FISHERY BULLETIN: VOL. 71, NO. 2 



waters with salinities less than 32.2"/oo (Owen, 

 1968) were found within 30 miles of shore 

 near the mouth of the Columbia River (Sta- 

 tions 7-10, Figure 5a), as a lens of low- 

 salinity water located along the north-south 

 section 110 miles offshore (between Stations 

 22 and 25, Figure 5c), and greater than 50 

 miles offshore along the Newport transect 

 (Stations 25-30, Figure 5e). The warmest water 

 encountered on the cruise was along the north- 

 south section, 110 miles offshore, where water 

 15 °C and warmer was localized in a lens to 

 a maximum depth of 20 m and surface temi)era- 

 tures as warm as 15.7''C were recorded (Figure 

 5d). This water, which was warmer than 

 average in July, coincided with the low-salinity 

 lens from the Columbia River plume. The 

 correlation between low salinity and warm 

 temperature early in the summer has been 

 previously observed by Owen (1968) who de- 

 scribed a causal basis. The strong pycnocline 

 produced by the low-salinity water constrains 

 mixing, and near-surface waters are heated 

 by insolation more rapidly than surrounding 

 waters. This relationship between salinity and 

 temperature depends on heating rates and 

 varies with season. Evans (1972) found that 

 highest temperatures in the plume occurred 

 inshore of the salinity minimum and that heat 

 content was not a good indicator of the plume 

 even though the temperature pattern is. 



InfraredSST— 15 July 

 (Figure 6) 



Our first sea-surface temperature (SST) flight 

 was made by coincidence on the day that 

 albacore catches were first reported off Oregon. 

 Fish were caught about 120-160 miles off 

 Heceta Head (Figures 2 and 6) where the 

 fishing vessel Sph'it reported surface tempera- 

 tures of 16 °C. This warm water was probably 

 associated with a lens of low-salinity Columbia 

 River plume water, similar to the situation 

 found earlier in July on the cruise (Figure 5). 

 As a result, the early location of the fishery 

 and its subsequent movement to the north 

 (Figure 2) may have been along plume waters, 

 which are often the warmest waters available 



off Oregon during the early summer (Owen, 

 1968). 



I I I M I 



I I I I I I I I I M I I I I I M I 



J/G BOATS - FISH /HR 



□ 0-10 



□ 10-25 

 E] >25 



I I I I I I 



•DESTRUCTION 



Figure 6. — Sea-surface temperatures (degrees Celsius) 

 recorded by infrared radiometry on 15 July 1970. The 

 flight track of the aircraft is shown by the narrow 

 lines. Catch rates of albacore are indicated for jig 

 boats by shading of 10' blocks. In other figures, dashed 

 lines denote isotherms based on temperatures recorded 

 by fish boats. Daily catches of bait boats are shown by 

 encircled numbers. 



Coastal upwelling was obvious on this flight 

 as a long band of cold (8°-9°C) water along 

 most of the coast (Figure 6). Although average 

 winds on 15 July were not from the direction 

 to induce upwelling, winds on the preceding 

 days were northerlies (Figure 3) and hence 

 conducive to coastal upwelling. Mixture of 

 these upwelled cold waters with the warmer 

 Columbia River water probably masked the 

 inshore portion of the Columbia River plume 

 which often contrasts with upwelled water 

 as a tongue of warm water emanating from 

 river mouth in early summer (Budinger, Coach- 

 man, and Barnes, 1964; Owen, 1968; Pearcy 

 and Mueller, 1970). 



494 



