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 ANCHOVY LARVAE 



CALIFORNIA CURRENT 

 (SAUR INDEX 



lOm TEMPERATURE 



UPWELLING 



I I I I I I I 



OCT 



JAN 



APR 



JUL 



OCT 



JAN 



Figure 8. — Yearly cycle o( EngrauHs mordax larva abundance 

 and selected environmental parameters [mean annual cycles 

 (1953-60)] off California (reproduced from Lasker and Smith 

 1976). A) Larva abundance. B) California Current strength 

 indicated by sea level difference approximations (Saur 

 1972). C) Temperature at 10 m depth. D) Upwelling (Bakun 

 1973). Dashed lines indicate period of peak spawning between 

 January and April. Horizontal lines are for reference only. 



Oregon. Relatively little nearshore spawning 

 takes place in the coastal upwelling zone off Ore- 

 gon which is probably related to the low water 

 temperatures there during the spawning season. 

 Lasker (in press) demonstrated that upwelling 

 may disperse proper-sized food particles, mostly 

 dinoflagellates, and thereby reduce survival of 

 first feeding northern anchovy larvae. These di- 

 noflagellates are replaced by smaller diatoms 

 which are nutritionally inadequate for survival of 

 northern anchovy larvae. 



RELATIONSHIP WITH 

 COLUMBIA RIVER PLUME 



Data from this study and that by Richardson 

 (1973) provide evidence that a northern anchovy 

 spawning center within the northern subpopula- 

 tion is closely associated with the Columbia River 



100- 

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 40- 

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ANCHOVY 

 LARVAE 



GEOSTROPHIC 

 FLOW 



SURFACE 

 TEMPERATURE 



JFMAMJJASOND 



Figure 9. — Yearly cycle of Engraulis mordax abundance and 

 selected environmental parameters off Oregon. A) Larva 

 abundance in 1971-72 off Newport, Oreg. (Richardson text foot- 

 note 5) . B) Estimates of alongshore geostrophic flow between 28 

 and 46 km off Newport at the surface ( solid line) and 50 m ( dotted 

 line) after Huyer ( 1977). C) Monthly mean of surface tempera- 

 tures recorded in six 2° squares off Oregon and Washington ( lat. 

 42°-48° N; long. 124°-128° W) from 1947 to 1958 from Johnson 

 (1961). D) Mean monthly values of upwelling indices for the 

 20 yr period 1948-67 at lat. 45° N, long. 125° W from Bakun 

 (1973). Dashed lines indicate period of peak spawning. Hori- 

 zontal lines are for reference only. 



plume. Reasons for such an association may be 

 related to conditions necessary to induce or trigger 

 spawning in adults or conditions necessary for the 

 survival of the eggs and larvae. Increased river 

 flow and plume size, associated with snow melt 

 and day length, may provide a cue for the offshore 

 spawming migration of adults. Temperature may 

 not be a major factor in the association as both 

 oceanic and plume waters warm to temperatures 

 >13° C (Johnson 1961) needed for spavming, al- 

 though plume waters warm earlier (Owen 1968). 



872 



