Brown-Peterson et al.: Reproductive biology of Brevoortia patronus in the Gulf of Mexico 
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Histological sections of gonadal tissue in the spawning capable phase from Gulf menhaden 
(. Brevoortia patronus) collected from the northern Gulf of Mexico in 2014. (A) Female in spawn- 
ing capable phase, showing asynchronous oocyte development and evidence of batch spawning 
(postovulatory follicle [POF] complex); fish captured 6 October 2014. (B) Female in actively 
spawning sub-phase, showing asynchronous oocyte development and a distinct batch of oo- 
cytes in the germinal vesicle migration stage of oocyte maturation (OM), just prior to spawn- 
ing; fish captured 28 October 2014. (C) Male in early germinal epithelium (GE) sub-phase of 
spawning capable reproductive phase, with the tubules outlined by a continuous GE undergo- 
ing active spermatogenesis; fish captured 6 October 2014. (D) Male in late GE sub-phase of 
spawning capable reproductive phase (note that spermatocysts are uncommon along tubules 
as spermatogenesis decreases); fish captured 28 October 2014. Am=anastomosing tubules; 
St=spermatid; Sz=spermatozoa; Vtgl=primary vitellogenic oocyte; Vtg2=secondary vitellogenic 
oocyte; Vtg3=tertiary vitellogenic oocyte. 
Figure 2 
Female GSI remained elevated but gradually decreased 
from late October through March, whereas male GSI 
remained elevated from early October through March 
and there was no gradual decline during the reproduc- 
tive season (Fig. 3). Mean male and female GSI values 
suggest a spawning season extending from early Octo- 
ber through the end of March. 
Histological analysis allowed refinement of the Gulf 
menhaden spawning season. All females captured in 
late August were in the regenerating phase, and fe- 
males first began to exhibit gonadal recrudescence in 
mid-September (Table 1A). By early October, >50% of 
females were spawning capable (Table 1A). Histological 
evidence that Gulf menhaden begin spawning in early 
October includes the presence of some females in the 
actively spawning subphase, as well as 22% of spawn- 
ing capable females having POF (Fig. 2A). By late Octo- 
ber through late February, all sexually mature females 
captured were spawning capable, with 41% and 35% 
of these actively spawning in October and January, re- 
spectively (Table 1A). Although many females were in 
the regenerating reproductive phase by March (Table 
1A), some remained spawning capable in mid-March, 
and 66% of those were actively spawning. Thus, his- 
tological analysis showed that female Gulf menhaden 
were actively spawning from early October through 
mid-March, a 5.5-month spawning season that was 
similar to that seen in the GSI data (Fig. 3). 
Male Gulf menhaden began gonadal recrudescence 
sooner than females; active spermatogenesis was oc- 
curring in 49% of males captured in late August as 
they entered the early developing or developing phases 
