176 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
@ established in 1881 <a 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Abstract—Gray triggerfish (Balistes 
capriscus) is a common resident of 
reef habitats in the northern Gulf of 
Mexico. It is targeted by fishermen 
and recently considered not overfished. 
However, stock status is highly depen- 
dent on indirect mortality estimates 
from sport and commercial fishery 
landings that may have errors. To 
enhance management efforts, we used 
acoustic telemetry to directly estimate 
fishing mortality (Ff), natural mor- 
tality (WM), and total mortality (Z) for 
gray triggerfish on artificial reefs in 
the northern Gulf of Mexico. Over the 
study period, 30 fish emigrated, 4 fish 
were caught by fishermen, 4 fish died of 
natural causes, 8 fish were active when 
their transmitter battery expired, and 
3 fish were still active at the end of the 
study. Annual F was 0.23 (95% confi- 
dence interval [CI]: 0.07—0.50) and was 
lower than in past stock assessments. 
This rate indicates that earlier man- 
agement efforts were successful. How- 
ever, our F estimate is possibly greater 
than a recent management goal of 0.17 
based on a 30% spawning potential 
ratio. Therefore, gray triggerfish stocks 
may still be experiencing overfishing. 
Annual M was 0.25 (95% CI: 0.07-0.57) 
and supports the management applied 
M of 0.28. Annual Z was 0.48 (95% CI: 
0.18—-0.85), which was not considered 
sustainable under the most recent 
stock assessment and supports the 
management decision to increase fish- 
ery restrictions. 
Manuscript submitted 3 January 2022. 
Manuscript accepted 23 May 2022. 
Fish. Bull. 120:176—186 (2022). 
Online publication date: 3 June 2022. 
doi: 10.7755/FB.120.2.7 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Mortality estimates for gray triggerfish 
(Balistes capriscus) in the northern Gulf of 
Mexico based on acoustic telemetry 
Megan K. McKinzie 
Stephen T. Szedimayer (contact author) 
Email address for contact author: szedist@auburn.edu 
School of Fisheries, Aquaculture and Aquatic Sciences 
Auburn University 
8300 State Highway 104 
Fairhope, Alabama 36532 
Gray triggerfish (Balistes capriscus) is 
exploited by sport and commercial fish- 
eries throughout the northern Gulf of 
Mexico and southeastern United States 
(SEDAR, 2015). Historically, this spe- 
cies was neither heavily targeted nor 
considered an important food resource. 
However, its value has increased in 
recent years as fishing restrictions on 
red snapper (Lutjanus campechanus) 
and other important species of reef fish 
have increased (SEDAR, 2013). This 
rising interest has also led to increased 
concern about the status of the stock of 
gray triggerfish in the Gulf of Mexico. 
In 2011, the Gulf of Mexico stock of 
gray triggerfish was considered over- 
fished and experiencing overfishing 
(SEDAR, 2011). As a result, the Gulf of 
Mexico Fishery Management Council 
reduced the annual catch limit, set a 
spawning season closure from 1 June 
through 31 July, a sport bag limit of 
2 gray triggerfish per fishermen per 
day, and a commercial trip limit of 
12 gray triggerfish per trip (GMFMC, 
2012). A more recent stock assessment 
in 2015 indicated that the gray trig- 
gerfish stock was no longer experienc- 
ing overfishing, but the stock was still 
overfished (SEDAR, 2015). In 2017, a 
new rebuilding plan for gray triggerfish 
was developed, and through this plan a 
less restrictive definition of overfished 
was adopted and characterized the 
stock as no longer overfished but still 
rebuilding (GMFMC, 2017a). The new 
rebuilding plan further reduced the 
recreational bag limit to 1 gray trigger- 
fish per fishermen per day, increased 
the recreational minimum size limit for 
gray triggerfish to 381 mm fork length 
(FL) (15 in FL), increased the commer- 
cial trip limit for gray triggerfish to 
16 fish per trip, and added in an addi- 
tional seasonal closure from 1 January 
through 28 February (GMFMC, 2017b). 
Therefore, questions concerning the 
stock status of the gray triggerfish 
remain, reinforcing the need for a new 
benchmark stock assessment. 
Especially important for gray trigger- 
fish stock assessments are estimates of 
mortality. Prior to the implementation 
of the fishery management plan for reef 
fish resources of the Gulf of Mexico in 
1984 (GMFMC, 1981), the total mortal- 
ity (Z) for this stock of gray triggerfish 
was estimated to range from 0.40 to 
0.67 during 1979-1982 (Johnson and 
Saloman, 1984). More recent estimates 
based on catch-curve analyses indi- 
cate that the mean Z for the period 
of 1986-2011 was 0.95 (Burton et al., 
2015), which exceeds the estimated 
maximum sustainable Z of 0.45 (with 
fishing mortality [F] of 0.17, based on 
a 30% spawning potential ratio, and 
