296 
Fishery Bulletin 115(3) 
Table 3 
Comparisons of historic and current mean fork length (FL), in millimeters, mean condition (K), and 
mean gonadosomatic index (GSI) with standard errors (SEs) in parentheses, of reproductively active 
male and female Gulf menhaden ( Brevoortia patronus) collected from the northern Gulf of Mexico 
at the beginning of the reproductive season. Historic data are for 1964 through 1970; current data 
are from 2014. Reproductively active fish are defined as GSI>1.0 for females and >0.5 for males. 
Significant differences are in bold. 
Month 
Date 
n 
FL (SE) 
f-value 
P 
Fork length 
Female 
September 
Current 
2 
202.0 (9.0) 
-1.93 
0.086 
Historic 
9 
217.3 (3.3) 
October 
Current 
105 
192.0 (1.17) 
2.22 
0.03 
Historic 
43 
184.9 (3.0) 
Male 
October 
Current 
103 
185.9(1.1) 
2.38 
0.019 
Historic 
7 
175.7 (4.8) 
Condition 
Female 
September 
Current 
2 
2.098 (0.086) 
0.197 
0.848 
Historic 
9 
2.069 (0.064) 
October 
Current 
105 
2.094 (0.027) 
2.708 
0.008 
Historic 
43 
2.073 (0.022) 
Male 
October 
Current 
103 
2.156 (0.013) 
1.620 
0.108 
Historic 
7 
2.070 (0.054) 
Gonadosomatic index 
Female 
September 
Current 
2 
1.63 (0.59) 
-0.348 
0.726 
Historic 
9 
2.02 (0.50) 
October 
Current 
105 
5.44 (0.32) 
4.143 
<0.001 
Historic 
43 
3.75 (0.25) 
Male 
October 
Current 
103 
5.12 (0.28) 
2.319 
0.047 
Historic 
7 
3.53 (0.63) 
(Lewis and Roithmayr, 1981), and the low r 2 value for 
the fecundity-size relationship is typical among batch 
spawning fish species. We counted only oocytes >500 
pm for fecundity estimates — sizes that correspond to 
oocytes about to be spawned (i.e., hydrated oocytes or 
oocytes undergoing OM), whereas Lewis and Roith- 
mayr (1981) counted all oocytes >360 pm, which in- 
cluded vitellogenic oocytes that would not be released 
in a batch. Although there are no previous estimates 
of RBF for Gulf menhaden for comparison purposes, 
Lajud et al. (2016) reported RBF ranged from 50-381 
eggs/g ovary-free body weight in the Brazilian menha- 
den, within the RBF range of 60-212 eggs/g ovary-free 
body weight previously reported by Macchi and Acha 
(2000) for the same species; both values are similar to 
our estimates of 31-328 eggs/g ovary-free body weight 
for Gulf menhaden. 
Despite the lower estimate of BF presented here, the 
total annual estimated fecundity is 11-23 times great- 
er than the values provided by Lewis and Roithmayr 
(1981) for fish of all sizes (Fig. 8) as a result of combin- 
ing BF estimates with spawning frequency estimates. 
The methods we used to determine spawning frequency 
could result in either underestimation of spawning fre- 
quency (due to degradation or destruction of POF due 
to sample treatment) or an overestimation (due to con- 
gregation of females undergoing OM in the sampled 
area), and for this reason we provide a high and low 
range which results in a more accurate estimation of to- 
tal annual fecundity than that of previous reports. Our 
spawning frequency estimates are higher than those of 
the only other report of spawning frequency for a spe- 
cies of menhaden (Brazilian menhaden, every 8 days 
[Macchi and Acha, 2000]). Gulf menhaden appear to 
spawn more frequently than European pilchard ( Sar - 
dina pilchardus, every 11-12 days) and Pacific sardine 
(every 10 days) — batch spawning clupeids with indeter- 
minate fecundity and group synchronous oocyte devel- 
opment (Ganias et al., 2004; Lo et al., 2010). However, 
Brazilian sardinella ( Sardinella brasiliensis) spawn as 
frequently as every 2 days during the peak spawning 
season (Isaac-Nahum et al., 1988) — a frequency that is 
similar to ours for Gulf menhaden. 
Estimates produced from the re-analysis of the stock 
assessment indicate that some model output, includ- 
ing the number-at-age, age-specific fishing mortality, 
and spawners-per-recruit are sensitive to alterations 
in age-specific annual fecundity. A primary use for 
determining length- and age-specific fecundity is for 
inclusion in assessment models for determination of 
