FISHERY BULLETIN: VOL. 78, NO. 4 



128° 127° 



-1 — I — I — I — I — I — ' 



126° 



45" 



43° — • 



42' 



128° 



127° 



126° 



_1 I i L 



Big Lagoon 



North of Trinidad, CA 



Figure 6. — Returns of surface drifters released at the sampling 

 stations off Oregon and Washington during the July 1976 

 ichthyoplankton survey and returned by 21 August of that year 

 Lines represent drift paths from release point ( sampling station) 

 to return location. Depth contour is 183 m. 



Table 2. — Summary of collection data on Engraulis mordax 

 eggs and larvae off the Oregon-Washington coast from ichthyo- 

 plankton surveys conducted in 1975 and 1976. Seventy stations 

 were occupied on each survey. 



Item 



10-18 July 

 1975 



7-15 July 

 1976 



No, positive stations 



Eggs 



Larvae 



Eggs or larvae 



Eggs and larvae 



Mean no. eggs/10 m^ 

 All stations 

 Positive stations 



Mean no, larvae/10 m^ 

 All stations 

 Positive stations 



that eggs were taken was 194 km and few were 

 found beyond 157 km. All eggs were taken at sta- 

 tions where surface temperatures were >14° C. 

 Mean temperature at 3 m depth at positive sta- 

 tions was 15.18° and 16.09° C and mean salinity 

 was 30.69 and 30.07 Z. in 1975 and 1976. Egg con- 

 centrations did not correlate with high surface 

 chlorophyll levels and greatest concentrations 

 were in regions of low plankton volumes. Al- 

 though bongo samples were taken only at trawl 

 stations during the acoustic survey in 1977 ( Figure 

 5) catch trends of eggs were similar to the previous 

 two surveys (Methot' ). Northern anchovy eggs 

 were taken only on the four northern transects in 

 concentrations up to 11,165 under 10 m^ sea sur- 

 face. 



Northern anchovy larvae were more widely dis- 

 persed than northern anchovy eggs with 33 and 40 

 positive stations in 1975 and 1976 (Figures 3, 4; 

 Table 2). Thirty-eight and 45 stations had either 

 eggs or larvae in 1975 and 1976 and 12 and 18 

 stations had both, respectively. In 1975, highest 

 numbers of larvae, >1,000 under 10 m^ sea surface, 

 were found 120 km offshore, near and south of the 

 highest egg concentrations. In 1976, greatest larva 

 concentrations occurred 83 and 120 km offshore 

 between the Nehalem River and Cascade Head, 

 Oreg.; 194 km off Cape Perpetua; and 120 km off 

 Cape Blanco, Oreg. Overall mean abundance was 

 115 and 278 under 10 m^ sea surface in 1975 and 

 1976, and 487 and 245 under 10 m^ at positive 

 stations. In 1975 larvae occurred mainly in a cor- 

 ridor paralleling the coast beyond the continental 

 shelf while in 1976 they were more widely distrib- 

 uted and also occurred closer to the coast. The 

 sampling grid apparently bordered their center of 

 abundance to the north and offshore but not to the 

 south. As with the eggs, larvae were generally not 

 found in regions of active upwelling. Mean length 

 of larvae on each transect in 1975 increased pro- 

 gressively from 3.0 mm in the north to 11.2 mm in 

 the south, evidence of drift south from the spawn- 

 ing center based on egg distributions and seasonal 

 flow patterns. In 1976 mean length of larvae per 

 transect increased from 4.5 mm off the Nehalem 

 River to 7.0 mm off Cape Blanco but the trend was 

 not as pronounced as in July 1975. This reduced 

 trend may be partly a result of decreased north- 

 erly winds, evidenced by reduced upwelling, and 

 reduced southward transport compared to 1975. 



'2R. D. Methot, Scripps Institution of Oceanography, Graduate 

 Department. La Jolla, CA 92093, unpubl. data. 



866 



