184 
Fishery Bulletin 120(2) 
Reporting rates less than 100% were attributed to tag 
shedding, unintentional noncompliance, or intentional non- 
reporting due to disagreements over management restric- 
tions (Schwartz, 2000; Pollock et al., 2001; Denson et al., 
2002; Gaertner and Pierre-Hallier, 2015; Williams-Grove 
and Szedlmayer, 2016a). 
Another advantage of telemetry is that it can be used 
to provide fishery-independent estimates of F and M, 
but reports of recaptured fish by fishermen are still 
important for validating the telemetry-based estimates 
(Hightower and Pollock, 2013; Topping and Szedlmayer, 
2013; Williams-Grove and Szedlmayer, 2016a; Mudrak 
and Szedlmayer, 2020). In addition, data on tag returns 
by fishermen provide a rare opportunity to understand 
fishermen behavior (Pine et al., 2003) and can be used 
to generate species-specific reporting rates of tagged fish 
(Mudrak and Szedlmayer, 2020). 
In this study, one natural mortality event was observed 
during each year of the study, except in 2017. The overall 
annual estimate of M was 0.25 (95% CI: 0.07—0.57) for all 
years of the study (2013-2017) and was similar to the M 
of 0.28 that was used in the stock assessment model for 
2015 (Burton et al., 2015; SEDAR, 2015). Both the 2015 
stock assessment and the telemetry approach used in this 
study are validated by the similarity of the values of M 
estimated with the 2 totally different methods. 
Interestingly, one gray triggerfish (T35) was identified 
as a fish that experienced natural mortality rather than 
as an emigrated fish on the basis of patterns of detections 
with receivers at surrounding reef sites after the fish left 
the VPS site. Detections of fish T35, after almost continu- 
ous tracking for 426 d at the VPS site where it was tagged 
and released (Fig. 2), were recorded at 15 different sur- 
rounding reef sites and indicate that 38 directed move- 
ments occurred over a 5-d period, with a total distance 
moved of 91 km. This pattern of substantially increased 
horizontal movement matches movement patterns of a 
tagged sandbar shark (Carcharhinus plumbeus) and a 
tagged bull shark (C. lewcas) detected with telemetry in 
the same study area (Altobelli and Szedlmayer, 2020). 
Therefore, these detections of fish T35 indicate the move- 
ments of a predator rather than of a gray triggerfish. 
Conclusions 
In this study, we successfully identified the fates of 100% 
of tagged gray triggerfish residing on artificial reefs in the 
northern Gulf of Mexico after a 3-d recovery period, inde- 
pendent of tag returns by fishermen, and used telemetry 
from VPS sites for direct estimation of F, M, and Z. Valid 
detections from receivers at surrounding reef sites were 
used to successfully verify that fish emigrated. Mortalities 
identified with telemetry were confirmed by using infor- 
mation on tag returns by fishermen, on the lack of detec- 
tions with single receivers after fish were caught, or on 
detection patterns that indicate predator movements. The 
estimate of M from this study supports values applied in 
management efforts, and the F from this study indicates 
that previous management efforts have been successful in 
reducing F but that the stock may still be experiencing 
overfishing. This study also highlights the importance of 
bycatch mortality of gray triggerfish (i.e., as fishermen 
pursue other species, such as red snapper, gray triggerfish 
are caught despite a closed season for this species). 
One difficulty in this study was comparing mortality 
estimates for a relatively small area off the coast of Ala- 
bama to estimates for the entire Gulf of Mexico. There- 
fore, the telemetry estimates from this study may be 
limited. Still, estimates of mortality based on telemetry 
methods are likely more accurate than estimates based 
on landings data from phone or mail surveys (i.e., based 
on fishery-dependent data from the Marine Recreational 
Information Program; SEDAR, 2015). Therefore, the 
expansion of the use of acoustic telemetry for estimation 
of mortality rates could improve the management of gray 
triggerfish. 
Acknowledgments 
We thank A. Altobelli, R. Beyea, L. Biermann, A. Everett, 
K. Fedewa, J. Grove, J. Herbig, S. Landers, E. Levine, 
P. Mudrak, A. Osowski, C. Roberts, M. Szczebak, and 
N. Wilson for their assistance with fieldwork. This proj- 
ect was supported by Sport Fish Restoration funding 
through the Marine Resources Division of the Alabama 
Department of Conservation and Natural Resources. 
This is a contribution of the Alabama Agricultural Exper- 
iment Station, and the School of Fisheries, Aquaculture, 
and Aquatic Sciences, Auburn University. 
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