366 
Fishery Bulletin 118(4) 
QO 
S 
2 
aS) 
_ 
= 
@ 
— 
o 
D 
= 
xs) 
< 
© 
= 
2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 
Year 
Figure 1 
Annual landings of Pacific hake (Merluccius productus) 
from the northern Gulf of California in Mexico during 2000— 
2019, in metric tons, from the Mexico National Aquaculture 
and Fishing Commission database of landing notifications. 
Data for 2019 include landings only up to 4 September. 
studied in the United States and Canada (McFarlane and 
Beamish, 1985; Smith et al., 1992; Saunders and McFar- 
lane, 1997; Benson et al., 2002; King et al., 2012). However, 
studies of Pacific hake in Mexico are few and scattered. 
The government of Mexico began issuing permits for the 
commercial catch of Pacific hake in 2018 to states around 
the Gulf of California (Sonora, Baja California, and 
Sinaloa). Currently, the only rule to control fishing effort 
is a limit of the number of permits to 80 (DOF, 2018). The 
fishing season for this species occurs, on average, during 
winter and spring (January—March) each year, and the 
largest portion of landings come from Sonora. 
Little is known about the biology and population dynam- 
ics of Pacific hake in the NGC. It has been hypothesized 
that this population belongs to a different species, the Cor- 
tez hake (M. hernandezi) (Mathews, 1985), mainly because 
of its maximum size of 107 cm total length (TL), much 
larger than that of the unfished population of what had 
been considered Panama hake (M. angustimanus), a spe- 
cies that was also called the dwarf hake, from the southern 
Gulf of California and Baja California Sur (33.5 cm TL) 
(Mathews, 1975; Balart-Pdez, 2005). Nevertheless, results 
from molecular and meristic studies indicate the presence 
of a single species, M. productus, in North America with 
different population units (Silva-Segundo et al., 2011; 
Garcia-De Leon et al., 2018). 
This study aimed to describe relevant features of the 
fishery and biology of the Pacific hake caught in the NGC. 
We report for the first time the variability of catch rates 
and population structure, by length and sex, of this species 
in this region, as well as the morphometric relationships 
(length—weight and length—length). This information can 
be used as a baseline for future stock assessments and fish- 
eries management. 
Materials and methods 
Data and sample collection 
The fishery was monitored by an on board observer pro- 
gram from 2015 through 2019 during the January—March 
fishing season with a percentage of coverage of total trips 
ranging from 5% (in 2016) to 12% (in 2019). The fleet that 
targeted Pacific hake was based in Puerto Penasco (76%) 
and Guaymas (12%), Sonora; Mazatlan, Sinaloa (8%); and 
San Felipe, Baja California (4%). During 77 trips on board 
25 commercial ships, 817 trawl tows were completed. 
The fishery used diurnal bottom trawling, and vessels 
deployed trawl net sets from 0600 to 1800. The width of 
the net mouth was 30 m on average and opened verti- 
cally (to about 4 m) as a result of a floating line in the top 
rope and a ballast chain in the lower rope of about 450 kg. 
The mesh size in the codend of nets ranged from 6.35 to 
12.70 cm (2.5—5.0 in), and the most common (89%) mesh 
sizes were 10.16 cm (58%), 7.62 cm (18%), and 8.89 cm 
(13%). The average speed and duration of trawl tows 
were 4.37 km/h (standard deviation [SD] 0.55) (2.36 kt 
[SD 0.30]) and 3.53 h (SD 1.27), respectively. The depth of 
trawl tows varied, with a range of 111-335 m and a mean 
of 253.2 m (SD 28.75). Trawl tows followed the slope of the 
Delfin Basin, always south of the Upper Gulf of California 
and Colorado River Delta Biosphere Reserve and a refuge 
for vaquitas (Phocoena sinus) in a fishing zone called the 
horseshoe by fishermen because of its shape (Fig. 2). 
On board fishing vessels, fishermen head and gut 
Pacific hake. A total of 2853 Pacific hake were weighed 
before and after processing. We estimated that an aver- 
age of 38.74% (SD 7.30) of total weight was lost during 
processing. Then, to account for the percentage of loss, the 
processed weight was multiplied by a conversion factor 
(FAO’) of 1.65 (SD 0.19). 
After processing, fish are arranged in plastic boxes that 
weigh ~70 kg, washed with seawater, and stored between 
ice layers in the cargo hold. During this process, small 
(<40 cm TL) and damaged Pacific hake are discarded. 
Nominal catch (NC) of Pacific hake per tow was estimated 
with the following equation: 
NC = CF (B x W)+D, (1) 
where CF = the conversion factor needed to estimate live 
weight from Pacific hake gutted and headed; 
B =the number of boxes stored; 
W = the weight of each box (~70 kg); and 
D = an observer's estimate of the weight of Pacific 
hake discarded. 
1 FAO. 2000. Conversion factors: landed weight to live weight. 
FAO Fish. Circ. 847, 176 p. FAO, Rome. [Available from website.] 
