not go on without serious diminution of the population, resulting in both 

 markedly lower annual catches and a marked and perhaps intolerable de= 

 crease in average size of fishT 



At the moment there is no basis for making the choice, but the pro- 

 gram charted in the right-hand portion of the diagram, facing page 1 

 which is now to be discussed, is designed to distinguish between the 

 effects of the extrinsic and intrinsic influences » 



Source Data 



Egg and larvae samples o - By a plankton=coliecting program designed 

 to sample the egg and larval pilchard population in waters of the spawning 

 region, it is planned to obtain material for two sets of data on each sea= 

 song 1) The numbers of eggs spawned and 2) the survival of the larvae to 

 the post-planktonic stage o 



To serve these purposes, quantitative collections of eggs and larva® 

 must be madeo Features of quantitative technique so far employed in this 

 branch of the program are use of; The oblique method of tmiring to sampi* 

 all egg-and-larva-bearing stratai current meters in the nets to measure 

 the quantity of water strained in each haulj regular pattern of stations? 

 and regular periodicity in making oollectiono Additionally, there have 

 been special collections or special methods employed in the regular collec= 

 tions to test the reliability of the tow-net method for sampling eggs and 

 larvae o These special inquiries have convinced us that quantitative work 

 is feasible, if also difficulto Some of the techniques still have to be 

 improve d» 



Hydro graphic and meteorological da tap = Observations on hydrographic 

 conditions taken simultaneously with the collection of eggs and larvaej, 

 are intended to provide a record of conditions to be correlated with the 

 time, place, and volume of spawning and with the survival of larvae « It 

 is already known that the dominant features of oceanic circulation along 

 the west coast, and particularly the maintenance of fertility of the wa= 

 ters through the upwelling process, are connected with the winds. With 

 the establishment of the relationships of the oceanographic features to 

 the meteorological influences, on the one hand, and to the amount of spawn= 

 ing or to the survival of larvae, on the other, it may be possible to es= 

 tablish directly the relationship of amount of spawning or survival of 

 larvae, or both, to the meteorological conditions » Hence simultaneous 

 observations on hydrography, meteorology, and the young stages of sardines 

 promise to elucidate the influences on recruitmento 



The particular oceanographic observations so far programmed, include? 

 Those on temperature and salinity down to 500 meters regularly^ and pilot 

 observations to greater depths j determination of oxygen and phosphate 

 content for the same stratai and counts of the diatom population for each 

 tem=meter level to 60 meters in deptho All of these observations and 



22 



