Allman and Grimes: Spawning, settlement, and growth of Lut/anus gnseus from tfie West Florida sfielf 



397 



n 1996 



2/20 3«1 4/20 5/20 6/19 7/19 8/18 9/17 



30 

 25 

 20 

 15 

 10 

 5 



n Panhandle 

 B Big Bend 

  Southwest 



1997 



Jlii 



iJn, 



n 



11/11 12/11 1/10 2/9 3/11 4/10 5/10 6/9 7/9 8/8 9/7 



Fertilization date 



Figure 6 



Fertilization-date distribution for 1996 and 1997. 



square test revealed only a marginal difference (P<0.10) 

 from a uniform distribution in fertilization dates across 

 lunar month. 



As in 1996, fertilization in 1997 began in mid-June, 

 peaked in early August, and included birth dates from all 

 three regions; however, the distribution for 1997 was bi- 

 modal. Spawning began in November of 1996 and peaked 

 in late January of 1997, then declined into April. With 

 the exception of two individuals collected in late February 

 from the Panhandle, all individuals from the first fertiliza- 

 tion-date peak were from the Southwest. The last back- 

 calculated fertilization date for the year was in early Sep- 

 tember from the Panhandle. Fertilization dates for 1997 

 did not conform to a lunar cycle because a chi-square test 

 indicated no significant difference from a uniform fertil- 

 ization-date distribution across lunar month. 



Results from the reproductive condition of adult gonads 

 were compared with results from back-calculated fertiliza- 

 tion dates from otoliths to determine if survivingjuveniles 

 were derived from a subset of the original propagules. We 

 compared otolith data with oocyte diameters because large 

 ova are indicative of ripe females (i.e. >0.59 mm maximum 

 oocyte diameter) (Davis and West, 1993). In 1996, the 

 maximum oocyte diameter distribution indicated that fe- 

 males were in spawning condition from May to September 

 and that a peak in spawning activity occurred in mid-July 

 (Fig. 7). Spawning activity, signified by the presence of hy- 

 drated oocytes, also occurred from May through mid-Sep- 

 tember. Only one female with postovulatory follicles was 

 found in 1996, collected in mid-July. Male spawning times 

 (i.e. May-September) mirrored those of females; however, 

 only five males contained ripening spermatids, and none 

 contained spermatazoa in 1996. All gonads collected in 

 1996 were from the Panhandle. 



40 -, 



30 



20- 



10 ~ 



- 



aM 



1 1 1 \ 1 1 \ r 



1/10 2/29 4/19 6/8 7/28 9/16 11/5 12/25 



08- 

 7. 

 06- 

 0.5- 

 04- 

 3- 

 0,2- 

 1- 

 00- 



B 



— I 1 1 1 1 1 r 



1/10 2/29 4/19 6/8 7/28 9/16 11/15 12/1 



5 - 



3 - 



2- 



+ F 

 otvl 



■M-l-M-MH-*»f 



HO 00«» ««C»4» «» O 0« 



1— I #0 ++++++»+♦ 



T 1 1 1 1 1 1 T 



1/10 2/29 4/19 6/8 7/28 9/16 11/5 12/25 



Sampling date 



Figure 7 



Comparison of spawning time as determined by 

 back-calculation from otoliths (A), maximum oocyte 

 diameter (B) and histological stage (C) for 1996. 

 All fish were collected from the Panhandle. 



In 1997 gonad data were available from all three 

 regions and the results of comparisons of gonads from 

 the three regions may indicate the presence of juveniles 

 that were not derived from local spawning. Gonad data 

 for all regions indicated peak spawning during mid-July 

 (Fig. 8). Gonad data from the Panhandle suggested spawn- 

 ing times similar to those for the otolith data, i.e. a May 

 through September spawning period and a summer peak. 

 However, the back-calculated fertilization dates from late 

 February and early March did not correspond to oocyte 

 diameter or histological-stage data. Very few juveniles 



