Marm-Enrfquez and Muhlia-Melo: Environmental and spatial preferences of Coryphaena spp. 
1 7 
Mean geographic locations (centroids) of survey quadrants (l°xl°) 
with high (>42.62 fish/set) monthly mean incidental catch per unit 
of effort for dolphinfish (Coryphaena spp.) in the Pacific Ocean off 
Mexico during 2004-2013 
feed on—a climb that occurs ~4-5 months after the 
peak in trade winds and upwelling activity. 
Year-to-year variation in ICPUE was also quite 
variable. During our study period, higher ICPUE oc¬ 
curred during 2004, one of the years with higher SST 
values (results not shown); according to NOAA’s Oce¬ 
anic Nino Index (ONI, available from website), there 
was a moderate to strong warm episode during 2004. 
Lower ICPUE was recorded during 2008, a year with 
low SST and negative (i.e., “cold period”) ONI values. 
Another period of low ICPUE occurred during 2011- 
2012, a period dominated by negative ONI values; 
however, during 2013 a high ICPUE peak agreed with 
a year of negative ONI values, and therefore year- 
to-year variability of ICPUE has a week correlation 
with ONI and indicates that biotic and abiotic factors 
other than SST may influence relative abundance of 
dolphinfish. 
To the best of our knowledge, this study provides the 
first approach to assess ontogenetic variations in dol¬ 
phinfish habitat preferences. For both small and large 
fish, ICPUE showed a peak at ~25°C, nearly 2°C lower 
than the peak for medium-size fish (~27°C). Kraul (1999) 
suggested that dolphinfish growth rate is very sensitive 
to temperature, which would imply larger discrepancies 
in thermal preferences for small and large fish and is 
opposite to what we observed. One explanation might 
be that medium-size fish have different metabolic needs 
than small and large fish, perhaps because they are 
reaching size at first maturity (Alejo-Plata et al., 2011). 
However, this hypothesis needs to be validated, perhaps 
with a controlled experimental design, such as those 
designed for aquaculture purposes. 
Fitted models show that there was 2 interesting 
peaks of ICPUE at relatively high (>1 mg/m 3 ) chl-a 
concentrations for small and medium-size fish. Kitchens 
and Rooker (2014) found that dolphinfish 
larvae density increases with higher con¬ 
centrations of chl-a—a finding that sug¬ 
gests that fast-growing larvae survive in 
areas of enhanced food availability, such 
as cold-core eddies and fronts. The fact 
that some fish <60 cm TL are caught in 
these “high” chl-a concentrations might be 
explained by the energetic needs that dol¬ 
phinfish require in their early, fast-growth 
life stage (Zuniga-Flores, 2009). Addition¬ 
ally, Olson and Galvan-Magana (2002) 
found that dolphinfish body and prey size 
are positively correlated, and therefore 
smaller dolphinfish might explore areas of 
high productivity, where smaller prey are 
expected to be more abundant. Olson and 
Galvan-Magana (2002) also found that 
dolphinfish food consumption rates are 
different for males and females in early 
life stages, and therefore sex could also 
be playing an important role in the differ¬ 
ences presented in our study. 
Overall, dolphinfish shows a clear pref¬ 
erence for SSTs between 23°C and 28°C, chl-a con¬ 
centration < 0.2 mg/m 3 , and SSH values from -0.05 
to 0.05 m. Dolphinfish thermal preferences have been 
reported by other authors, such as Martmez-Rincon et 
al. (2009), who suggest that temperatures below 20°C 
may limit the metabolism and growth of this species. 
Norton (1999) reports that dolphinfish move to warmer 
waters when a decrease in SST occurs, and that fish 
habitat expands northwards during events of extreme 
increase in SST. In addition to the 2 areas with high 
catch that were mentioned earlier, low ICPUE occurred 
in an area around 11-18°N and 97-110°W, in the zone 
of the Eastern Pacific Warm Pool. As stated before, 
some authors suggest that dolphinfish abundance in¬ 
creases with high temperatures (Zuniga-Flores et al., 
2008); however, our findings suggest that optimal tem¬ 
peratures for dolphinfish are between 25°C and 28°C 
(with an important decrease in ICPUE at temperatures 
>28°C), which could explain the low ICPUE area in 
the Eastern Pacific Warm Pool, an area that is char¬ 
acterized by high (>27.5°C) SST values all year long 
(Fiedler and Talley, 2006). 
A wide range of SSH values were found in the study 
area, although high ICPUE occurred only over a nar¬ 
row range of both positive and negative values. Posi¬ 
tive SSH values indicate a zone of convergence (anticy- 
clonic activity) in the Northern Hemisphere (Lalli and 
Parsons, 1997) and indicate that dolphinfish associate 
with anticyclonic structures—a behavior that has been 
reported for other large pelagic fish, such as the alba- 
core (Thunnus alalunga ) (Zainuddin et al., 2006). 
Additionally, in respect to the possible effect of mi¬ 
grations during the seasonality of dolphinfish catch, 
Kraul (1999) suggested that dolphinfish can spawn 
several times a year, that some cohorts are “stronger” 
than others, and that the survivors of those strong 
