GRIMES and HUNTSMAN: REPRODUCTIVE BIOLOGY OF THE VERMILION SNAPPER 



o 

 z 



, Males 

 I Females 



8 

 6- 



4 

 2 



O 4 

 « 2 



May 



1972 



" ii 



. '\ •°. 



June 



t 



10.3 



July 



° 3 O O I ° 



. August 



September 



300 400 500 600 300 



TOTAL LENGTH (mm) 



400 



500 



600 



Figure 3. — Individual gonad index (gonad weight/( total length)^) values for vermilion snapper over the spawTiing months of 1972 and 



1973 plotted against total length. 



precocious individuals may mature in their second 

 year (100-186 mm TL) at about 150 mm TL. We 

 determined age and size at maturity by examining 

 a plot of monthly mean gonad index of females 

 collected in the spawning season (June- 

 September) by total length (Figure 4). Further- 

 more, spawning season (April-September) gonad 

 index values for males and females (Figure 3) and 

 monthly mean gonad index for each age-group of 

 fish (Figure 5) show that fish age 4-9 0324 mm 

 TL) ripen earlier (April or May vs. June) and re- 

 mained in reproductive condition longer (April to 

 September vs. June to August) than younger 

 spawning fish. 



Sex Ratio 



Sex ratio varies significantly from 1:1. From 

 1972 to 1974 we sexed 874 fish; 546 (62.5%) were 

 females and 328 (37.5%) were males (1 df; x^ = 

 54.4; P<0. 001). The total sample was analyzed by 



YEARS OF LIFE 



-4—1 5 1- 



-7*8 — 1-9-|-10-| 



138 163 186 213 238 263 288 313 338 363 388 413 438 463 488 513 538 563 588 

 25mm TOTAL LENGTH INTERVAL 



Figure 4.— Mean gonad index plotted by 25 mm TL intervals for 

 female vermilion snapper during the spawning season (June- 

 August). Approximate size at age was determined from Grimes 

 (1978). 



year of collection and sex ratios were judged sig- 

 nificantly different from 1:1 in all years (Table 3). 

 Higher proportions of females (62.5%) were col- 



141 



