seasonal prey shifts and bioenergetics daniel d. magoulick arkansas cooperative fish and wildlife...
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Seasonal prey shifts and bioenergetics
Daniel D. Magoulick
Arkansas Cooperative Fish and Wildlife Research UnitDepartment of Biological Sciences
University of Arkansas - Fayetteville
Questions• What fish species prey on zebra mussels
in Lake Dardanelle and the Arkansas River?
• Do fish predators prefer zebra mussels over other prey? Is this affected by fish size or season?
• Are zebra mussels a profitable prey item for fishes in Lake Dardanelle?
Dardanelle Dam
Illinois BayouSpillway
N
RiverChannel
LEGEND
CreekChannel
City ofRusselville
Study Site
Predation Experiment Site
Fish CollectionSite
Number Percent Fish Containing Containing
Predator N Size (mm) D. polymorpha D. polymorpha Blue catfish (Up to 6/98) 586 229-686 310 52.90 Blue catfish (7/98-1/99) 257 305-635 1 0.4 Channel catfish 798 76-533 0 0 Freshwater drum (S) 340 76-190 0 0 Freshwater drum (L) 164 191-584 79 48.17 Bluegill 201 127-203 0 0 Redear sunfish 236 51-254 236 100.00 River carpsucker 67 279-508 0 0 Spotted sucker 36 229-432 0 0 Common Carp 19 381-686 0 0
Blue Catfish Prey SelectionLake Dardanelle 1996-1999
0
20
40
60
80
100
Per
cent
age
of F
ish
(%)
7/96 9/96* 1/97 3/97 4/97 9/97* 12/97 1/98 3/98 5/98 6/98 8/98 9/98 1/99
Sample Dates
ZM
Shad
Other
Empty
0
20
40
60
80
100
Per
cent
pre
y us
e
J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J
1996 1997 1998
Blue Catfish Prey SelectionLake Dardanelle 1996-1999
0
20
40
60
80
100
Per
cent
age
of F
ish
(%)
7/96 9/96* 1/97 3/97 4/97 9/97* 12/97 1/98 3/98 5/98 6/98 8/98 9/98 1/99
Sample Dates
ZM
Shad
Other
Empty
0
20
40
60
80
100
Per
cent
pre
y us
e
J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J
1996 1997 1998
Zebra Mussels Consumed by Blue CatfishPredator Size Classes
0
10
20
30
40
Nu
mb
er
of F
ish
203.2 254 304.8 355.6 406.4 457.2 508 558.8 609.6 660.4 >711.2Blue Catfish Size Classes (mm)
Fish Containing Zebra Mussels Total Number of Fish/Size Class
(N = 463)
Length of Zebra MusselsIngested by Blue Catfish
0
5
10
15
20
25
30
Len
gth
(m
m)
228.6 254 279.4 304.8 330.2355.6 381 406.4431.8 457.2 482.6 508 533.4558.8 584.2 609.6 635Blue Catfish Size Class (mm)
(N = 140)
Major Points• Blue catfish are a new and important
predator of zebra mussels.– 53% of blue catfish contained zebra mussels
• Blue catfish show seasonal prey shifts, consuming zebra mussels in summer and shad in winter.– Alternation between native species and
introduced species
• All size classes of blue catfish consume zebra mussels extensively.
Ash Free Dry Mass
Season
Joul
es g
-1(x
1000
)
0
5
10
15
20
25
30
35
Threadfin ShadGizzard ShadZebra MusselAsiatic Clam
Spring Sum/Fall Winter
Whole Organism Dry Mass
Season
Joul
es g
-1(x
1000
)
0
2
4
20
25
30
Threadfin ShadGizzard ShadZebra MusselAsiatic Clam
Spring Sum/Fall Winter
Zebra Mussel Consumption and Growth of Freshwater Drum in Lake Erie
Graph From Study by French and Bur (1991)
175
225
275
325
375
Mea
n b
ack-
calc
ula
ted
to
tal
len
gth
(m
m)
2 3 4 5 6 7Age
present study (1991)
1978 (Bur 1984)
1958 (Edsall 1967)
Major Points
• Energy content of bivalves was significantly less than that of shad.
• Energy content showed a significant interaction between prey species and season.
• Shad had significantly greater energy content than bivalves in any season.– Whole organism energy content of shad was order
of magnitude greater than bivalves.• Quantity vs. quality?
Conclusions• Zebra mussels have become an important prey
item for freshwater drum, redear sunfish, and blue catfish in Lake Dardanelle and the Arkansas River.– Adult blue catfish forage extensively on all sizes of
zebra mussels.– Blue catfish show a seasonal prey shift, feeding on
zebra mussels in summer and shad in winter.
• Zebra mussels and asiatic clams are significantly lower in caloric value than gizzard and threadfin shad.– Quantity vs quality?– Prey profitability? (Capture success, handling time,
evacuation rates, prey density, season)
38
Blue Catfish Prey Consumption based on Bioenergetics Model
Greater biomass of zebra mussels than shad were consumed by all size classes
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