214 
Fishery Bulletin 115(2) 
A B 
Age (dah) Age (dah) 
Figure 4 
Relationships of standard length (SL) to age in days after hatching (dah) estimated with Laird-Gompertz 
growth models for each grouping of data from analysis of larval Gulf menhaden (Brevoortia patronus) collected 
at Bayou Tartellan from October 2006 to April 2007 and from September 2007 to April 2008 (A) For the age 
grouping, larvae with a measured age less than 31 dah are indicated as points in black with the corresponding 
black model line, and larvae greater than 31 dah are indicated as points in gray with the corresponding gray 
model line. (B) For the length grouping, larvae with a measured SL less than 16 mm are indicated as points 
in black with the corresponding black model line, and larvae greater than 16 mm SL are indicated as points 
in gray with the corresponding gray model line. Model parameterizations were calculated with the equations 
provided in the figure. 
ther offshore as the season progressed (Whitehead, 
1985; Vaughan et ah, 2007). Spawning was bimodal in 
both years and peaked during fall in either October or 
November, depending on year. This peak was smaller 
than the second, late-winter peak, which occurred in 
either late January or early February for years 1 and 
2, respectively. This large second spawning peak is con¬ 
sistent with previously reported spawning peaks that 
occurred in late January and February (Shaw et ah, 
1988; Powell 1994; Raynie and Shaw, 1994; Vaughan 
et ah, 2000). In particular, collection of small (3-5 mm 
SL) and young (7-12 das) larvae in late September 
to early October had back-calculated spawning dates 
that suggested a much earlier spawning season (i.e., 
September) and a much shorter recruitment corridor 
than previously reported. Overall, the larvae of the fall 
spawning peak were generally smaller (mean: 14 mm 
SL), and younger (22 das) than the larvae that com¬ 
posed the winter peak (mean: 19 mm SL; age: 41 das). 
The fall peak, however, corresponded with a shorter re¬ 
cruitment corridor and transit time (i.e., approximately 
3 weeks) compared with the winter peak with transport 
times of approximately 6 weeks. The fall transit time, 
therefore, is much shorter than the transport time of 
4-10 weeks estimated by Shaw et al. (1988) but cor¬ 
responds well with adults being distributed along the 
coast in nearshore waters during late summer or early 
fall before moving farther offshore in October (Ahren- 
holz, 1991) and perhaps being somewhat constrained 
by the Louisiana hypoxic zone (Vaughan et ah, 2007). 
The greatest larval growth rate was determined to 
occur a few days before the beginning of the ontogenet¬ 
ic transformation from a selective particulate feeding 
to omnivorous filter feeding, and during the shift from 
oceanic waters through the coastal boundary zone into 
the estuary, but there was some variability between 
sampling years. The 2-cycle Laird-Gompertz model es¬ 
timated a maximum growth rate for the initial larval 
stage of 0.72 mm/day at 33 das, which was similar to 
the individual age-grouped Laird-Gompertz model of 
0.71 mm/day at 33 das, and both models had higher 
maximum growth rates than those estimated with the 
SL-grouped Laird-Gompertz model (0.41 mm/day). 
The individual Laird-Gompertz models grouped by SL 
showed agreement and had a mean calculated growth 
of 0.38 mm/day that agrees with previously reported 
values of 0.36 mm/day (Raynie, 1991) and 0.37 mm/ 
day (Warlen, 1988). However, the agreement among 
the 2-cycle Laird-Gompertz models in our study, the 
individual Laird-Gompertz models grouped by age, 
and the results by Raynie and Shaw (1994), suggests 
that timing of the onset of metamorphic development is 
tied to age and ultimately ontogeny based on shifting 
prey fields (Ditty, 2002). Any differences in length at 
