Lacking available records of offshore wind force, a series was derived 

 from barometric pressure data given on daily weather maps published by the 

 United States ''.leather Bureau (cf. Sverdrup, 1936.2). First were tabulated 

 the daily barometric pressures at each of the four corners of a 300-mile 

 square placed off the coast of southern California (cf. table 6). From 

 these data were obtained two series of differeu^'.es representing pressure 

 gradients which vfould be expected to produce winds parallel and at right 

 angles to the coast line, respectively; and their differences were- summed 

 by periods of time as described below. 



The resiolting two series of sums wer«j treated, with due regard to the 

 effect of the earth's rotation, as if they were conponents, the resultant 

 of which is proportional to direction and extent of wind movement. The 

 direction proved to be northwesterly for each period of the entire series 

 studied. 



Sums w^ere made, as indicated above, for calendar years, and averaged 

 for the period 1932-38, inclusive, to furnish a norm from which deviations 

 v/ere determined, as had been done with .growth and temperature data, discussed 

 above. The same pr.ocodurc was followed using various periods of time and 

 various combinations of months. Without exception the yearly deviations 

 from normal indicated -v/ind force were found to be correlated positively with 

 anomalies in the first year's growth of pilchard. Hov,'ever, the period April 

 through the following torch gave a somewhat better correlation than other 

 periods, and has been shovm in the fourth curve of figure 6. This period 

 corresponds with the first y<iar's grov/th as registered on the scales: i.e., 

 between the time of spavming and the time the first annulus is formed. 



Other data bearing on the environment of the pilchard,- made available 

 by the Scripps Institution of Oceanography, are average monthly svirface sa- 

 linities for the sane localities as cited in footnote 2, page l6. Those 

 taken at the Scripps Institution pier v/ere treated In the same way as de- 

 scribed for the average monthly temperature records (page l6). Deviations 

 from a norm based on the twelve-^onth period April to the following March - 

 the same as that used for v;ind force - were plotted as the sixth curve of 

 figure 6. This curve bears a strong similarity to the other five. 



Thus is indicated a positive correlation between the force of northirest 

 vdnds, the salinity of the surface v^ater, and the first year's gro^rth of 

 pilchards; and a negative correlation between the latter and surface tem- 

 peratures. To have demonstrated this required that the year classes, as 

 determined from scales, be allocated correctly to the years in which they 

 had been produced. It required also that a high enough order of accuracy 

 be maintained in the scale reading to preserve the distinctive character 

 of the curves. 



A further conclusion to be drawn from these curves is that the fish 

 of a given year class normally have a common history during their first year. 

 They are subject to the same vicissitudes of marine climate and therefore 

 probably also of food supply. 



113 



