Brown-Peterson et al: Reproductive biology of Brevoortia patronus in the Gulf of Mexico 
293 
- ^=0.287 
• 
P=0.033 
- log 10 BF = 4.695(log 10 FL) - 6.547 
• 
• 
___ — - — * • 
• ^ - 
• 
• • 
• 
2.20 2.22 2.24 2.26 2.28 2.30 2.32 
Log 10 FL (mm) 
Figure 5 
Batch fecundity of Gulf menhaden ( Brevoortia patronus) col- 
lected from the northern Gulf of Mexico during 2014 through 
2016 (ra=16). Log 10 transformation resulted in a significant re- 
lationship between fork length (FL) and batch fecundity (BF). 
r 2 =coefficient of determination. 
ty and an extended spawning season. These conflicting 
lines of evidence lead us to conclude that Gulf menha- 
den likely have indeterminate fecundity, but also show 
some characteristics of determinate fecundity. 
Modeling stock assessments 
The incorporation of “high” estimates of annual fecun- 
dity (based on age-1 with 71 spawnings/year and age- 
2+ with 79 spawnings/year), “low” estimates of annual 
fecundity (based on age-1 with 35 spawnings/year and 
age-2+ with 38 spawns/year), and alternative maturity 
schedules affected stock-level estimates. Altering the 
fecundity estimate in the high and low scenarios in- 
creased estimated annual egg production 100- to 1000- 
fold for each year of the assessment model (Fig. 7A). 
Altering the maturity schedule to include age-1 repro- 
duction (68% of age-1 individuals capable of spawning) 
resulted in an approximately 10-fold increase in stock- 
level egg production for each fecundity scenario (Fig. 
7A) but reduced the proportion of maximum spawning 
per recruit in each of the scenarios (Fig. 7B). The per- 
cent change in estimated numbers-at-age between the 
scenarios that included age-1 reproduction and base 
model estimates indicated that there was a greater 
number of individuals in each age class for all years 
examined, particularly in the age-3 and age-4+ groups 
(Suppl. Fig. 2A) (online only). In 2012, the estimated per- 
cent decrease in number at age was small for the age 
classes 1 and 2 (<1%) but was reduced 9.3%, 4.2% and 
9.8% for ages-0, 3 and 4, respectively. The estimated 
increase in annual F was small and generally consis- 
tent across age classes for each year, with an observed 
increase in F in age classes 0, 2, 3, and 4 of 
-1.5% and an increase in the estimated F rate 
for age-1 of <0.5% (Suppl. Fig. 2B). Estimated 
selectivity of age-1 fish in the commercial re- 
duction fishery for the updated fecundity esti- 
mates was marginally greater than that esti- 
mated in the base model formulation (0.050 vs. 
0.051). Estimated log-transformed catchability 
of the 2 fishery-independent gears (gill and 
seine nets) used to sample the stock exhibited 
minor differences in the base model formula- 
tion (1.251 and 1.177 for the high and low es- 
timates, respectively). Catchability of the seine 
gear was reduced from 0.127 to 0.125. 
Comparisons of historical data 
Annual sample sizes from the Gulf menhaden 
fishery during 1964 through 2014 ranged from 
4611 in 2010 to 16,823 fish in 1994 (Suppl. Ta- 
ble) (online only). Low sample size in 2010 was 
the result of closures of fishing areas due to the 
Deepwater Horizon oil spill. Mean estimated 
slope and intercept for the length-weight rela- 
tionships varied over time (Suppl. Fig. 3) (on- 
line only). The highest slope was 3.98 in 1991 
and the lowest slope was 2.52 in 1986. Slope 
translates into how heavy a fish is compared with its 
length. Slopes of 3.0 indicate a proportional fish; slopes 
<3.0 indicate a skinnier fish and slopes >3.0 indicate 
a heavier fish. Intercept values varied between -15.92 
in 1991 to -8.39 in 1986. Variability in the slope and 
intercept values was generally random, but there were 2 
time periods (late 1980s and late 2000s) that had about 
5 years of lower than average slope, therefore indicating 
Gulf menhaden were less robust during those times. 
We found significant differences in reproduction- 
related measures in both males and females between 
1964-1970 and 2014. Reproductively active females 
in October 2014 were significantly larger (£ 146 =2.22, 
P=0.03), had a higher K (f 146 = 2.708, P=0.008), and a 
greater GSI G 146 =4.143, P<0.001) than those from 1964 
through 1970 (Table 3). However, no significant differ- 
ence existed between years in September for any of 
these measures. Reproductively active males in Octo- 
ber 2014 showed significantly greater FL (£ 108 =2.387, 
P=0.019) and GSI (* 108 =2.319, P= 0.047) than those 
from 1964 through 1970 (Table 3); whereas no signifi- 
cant difference in male condition was found in Octo- 
ber, fish from 2014 had higher K than those from 1964 
through 1970. 
Discussion 
Gulf menhaden continues to be one of the most eco- 
logically and economically important stocks in the 
northern GOM and plays an important role in the tro- 
phic structure of the region (Sagarese et al., 2016). We 
provide new reproductive information and document 
