MERRINER: REPRODUCTIVE BIOLOGY OF THE WEAKFISH 

 3.00-1 



2.50 

 2.00 H 

 1.50 

 1.00 

 0.50 

 0.00 H 



MALES 

 n= I I 7 



S 900 n 



a 



< 



8.00- 

 7.00- 



8 6.00- 



5.00- 

 4.00- 

 3.00- 

 2.00- 

 1.00- 

 0.00- 



FEMALES 

 n= 577 



-I— 

 M 



-I— 

 A 



-I— 

 M 



n r 



J J 



MONTH 



-r- 

 A 



-I [— 



N 



-1 

 D 



Figure 2. — Mean monthly gonad index for male and female 

 weakfish of all age-classes expressed as percent body weight. 



and females were in spawning condition from 

 March through September. 



Age weakfish (no scale annulus) exhibited a 

 seasonal gonad index pattern similar to that of 

 older fish. The peak index values for age 

 females occurred in June, a month later than age 

 I females (Figure 3). Gonads of age females ac- 

 counted for only 4% of the total body weight 

 whereas they represented over 8% of body weight 

 in age I females. 



Over one-half of the age weakfish collected 

 were classified as mature (Table 4). Of the 201 

 age females, 105 or 52% were mature. Of the 



Table 4. — Number of immature and mature age-group 

 weakfish from North Carolina by month. 



4.0 

 3.0 H 

 ^ 2.0 



s« 



■^ 1.0 



X 



'H 0.0 



AGE-CLASS 

 n=52 



o 



< 8.0 



O 



^ 6.0 4 



4.0 



2.0 

 



AGE-CLASS I 

 n=3l8 



M 



A M J J 

 MONTH 



A S N 



Figure 3. — Mean monthly gonad index for female weakfish 

 of age-class and I expressed as percent body weight. 



263 age males, 163 or 62% were mature. Dele- 

 tion of obvious young of the year fish collected 

 after 3 to 4 mo growth elevated the percent ma- 

 ture to 91 for males and 68 for females in age- 

 group 0. 



Male weakfish attain sexual maturity at a 

 smaller size than do female weakfish and both 

 sexes attain sexual maturity at smaller size in 

 the vicinity of Morehead City than in Pamlico 

 Sound (Table 5). The standard length range in 

 which 50% of the weakfish were classified as ma- 

 ture, ripe, or ripe running was considered the size 

 at which sexual maturity is attained. Weakfish 

 less than 100 mm SL were not sexually mature in 

 either area. Males from the Morehead City area 

 reached the 50% criterion at about 130 mm SL (n 

 = 1). Male weakfish from Pamlico Sound fulfill 

 the criterion for population maturity at about 150 

 mm SL (n = 13, 61% mature). Female weakfish 

 fi-om the Morehead City area attain maturity at 

 about 145 mm SL (n = 11, 54% mature), while 

 female weakfish from the Pamlico Sound area at- 

 tain sexual maturity at about 190 mm SL {n = 28, 

 57% mature). 



Size of the individual fish rather than age is the 

 dominant factor affecting the attainment of sex- 

 ual maturity by weakfish. In the vicinity of 

 Morehead City, male weakfish of age-group I but 

 less than 170 mm SL were mature (n = 12, 1 

 immature) (Table 6). All age II male weakfish 

 examined from that area were mature (n = 26). 

 Females of 175 mm SL or larger from the same 

 area with no annulus on their scales were ma- 

 ture. There was only one immature fish among 



21 



