Van Noord et aL: Oceanographic influences on the diet of myctophids in the eastern Pacific Ocean 
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Figure ? 
Map of terminal node groups 3, 4, and 5 in the classification tree of myctophid prey composition and showing the boot- 
strapped diet proportions for the myctophids grouped at each terminal node. Map displays symbols, which indicate the sam- 
pling stations where myctophids were feeding similarly according to the classification tree analysis. All stations occurred 
in waters >3000 m and bathymetric contours (in m) are displayed to show the depth ranges of our sampling. Diet diversity 
(D) values ranging from 0 (no diet diversity) to 1 (high diet diversity), are shown above each graph. Color gradients are pro- 
vided for ease of viewing. Abbreviations are as follows: A=amphipod; C=copepod; E=euphausiid; A.Hyp=hyperiid amphipods; 
A.Otr=unidentifiable and rare ampliipod types; A.Pla=platyscellid amphipods; A.Pro=pronoid amphipods; C.Cal=calanid 
copepods; G.Can=candaciid copepods; C.Cyc=;cyclopoid copepods; C.Euc=euchaetid coepods; C.Eucl=eucalanid copepods;“C. 
Otr=unidentifiable and rare copepod types; C.Pon=pontellid copepods; C.Tem=temorid copepods; E.Eup=euphausiids,; 
LF=:larvaI fishes; M=mollasks, O.Ca=Cypridina americana (ostracod); O.Hal=HaIocyprida ostracods. 
es in the prey community (Fiedler et al., 2013). These 
studies document the dynamic nature of the feeding 
habits of fish, and show/ that feeding patterns are not 
necessarily static; fish clearly respond to oceanographic 
conditions, in addition to displaying intrinsic behaviors 
that result in a more typical pattern of resource parti- 
tioning. This dynamic feeding behavior highlights the 
necessity of obtaining samples that adequately cover 
both temporal and spatial scales. 
We sampled only surface migrating myctophids and 
therefore the interpretation of our data and implica- 
tions for the broader myctophid community are limited. 
We did not include deeper dwelling individuals, and 
this limitation could alter both the feeding patterns 
observed and the size class of myctophids encountered. 
Sampling a broader spectrum of the myctophid popu- 
lation by using a suite of sampling gear that would 
cover the entire depth range for these fish could help 
to elucidate distributional patterns in the ETP and bet- 
ter address the role of resource partitioning in this fish 
community. As with all studies of fish feeding habits, 
taxonomic resolution of stomach contents impacts in- 
terpretation of the results. A finer taxonomic resolution 
may reveal a more subtle species-level diet partition- 
ing among the myctophids. Prey size is also a function 
of the resolution of stomach samples and because we 
were unable to consistently quantify prey size in this 
study, it is possible that some species of myctophids 
partition diets on the basis of prey size rather than 
species, or some combination of size and species. As 
with most studies, a greater temporal sampling reso- 
lution would be beneficial for addressing longer term 
nuances in feeding ecology, and future work would 
benefit from seasonal and yearly sampling. Both these 
improvements are reinforced by the fact that our cur- 
rent analysis has shown the importance of physical 
variables in fish diet studies and highlights the need 
to include spatial, oceanographic and biological factors 
when evaluating feeding patterns of myctophids and of 
fish in general. 
Acknowledgments 
This research was partially funded by the University 
of San Diego and a Stephen Sullivan Memorial Schol- 
arship. We thank the many scientists at the South- 
west Fisheries Science Center, NOAA, who made these 
samples available, including: L. Ballance, P. Fiedler, V. 
Andreassi, C. Hall, M. Kelley, R. Pitman, and G. Wat- 
