Ortega-Garcia et al.: Growth of Nematistius pectoralis in the eastern Pacific 
119 
= ( 2 ) 
where = length (FL in centimeters) at age t; 
= average maximum length; 
k =the individual growth coefficient; 
^o=the hypothetical age when the length is 
equal to 0; and 
^ =age. 
A power function was also tested; however, because our 
results were similar to those of the von Bertalanffy 
growth model, only results from the von Bertalanffy 
growth model were included for consistency and com- 
parison with other growth studies. 
Growth parameters were estimated independently 
During the sampling period, 290 
roosterfish (190 specimens from 
Baja California Sur and 100 speci- 
mens from Costa Rica) were mea- 
sured and weighed. Specimens from 
Baja California Sur (66 males, 74 
females, and 50 fish of unknown 
sex) ranged from 5.2 to 133.0 cm 
FL and from 0.01 to 25.87 kg in 
weight. Specimens from Costa Rica 
(47 males, 18 females, and 35 fish 
of unknown sex) ranged from 8.3 to 
116.0 cm FL and 0.01 to 17.80 kg 
(Fig. 2). 
The estimated parameters of the 
LWR by area and sex are provided 
in Table 1. Comparisons of growth 
parameters (values of the exponent 
b) revealed that all LWRs were not 
significantly different from a value 
of 3 (Student’s ^-test: P>0.05) and indicated that roost- 
erfish growth is isometric (Table 1). Given the find- 
ing of isometric growth for both location and sex, the 
length and weight data were pooled into one represen- 
tative LWR for this study (Fig. 3, Table 1). 
For age estimation, 182 pairs of sagittal otoliths 
were collected and processed, 103 pairs from fish col- 
lected in Baja California Sur (5.2-120.0 cm FL) and 79 
pairs from fish collected in Costa Rica (13.5-116.0 cm 
FL). Of these pairs, 130 pairs or 71.5% (Baja California 
Sur=68 and Costa Rica=62) were readable and used in 
the age estimation analyses. The remaining 52 otolith 
pairs (Baja California Sur=35 and Costa Rica=17) were 
discarded for one or more of the following reasons: the 
otoliths were broken, crosscuts did not include the core. 
Figure 1 
(A) Right sagitta of a 63.5-cm-FL roosterfish (Nematistius pectoralis) cap- 
tured in Baja California Sur, Mexico, in 2014. Dotted white lines represent 
a transverse section through the core, which is indicated by the black circle. 
(B) Sagitta showing daily growth increments (that consists of two rings: gray 
and white) from a 5.2-cm-FL roosterfish (18 d in age) captured in Baja Cali- 
fornia Sur in 2014. 
for both study areas (Baja California 
Sur and Costa Rica), and an analysis 
of the residual sum of squares was 
used to evaluate the possible differ- 
ences in parameters between the 2 
locations (Ratkowsky, 1983). 
Parameters for both the LWR 
and von Bertalanffy growth model 
were estimated by using nonlinear 
least squares by means of an itera- 
tive process with the Gauss-Newton 
algorithm (Bates and Watts, 1988), 
which allows estimation of nonlin- 
ear model parameters without need- 
ing to transform the data into a 
linear function. Statistical analyses 
were performed with R statistical 
software, vers. 3.2.3 (R Core Team, 
2015). Significance was determined 
by using a ^-test with an alpha level 
of 0.05. 
Results 
