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Diet of Olympic Mudminnow Spatial and Temporal Variation
Andi Kopit, Roger Tabor, and Christina Meister U.S. Fish and Wildlife
The Evergreen State College
What’s for
lunch?
Acknowledgments Webster Tree Farm (WDNR) – John Trobaugh Capital Land Trust USFWS employees Brad Thompson Teal Waterstrat Kira Mazzi Zachary Moore Michael Elam
Background
John W. Meldrim conducted the first study that looked at mudminnow diet
Meldrim, J.W. 1968. The ecological zoogeography of the Olympic mudminnow. University of Washington, Seattle.
Objectives
1. Basic understanding of the Olympic Mudminnow diet
2. Observe how their diets vary from site to site and between seasons
3. Do they consume pests to any extent?
Sample Design
Samples collected from three collection
sites once a month Collected samples from February to
August 2012 Samples collected once in June at three
other sites ~ 20 samples at each site on each date
Collection Sites
Green Cove Large wetland
Fish species present: only Mudminnow
Hopkins Ditch Low gradient stream
Fish species present: Mudminnow, Stickleback, Sculpin, Cutthroat, and Coho
Woodard Creek Storm water retention pond
Fish species present: only Mudminnow
Steamboat Bog Sphagnum moss bog
only mudminnow present
Adna Wetland Large wetland
Connor Creek Low gradient coastal stream June Collection
Sites
Other fish species present
Field collections Fish collected by dipnetting Gastric lavage (1.5-mm-
diameter copper tube) Sampled fish > 40 mm MS-222 as anesthetic Weight, length, and sex
recorded Stomach sample collected in
a sieve
Lab Analysis
Macroinvertebrates identified, sorted, counted, and weighed Aquatic insects and large
crustaceans identified to family Other prey identified to order or
other convenient taxon
Data Analysis Percent by Weight (%W) Percent by Number (%N) Frequency of Occurrence (FO) Index of Relative Importance (IRI)
• (%N+%W)*FO Diet Overlap – Schoener’s Index
• Range of values: 0 - 1 • Values > 0.6 – significant overlap
Diet Breadth – Levin’s Index • Range of values: 1 – infinity • Values < 2 indicate little diet breadth
http://72.44.83.99/forum/viewthread.php?thread_id=27397&pid=122174
Results gfp.sd.gov
bugguide.net
bugguide.net
bugguide.net
0
20
40
60
80
100
Perc
ent
Size class (mm)
Other
Ostracods
Cladocerans
Copepods
Mollusks
Oligochaetes
Other Aq insects
Aq diptera
23 19Winter Spring Summer
34 26 1 15 17 10
0
20
40
60
80
100
Perc
ent
Size class (mm)
Other
Ostracods
Cladocerans
Copepods
Mollusks
Oligochaetes
Other Aq insects
Aq diptera
23 19Winter Spring Summer
34 26 1 15 17 10
Green Cove wetland
A) Percent by number
B) Percent by weight
Hopkins Ditch Low gradient stream
A) Percent by number
B) Percent by weight 0
20
40
60
80
100Pe
rcen
t
Size class (mm)
Other
Ostracods
Cladocerans
Copepods
Mollusks
Oligochaetes
Other Aq insects
Aq diptera
5 10Winter Spring Summer
23 28 10 14 14 145
0
20
40
60
80
100
Perc
ent
Size class (mm)
Other
Ostracods
Cladocerans
Copepods
Mollusks
Oligochaetes
Other Aq insects
Aq diptera
5 10Winter Spring Summer
23 28 10 14 14 145
Woodard Creek Stormwater retention pond
A) Percent by number
B) Percent by weight
0
20
40
60
80
100
Perc
ent
Size class (mm)
Other
Ostracods
Cladocerans
Copepods
Mollusks
Oligochaetes
Other Aq insects
Aq diptera
10 7Winter Spring Summer
24 20 22 14 14 1423
0
20
40
60
80
100Pe
rcen
t
Size class (mm)
Other
Ostracods
Cladocerans
Copepods
Mollusks
Oligochaetes
Other Aq insects
Aq diptera
10 7Winter Spring Summer
24 20 22 14 14 1423
0
20
40
60
80
100
40 - 4
9
50 - 5
9> 6
0
40 - 4
9
50 - 5
9> 6
0
40 - 4
9
50 - 5
9> 6
0
Size class (mm)
Perc
ent I
RI
OtherOstracods
CladoceransCopepods
MollusksOligochaetesOther Aq insects
Aq diptera
10 7
Winter Spring Summer24 20 22 14 14 1423
Woodard Creek Index of Relative Importance
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1 vs 2
1 vs 3
2 vs 3
1 vs 2
1 vs 3
2 vs 3
1 vs 2
1 vs 3
2 vs 3
Comparison
Ove
rlap
inde
x
Winter Spring Summer
Woodard Creek Size Class Comparisons - Diet Overlap Index
1 = 40 – 49 mm 2 = 50 – 59 mm 3 = > 60 mm
0
20
40
60
80
100
Perc
ent
Size class (mm)
Other
Ostracods
Cladocerans
Copepods
Mollusks
Oligochaetes
Other Aq insects
Aq diptera
Conner Cr Steamboat Cr Adna Green Cove Hopkins Woodard CrWetland Wetland Ditch
Diet Composition – June-July 2012 Percent by weight
Site Conner Cr Steamboat
Cr Adna
Wetland
Green Cove
Wetland Hopkins
Ditch Woodard
Cr
Conner Cr
Steamboat Cr 0.064
Adna Wetland 0.035 0.354
Green Cove Wetland 0.071 0.221 0.368
Hopkins Ditch 0.102 0.141 0.158 0.290
Woodard Cr 0.069 0.192 0.362 0.802 0.248
Diet Overlap Index Values June-July 2012
Values > 0.6 indicate significant overlap
Diet Breadth Index Values June-July 2012
0
1
2
3
4
5
6
7
ConnerCreek
SteamboatBog
AdnaWetland
Green CoveWetland
HopkinsDitch
WoodardCreek
Die
t bre
adth
inde
x
Site
Variation in Prey Size
Observed prey size range: < 1 mm to 15 mm
Consumption of Pests
Mosquitoes (Culicidae)
Biting Midges or No-see-ums (Ceratopogonidae)
glerl.noaa.gov
Consumption of Pests
Site - Month Sample
Size Number observed
Percent of diet by weight
Green Cove wetland - May 20 47 2.8
Steamboat Creek bog - June 18 247 23.4
A) Culicidae – mosquitoes - documented only at Woodard Creek in July and August
Month Sample
Size Number observed
Percent of diet by weight
July 21 3 1.4
August 21 6 5.4
B) Ceratopogonidae – biting midges (no-see-ums) - documented at each site
Summary
Mudminnow diet varied seasonally Mudminnow diet usually varied from site
to site Diet often varied with fish size Prey size varied widely Overall, mudminnow appear to an
opportunistic feeder
Summary Consumption of mosquitoes was
observed at one site during the summer Because mudminnow can be locally
abundant, they may be beneficial in reducing the abundance of some pests
