OCEANOGRAPHIC CONDITIONS IN THE NORTHEAST PACIFIC 

 AND THEIR RELATION TO THE ALBACORE FISHERY 



OCEAN 



By ROBERT W. OWEN, JR., Oceanographer, Fishery- Oceanography Center, Bureau of Commercial Fisheries, 



La Jolla, CaUfornia 92037 



ABSTRACT 



This paper describes initial environmental conditions 

 8ncountered by albacore, Thunnus alalunga (Bonna- 

 terre), in their annual entry to the region off the north- 

 west coast of the United States, describes the physical 

 mechanisms that produce these conditions, and indi- 

 cates their influence on the highly variable number of 

 ilbacore available to the fishery. The region studied 

 extends from the coast of Oregon and Washington to 

 long. 132° W. between lats. 41° N. and 48° N., within 

 which the northernmost part of the American coastal 

 fishery for albacore usually has been confined. 



Upwelling, effects of runoff from land, and the excess 

 of precipitation over evaporation produce annually 

 recurrent patterns of distribution of variables. This 

 recurrent aspect is used to distinguish three spatial 

 provinces above and two provinces below the main 

 halocline, each of which reflects the balance of processes 

 affecting it. Variations in the distributions of variables 

 from year to year are shown to be attributable to 



changes in wind field, in fresh-water discharge from 

 land, and in advection. These variations do not, how- 

 ever, obscure the basic patterns generated by dominant 

 processes. 



The distribution of available albacore over the study 

 area is inferred to be sensitive to spatial and year-to- 

 year differences in temperature and in salinity. Higher 

 temperatures, produced by greater retention of heat 

 in the surface layer of the province dominated by effects 

 of land runoff, may give rise to greater concentrations 

 of albacore in this province. Salinity, to which temper- 

 ature is inversely related, may control the degree to 

 which spatial temperature differences can be effective, 

 possibly by its influence on osmotic pressure. V future 

 investigation confirms this hypothesis, success of the 

 fishery will be predictable from preseason information 

 on wind field, geostrophic flow, and Columbia River 

 discharge. 



The yield of the seasonal fishery for albacore 

 {Thunnus alalunga) off Oregon and Washington 

 is characteristically variable. Within the period 

 1951-64, annual landings in these States ranged 

 from 0.6 to 13.5 million pounds. Nearly all alba- 

 core landed in Oregon and Washington in 1954 

 and 1955 were caught south of lat. 40° N.; con- 

 sequently, the northern fishery was considered 

 to have failed completely in these years. 



The region off the Oregon-Washington coast 

 usually represents the northernmost end of the 

 range within which commercially harvestable 

 concentrations of albacore have been found 

 along the North American coast. The fishery 

 spans a shorter time interval than that to the 

 south, perhaps because environmental conditions 

 are tolerable to albacore for a shorter time. 

 Fishing usually begins there in mid-July, attains 

 a maximum effort and catch in late August and 

 September, and largely ends by the end of Octo- 

 ber. The California fishery, by contrast, often 

 starts a month earlier and ends a month later. 

 Moreover, fishing intensity off Oregon and Wash- 

 ington is more sensitive to weather, to the price 



Published March 1968. 

 FISHERY BULLETIN: VOLUME 66, NO. 3 



of albacore, and to diversion from tuna trolling 

 to salmon fishing and bottom fishing than off 

 California. Variation in the yield of albacore 

 from the Oregon-Washington fishery cannot be 

 assigned solely, however, to variation in fishing 

 intensity, because the yield also depends on the 

 fluctuations in availability of albacore in the 

 region. 



The number of fish available to a fishery at a 

 particular time is often a complex function of 

 abundance and behavior, both of which may be 

 markedly affected by the environment. Influence 

 of the environment upon albacore off Oregon and 

 Washington has been detectable only through 

 relations of sea temperatures to landings of the 

 commercial fishery (Johnson, 1962) and to catches 

 by Bureau vessels (Alverson, 1961). Water clarity, 

 which varies largely with the concentration of 

 particulate matter, also has been thought to affect 

 albacore availability (Murphy, 1959) ; to date, 

 however, this hypothesis has not been tested off 

 the Oregon-Washington coast. Powell and HUde- 

 brand (1950) noted a relationship of tuna catches 

 with observed ocean conditions; albacore were 



503 



319-171 O - 68 - 5 



