Ortega-Garcia et al.: Growth of Nematistius pectoralis in the eastern Pacific 
123 
robust comparisons between these studies are not pos- 
sible because the work of Chavez-Arellano (2016) was 
not focused on age determination; he assessed only dor- 
sal spine suitability for aging purposes. Despite differ- 
ences in our study and that of Chavez-Arellano (2016), 
both works support the hypothesis of rapid growth in 
this species, especially in the first year of life. As has 
been reported for others species like the dolphinfish, 
additional structures (e.g., scales) may prove useful in 
future age assessments of the roosterfish (Schwenke 
and Buckel, 2008). 
Although field validation is necessary to confirm the 
proposed growth hypothesis for roosterfish, the inclu- 
sion of small size classes (5 cm FL) and a large size 
range provides support for the use of DGIs for age esti- 
mation. Oxenford and Hunte (1983) assumed DGIs for 
dolphinfish, and Uchiyama et al. (1986) subsequently 
validated those values with both hatchery-reared and 
fish caught in the wild. For some species, DGIs have 
been validated by experiments with fish reared in cap- 
tivity, otolith marking, radiochemical dating, or various 
other techniques (Prince et al., 1991; Campana, 2001). 
Ideally, validation experiments should include the pe- 
riod during which the initial growth ring is formed and 
should evaluate the regularity of growth-ring forma- 
tion during all life stages (e.g., spawning, migration, 
and periods of starvation) because all of these factors 
may influence the regularity of deposition rates (Uchi- 
yama et al., 1986). 
Values of L„ estimated from the von Bertalanffy 
growth equation were greater than the length of the 
largest roosterfish sampled in our study (133 cm FL) 
and slightly lower than the maximum length recorded 
by Robertson and Allen (2015). This difference likely 
occurred because the estimated parameters were based 
only on the initial phases of growth for roosterfish (up 
to 1.49 years). 
The relatively rapid growth rate that we report here 
is similar for both regions (Baja California Sur and 
Costa Rica), despite differences in oceanographic condi- 
tions (e.g., annual sea-surface temperature) or potential 
prey sources and availability. These similarities may be 
due to the lack of larger individuals in this study (e.g., 
readability of fish >86 cm FL), a scenario that may 
have masked potential ontogenetic differences. It may 
also be that roosterfish from the 2 regions have deposi- 
tion rates that differ from each other. If ring formation 
occurs at a rate that is less than one ring per day, it 
may be that this study underestimates the actual age 
of the fish surveyed. Regardless, this work presents the 
first data supporting a growth hypothesis for this spe- 
cies, and future investigations should focus on the use 
of field validation techniques. 
Acknowledgments 
We wish to thank the Pfleger Institute of Environmen- 
tal Research and the Institute Politecnico Nacional for 
the research grant SIP20150861. We also are grateful to 
C. McCue and M. Gutierrez for their help during sam- 
pling and to the sportfishing fleet at Cabo San Lucas, 
Baja California Sur, Mexico. The senior author and R. 
Rodriguez-Sanchez received a Comision de Operacion 
y Fomento de Actividades Academicas fellowship. We 
thank the anonymous reviewers for their constructive 
comments, which helped us to improve the manuscript. 
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