FISHERY BULLETIN: VOL. 75, NO. 4 



ticularly between November 1969 and May 1970 

 and between January and July 1971. Similarly to 

 NH 3, the importance of A. clausii is greatly re- 

 duced and the importance of A. longiremis and C. 

 marshallae are increased relative to NH 1. The 

 NH 10 plot follows the NH 5 plot closely during 

 1970 and 1971 with one exception: in September 

 1970 A. clausii was a significant component at NH 

 5 but not at NH 10. 



DISCUSSION 



The annual cycle in the species composition of 

 the zooplankton community along the Oregon 

 coast must result from the annual cycle of the 

 nearshore circulation, which is well described by 

 Huyer et al. (1975). There is an exact correspon- 

 dence between the sources of currents implied by 

 the direction of flow in each season and the geo- 

 graphic affinities of the species occurring in the 

 water. In summer, when the net water transport is 

 to the south, species with northern affinities 

 dominate. In winter, when transport is northward, 

 species with southern affinities are mixed with the 

 indigenous fauna. Abundances are about an order 

 of magnitude higher in summer than winter, pre- 

 sumably because of production stimulated by 

 coastal upwelling. We term the summer domi- 

 nants "indigenous" both because they are present 

 throughout the year and because they are the 

 forms which reproduce and complete their life cy- 

 cles in the Oregon nearshore zone. None of these 

 forms is endemic, however, in that the distribu- 

 tions of all of them extend north around the rim of 

 the Gulf of Alaska and into the Bering Sea. New 

 studies now in progress are intended to describe 

 the distributions within the upwelling ecosystem 

 of the life cycle stages of the summer dominants, 

 and to explain the maintenance of their popula- 

 tions within the system of nearshore currents. 



A similar interpretation of seasonal changes in 

 zooplankton species present off Oregon was of- 

 fered by Cross and Small ( 1967). They used Acar- 

 tia danae as an indicator of transport from the 

 south (following Frolander 1962), and Centro- 

 pages abdominalis (called C. mcmurrichi in their 

 paper) as an indicator of flow from the north. In the 

 present study A. danae was very infrequent, and a 

 variety of other species (Paracalanus parvus, 

 Ctenocalanus vanus, Clausocalanus pergens, etc.) 

 appear to be much better indicators of southern 

 sources. The studies were different in that the 

 earlier one sampled farther offshore, and it began 



with the notion that A. danae would be an indi- 

 cator, rather than examining the fauna as a whole. 

 While there is a generally similar sequence each 

 year in the changes of the copepod species and 

 their abundance, there are also marked differ- 

 ences in these changes between years. These were 

 discussed for the upwelling season by Peterson 

 and Miller (1975). We would like to add to that a 

 brief evaluation of some differences between the 

 winters of our study. Temperature-salinity dia- 

 grams including all of the data collected at our 

 inshore stations during the months of October 

 through March are shown in Figure 5. The winter 

 of 1969-70 was warmer than the other winters. 

 Progressive vector diagrams of the winds in each 

 of the winter periods of our study are shown in 

 Figure 6. The winds during 1969-70 were differ- 

 ent from those of 1970-71 and 1971-72. During 

 the fall and winter months of 1969-70 there were 



15 - 



*° ° »« 



10 



1969-70 



J I L 



25 



30 



35 



o 



LJ 



cr 



z> 



< 

 rr 



LU 

 Q_ 



UJ 



I 5 



1970-71 



°o°° 

 o 



o o 



orf> 



8 o 



25 



30 



35 



10 



% ° 



1971 -72 



j i 



J I I L. 



25 30 35 



SALINITY (%o) 



FIGURE 5. — Temperature-salinity scatter diagrams combining 

 data from stations NH 1, NH 3, NH 5, and NH 10 along the 

 Newport, Oreg., transect for the winters of 1969-70, 1970-71, 

 and 1971-72 from October through March. 



722 



