FISHERY BULLETIN: VOL. 72. NO. 2 



Figure 7. — Trajectories of four drogues during the study of 22 May to 1 June 1970. Observed positions of the drogues are indicated by 

 circles and triangles for each pair of drogues, and the date and time of the triangulation are indicated by the one-four or two-four digit 

 sequence of numbers near the symbols. Reset drogues indicated by primes refer to other drogues placed into the water after ones placed 

 earlier either ran a<ground or broke down. Refer to the text for further details. 



be considered below as one of the physical vari- 

 ables which may affect the offshore distribution of 

 Pleurobrachia and present a bias in the sampling 

 program for estimates of ctenophore abundance in 

 the coastal waters. In the study during April 1970 

 three drogues set in a line about 1 km apart in a 

 north-south direction moved southeast toward 

 Point La Jolla on flood tide and changed direction 

 on ebb tide, moving west or southwest (Figure 6). 

 After moving beyond Point La Jolla all drogues 

 continued toward the south. Note that after 0800 h 

 the two drogues closest to the shore apparently 

 became detached from their surface floats in kelp 

 beds, because only the floats were recovered at the 

 end of the study, 1800 h 5 April. No dramatic 

 changes in direction occurred with changes in the 

 surface tide for the drogues off Pacific Beach. 

 Wind data were not recorded for this study, but the 

 weather reports for 4-5 April indicated easterly 



winds at 6 m/s in the morning becoming westerly 

 at 4^7 m/s in the afternoon. 



The current velocities measured with drogues 

 in La Jolla Bight for periods up to a week 

 confirmed the presence of a counterclockwise gyre 

 over or nearby the La Jolla Canyon complex (Fig- 

 ure 7). The four drogues moved northward, gener- 

 ally paralleling the shore and finally ran aground 

 or broke down near Encinitas and Carlsbad, sea- 

 sonal sampling stations 3 and 2, respectively. 

 Drogues which ran aground or lost the subsurface 

 parachute or vane were reset nearby the other 

 drogues. Drogues no. 2 and 3 were reset about 5 

 km from shore, and they continued to move 

 northward parallel to shore until they were lost. 

 Drogues no. 1 and 4, however, tended to move 

 offshore. Drogue no. 1 made a large counter- 

 clockwise loop about 16 km long and returned to 

 cross its original path about 5 days later. Mean 



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