 4). 



DISCUSSION 



Many of the specialized studies of biological 

 populations and production in Peruvian coastal 

 waters have been done during the late summer 

 or early fall months of the southern hemisphere, 

 i.e., February to April. The relatively large 

 amount of data available from the Instituto del 

 Mar del Perii provides seasonal coverage of the 

 important food chain variables and allows us 

 to place the conditions we found in this study 

 during austral late fall-early winter in their pro- 

 per perspective. The transport of nutrient-rich 

 water to the surface through upwelling occurs 

 throughout the year but it is generally most in- 

 tense in winter (.see Wooster and Reid, 1963; 

 Zuta and Guillen, 1970). However, biological 

 production, mainly as evidenced by standing crop 



870 



