FISHERY BULLETIN: VOL. 72, NO. 1 



I24»00 W. 



TOLEDO 



44' 

 96' 

 N. 



CONTOUR INTERVAL 12 FEET 

 DATUM MEAN LOWER LOW WATER 



Contour! complied from U. S 

 C. AGlS I9S3 •moom tliMt 



44" 

 36 



N. 



124* 00' W. 



Figure 1. — Yaquina Bay estuary, showing location of stations: Bridge, Buoy 15, 21, 29, and 39. 



difference from surface to bottom) during other 

 seasons (Burt and McAlister, 1959; Kulm and 

 Byrne, 1967; Zimmerman, 1972). Salinity is 

 lowest and also most variable during the winter 

 period of high precipitation. Temperatures, 

 however, are most variable during the summer, 

 owing to periodic advection of cold upwelled 

 waters into the bay and to local heating (Fro- 

 lander. 1964; Frolander et al.. 1973). 



SAMPLING METHODS 



A 12.5 cm diameter Clarke-Bumpus (CB) 

 Sampler with nylon (Nitex")" net of 0.233 mm 

 mesh aperture was used to collect 393 plankton 

 samples from January 1960 to December 1970 

 and to provide a long time series for analysis 

 at one station (Buoy 21) located in Yaquina 

 Bay about 4.3 nautical miles from the ocean 

 (Figure 1). In addition, both the CB and a 20.2 

 cm diameter nonclosing Bongo Sampler were 

 towed together at five stations (Bridge and 

 Buoys 15, 21, 29, and 39) from June 1969 to 

 June 1970 (223 tows). The bongo had nylon 



2 Reference to trade names does not imply endorsement 

 by the National Marine Fisheries Service. 



nets with 0.233 mesh on one side and a 0.571 

 mesh on the other and was attached 1 m below 

 the CB on the same towing cable. The CB net 

 was 61.6 cm long with the filtering area of the 

 mesh to mouth area ratio of 6.2:1. The bongo 

 nets were cylindrical-conical, 177 and 161 cm 

 long for the 0.233 and 0.571 mesh nets respec- 

 tively. Both bongo nets had a filtering area to 

 mouth area ratio of 10.5: 1. 



Samples were collected from small boats, 

 generally at weekly intervals during the sam- 

 pling period. Oblique-step tows were made at 2 

 knots. At the three deep stations (Bridge, Buoys 

 15 and 21) the net was towed horizontally at 

 each of three depths for 4 min: about 1 m above 

 the bottom, at mid-depth and 1 m below the 

 surface. At the two shallow stations in the upper 

 estuary the nets were towed at each of two 

 depths for 6 min: 1 m above the bottom and 1 m 

 below the surface. Tows were made during day- 

 light, in mid-channel, against tidal currents, 

 and did not coincide with any particular tidal 

 stage. However, several 24-h series of CB tows 

 (123 tows) were made during the 11-yr period 

 to assess diel and tidal variations at single 

 stations. 



202 



