FISHERY BULLETIN: VOL. 74, NO. 2 



broad, and shallow current flowing equatorward 

 (Wooster and Reid 1963). The nearshore currents 

 vary seasonally and are dependent upon wind di- 

 rection and strength. During the fall and winter 

 months when the winds are predominantly from 

 the southwest, a subsurface countercurrent flow- 

 ing northward along the coast develops into the 

 Davidson Current. Drift bottle studies by Wyatt 

 et al. (1972), Burt and Wyatt (1964), and 

 Schwartzlose (1964) indicate that the Davidson 

 Current first develops along the Oregon-Wash- 

 ington coast in September reaching maximum 

 speeds between 0.5 and 2 knots within 20 miles of 

 the coast during the month of November. 



The major change in the surface currents from 

 northward to southward occurs in March and 

 April (Wyatt et al. 1972). The phenomenon of 

 coastal upwelling occurs when the northwesterly 

 winds intensify and sometimes persist from May 

 to September. As the surface waters are trans- 

 ported offshore and to the southwest, cold, high 

 salinity waters from below a permanent pycno- 

 cline (60-100 m) are brought to the surface (Smith 

 et al. 1966). This zone of active upwelling occurs 

 within 20 miles of the coast but its effects can be 

 observed to the edge of the slope. 



The area within 5 miles of the coast has not 

 been studied in much detail but is believed to be 

 dominated by mixing processes (Mooers 1970). 

 The surface currents are generally well corre- 

 lated with the wind direction, but tidal currents 

 predominate when the wind is reduced. A very 

 strong alongshore current with an onshore com- 

 ponent is indicated within 3-5 miles of the coast 

 (Keene 1971; Wyatt et al. 1972; Holton and 

 Elliot 1973). 



The dominant processes modifying surface 

 water properties off" the Oregon coast during the 

 winter are rainfall and river runoff; while during 

 the summer, the major processes are upwelling in 

 conjunction with heating and mixing with the 

 Columbia River plume water (Pattullo and Den- 

 ner 1965). Surface temperatures and salinities 

 taken on early life history cruises from June 1969 

 through August 1971 at stations NHOl-NHlO are 

 presented in Figures 1 and 2. Temperatures 

 range annually from about 7° to 17°C and are 

 highest from May through October, peaking in 

 September. More variability is evident during the 

 summer due to surface heating interrupted by 

 local upwelling of near 7°C bottom water. Surface 

 salinity values are generally low during the 

 winter and high in the summer reflecting sea- 





< 



a: 



5 



5 



15 — 



10 — 



1 — I — I — rn — I — I — r~i — i — r~i — r 



"1 I I I I r 



JJASONDU rMAMJ JASOND|J FMAMJJA 



1969 



1970 



1971 



Figure l.— Surface temperature (°C) at stations NHOl, NH03, 

 NH05, and NHIO from June 1969 through August 1971. 



sonal precipitation and upwelling, respectively. 

 The annual range of salinity is from about 25 to 

 35"L. Low salinity values at stations NH03 and 

 NH05 from November through April are proba- 

 bly associated with the Yaquina Bay plume 

 which flows north along the coast during the 

 winter (Kulm and Byrne 1966). 



METHODS 



Sampling Program and Gear 



This study was conducted primarily on a 

 trackline off Newport, Oreg. (lat. 44°39.1'N) 

 across the continental shelf and slope. The 12 sam- 

 pling stations are designated on the Newport 

 Hydrographic line (NH) in Table 1, which cor- 

 respond in distance to nautical miles from the 



354 



