Trophic relationships of five species of demersal
fishes in the northeastern Chukchi Sea
Lorena Edenfield*, Brenda Norcross, Sara Carroll, and Brenda Holladay
School of Fisheries and Ocean Sciences, University of Alaska Fairbanks
*[email protected]
Background:
Results and Discussion:
Fishes in the Arctic are important
components of the ecosystem,
both as predators and as prey. As
the Arctic warms and sea ice
decreases, prey availability for
fishes and other predators is
expected to change.
Diet:
Differences in diet were observed among species and among size classes within species.
100
Arctic cod
0-50 mm
51-75 mm
76-100 mm
101+ mm
80
60
• Amphipods were important for all species
• Copepods were central to the diet of all sizes of Arctic cod
40
20
0
100
Arctic staghorn sculpin
• Polar eelpout and stout eelblenny had very diverse diets
80
This study examined stomach
contents and stable isotopes of
five fish species collected in 20092010 in the Chukchi Sea.
Percent Index of Relative Importance
The species selected represent
major taxonomic families of the
Chukchi Sea.
60
Map of study area. Most fish were
collected from Klondike and Burger
areas.
• MDS clusters show strong similarities within species, despite the
differences observed in importance of prey taxa
40
20
0
100
stout eelblenny
80
60
40
20
0
100
polar eelpout
80
60
40
Methods:
20
0
100
Bering flounder
80
Stable Isotopes:
15N and 13C values can
describe trophic structure
and carbon source for fish
and fish prey.
High %IRI = important
prey item
High 15N = higher
trophic level
High
13C
= benthic
source
40
Arctic cod
Arctic staghorn sculpin
stout eelblenny
polar eelpout
Bering flounder
20
rim
p
Sh
er
er
C
ru
st
ac
ea
n
Po
ly
ch
ae
te
O
th
O
th
de
N
em
at
o
sc
M
ol
lu
sh
Fi
ys
id
Eu
ph
au
si
id
/M
C
ra
b
d
ep
o
ip
od
0
Percent Index of Relative Importance for all species
18
Stable isotopes:
Differences were found among species in
trophic level and feeding strategy
(benthic vs. pelagic).
Arctic cod
Arctic staghorn sculpin
16
Stout eelblenny
Polar eelpout
• Arctic cod consumed pelagic prey at the
lowest trophic level, while polar eelpout fed
on benthic prey at the highest trophic
level.
• Bering flounder, Arctic staghorn sculpin,
and stout eelblenny fell in between Arctic
cod and polar eelpout in terms of trophic
placement and feeding strategies.
What does this mean?
Black = 0-50 mm
Yellow = 51-75 mm
Blue = 76-100 mm
Orange = 101+ mm
MDS plot of diets. Dotted line is 40% similarity and solid line is 60% similarity.
 15N [‰]
MDS plots show similarity of
diets among species and size
classes.
60
C
op
380 Arctic cod
(Boreogadus saida)
123 Arctic staghorn sculpin
(Gymnocanthus tricuspis)
203 stout eelblenny
(Anisarchus medius)
181 polar eelpout
(Lycodes polaris)
130 Bering flounder
(Hippoglossoides robustus)
Diet:
Index of Relative Importance
(IRI) takes three diet factors
into account:
• presence,
• Numbers
• weight.
Thus, smaller and more
numerous prey, such as
copepods, aren’t “worth”
more to the index than
heavier, less common prey,
such as fish.
A
m
ph
We analyzed diet and stable
isotope signatures for four size
classes of:
Bering flounder
14
Amphipod
Copepod
12
Euphausiid/Mysid
Fish
10
Mollusc
Nematode
OtherCrustacean
8
Polychaete
Shrimp
6
-24
Stable isotope ratios by size class and species
-22
-20
-18
 13C [‰]
-16
Stable isotope ratios for selected fish and prey
We observed differences between diets of fish species, size class, and the associated trophic level of the fish species. Some
species relied almost exclusively on low-trophic, pelagic prey, while others had a diverse diet including high-trophic benthic prey. The
fishes studied are prey for other Arctic predators. If climate change results in changes in the availability of prey of fishes, the trophic
structure of the Arctic ecosystem could also shift.
Acknowledgements:
•
•
UAF Fisheries Oceanography Laboratory
technicians
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