only on sandy bottoms within this food-rich 

 area of intense upwelling, from the 4-m contour 

 out to about the 75-m contour (about 10 nautical 

 miles offshore). The fishery is usually confined 

 to less than 50-m depth (Waldron, 1958). If 

 crabs are dependent upon food produced in the 

 pelagic environment, their survival and thus 

 their fishery may be influenced by annual varia- 

 tions in upwelling and food production. 



Materials and Methods 



Bakun (in press) has generated quantitative 

 indices of upwelling based upon monthly mean 

 wind stress on the sea surface at points near 

 the coast. The indices are calculated for each 3° 

 of latitude ranging from Baja California (lat. 

 18°N) to the Gulf of Alaska (lat. 60°N). 

 Knowing wind stress one can compute the ex- 

 pected offshore Ekman transport and resolve 

 the component of Ekman transport perpendicu- 

 lar to the coast. Bakun's data are derived from 

 analyses of monthly mean atmospheric pres- 

 sure fields, rather than from numerous but gen- 

 erally spotty direct wind observations. For an 

 explanation of the methods used to convert 

 pressure fields into geostrophic wind fields, 

 see Bakun (in press). 



The magnitude of the offshore component 

 of the Ekman transport is considered by Bakun 

 to be an index of the amount of water upwelled 

 to replace that driven offshore. Negative values 

 of the index are possible and indicate net on- 

 shore transport of water (downwelling) for that 

 particular month. Negative values occur only 

 during the winter months. A low positive value 

 would indicate either weak offshore transport 

 or alternating periods of upwelling and down- 

 welling within that particular month. Positive 

 values occur during summer months, and some 

 spring and fall months. Maximum positive 

 values (i.e., most intense upwelling) occur in 

 July at all points north of San Francisco. I will 

 refer to the upwelling season as the summer up- 

 welling season since monthly indices are highest 

 in June, July, and August. 



Data on total pounds of Dungeness crab 

 landed in Oregon and Washington were taken 

 from the annual reports of the Pacific Marine 

 Fisheries Commission (1959-70). The pre-1959 



data were read from graphs in the same reports. 

 Northern California data were taken from an- 

 nual reports of the California Department of 

 Fish and Game (1948-70). Data for 1970-71 and 

 1971-72 seasons were obtained from C. Dale 

 Snow, Oregon Fish Commission (pers. comm.). 



Monthly upwelling index data were summed 

 for those months representing the upwelling 

 season (as defined by Bakun) at the selected 

 latitudes. These months are the only ones which 

 may have positive values of the index. In some 

 years, negative values occurred during certain 

 spring and autumn months. Nevertheless these 

 negative values are included in the summed 

 upwelling season index. For Washington, up- 

 welling indices calculated for lat. 48°N, long. 

 125 °W were used. The May through September 

 values were summed, thus generating an up- 

 welling-season index. For Oregon, indices for 

 lat. 45 °N, long. 125° W were summed over 

 April through September. For northern Cali- 

 fornia, indices calculated for lat. 42 °N, long. 

 125 °W were summed over March through Sep- 

 tember. Only the California data representing 

 the Eureka region will be considered here be- 

 cause the San Francisco region crab fishery has 

 apparently collapsed since the 1961-62 season, 

 as will be shown later. 



Although upwelling index data are available 

 for as early as 1946, west coast crab data for 

 only as early as 1948-49 are considered because 

 of the nature of the Oregon data. Until the 

 1948-49 season, both males and females could 

 be harvested in Oregon, at 6-inch carapace 

 width. Since then, only males of 6V4-inch cara- 

 pace width have been legal. Therefore to make 

 all data sets comparable, the 1948-49 season 

 was chosen as the starting point. 



Results 



Figure 1 is a plot of crab catches in Washing- 

 ton. Oregon, and the Eureka and San Francisco 

 regions of California. Since 1954-55, seasonal 

 catch trends are quite similar for all three states. 

 In each state, a trend of declining catches over 

 the seven seasons from 1957-58 until 1963-64 

 is apparent, with the exception of high catches 

 in northern California from 1958-59 through 

 1960-61, and in Oregon for 1959-60 and 1960-61 



904 



