FISHERY BULLETIN: VOL. 84, NO. 3 



The proportion of females classified as stage 1, 

 virgin individuals, is at a minimum during the 

 spawning season, comprising <10% of the females 

 sampled during February, March, and April. How- 

 ever, during the summer more than half of the 

 females were classified as stage 1 (Fig. 3A). Stage 

 2 females, maturing virgins and recovering spents, 

 are at a minimum in August (when most females are 

 classified as stage 1). From September until January 

 between 40 and 60% of the females are classified 

 as stage 2. During the spawning season, and just 

 after, the percentage of stage 2 females dropped 

 between 30 and 40%. The August to September 

 decline in the percentage of stage 1 females is 

 primarily caused by the sharp increase in the pro- 

 portion of stage 2 females. Thus, the combined per- 

 centage of stages 1 and 2 females is probably a 

 reasonable inverse indicator of the seasonality of 

 spawning. However, during the spawning season an 

 unknown proportion of those classified as stages 1 

 and 2 are females that have recently spawned and 

 are between multiple spawnings. 



Stage 3 females (ovary enlarged, occupying about 

 half of the length of the ventral cavity) have a con- 

 siderably different pattern. There is a gradual in- 

 crease from about 5% in August to about 30% in 

 January. This percentage is maintained until April, 

 i.e., through the spawning season; it then drops to 

 about 5% in June. The monthly percentages of the 

 higher maturity stages (4,5, and 6) clearly delineate 

 the spawning season as primarily a January-May 



event (Fig. 3B). The relatively constant low level of 

 stage 7 females is unexpected as the maximum pro- 

 portion of spent fish would be expected to occur just 

 after the peak of spawning. 



Maturity Stage Relationships 

 with Size and Age 



To examine potential relationships between the 

 size and age of northern anchovy and the duration 

 and magnitude of maturity stages we calculated the 

 monthly percentages of grouped maturity stages for 

 four size classes (81-100, 101-120, 121-140, and 

 141-160 mm SL) and four age groups (1, 2, 3, and 

 4 + ). Age group 1 includes fish prior to and after 

 their first potential spawning season (i.e., young-of- 

 the-year fish in July through the following June). 

 Age group 4 + includes fish in their fourth and sub- 

 sequent spawning seasons. The grouped maturity 

 stages (1, 2, 3, and 4-7) are the same as those pre- 

 sented earlier. 



Size has a large effect on both the duration and 

 magnitude of maturity stages in northern anchovy. 

 With the exception of those sampled from February 

 to April nearly all of the 81-100 mm SL females were 

 classified as immature or resting (Fig. 4A). In addi- 

 tion, the majority of this size anchovy have gonads 

 too small to determine their sex without magnifica- 

 tion (Table 2). As the size class increases the per- 

 centage of stages 1 and 2 decreases; this occurs in 

 all months; however, the minimum percentage of 



90- 



80- 



70 



& 60 



§ 50H 

 p 



40- 



30- 



20- 



10 



STAGE 1 



/ \ STAGE 2 



\ 



.• J N 



/» ' '■ 





\ 





t 

 STAGE 3 -••.-■ 



—1—1 1 1 1 1 t ' 1 » 



/ \ 



— V 

 JUL HUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN 



MONTH 



-i 1 ■! 7 *-' i 



JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN 



MONTH 



Figure 3.— The monthly percentages of individual maturity stages for female northern anchovies. A. Stages 1-3. B. Stages 4-7. 

 508 



