McKinzie and Szedimayer: Mortality estimates for Balistes capriscus based on acoustic telemetry 
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Time (week) 
Figure 5 
Weekly survival (S) of gray triggerfish (Balistes capriscus) from total mortal- 
ity in the northern Gulf of Mexico from 2013 through 2017. The dashed lines 
indicate the proportions of fish surviving after each weekly interval. Instanta- 
neous total mortality rates were calculated from S after 1 year at liberty. Black 
points indicate conditional estimates of S for weekly time intervals when a 
mortality occurred. Error bars indicate standard errors. The annual total 
mortality rate, calculated as —-In0.1 
(62/241) 
, was 0.48 (95% confidence interval: 
0.18-0.85) during the 241-week study period. 
All fishing mortalities of gray triggerfish in 2017 occurred 
in July during the extended sport fishery season for red 
snapper (NMFS’). Therefore, we suggest that the sport fish- 
ery for red snapper affected a non-target species, gray trig- 
gerfish, because of their shared dependence on natural and 
artificial reef habitats (Simmons and Szedlmayer, 2011, 
2018; Jaxion-Harm et al., 2018). Previous telemetry studies 
have confirmed that both species are reef dependent, main- 
tain long-term residencies, and have high site fidelity to 
individual reef structures (Szedlmayer and Schroepfer, 
2005; Topping and Szedlmayer, 2011; Piraino and 
Szedlmayer, 2014; Herbig and Szedlmayer, 2016; 
Williams-Grove and Szedlmayer, 2016b, 2017; McKinzie, 
2018). Increased F has also been linked to fish species that 
congregate at predictable or known locations (Roughgarden 
and Smith, 1996; Hutchings, 2000; Worm et al., 2009; 
Williams-Grove and Szedlmayer, 2016a). 
At the time of our study, the Gulf of Mexico stock of gray 
triggerfish was overfished and not rebuilding on target. 
In addition, the population size and spawning stock bio- 
mass were near historic lows (GMFMC, 2017b). However, 
because of recent changes to the minimum stock size 
3 NMFS (National Marine Fisheries Service). 2017. NOAA 
announces the 2017 Gulf of Mexico red snapper recreational 
seasons. FB17-023 Gulf of Mexico Fishery Bulletin. [Available 
from website, accessed February 2022.] 
threshold, the stock is no longer considered overfished, but 
it is still not rebuilding on target (GMFMC, 2017a). Any 
additional fishing pressure on gray triggerfish, particu- 
larly during critical periods, such as spawning when the 
fishery is closed, could further slow stock recovery (van 
Overzee and Rijnsdorp, 2015). 
Historically, rates for reporting of tagged fish by fish- 
ermen were indirectly measured with secretly implanted 
tags, port or processor surveys, landings data, and 
multiple-tag studies (Pollock et al., 2001; Pine et al., 2003). 
In multiple-tag studies, reporting of recovery of high-reward 
tags is assumed to be 100%, and the difference between the 
reporting for recovery of standard tags and that for high- 
reward tags is used to adjust the reporting rate (Pollock 
et al., 2001; Bacheler et al., 2009; Hightower and Pollock, 
2013). In this study, we used a high reward ($150) for all 
tags, and reporting rates were 100%, based on the num- 
ber of fishing mortalities determined by using telemetry. 
However, these results should be interpreted with caution 
because of small sample sizes, and always assuming 100% 
return rates for high-reward tags may cause underes- 
timates of F (Pollock et al., 2001; Pine et al., 2003). For 
example, in previous telemetry studies in which tag report- 
ing rates were directly estimated, reporting rates were 
<100%: 17% (Hightower et al., 2001), 89% (Topping and 
Szedlmayer, 2013), 63% (Williams-Grove and Szedlmayer, 
2016a), and 77.1% (Mudrak and Szedlmayer, 2020). 
