Zamora-Garcia et al.: Catch rate, length, and sex ratio of Merluccius productus in the Gulf of California 371 
Size distribution, sex ratio, and maturity 
The sizes of Pacific hake sampled ranged 
from 11.8 to 89.2 cm SL (15.2-108.8 cm 
TL) with a mean of 47.4 9cem SL (SD 13.7) 
(58.2 cm TL [SD 17.6]). During 2015-2017, 
the length-frequency distribution was 
bimodal. Pacific hake in the size class of 
15-25 cm SL were most common, and fish 
in the size classes of 30-45 cm SL and 
45-65-cm SL were caught in low num- 
bers. In 2018 and 2019, a more normal 
distribution of SLs was observed with 
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no clear size classes or flattened inter- 
vals. The dominant sex of Pacific hake 
at SLs >70 cm was female, and females 
had significantly larger sizes (F=807.09, 
P<0.05) than males (Table 2, Fig. 5). As 
expected, adults had significantly higher 
SL than juveniles (F=5174.49, P<0.05), 
and there was a trend across years 
(F=135.91, P<0.05). 
Adults accounted for 72% of all sam- 
T T a T lama 
2015 2016 2017 2018 2019 Jan 
Year 
Figure 4 
Observed (black dots) and predicted (black lines) geometric means for 
(A and B) catch per unit of effort (CPUE) and (C and D) mean standard 
length of Pacific hake (Merluccius productus) caught in the northern Gulf of 
California in Mexico during 2015-2019, by year and month. The gray shaded 
area in each plot represents the 95% confidence interval of the predicted mean 
from the generalized additive model. 
(P<0.05), a specific trend in mean SL was not observed 
(Fig. 4C). The monthly variability of mean SL indicates 
that the highest mean SLs occurred during January 
(49.1 cm [95% CI: 47.2-51.1 cm]) and February (50.3 cm 
[95% CI: 49.2-51.6 cm]) and that CPUE decreased 7% 
by March (47.1 cm [95% CI: 45.9—48.3 cm]), as shown in 
Figure 4D. 
Variability of sex ratio 
The final model of logSR explained 12.9% of the total devi- 
ance. The GAM used only a smoother for depth and the 
parametric effect of year as well as the interaction of month 
and year (Table 1). Results from the use of a smoother of 
depth indicate that tows with male-biased catch were con- 
ducted at depths <225 m and >275 m and that, at depths 
of 225-275 m, logSR tended to be zero (1:1 male-to-female 
ratio) or below (Fig. 3F). 
No difference was found between months in logSR, but 
a difference was observed between years. However, the 
relevance of the month and year interaction means that 
there is no consistent trend of change of logSR during the 
fishing season. 
pled Pacific hake, 70% of females, and 
73% of males. Results of the Tukey’s hon- 
est significant difference test indicate 
that all mature females were significantly 
larger than mature males, and the differ- 
ence was consistent across years. In 2015 
(adjusted P=0.99) and 2019 (adjusted 
P=0.99), no difference was detected in SL 
between sexes in juveniles (Fig. 6). 
Results from the series of chi-square 
tests indicate a male-skewed sex ratio 
for all sampled Pacific hake (male-to- 
female ratio of 1.12:1.00, P<0.05), but 
particularly for adult specimens (male-to-female ratio 
of 1.16:1.00, P<0.05). For juveniles, the sex ratio was 
1.00:1.00 (P=0.70). There was no specific annual trend 
in the sex ratio for juveniles, but for adults, there were 
significantly more males in 4 out of 5 years. In 2018, we 
observed a female-biased sex ratio for all sampled Pacific 
hake (male-to-female ratio of 0.91:1.00). However, data 
split by maturity stage indicate that the sex ratio of 
adults favored males (male-to-female ratio of 1.09:1.00) 
and that females were dominate among juveniles (male- 
to-female ratio of 0.36:1.00). Although there was no sig- 
nificant bias in the sex ratio in 2019 (P=0.09), males 
were still more abundant (Table 3). 
Biometric relationships 
We found differences in the LWR between years (F=216.55, 
P<0.05). The highest allometric coefficient (6) was esti- 
mated for 2015, followed by the lowest estimate for 2016; no 
differences were observed between 2016 and 2017 (F=1.96, 
P=0.34). For 2018 and 2019, an increasing tendency was 
observed, but differences remained present (F=86.81, 
P<0.05). Differences in the LWR by sex were found in the 
