caught in blue, warm water but not in green, cold 

 coastal water. As they noted, however, this effect 

 probably is attributable to temperature rather 

 than to water color. Other environmental variables 

 that have received attention as possible deter- 

 minants of albacore availability and abundance 

 (or density) include salinity and concentration of 

 forage. No examples of observed relations of these 

 factors to numbers of accessible albacore are 

 available, however, and the relation of tempera- 

 ture to albacore was only grossly defined in 

 previous studies. 



The purposes of this paper are to describe the 

 environment thai albacore encounter when they 

 first enter the region off the coast of Oregon- 

 Washington, to suggest the physical mechanisms 

 that produce these conditions, and to indicate 

 which of these conditions appear to influence the 

 number of albacore available to the fishery. 



DATA SOURCES 



Data from which distributions of variables were 

 derived were collected in July 1961-64 on Cruises 

 51, 55, 60, and 66 of M/V John N. Cobb, a coopera- 

 tive program with the Bureau of Commercial 

 Fisheries Exploratory Fishing and Gear Research 

 Base, Seattle, Wash. (Owen, 1963, 1967a); in 

 July 1961-62 on Cruises BB-290 and BB-310 of 

 R/V Brown Bear, Department of Oceanography, 

 University of Washington, Seattle; and in July 

 1963-64 on Cruises 6307 and 6407 of R/V Acona, 

 Department of Oceanography, Oregon State 

 University, CorvaUis, Oreg. Data from which 

 averages of catch per unit of effort for the com- 

 mercial fishery were computed are from Ayers 

 and Meehan (1963) and from James M. Meehan 

 of the Fish Commission of Oregon (personal 

 communication) . 



OCEANOGRAPHIC PROCESSES AND DIS- 

 TRIBUTIONS OF VARIABLES 



The study area (fig. 1) is part of the subarctic 

 Pacific Ocean and hence exhibits its principal 

 characteristics: dilution of the surface layers by 

 excess of i)reci|)itatioii over evajjoration; and 

 presence of a well-defhied, permanent halochne 

 in which year-round temperatures are nearly 

 identical with winter tenijieratures of the surface 

 layers (fig. 2). The oceanography of the subarctic 

 Pacific was reviewed by Uda (1963), and by 

 Dodunead, Favorite, and Hirano (1963). 



T==t7 



m\ 



OFFSHORE 

 PROVINCE 



Figure 1. — Oceanograph ic provinces (schematic) off the 

 Oregon-Washington coast in summer. Dashed line 

 represents general limit of study area. 



Figure 2. — Schematic diagram of vertical temperature 

 and salinity structures in the eastern subarctic Pacific 

 in summer and winter. 



Processes that determine the distribution of 

 salt and heat over the subarctic region combine 

 in the study area with effects of nearshore up- 

 welling, river discharge, and bottom topography 

 to produce the distributions of variables reported 

 here. Oceanograi)hy in part of the area was 

 reviewed by Budinger, Coachman, and BarneSi 

 (1964), and an annotated bibliography on the area 

 influenced by the Columbia River discharge was 



504 



U.S. FISH AND WILDLIFE SBRVICOB 



