Growth During the Larval and Juvenile Stages of 

 the Northern Anchovy, Engraulis mordax, in the California 



Current During 1980-84 



John L. Butler 



ABSTRACT: Increment widths and back-calcu- 

 lated growth rates for northern anchovy, Engraulis 

 mordax, did not differ during the years 1980-84. 

 This evidence of stable lanal growth rates does not 

 support the theory that it is the variation in lar\'al 

 growth rates that directly affects the magnitude of 

 recruitment. Furthermore, since growth rates re- 

 mained stable, even though zooplankton volumes in 

 198.3 were well below the long-term mean, it follows 

 that suniving post-first-feeding larval anchovies 

 may not be food limited. 



The size of juvenile northern anchovy was re- 

 duced during the 1982-83 El Nino "phenomenon" in 

 the California Current. Mean lengths of anchovy 

 juveniles collected in the fall were greatest in 1980, 

 least in 1982, and intermediate in 1981, 1982, and 

 1984. Growth rates back calculated from otolith 

 increment widths did not differ significantly be- 

 tween the 1980 and 1983 cohort, until 100 days after 

 first feeding. Reduced growth after 100 days largely 

 determined the smaller size of 1983 anchovy juve- 

 niles. Condition factor was also reduced in the 1983 

 cohort. The 1982 cohort was not greatly affected, 

 because El Nino did not have a pronounced effect 

 off the North American coast until well after the 

 1982 northern anchovy spawning season. 



Through the years, the overall abundance of 

 many pelagic fishes varies with the strength of 

 individual year class; changes in mortality rates 

 early in life (Hjort 1914, 1926), rather than par- 

 ent stock size, may determine the size of individ- 

 ual year classes. Considerable controversy, how- 

 ever, surrounds details of the e.xact stage and 

 mechanism through which changes in individual 

 year-class strength occur. 



The co-occurrence of fish larvae and their food 

 is a mechanism that has been proposed to explain 

 variations in year-class strength (Hjort 1914, 

 1926). Lasker (1978) has shown that food avail- 

 ability may affect survival of fii'st-feeding north- 



John L. Butler, Southwest Fisheries Center, National 

 Marine Fisheries Service. NOAA, P.O. Bo.x 271, La Jolla, 

 CA 92038. 



ern anchovy, Engraulis mordax, larvae in the 

 sea. Food availability may not affect the survival 

 beyond the first-feeding stage; however, Methot 

 (1981) found that early larval anchovy growth 

 rates in the sea were the same as those of well- 

 fed, laboratory-reared larvae. Survival through 

 the larval stage does not determine the magni- 

 tude of the northern anchovy recruitment 

 (Peterman and Bradford 1986; Peterman et al. 

 1988). Thus food availability for larvae may not 

 determine the year-class strength and whether 

 food availability affects juvenile survival are yet 

 to be investigated. 



A simulation model of the northern anchovy 

 population indicates that the gi'owth rate of late 

 larvae and early juveniles may affect the magni- 

 tude of recruitment (Smith 1985). If mortality 

 rates in the marine environment are size-spe- 

 cific, as predicted by Peterson and Wroblewski 

 (1984), and if gi'owth rates determine the dura- 

 tion of the most vulnerable stages, reduced 

 gTovii;h should adversely affect survival. The ex- 

 tent to which gi'owth rates of late larvae and 

 juveniles vary is unknown. 



The growth rate of juveniles also affects adult 

 size. Off southern Baja California, the adult size 

 of northern anchovy is entirely determined by 

 juvenile growth, because these fish show no 

 growth after 18 months (Parrish et al. 1985). 

 Analysis of the regional patterns of gi'owth of 

 northern anchovy shows that the average length 

 of fish at a given age increases from south to 

 north. The length at 18 months ranges from 

 101.1 mm off southern Baja California to 126.6 

 mm off central California (Parrish et al. 1985). 



Because batch fecundity is a function of body 

 size in broadcast spawners, the juvenile and 

 adult gi'owth rates determine the reproductive 

 capacity over the adult lifespan. Competition 

 among juveniles for resources affects adult fer- 

 tility in other species (Prout and McChesney 

 1985), and, if growth of juvenile pelagic fishes is 

 food Hmited, competition among juveniles may 



Manuscript Accepted April 1989. 

 Fishery Bulletin, U.S. 87; 645-652. 



645 



