C CAL OF . C CAL IN 



FISHERY BULLETIN: VOL. 75, NO. 2 

 THAL AMPH SIPH 



55 56 57 58 59 CApE QF CAPE IN 



55 56 57 58 59 55 56 57 58 59 

 YEAR 



FIGURE 5.— Graphs for each of the well-sampled CalCOFI zones 

 (see Figure 1) of the first principal component of the year-to-year 

 fluctuations in biomass of all the 17 taxa. Each graph is drawn 

 with a mean of zero and the vertical scale is in SD units. 



55 56 57 58 59 55 56 57 58 59 55 56 57 58 59 



55 56 57 58 59 



YEAR 



FIGURE 6. — Graphs for each taxon of the first principal compo- 

 nent of the year-to-year fluctuations in biomass for all the well- 

 sampled CalCOFI standard zones. A key to the abbreviations of 

 the names of the taxa is given in Table 1. They are in the same 

 order as in Table 4 (see text). Each graph has a mean of zero and 

 the vertical scale is in SD units. 



spheric pressure) for 1955-59 is shown in Figure 7. 

 Differences greater than 58 cm are believed to 

 indicate a stronger than normal flow and differ- 

 ences less than 58 cm a less than normal flow. It 

 can be seen that the period of less than normal 

 flow in 1957-58 corresponds well with the timing 

 of the increase in temperature in the southern 

 California offshore zone. In the California Cur- 

 rent region, and indeed over most of the eastern 

 North Pacific, the increase in temperature per- 

 sisted through 1958 and 1959 while the sea level 

 differences indicate a normal or above average 

 flow during this time. The period of below normal 

 flow corresponds with El Nino off the coast of Peru 



and perhaps with an anomalous weakening of the 

 trade winds of the southern hemisphere and a 

 concurrent reduction of equatorial upwelling 

 (Bjerknes 1966; Favorite and McLain 1973). 



Wickett (1967) found a relationship between 

 the year-to-year changes in zooplankton volume 

 for the CalCOFI survey (Thrailkill 1963) and the 

 mean meridional Ekman transport (Fofonoff 

 1962) for January to August in the previous year 

 at lat. 50°N, long. 140°W (over 1,000 miles 

 upstream from the CalCOFI survey area) for the 

 years 1952-59. He suggested that a major cause of 

 variation in the abundance of zooplankton in the 

 California Current region is the change in the 



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