Cruise tracks of M/V Cobb were planned 

 in cooperation with oceanographers at the 

 University of Washington and Oregon State 

 University; in this way efficient coverage of 

 much larger areas was possible. Basic 

 oceanographic data are to be published by 

 the collecting agencies. The figures presented 

 here, however, were constructed from all 

 available July data in the respective years. 

 July station locations of vessels taking ocean- 

 ographic data in the area in 1961-64 are de- 

 picted in figures 79-82 to specify coverage 

 by each of the participating groups. Ocean- 

 ographic and exploratory fishing data col- 

 lected aboard M/V Cobb in July 1961, together 

 with a statement of methods, were summarized 

 by Owen (1963). Observations made in 1962- 

 64 were summarized by Owen (manuscript). 

 Interpretations in this publication do not neces- 

 sarily constitute concurrence by members 

 of the other agencies. 



ENVIRONMENT AND CATCH 



Oceanographic conditions and their effect 

 upon the albacore fishery off Washington and 

 Oregon are discussed in a separate paper 

 (Owen, manuscript)/ Some of the patterns of 

 property distribution are of sufficient inter est, 

 however, to warrant comment here. 



One of the most striking modifications of 

 the subarctic character of the study region 

 is provided by fresh-water effluent, prin- 

 cipally from the Columbia River. This effluent 

 is transported generally southwest in summer 

 from its source at 47.2° N,, and, through 

 lateral mixing, produces the plumelike dis- 

 tribution of salinity shown in figures 5-8. This 

 low- salinity plume extends to depths in excess 

 of 30 m. (figs. 53-56); if one assumes the 

 plume limit to be defined by the 32.2 p.p.t. 

 isosal, the plume extends more than 200 

 nautical miles (370 km.) offshore and 400 

 nautical miles (740 km.) south of its main 

 source. The limits of the plume thus largely 

 exceed the present range of the fishery for 

 albacore off Oregon and Washington, with the 

 exception of 1964, when the July plume was 

 greatly constrained (fig. 8). The plume is not 

 as well defined off Washington in summer, 

 however, because it is not wholly derived 

 from Columbia River effluent but from weaker 

 or more distant sources as well. 



Distributions of near-surface temperature 

 appear to be influenced by the presence of 

 the plume. Either reduced depth of the mixed 

 layer or diminished heat flux through the 



3 Owen, Robert W. Manuscript. Northeast Pacific alba- 

 core-oceanography data, 1962-64. 



* Owen, Robert W. Manuscript. Oceanographic condi- 

 tions off the American Pacific Northwest and their rela- 

 tion to the albacore fishery. 



thermocline, both associated with large density 

 gradients near the lower plume limits, would 

 produce the higher plume temperatures shown 

 in figures 1-4. 



A second conspicuous modification of near- 

 surface waters is produced by nearshore up- 

 welling of colder, more saline water. Upwelling, 

 the characteristic response to the wind-driven 

 seaward displacement of surface water that 

 accompanies the spring shift in wind direc- 

 tion from southwest to northwest, dominates 

 other processes in the region between plume 

 and coast to produce the cold (T < 14° C.), 

 saline (S > 32.2 p.p.t.) near-surface water 

 shown in figures 1-4 and 5-8. Subsurface 

 effects of upwelling are indicated by the sharp 

 coastward ascent of temperature and salinity 

 isopleths depicted in the vertical profiles of 

 these variables (figs. 49-52 and 53-56). 



Comparison of the distributions of albacore 

 catches from the Cobb presented in figures 

 75-78, with patterns of salinity distribution 

 reveals that the albacore catch is greater 

 near and within the plume. This relation sug- 

 gests either that albacore in commercial 

 quantities first enter the plume region from 

 the south, then proceed offshore, or that the 

 plume region serves in some way to concen- 

 trate albacore entering from the west as well 

 as the south. Support for the latter possibility 

 is indicated by results of albacore fishing 

 by U.S. Navy picket vessels some 200 nautical 

 miles (270 km.) west of the study area (Flittner, 

 1961, 1963, 1964, and personal communica- 

 tion). Catches from picket vessels which oc- 

 curred before the first Cobb catch in each year, 

 show that albacore are present to the west of 

 the plume region in July. The distribution of 

 albacore is thus indicated to be continuous 

 between these catch sites, so that albacore 

 may enter the Oregon-Washington fishery 

 from the west as well as from the south. 



One manner in which the plume may act 

 to produce higher concentrations of albacore 

 is through its effect on mixed-layer tem- 

 perature. The constraint of heat in the plume 

 results in higher temperatures than at com- 

 parable latitudes offshore. These temper- 

 atures and the cooling effect of coastal up- 

 welling produce a ridge of warmer water 

 that corresponds with the plume itself. A region 

 of more favorable environment may thus arise 

 in which albacore tend to remain and to form 

 larger, more fishable schools. 



ACKNOWLEDGMENTS 



Special acknowledgment is made to the Data 

 Collection and Processing Group of Scripps In- 

 stitution of Oceanography for their part in 

 initial processing of data from hydrographic 

 casts, and to the Department of Oceanography, 

 University of Washington, for their analysis of 

 Cobb salinity samples in 1962. The following 



