FISHERY BULLETIN: VOL. 83, NO. 4 



age composition of anchovies taken by the Sea 

 Survey Program is very close to that taken by the 

 fishery; conversely, the age composition of the 

 fishery is unlike that taken in areas < 50 fathoms 

 (Fig. 7). The California fishery no longer has a 5-in 

 size limit; however, the closure of the nearshore area 

 appears to be the dominant factor in reducing the 

 catch of young anchovies. 



1 



2 3 4 

 AGE 



5 6+ 



Figure 7.— Comparison of the age com- 

 position of northern anchovies taken in 

 the San Pedro purse seine fishery with 

 those taken in areas with <50 fathoms 

 and >50 fathoms of water in the mid- 

 water trawl Sea Survey Program. 



DISCUSSION 



Our data show that the growth rate and the age 

 composition of northern anchovies vary geographi- 

 cally. The greatest differences in growth appear to 

 occur during the juvenile stage; growth in adults 

 shows much less regional variation. Juvenile growth 

 is greatest in central California and in the offshore 

 areas of the Southern California Bight. In the in- 

 shore regions there is a trend toward reduced 

 juvenile growth from central California to southern 

 Baja California. Average size at age IV2 falls from 

 123.6 mm to 91.8 mm over this area. Growth in adult 

 anchovies appears to be the greatest in northern 

 California, and it is also relatively high in British 

 Columbia (Pike 1951), central California, and north- 

 ern Baja California. Adult growth appears to be 

 relatively low in the Southern California Bight; this, 

 however, may be an artifact as this area probably in- 

 cludes resident fish plus slower growing fish which 

 have moved into this region from the south. Age com- 

 position showed a large variation among regions, and 

 the pattern of this variation appears to be closely 

 related to the gyral circulation within the Southern 



California Bight. There is also a strong relationship 

 in age composition to the depth of water at trawl 

 sites. Adult anchovies dominated the catches in the 

 offshore, deepwater regions of the Southern Califor- 

 nia Bight and in central California. Age also had a 

 strong latitudinal gradient with adult fish domi- 

 nating in the north and young-of-the-year and year- 

 ling fish dominating in the shallow water areas off 

 central and northern Baja California. Adult an- 

 chovies appear to be concentrated in areas of the 

 Bight where prevailing currents will result in 

 southerly and inshore larval transport (Parrish et al. 

 1981). At recruitment, anchovies appear to be heavily 

 concentrated in shallow water, and young fish ap- 

 pear to be concentrated in the nearshore area where 

 they will tend to be advected northward by the 

 southern California gyra 



As vidll be discussed later, the interpretation of the 

 regional differences in juvenile growth is dependent 

 upon the stock structure in the various regions. 

 Earlier studies (McHugh 1951; Vrooman et al. 1981) 

 showed that the boundary between the southern and 

 central stocks was in the northern Sebastian Vis- 

 caino Bay area. This is supported by the present 

 study, and, as previously mentioned, the boundary 

 is further north in the summer and fall and further 

 south in winter and spring. We feel that there is am- 

 ple evidence that the southern stock had the smallest 

 juvenile growth rate and that growth during the 

 adult phase is minor. Vrooman et al. (1981) suggested 

 that the boundary between the northern and cen- 

 tral stocks occurs in the central California area; both 

 northern and central stocks occurred in samples 

 taken at San Francisco (lat. 37°50'N) and Monterey 

 (lat. 36°50'N). Their data might be interpreted to 

 suggest that a fourth stock occurred in the San Fran- 

 cisco and Monterey samples, and in addition it has 

 been suggested (Parrish footnote 3) that this fourth 

 stock spawns during the fall in central California and 

 the offshore areas of the Southern California Bight. 

 Unfortunately the Vrooman et al. (1981) study did 

 not have any samples from the region between 

 Monterey (lat. 36°50'N) and Newport (lat. 33°30'N), 

 nor were there any samples from the offshore areas 

 of the Southern California Bight. It is therefore not 

 presently possible to determine the amount of stock 

 mixture over much of the accepted range of the cen- 

 tral stock. 



Variation in juvenile growth of northern anchovies 

 in the different regions may be due to genetic fac- 

 tors, differences in the seasonality of spawning, or 

 environmental factors. The northern stock has a 

 relatively short spawning season with a strong peak 

 in July (Richardson 1980). The central stock has a 



494 



