Hov.'evor, the data for tho present study were gathered in t^.'o different years 

 (1939 and 19Ul) and over a considerable ar.ca, so that they may permit of 

 sone generalization. 



It may have been noted that the concentrations of cgs^s and larvae are 

 correlated \.dth depth as well as temperature, since the latter two are them- 

 selves highly correlated. However, there are some instances where the deeper 

 extension of v;-arm water corresponds v/ith a deeper distribution of eggs or 

 larvae (cf. fig. 2). Also, there is some logical basis for a correlation 

 with temperature, v^rhich might act either as the cause of direct reaction 

 of the larvae, or as an indicator of density differences affecting the dis- 

 tribution of eggs. 



It is not intended to argue that tenporatuTG itself necessarily controls 

 the vertical distribution of pilchard eggs and larvae. Their location may 

 be determined by complex reactions of the spawners to a combination of physi- 

 cal conditions, including salinity, food, density, etc. To the extent that 

 these would induce spasming in a homologous portion of the layer of water 

 above the thermocline, temperature m;iy be merely an indicator and not a cause. 

 This, of course, doiis not detract from the usefulness of temperature as a 

 guide to vertical distribution. 



As a basis for predicting the proper depths to v.-hich to send nets on 

 regular surveys, the regressions of egg and larvae concentrations on tem- 

 perature indicate that hauls should be made deep enough to go below temper- 

 atures of 10.5° C. for eggs -md 12.0° for larvae. Distribution of the large • 

 larvae during the daytime show^s the need for fishing to a depth greater 

 than 73 meters between sunrise and sunset. 



APPENDIX A 



TABLI5S OF DETAILED TOV/ING DuIa 



Explanation of tables : The hauls at each station and the observations 

 during each haul are arranged chronologically and numbered consecutively, 

 beginning with one. Time is ship's time, ■v'ith hours numbered from 1 for 

 Ija.m. to 2U for midnight. Meters of wire out (m. out) refers to the length 

 of towing viire from the surface of the sea to the point of attachment of 

 the not. The stray angle {°/) is the departure of the tow'ing wife from 

 the vertical, expressed in degrees. A dash (-) represents a missing ob- 

 servation. 



189 



