Table 2. — Number of female Gulf menhaden sampled from 

 October 1976 to February 1977 by fork length, month, and stage 

 of sexual maturity (immature or mature). 



Oct 



Nov, 



Dec. 



Fork 

 length 

 (mm) 



Imma- Ma- 

 ture' ture 



Imma- Ma- 

 ture ture 



Imma- Ma- 

 ture ture 



Jan. 



Ma- 

 ture 



Feb. 



Ma- 

 ture 



120-129 

 130-139 

 140-149 

 150-159 

 160-169 

 170-179 

 180-189 

 190-199 

 200-209 

 210-219 

 220-229 

 230-239 

 240-249 

 250-259 



1 



15 



17 



20 



14 



3 



3 



1 



1 



3 

 8 



15 



15 



12 



11 



1 



1 



4 



1 



1 

 6 

 10 

 2 

 2 

 3 

 1 

 2 

 5 

 1 

 1 



' Fish with intermed late ova (as the largest ova present) were included in this 

 category. 



1). For both aged and unaged fish >140 mm that we 

 examined, 73% contained maturing ova in Oc- 

 tober, 91% in November, 55% in December, and 

 100% in January and February (Table 2). From 

 this information we concluded that Gulf menha- 

 den spawn for the first time at age 1, after they 

 have completed two seasons of growth, and then 

 continue to spawn each year thereafter. 



< 

 z 

 o 

 o 



>- 

 O 

 O 

 m 



< 



UJ 



.11 

 .10 

 .09 

 .08 

 .07 



" 



.061- 

 .05 

 .04 

 .03 

 .02 

 .01 

 



Age 1 FEMALES 



, Age 2 



Age 3 



, Aged and Unaged Fish 

 Combined 



j- 



-L 



\ X 



_L 



OCT NOV DEC JAN FEB 



1976 1977 



Figure l. — Relation between mean of gonad weight/body 

 weight and month for unaged and different age-groups of female 

 Gulf menhaden. 



Time and Frequency of Spawning 



Previous studies of egg and larva collections 

 (Turner 1969; Fore 1970; Christmas and Waller 

 footnote 2) and of increases in gonad weights 

 (Suttkus and Sundararaj 1961; Combs 1969) have 

 indicated that spawning begins in October and 

 ends about March. Our data also show that spawn- 

 ing occurs within this time period. For each month 

 we plotted the mean gonad weight as a percentage 

 of body weight for those fish we were able to age 

 (Figure 1). For females the means, which were 

 already high in October, indicating that gonadal 

 development had begun, increased in November 

 and December and then decreased in January and 

 February. Generally, males followed the same pat- 

 tern as females when both aged and unaged were 

 combined (Figure 2). We can not explain why the 

 relative gonad weights of age-1 females were 

 higher than those of older fish, unless some of the 

 older fish had partially spawned by the time they 

 were collected, thereby decreasing their gonad 

 weight. 



The number of times an individual fish will 

 spawn during a season may be inferred from the 

 difference in size between groups of ova. If there is 



a 



< 

 z 

 o 



CD 



> 

 O 



O 



CQ 



Z 

 < 

 UJ 



.11 



.10 

 .09 

 .08 

 .07 

 .06 

 .05 

 .04 

 .03 

 .02 

 .011- 

 



Age 1 



Age 2 MALES 



Age 3 



. Aged and Unaged Fish 



Combined 



j- 



OCT NOV 

 1976 



DEC 



J_ 



_L 



JAN FEB 

 1977 



FIGURE 2. — Relation between mean of gonad weight/body 

 weight and month for unaged and different age-groups of male 

 Gulf menhaden. 



949 



