McGOWAN: SPAWNING OF NORTHERN ANCHOVY 



EGGS 

 10000- 



9000 



8000 



7000 



6000-- 



5000 



4000 



3000 



2000 



Figure 3.— Relative abundances of northern -|000 

 anchovy eggs and larvae at each station show- 

 ing the difference between station 3 and the q 

 other stations. 



LARVAE 

 1000 



900 



MEAN CATCH EGGS AND LARVAE 

 AT EACH STATION 



NUMBERS ARE PER 1000 METERS CUBED 



 LARVAE 



-I 1 1 i 1 



2 3 4 5 6 



STATION 



0.01 with 5 degrees of freedom). Station 3 deviated 

 most from the expected ratio. Station 1 also differed 

 by having relatively fewer larvae than expected. 



Zooplankton 



Zooplankton catch varied from 13.6-9,560 indivi- 

 duals/m 3 . Mean catch was 1,170/m 3 . No seasonal 

 pattern was apparent (Fig. 2). There was a gradual 

 increase in zooplankton abundance over the course 

 of the study. This linear trend was significant (P < 

 0.01). Copepods, especially A cartia spp., dominated 



the catches (Table 3). Brachyuran (crab) zooeae and 

 cirrepedian (barnacle) nauplii and cyprids were occa- 

 sionally abundant. Potential predators on northern 

 anchovy larvae, such as chaetognaths and pontellid 

 copepods, were often present but in relatively low 

 numbers. Counts of zooplankton for each sample are 

 reported in McGowan (unpublished M. A. Thesis, San 

 Francisco State University, San Francisco, CA). 

 Zooplankton catch was significantly correlated 

 with all variables except surface salinity and salin- 

 ity stratification. Negative correlations were ob- 

 served with egg density, surface temperature, 

 temperature stratification, and Secchi depth. Posi- 

 tive correlations were found with larvae and 

 microzooplankton . 



Microzooplankton 



Microzooplankton catch at the surface (0.080 mm 

 mesh net) varied from 1 to 300 per liter (mean = 

 28.8). No clear seasonal trend was apparent (Fig. 

 2). Copepod nauplii were the most abundant micro- 

 zooplankton followed by tintinnids and rotifers 

 (Table 4). Dinoflagellates such as Ceratium and 

 Peridinium were occasionally more abundant than 

 copepod nauplii. The spiny, armored Ceratium 

 species were not included in the density estimates 

 because northern anchovy larvae prefer unarmored 

 forms (Scura and Jerde 1977). Microzooplankton 

 density was negatively correlated with Secchi disk 

 depth (r = -0.34, P = 0.004) and positively corre- 



885 



