and the other southeast of Santa Barbara Island. Polychaeta and 

 Ctenophora were most numerous in the southeastern part of the survey 

 area, and they were not collected at all stations. 



The small number of fish eggs collected were distributed over 

 four of the stations in the center of the survey area. Fish larvae 

 were collected on haul number 8 only. 



VI. SUMMARY AND CONCLUSIONS 



The cold, low salinity California Current resulted in seaward 

 decreases in surface temperatures and salinities. During both the 

 September and October operational periods, a sharp temperature gradient 

 existed at the surface in the vicinity of San Nicolas Island. In 

 September, a mixed layer existed to a depth of about 20 meters, but 

 in October, the mixed layer was only to 10 meters. 



Dissolved oxygen determinations were made on the September stations. 

 A mixed layer of dissolved oxygen generally occurred in the upper 

 15 meters. Dissolved oxygen concentration averaged about 5.5 ml/1 

 at the surface and about 2.0 ml/1 at 200 meters (656 feet). Minimum 

 concentrations existed at about 675 meters (2215 feet) . 



The sound channel was bottom bounded due to the shallow depths 



of the survey area, and the sound velocity axis occurred at a depth 



of 850 meters (2800 feet) . Surface duct development was usually 



restricted to the upper 10 meters and was observed most frequently 

 in September. 



At two 24-hour anchor stations, Nansen cast and sound velocimeter 

 data showed temperatures, salinities, and sound velocities to oscillate 

 in a sinusoidal manner throughout a day. At one of the anchor stations, 

 maximum and minimum sound velocities corresponded with high and low 

 tides, respectively. At the second anchor station, this situation 

 was nearly the reverse. An explanation for this variation was the 

 separation of the two anchor stations by San Nicolas Island and the 

 effects of the earth's rotation and internal waves acting together 

 in varying combinations at the stations. 



Current data from parachute current drogues, current meters, 

 and computed dynamics showed the San Nicolas Basin to be the center 

 of a counterclockwise elliptical circulation. A unidirectional flow 

 of surface and subsurface waters existed in the survey area with 

 one exception in the area northeast of San Nicolas Island. Drogues 

 and dynamic computations showed maximum current speeds of about 

 25 cm/sec around the periphery of San Nicolas Basin. Lesser speeds 

 existed towards the center of the basin and with increasing depth. 

 Current meters indicated an overall clockwise rotational tidal current 

 to exist 2 miles northeast of San Nicolas Island. A resultant east- 

 southeasterly flow of about 8 cm/sec was derived from the current 



46 



