Stoneflies
Yet another group of aquatic life disappearing from rivers
John Woodling
Colorado Mesa U
Environmental Sciences Department
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Plecoptera (stoneflies) are the most primitive insect order that
can flex or fold wings in some manner.
Early Triassic period stoneflies (250 million years ago) are
much like the species found today throughout the world.
Stoneflies survived the event that killed off Dinosaurs 65
million years ago.
Stoneflies do not appear to be able to survive human society.
43% of all United States stonefly species are at
risk
Stoneflies in United States
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In Illinois 25%(1) of all stonefly taxa have become
extirpated since the 1950s.
In Indiana 11.5%(1) of all stonefly taxa have become
extirpated since the 1950s.
Other studies are reporting the same pattern in other
states for other aquatic insect orders.
Stoneflies in Colorado
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Not a lot of studies where one stream reach sampled
through time for aquatic insects.
The Colorado Division of Wildlife* did a long term
sampling of Eagle River (on going from 1989), aquatic
insect samples from 1993 until 2011 (no samples 2006 –
2010).
Site at Arrowhead Golf Course chosen as Reference
Location
Site downstream of Minturn and above Gore was
impacted by Eagle Mine. Arrowhead bugs better.
* =And a lot of others, HAZMAT, CBS, ERWC, EML LLC, local volunteers and schools
Stoneflies in Colorado
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Aquatic insects sampled from 1993 to 2005 and again in
2011 by DOW*.
All sampling used the same techniques.
All samples identified by Aquatics and Associates from
1993 through 2005 and by David Rees in 2011
Data collation and photography by Colorado Mesa U.
Aquatic Entomology classes of 2009 and 2011.
* = And a lot of others, HAZMAT, CBS, ERWC, EML LLC, local volunteers and schools
Stonefly families
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The order Plecoptera is divided into
families including
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Perlidae – the golden or summer stones
Nemouridae – spring stones or tiny winter
black stoneflies
Pteronarcidae – Salmon flies, giant stones
Perlodidae – Springflies, yellow sallies
Stoneflies – functional feeding groups
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Stoneflies can also be separated into groups based on
what species consume.
Pteronarcella badia is a shredder and eats plant
material.
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Shredders turn leaf litter or algae into insect body mass. That
insect mass is an important trout food.
Isoperla fulva and Isogenoides sp. are predators.
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Aquatic insect predators are also an important component of
trout food.
Number of Pteronarcella badia collected each
year at Eagle River at Arrowhead (Site 6)
100
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80
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60
None were collected in
2004, 2005 and 2011.
No official samples from
2006-2010*.
40
*=0
0
1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
20
Number collected
* = I did look for P. badia in 07-2010
Number of two predatory stoneflies collected
each year at Eagle River at Arrowhead (Site 6)
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1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
45
40
35
30
25
20
15
10
5
0
number Isoperla fulva
number Isogenoides sp.
No samples from 20062010.
Isogenoides, photo credit
“Discover Life”
Number of 3 dominant stoneflies each year at
Eagle River at Arrowhead (Site 6).
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140
120
100
80
60
40
20
Number of Pteronarcella
Number of Isoperla fulva
Number of Isogenoides sp.
Number of all other stoneflies
2011
2009
2007
2005
2003
2001
1999
1997
1995
1993
0
Dominant taxa
from 1993 to
about 2000
gone in 2005
and 2011.
Number of Nemouridae (shredders) collected
each year at Eagle River at Arrowhead (Site 6)
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1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
8
7
6
5
4
3
2
1
0
Number collected
None were collected in
2004, 2005 and 2011.
No samples from 20062010.
Stoneflies – in the Eagle River at Arrowhead
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Stoneflies are only an incidental component of aquatic
community at the Arrowhead Golf Course as of the
spring of 2011.
A large component of the aquatic biota in the Eagle
River is gone.
Shredders seem to be the most severely impacted
group. The same observation made in Illinois and
Indiana.
Stoneflies – in the Eagle River and Colorado River
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Study by Timberline Aquatics demonstrated that aquatic
macroinvertebrates in the Eagle River from Vail to
Edwards reduced in numbers and types of mayflies,
stoneflies and caddisflies.
DPW has noted decrease in Pteronarcidae in mainstem
Colorado River upstream of Eagle River.
Few stoneflies captured in mainstem Colorado River
from Glenwood Springs downstream to Grand Junction,
Colorado by CMU entomology class.
Number of Nemouridae collected yearly, Eagle
River above Gore compared to Arrowhead
60
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50
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40
30
20
0
1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
10
Arrowhead
Above Gore
None were collected in
2004, 2005 and 2011.
No samples from 20062010.
Number of Pteronarcella badia collected each
year at Eagle River above Gore Creek
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*=0
1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
80
70
60
50
40
30
20
10
0
Number collected
No samples from 20062010.
Same pattern as
Arrowhead?
Stoneflies – Limiting environmental factors
Eagle River
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Eagle River substrate at Arrowhead not a typical
mountain stream.
Lots of nitrogen and phosphorus in water column
Substrate cobble covered by fine sediments in April of
each year.
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Sediments appear as fine brown material along with algal and
fungal mats covering stream cobble.
Sediments are periodically black and anaerobic with a smell of
sewage to a depth of several inches in eddies.
Stoneflies – The Contaminant sources in the
Eagle River
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Interstate 70 – from the top of Vail Pass to Vail. Traction
sand and magnesium chloride
Urbanization of valley floor
Domestic wastewater effluents
Loss of dilution water – transmountain diversions.
Tree spraying – has resulted in shredder loss in many
other parts of U.S. Vail encouraged tree spraying
starting in 2004?
The impact on stoneflies is probably due to a
combination of factors.
Number of Ephemerella infrequens collected
yearly, Eagle River at Arrowhead
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100
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80
60
40
0
1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
20
Arrowhead
No samples from 20062010.
E. infrequens one of few
mayfly species that
colonizes sand and gravel
(2).
Number of Drunella mayflies collected yearly,
Eagle River at Arrowhead
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300
250
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200
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150
100
0
1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
50
D. grandis
D. doddsi
No samples from 20062010.
One D. grandis collected in
2011.
D. grandis is more of a
habitat generalist than D.
doddsi and is found in
areas with gravels and
fines. D. doddsi is not
found in areas with small
gravels and fines (3).
Stoneflies – Influence of tree spraying on
numbers of Eagle River stoneflies.
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Town of Vail actively encouraged landowners to spray
trees for two different pests.
Shredders have decreased in many U.S. rivers due to
spraying programs.
Spraying is part of the problem with stoneflies in the Vail
area.
Stoneflies – Influence of sediments on numbers
of Eagle River stoneflies.
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Increased sedimentation has filled the interstitial spaces
on stream substrate in mainstem Eagle River
downstream of Gore Creek
Shredders have decreased in the Eagle River at
Arrowhead since the late 1990’s.
Increased sediments could be part of cause in declinde
of stonefly species and other taxa due to habitat loss.
Stoneflies – Influence of nutrients on numbers
of Eagle River stonefly shredders.
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Multiple studies have shown that addition of nutrients to
leaf litter increased the numbers of shredders present.
These studies lasted for one year.
Recent multi-year studies seem to indicate the reverse,
increased nutrients lead o increase fungal growth and
eventual reduction in the numbers of aquatic insects.
Stoneflies – How to protect Colorado species.
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Stop spraying trees on the side of the river
Reduce sediments, Highway and urban
Tertiary treatment of domestic wastewater
Stoneflies – Future in large rivers in the State of
Colorado.
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Stonefly perspective in mainstem Colorado Rivers =
“The Sky IS falling,” C. Little finally got it right.
The large river stonefly perspective from human eyes =
“We have met the enemy and he are us,” Pogo.
Lit cites.
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1. DeWalt, R.E., C. Favret, & D.W. Webb. 2005. Just how imperiled
are aquatic insects? A case study of stoneflies (Plecoptera) in
Illinois. Annals of the Entomological Society of America, 98:941–
950.
2. Hawkins, C.P. 1984. Substrate associations and longitudinal
distributions in species of Ephemerellidae (Ephemeroptera:Insecta)
from western Oregon. Freshwater Invertebrate Biology. 3:181-188.
3. Winget, R.N. 1993. Habitat partitioning among three species of
Ephemerelloidea. Journal of freshwater ecology. 8. 227-233.