Jakes-Cota et al.: Age and growth of Scorpaena mystes 
325 
estimate individual growth parameters, 
and 3) to test for significant differences 
in growth trajectories between males 
and females. 
Materials and methods 
Stone scorpionfish were collected once 
a month (21—22 individuals per month) 
in the artisanal fishery from May 2015 
through April 2016. The fish were 
taken by spearing while using semiau- 
tonomous diving equipment (hookah), 
at depths up to 30 m, at different fish- 
ing sites along 20 km of coastline south 
of the harbor of Santa Rosalia in Baja 
California Sur, Mexico. The standard 
length (SL) and TL were measured to 
the nearest millimeter, and the weight 
(W) was recorded to the nearest 0.1 g 
for each individual. Sex was deter- 
mined by using macroscopic exam- 
ination of the gonads, and the exact 
binomial test was used to test differ- 
ences in sex ratio. Pairs of sagittae were 
extracted, cleaned, and stored dry in 
plastic vials in the laboratory, and only the right otoliths 
were used for the analyses described in the rest of this 
section. 
To describe the length—weight relationship, we used this 
equation: 
W =aTL’, (1) 
where a = the intercept of the regression line; and 
b = the allometric coefficient, the slope of the regres- 
sion line. 
To describe the relationship independently for males and 
females with log-transformed length and weight data, we 
used this equation: 
log W =a + blog TL. (2) 
The a and 6 parameters were estimated by using a sim- 
ple linear regression analysis. A Student’s t-test was 
performed to evaluate whether the b-value was signifi- 
cantly different from 3, a value that indicates an isometric 
growth pattern (i.e., all body parts grow at approximately 
the same rate, and a fish has an unchanging body form 
throughout development). An analysis of covariance was 
used to test differences in b-values between males and 
females. 
The otolith radius (OR) (Fig. 1) was measured under 
a stereoscope (Stemi SV11', Carl Zeiss AG, Oberkochen, 
Germany) at 3.2x magnification by using the imaging 
' Mention of trade names or commercial companies is for identi- 
fication purposes only and does not imply endorsement by the 
National Marine Fisheries Service, NOAA. 
nucleus 
rostrum 
\ 
Figure 1 
Photograph showing the annular pattern in the sagittae of a 4-year-old male 
stone scorpionfish (Scorpaena mystes) caught in May 2015 in the Gulf of 
California in Mexico. Black dots indicate annuli. The black arrow indicates the 
measurement of the otolith radius. The scale bar is equal to 1 mm. 
software AxioVision, vers. 4.6 (Carl Zeiss AG). The ste- 
reoscope was attached to a digital camera (AxioCam 
MRc 5, Carl Zeiss AG). The relationship between TL and 
OR was described by using a simple linear regression 
analysis. 
Right otoliths were immersed in ethanol with the con- 
cave side down, and 2 independent readers counted the 
annuli once with a stereoscope, using reflected light 
against a dark background without prior knowledge of 
fish length or weight. Under reflected light, the nucleus 
(the core of the otolith) and the opaque bands appeared 
as light rings and the translucent bands appeared as dark 
rings (e.g., La Mesa et al., 2005, 2010; Bilgin and Celik, 
2009). The combination of an opaque band followed by 
a translucent band was considered to be an annulus, as 
has been done for other scorpionfish species (e.g., Massuti 
et al., 2000; La Mesa et al., 2005, 2010; Bilgin and Celik, 
2009). Annuli were counted from the nucleus toward the 
tip of the rostrum (the anterior projection of the otolith) 
along the same line (Fig. 1). The precision between readers 
was evaluated by using the mean coefficient of variation 
(CV) and average percent error (APE). Values of 5.5% for 
APE and of 7.6% for CV have been considered adequate in 
many aging studies (Campana, 2001). 
To validate the periodicity of the formation of opaque 
and translucent bands and to assign a unit of time (e.g., 
years) to the counted annuli, edge type analysis was 
used. For this analysis, the edge type of each otolith was 
recorded as either opaque or translucent, and, for each 
month, the percentages of opaque edges and of translu- 
cent edges in the total number of otoliths analyzed was 
plotted. 
