10 
Fishery Bulletin 116(1) 
et al., 2009; Farrell et al., 2014). In the Mediterranean 
Sea, dolphinfish are caught by using a special type of 
net (called llampuguera) around fish-aggregating devic¬ 
es (Massuti and Morales-Nin, 1997), and in the western 
Atlantic Ocean, they are caught commercially by using 
pelagic longlines, and recreationally by rod and reel 
(Farrell et ah, 2014). In South America, it is fished in¬ 
dustrially in the Pacific Ocean waters by using surface 
nets at night near Colombia and Venezuela (Lasso and 
Zapata, 1999) and by the longline fleets of Ecuador and 
Costa Rica (Patterson and Martinez, 1991; Campos et 
ah, 1993). In the Pacific Ocean, it is targeted mainly by 
the Japanese longline fleet (Kojima, 1961). 
There are few published works on catch rates and 
abundance of dolphinfish in relation to environmental 
parameters. Norton (1999) found, for example, that 
dolphinfish habitat expanded poleward in the east¬ 
ern tropical Pacific Ocean, owing to increase in down- 
welling forced by a long-distance wave transmission 
along the coast and a decrease in upwelling off the 
coast of northwestern Mexico, which causes an increase 
in SST. Zuniga-Flores et al. (2008) studied seasonal 
and interannual variation in dolphinfish catch rates in 
the Cabo San Lucas, Mexico sport fishery. They found 
a high correlation (-0.78, with 1-month delay) between 
monthly mean SST and their catch rate time series. 
Zuniga-Flores et al. (2008) reported that dolphinfish 
catch rates increase toward the second half of the year, 
when values of SST range between 26°C and 29°C. 
Martinez-Rincon et al. (2009) found that most 
(-79%) dolphinfish caught incidentally by the purse- 
seine tuna fleet in the eastern tropical Pacific Ocean 
were caught when SST values ranged between 25°C 
and 28°C, and that no seasonal or interannual spa¬ 
tial pattern was observed. In contrast, Farrell et al. 
(2014) suggest that chlorophyll-o (chl-a) concentra¬ 
tion and SST are the 2 environmental variables that 
explain the variations in dolphinfish catch from both 
the commercial longline and the recreational fisheries 
in the northwestern Atlantic Ocean. Higher catches 
occurred in waters with SST between 22°C and 27°C 
and chl-a concentrations <0.2 mg/m 3 . Farrell et al. 
(2014) concluded that dolphinfish are highly sensi¬ 
tive to changes in the biophysical environment be¬ 
cause a large number of variables was retained in 
the statistical model fitted to catch data. Apart from 
SST and chl-a concentration, another variable that 
could influence dolphinfish abundance is sea-surface 
height (SSH), which can be used as an indicator of 
some mesoscale oceanographic features, such as ed¬ 
dies; moreover, some SSH features have elucidated 
the preference of certain species for particular water 
masses, such as cyclonic eddies or currents (Zainud- 
din et al., 2006; Theo and Block, 2010). 
Our main objective was to assess environmental and 
spatial preferences of dolphinfish in the Pacific Ocean 
off the coast of Mexico by using 1) estimated incidental 
catch per unit of effort (ICPUE) data from the purse- 
seine tuna fleet and 2) SST, chl-a concentration, and 
SSH from remote sensing databases. 
Materials and methods 
Fishery database 
We analyzed a 10-year database of estimated dolphin¬ 
fish caught incidentally, reported by scientific observ¬ 
ers of the Inter-American Tropical Tuna Commission 
on board class 6 (>425 m 3 storage capacity; IATTC 1 * ) 
tuna purse-seine ships that operated from 2004 to 2013 
in the Pacific Ocean off the coast of Mexico from 10° to 
33°N and from 90° to 125°W. The database included 
the estimated number of dolphinfish caught monthly in 
l°xl° latitude-longitude survey quadrants, the num¬ 
ber of purse-seine sets that resulted in that estimated 
number of fish for each quadrant, the number of fish 
caught per size class of fish (small: <30 cm in total 
length (TL), medium: 30-60 cm TL, and large: >60 cm 
TL), the coordinates of latitude and longitude at the 
center of the quadrants, for each month and year. The 
following equation was used to calculate ICPUE: 
where DC ; = estimated catch (total number of dolphin¬ 
fish); and 
NS\ = the number of positive purse-seine sets 
(with at least one dolphinfish) that re¬ 
sulted in the estimated catch, all for ith 
quadrant. 
Environmental database 
Monthly means for 3 environmental variables over the 
same 10-year period were used in the analysis: SST, 
chl-a concentration, and SSH. Both SST and concen¬ 
tration of chl-a were obtained from BloomWatch360, a 
product of the NOAA CoastWatch West Coast Regional 
Node (available from website). With this product, each 
database has a unique 7-letter code. For the SST data¬ 
base, the code is TBssta, has a 0.1°x0.1° spatial resolu¬ 
tion, and represents a multimission (sent from differ¬ 
ent sensors) database. The data for chl-a concentration 
(with a database code of TMHchla) have a 0.05°x0.05° 
resolution, and include data up to September 2013. 
Data for chl-a concentration for the last 3 months of 
2013 were obtained from NOAA’s ERDAPP data server 
(available from website), have a 0.025°x0.025° resolu¬ 
tion (code erdMBChlamday). Both chl-a concentration 
data sets come from the Aqua-MODIS satellite. SSH 
data were obtained from the AVISO website (available 
from Copernicus at website), with a temporal resolution 
of 1 d, and a spatial resolution of 0.125°. Monthly av¬ 
erages were then calculated from January 2004 to De- 
1 IATTC (Inter-American Tropical Tuna Commission). 2009. 
Agreement on the International Dolphin Conservation 
Program. 21 st meeting of the parties. Vessel capacity class 
definitions related to the requirement for carrying an on¬ 
board observer. Doc. MOP-21-07, 2 p. IATTC, La Jolla, 
CA. [Available from website.] 
