FISHERY BULLETIN: VOL. 87, NO. 3, 1989 



cohort. Growth within cohorts varied most be- 

 tween 40 and 60 mm. 



In 1980 and 1983, northern anchovy growth in 

 weight increased rapidly at small sizes (Fig. 5). 

 Back-calculated growth rates for 1983 reached a 

 local maximum of 6.5 mg/d at about 40 mm and 

 then declined before slowly increasing to 7.5 

 mg/d at 79 mm. Back-calculated growth rates for 

 1980 showed a steady increase to about 11.5 

 mg/d at about 65 mm, which was maintained 

 until about 75 mm, after which growth declined. 

 The growth of northern anchovies hatched in 

 March 1983 peaked at an earlier time (about 

 June) in 1983 and at a smaller size (40 mm), 

 whereas the growth of anchovies hatched in 

 March 1980 peaked near the end of July 1980 and 

 at a larger size at (about 65 mm). 



geographic shifts in the population or to changes 

 in spawning date and samphng time in 1984. 



When size is adjusted for age and date of 

 spawning, growth of juvenile northern anchovy 

 was reduced in fish hatched in February through 

 April of 1984 compared with fish hatched in the 

 same months in 1980-82 (Fig. 1). This result is 

 consistent with the results from studies of other 

 fish populations on the west coast during El 

 Nino. Growth rates and condition factors were 

 also reduced in the Pacific herring, Clupea 

 harengus pallasi (Spratt 1987), the blue rock- 

 fish, Sebastes niystinus (Van Traskie"), and in 

 chinook, Onchorhynchus tshawytscha, and coho, 

 Oiichorhynchus kisidch, salmon (Pearcy and 

 Schoener 1987) during El Nino. 



Although the 1982-83 El Nino was fully devel- 



20 



10 - 



1980 



O 



cc 

 O 



U I I ^m^^ > . > • • 



40 50 



LENGTH (mm) 



Figure 5. — Mean back-calculated growth rates of northern anchovy 

 spawned in March 1980 and March 1983. Growth rate of mass in mg dry 

 weight per day. 



DISCUSSION 



Grovirth rates of late larval northern anchovy 

 did not vary in two otherwise extreme years, 

 1980 and 1983. Methot (1981) found httle vari- 

 ance in early larval growth in the sea. Smith 

 (1985) postulated that major changes in recruit- 

 ment would result from changes in growth rates 

 in the late larval period (10-35 mm) from 0.227 to 

 0.559 mm/d, a difference of 0.3 mm/d. In this 

 study, however, growth rates of the late larval 

 stage varied by <0.05 mm/d between 1980 and 

 1983. 



Northern anchovy juveniles grew less during 

 1983 and 1984, compared with the previous three 

 years. Fiedler et al. (1986) also reported reduced 

 growth of anchovy in 1983, but the mean size of 1 

 yr old fish indicated a dramatic recovery in 1984. 

 This apparent recovery may be in part due to 



oped by October 1982 along the coast of Peru, full 

 development of large scale warming off the North 

 American coast did not occur until January 1983 

 (Lynn 1983). Positive temperature anomalies 

 (>1°C) were evident both at the surface and at 

 depth throughout the California Current 

 (McGowan 1985; Norton et al. 1985). Negative 

 salinity anomalies associated with subsurface 

 temperature anomahes indicated intrusion of low 

 salinity water from the south and west into the 

 Southern Cahfornia Bight (Simpson 1983). 



These temperature anomalies represent a 

 large change in the heat content of the ocean but 

 are small relative to the thermal range of north- 

 ern anchovy. Thus the small size of juvenile 



^Van Traskie, D. 198.5. Growth of blue rockfish (Se- 

 bastes mystinus) during El Nifio. (Abstr. ) Calif. Coop. 

 Fish. Invest. Conf , Idyilwild, CA, Oct. 22-25, 1985. 



650 



