LAROCHE and RICHARDSON: REPRODUCTION OF NORTHERN ANCHOVY 



determined period of time after spawning (Figure 

 5). Similarly shaped oocyte size distributions were 

 used as indirect evidence of a single seasonal 

 spawning in the Hawaiian anchovy, Stolephorus 

 purpureas (Leary et al. 1975), the anchoveta, 

 Cetengraulis mysticetus (Howard and Landa 

 1958), and the Pacific and jack mackerels, Scomber 

 japonicus and Trachurus symmetricus (Mac- 

 Gregor 1976). 



A secondary batch of oocytes, numerically equal 

 to the group of hydrated oocytes about to be 

 spawned was not found in stage 10 fish. The 

 number of intermediate-sized, 0.46-0.62 mm, 

 yolked oocytes, the next most advanced oocytes in 

 ovaries of all stage 10 fish, was 427 oocytes/g 

 ovary -free body weight (mean of three subsam- 

 ples) in a 154 mm SL, stage 10 anchovy. This value, 

 expressed as an estimate of relative fecundity, was 

 about one-half the value of mean relative fecun- 

 dity often stage 10 fish (Table 6) and lay outside 

 the range of all 21 individual fecundity estimates 

 (Table 5). 



DISCUSSION 



Length and Age at First Maturity 



Published reports of size and age at first matur- 

 ity of anchovies in the central subpopulation are 

 somewhat conflicting. Clark and Phillips (1952) 

 found that only 30% of the fish in the size range 

 100-120 mm SL (ages I and II) were mature and 

 only 50% in the size range 120-139 mm SL (ages II 

 and III) were mature. Yet Huppert et al. (footnote 

 3) reported a recent study that found all northern 

 anchovies older than 24 mo, —120 mm SL, to be 

 mature. 



Sexual maturity is also attained in nothern an- 

 chovies of the northern subpopulation at the end of 

 the second year. Pike (1951) found that 96% of the 

 northern anchovies in the size range 105-109 mm 

 SL (age II fish), from commercial catches, were 

 mature while only 14% of the fish ranging from 100 

 to 104 mm SL (<2 yr old) were mature. Northern 

 anchovies off Oregon similarly do not attain sex- 

 ual maturity until after the second year (i.e., in the 

 third summer). The smallest northern anchovies 

 taken in this study in spawning condition were 104 

 mm SL (male) and 107 mm SL (female). Size at 

 maturity seems to be somewhat smaller in the 

 northern subpopulation, possibly reflecting dif- 

 ferences in growth rates between the two subpopu- 

 lations. 



Sex Ratio 



It appears that the overall sex ratio in both the 

 central and northern subpopulations is —1:1. 

 Klingbeil (1978) reported that the overall male to 

 female ratio of northern anchovies from sea sur- 

 vey samples off California combined for the years 

 1966-75 was 0.97:1. Monthly sex ratios in commer- 

 cial catches from February to August off British 

 Columbia were approximately 1:1 with females 

 slightly outnumbering males (0.77:1 the lowest 

 ratio) (Pike 1951). The male to female ratio of both 

 mature and immature anchovies off Oregon before 

 the spawning season (May) and immature fish 

 during and after the spawning (July and October) 

 was also about 1:1. 



Yet samples from both central and northern 

 subpopulations were found with unexpectedly 

 higher numbers of either males or females. 

 Klingbeil (1978) suggested that adult northern 

 anchovies may often be segregated by sex. al- 

 though no seasonal trends could be discerned in 

 their data. Hunter and Goldberg (1980) found that 

 in trawl collections of northern anchovies off 

 California dominated by males, 40% of the females 

 had spawned on the night of capture. But in female 

 dominated collections only about 10% of the 

 females had spawned the night of capture. They 

 suggested that changing sex ratios in northern 

 anchovy schools may be associated with reproduc- 

 tive behavior. The overall male to female ratio of 

 mature fish caught in July in areas of active 

 spawning off Oregon and Washington was 2.6:1, 

 with sex ratios in individual catches ranging from 

 1:1 to 8:1. The highest male to female ratios were 

 also associated with catches containing high 

 numbers of ripe females which were or soon would 

 be spawning. The percent of these ripe females in 

 male dominated schools off Oregon and Washing- 

 ton ranged from 33 to 40% and was similar to the 

 percent of most recently spawned females in male 

 dominated schools off California (Hunter and 

 Goldberg 1980). Pike ( 1951) found that the relative 

 number of male anchovies increased as the spawn- 

 ing season approached and in July males slightly 

 outnumbered females. But by August, at the end 

 of the spawning season, the male to female ratio 

 was 0.71:1. 



Fecundity 



The only previous estimate of northern anchovy 

 fecundity in the northern subpopulation. 



613 



