Burton et a!.: Age, growth, and mortality of Bahstes capriscus from the southeastern United States 
33 
Table 2 
Observed and predicted mean fork length (FL), measured in millime- 
ters, and natural mortality at age (M) data for gray triggerfish (Bali- 
stes capriscus) collected in 1990-2012 along the coast of the southeast- 
ern United States. Standard errors of the means (SE) are provided in 
parentheses. 
Age 
n 
Mean FL (SE) 
FL range Predicted FL 
M 
0 
i 
173 
_ 
181 
0.94 
1 
23 
305 (11) 
201-394 
257 
0.65 
2 
451 
333 (2) 
214-560 
312 
0.52 
3 
1470 
353 (1) 
190-530 
351 
0.45 
4 
1773 
375 (1) 
229-550 
380 
0.41 
5 
1336 
391 (1) 
221-526 
481 
0.38 
6 
684 
411 (2) 
300-546 
417 
0.36 
7 
313 
428 (3) 
295-543 
428 
0.36 
8 
130 
444 (4) 
330-567 
436 
0.35 
9 
53 
468 (6) 
330-546 
442 
0.34 
10 
22 
464 (11) 
360-550 
446 
0.34 
11 
6 
416 (30) 
323-513 
449 
0.34 
12 
4 
482 (23) 
417-520 
451 
0.34 
13 
1 
410 
- 
453 
0.33 
14 
1 
496 
- 
454 
0.33 
15 
1 
467 
— 
455 
0.33 
Total mortality 
Gray triggerfish were fully recruited to the headboat 
fishery by age 4, to the private recreational fishery by 
ages 4-5, and to the commercial fishery by age 5. Es- 
timates of Z were similar among all 3 of these sectors. 
Mean annual estimates of Z for the years 1986-2011 
(from all available data) were 0.94 for the headboat 
fishery and 0.89 for the other recreational fishery. Mean 
annual total mortality for the commercial fishery was 
0.91 for available data (1995-2011, except for 1997 and 
2002). Through the use of a pooled catch-at-age matrix 
across all sectors, Z was estimated at 0.95 (n = 15; stan- 
dard deviation=0.02; range=0.93-0.97). These results 
equate to an average annual mortality rate of 0.61 
across all 3 sectors. Ricker (1975) defined the annual 
mortality rate A as “the number of fish which die dur- 
ing a year (or season) divided by the initial population 
number.” 
Discussion 
Gray triggerfish are admittedly difficult to age. First, 
the use of an external bony structure, the first dor- 
sal spine, to age the fish has some inherent problems, 
such as possible resorption of the material or damage 
to the structure — both of which would not likely affect 
otoliths. Second, the interpretation of the increments 
on the spines was variable, for reasons such as the 
spacing between increments and the subjectivity of the 
presence of false annuli. Because of these problems, we, 
along with members of the staff of another laboratory 
that has been involved in aging fishery-independent 
samples of gray triggerfish, held a workshop to ad- 
dress issues with aging this fish. A robust set of cri- 
teria for interpreting the increments on the spine was 
established during this workshop. Using these newly 
established criteria, we reread a set of their samples. 
We found consistent agreement between readers and 
within readers in our own study, as evidenced by the 
APE calculations presented in the previous section. 
Therefore, the results of this study represent the best 
available information on the longevity and growth of 
gray triggerfish. 
The spine edge analysis conducted in this study 
strongly indicates that gray triggerfish deposit one an- 
nulus per year from March to June and that peak an- 
nulus formation occurs in April and May. This result is 
similar to findings in other studies where peak annulus 
formation occurred in June and July in gray triggerfish 
in the Gulf of Mexico (Johnson and Saloman, 1984) and 
in June in fish from the east coast of the United States 
(Moore, 2001) (Table 4). The timing of the deposition of 
a growth increment in Moore’s study was concurrent 
with peak spawning in June and July. Gray triggerfish 
in the Gulf of Mexico also have exhibited temporally 
similar times of annulus formation and peak spawning 
(Simmons and Szedlmayer, 2012). 
Weight-length relationships were nearly identi- 
cal for gray triggerfish from the SEUS and the Gulf 
of Mexico. The relationship between FL and TL was 
also similar: EL=30.33+0.79xTL for fish off the Atlantic 
