POWER: MODEL OF NORTHERN ANCHOVY DRIFT 



using the California Cooperative Oceanic Fisheries 

 Investigation (CalCOFI) coordinate system. The 

 CalCOFI grid is a regular coordinate system of 

 cross-shore "lines" and alongshore "stations". The 

 model and CalCOFI grids are oriented with respect 

 to the coast so that increasing station number 

 corresponds to increasing offshore distance and in- 

 creasing line number implies the downshore (south- 

 easterly) direction. Each line unit increment is 

 spaced 12 nm apart, and each station unit represents 

 4 nm. The grid for the model was defined to form 

 cells that were 37 km (20 nm) on a side, and the 

 fluxes of larvae were among grid ceil centers. Model 

 coverage was from CalCOFI lines 70 to 120, and ex- 

 tended offshore to CalCOFI station 120 (Fig. 1). 

 Unless northern anchovy utilize a strategy where- 

 by spawning is initiated in response to the presence 

 of an eddy or other short-term mesoscale features, 

 it can reasonably be expected that spawning time 



and location have evolved partially in response to 

 predictable current features. For this reason, 

 seasonal currents based on interannual means were 

 used in the model. Northern anchovy spawning 

 behavior relative to eddies, etc., is presently un- 

 known, and there are persistent seasonal trends in 

 spawning, e.g., northern anchovy spawn through- 

 out the year, but March is typically the peak time 

 of spawning (Smith 1972; Methot 1981). 



Geostrophic currents for the model were cal- 

 culated using the geopotential anomalies computed 

 by Lynn et al. (1982). Lynn et al. used CalCOFI data 

 collected between 1950 and 1978 to compute the 

 average geopotential anomaly relative to 500 m for 

 four seasonal periods (nominally January, April, 

 July, and October) at 175 locations in the Califor- 

 nia Current. Average geopotential anomalies were 

 computed for an additional 23 locations for this 

 study to augment the Lynn et al. (1982) coverage 



125 



120 



115 



35- 



125 



120 



115 



Figure 1.— Geographic grid used in the northern anchovy drift simulations, and the corresponding 

 CalCOFI line and station coordinate system. Lettered locations are starting points for simulation presented 

 in this paper. Mean geopotential anomolies (used for computing geostrophic currents) were calculated 

 for the locations indicated by dots (Lynn et al. 1982; this study). 



587 



