PEARCY: ALBACORE OCEANOGRAPHY 



Infrared SST— 22 July 

 (Figure 7) 



This was the day of the first large peak 

 in average jig boat catches. (Figure 1). Most 

 of the catches were made northwest of the 

 SST flight and were arranged in a northeast- 

 southwest pattern, possibly along the seaward 

 boundary of the Columbia River ])lume. Highest 

 catch rates (25-55 fish/hr) in this area were 

 reported by fishermen trolling along the 15.5 °C 

 isotherm. High catches were also made along 

 the 15.5 °C isotherm 55 miles off Cape Lookout 

 and along the 15 °C isotherm 70 miles off the 

 southern Washington coast. 



Figure 7. — Sea-surface temperature and albacore catch 

 rates, 22 July 1970. Dashed hnes are isotherms based 

 on temperatures reported by fishing boats. See Figure 

 6 for explanation of catch notation. 



The surface temperatures show an inshore- 

 offshore gradient produced by upwelling and 

 plume waters. Temperatures were generally 

 warmer than on 15 July (Figure 6), however, 

 suggesting less intense upwelling or more 

 heating of surface waters on 22 July than on 

 15 July. The plume is apparent as a tongue 



of warm water (maximum 16.8°C) extending 

 towards the mouth of the Columbia River. 



Infrared SST — 29 July 

 (Figure 8) 



This SST pattern for the day after the 

 second big peak in jig catches (Figure 1) 

 reflects obvious changes compared to previous 

 patterns. Temperatures are much warmer — 

 over 13°-14°C nearshore and over 18 °C within 

 25 miles of the coast. These high temperatures 

 are explained by the absence of northerly 

 winds to induce upwelling during 26-28 July 

 (Figure 3) and by the rapid heating of .surface 

 waters during this period of reduced wind- 

 induced mixing, especially in the low-salinity 

 plume that has been shifted close inshore. 



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• DESTRUCTION 



I I 1 I M I I I I 



Figure 8.— Sea-surface temperatures and albacore catch 

 rates, 29 July 1970. Dashed line is an isotherm based 

 on temperatures reported by fishing boats. See Figure 6 

 for explanation of catch notation. 



Fishing activity was localized almost en- 

 tirely in a tongue of 15.5 °C, blue-green water 

 off the Columbia River (Pearcy, 1971). All the 

 high catch rates during this day were reported 



495 



