IInpaets 01 Uvestock GrazIng
Actlvlti_ on Stream Iasect
Commuaiti_
and the
Riverine EavlrolUneat
Mac Strand and Ricbard
w: Merritt
"Erosion eats into our hills like a contagion,
and floods bring down the loosened soil upon
our valleys like a scourge. Water, soil, animals, and plants-the very fabric of prosperity-react to destroy each other and us. Science
can and must unravel those reactions, and
government must enforce the findings of science. "
-Aldo
Leopold(1923)
T
HIS STERN ADVISORY TO FEDERAL LAND MAN-
agers was Aldo Leopold's response to
years of rapidly degrading riparian
habitat caused by livestock grazing in the
southwestern United States. It was followed not
by long-lasting grazing reform, but by decades
of expansion of cattle production in riparian
habitats from the desert southwest to all points
north and east. Today in the western United
States, livestock (principally cattle) are grazed
on approximately 70% of the landscape, much
of which is public (F1eischner 1994). Recent
evidence of drinking water contamination,
imprudent grazing fee structures, and loss of
wildlife habitat has led concerned citizens and
scientists to encourage policy makers to restrict grazing, particularly in habitats vulnerable to irreparable damage (Sherer et aI. 1992;
WissmaretaI. 1994; Armouret aI. 1991, 1994;
F1eischner 1994). Range managers and ecologists generally agree that many currently
grazed habitats (e.g., alpine meadows [Kon-
AMERICAN
ENTOMOLOGIST
•
Volume 45, Number 1
doH 1993], sagebrush steppe [Taitet al. 1994])
cannot sustain conflicting societal demands for
inexpensive beef and high-quality water (Minshall et al. 1989, Mosely et al. 1993, Fleischner
1994). However, despite strong public and scientific will to limit the types of public habitat
available for pasturing livestock, grazing contracts continually are awarded with little recognition of differing habitat sensitivities, even
though restoration costs often far outweigh
income from grazing fees (Minshall et al.
1989, Armour et aI. 1994, Kondolf 1993).
Here, we review the evidence of livestock production impacts on riverine ecosystems. Emphasis is placed on examinations of direct responses of aquatic insects to the activities of
cattle (e.g., respiratory stress due to coating of
gill structures), and on studies that illustrate
the potential of grazing in riparian areas that
indirectly affect aquatic insects through habitat alteration (Fig. 1).
13
Life Before Cattle:
Effects of Native Bovids on
Riverine Ecology
"The river has more sand bars today than
usual, and more soft mud ...at 2 P.M. I was
obliged to land to let the Buffalow cross
over. ..nearly 1/4 of a mile in width this gangue
of Buffalow was ... two gangues of Buffalow
crossed a little below us, as noumerous as the
first. "
-William
Clark (1806)
These notes from the Lewis and Clark expedition diaries document what certainly
amounted to an intense disturbance of stream
bed ha bitat in the Yellowstone River caused by
North American bison (Bison bison [L.]).
Clark also noted several instances of very
muddy water flowing in small channels draining rangeland grazed by bison, indica ting erosion at a level high enough to cause effects now
deemed harmful to stream habitat. Prior to
wide-scale settlement by Europeans, an estimated 30-60 million bison roamed the grasslands and trampled the stream beds of North
America from central Canada to mid-Mexico,
including the vast majority of the lower 48
United States (Garretson 1965, McHugh 1972,
Danz 1997). Most of these animals moved
about the Great Plains in huge herds estimated
by several witnesses to include more than oneFig. 1. Some common effects
of overgrazing on the aquatic
environment (illustration by
Roger W. Strand).
million individuals (Danz 1997). Large, densely packed trails formed as generation after
generation of bison made their way from upland pastures to watering sites (Garretson
1965, McHugh 1972, Danz 1997). The erosion
and stream-bed trampling observed by Clark
(1806) may have been restricted to riverine
habitat lying along these historic pathways,
but it certainly must have influenced aquatic
insects in a manner similar to what occurs today in most heavily stocked cattle pastures and
rangeland.
The activities of bison surely had enormous
effects on riparian habitat and riverine insect
communities, but cattle production impacts
have eclipsed these effects, even where bison
influences were strongest (Minshall et al.
1989). Currently, more than 102 million cattle
are grazed on United States pastures and
rangeland alone (Danz 1997). Not only are
there far more cattle now than there were bison
when the first settlers reached the Great Plains,
but the combined effects of diet supplementation, predator abatement, and disease control
have freed cattle from factors that control the
size of ungulate populations in natural grazing
systems (McNaughton 1986, 1993; Hobbs
1996; Hobbs et al. 1996). Moreover, whereas
bison tend to concentrate their grazing activities on upland pastures, cattle prefer to graze in
and around streams (Minshall et al. 1989;
Armour et al. 1991, 1994; Fleischner 1994),
thus exerting a continuous disturbance to riv-
SOME EFFECTS OF OVERGRAZING ON AQUATIC INSECTS
Siltation
Substrata Simplification
Hyporhalc
Zone Burial
Suspended Sediment
Increasad
Solid Substrate Habitat
Diminished
14
AMERICAN ENTOMOLOGIST
•
Spring 1999
erine habitat instead of the periodic disturbance experienced by organisms in bison
range streams.
Effects of Cattle Grazing on
Riverine Ecology
Although cattle grazing effects are not necessarily negative from a range management
perspective (e.g., grassland primary production and species richness can be increased by
cattle grazing [Milchunas and Lavenroth
1993, Hofstede 1995]), the consequences of
cattle congregating in and around water can
pose a serious threat to native organisms (Table 1, Fig. 1) and, often, counter wildlife-management objectives (TarzweIl1938; Minshall
et al. 1989; Armour et al. 1991, 1994;
Fleischner 1994). Therefore, in the context of
wildlife management, cattle grazing in riparian habitat has been viewed historically as
harmful to riverine ecosystems (e.g., Leopold
1923,1946; Tarzwell1938; Resh et al. 1988;
Armour et al. 1991, 1994; Fleischner 1994;
Waters 1995). The term "overgrazing" often is
used to characterize cattle production practices that negatively affect aquatic ecosystems,
but there really is no agreement on exactly
what conditions fall within the purview of
overgrazing (Fleischner 1994). Leopold (1923,
1946) used the relative prevalence of permanent patches of exposed soil along stream
banks (Leopold's "earth scars") as an indication of unsustainable grazing in riparian habitat (e.g., Fig. 2A). Where these barren patches
are common, gully erosion and increased solar
input can combine to increase sediment input,
nutrient enrichment, and temperature variation (Modde et al. 1986, Tait et al. 1994,
Quinn et al. 1992a). These general disturbance
effects interact to fundamentally alter aquatic
habitat, with wide-ranging consequences for
aquatic insects.
soil (Bryant et al. 1972, Orodho et al. 1990)
combine to cause large increases in overland
flow. Damage is particularly severe in riparian
habitat used both as spring-summer pasture
and fall-winter feedlot (Owens et al. 1982).
Riverine fishes reportedly are very sensitive
to elevated concentrations of suspended sediments (Herbert and Merkins 1961, Berg and
Northcote 1985, Redding et al. 1987, Servizi
and Martens 1992), but little corollary evidence of direct effects exists for aquatic insects.
Ciborowski et al. (1977) observed drift increases by nymphs of Ephemerella subvaria McDunnough (Ephemeroptera: Ephemerellidae)
exposed to experimental sedimentation, but
habitat change resulting from deposited sediments (i.e., siltation) could not be ruled out as
the cause of drift increases. Culp et al. (1986)
added fine sediments to a British Columbia
stream and detected an immediate increase in
downstream movement (i.e., drift) by insects
most exposed to sediment particles bouncing
and sliding along stream bed substrates. This
scouring effect was unrelated to deposition
and, thus, suggests that suspended sediments
can directly affect aquatic insects, at least
when current velocities are great enough to
force sand or larger-size particles to collide
with insects occupying substrate surfaces.
However, the preponderance of evidence indicates that the most important effect of sedimentation for aquatic insects is habitat degradation by siltation rather than direct, physical
stress caused by exposure to suspended particles (Chutter 1969, Nuttall and Bielby 1973,
Rosenberg and Snow 1975, Newcombe and
McDonald 1991, Waters 1995).
More United States stream habitat is degraded by siltation than by any other form of
environmental pollution (Waters 1995). When
siltation is light and impermanent, effects on
aquatic insects are highly variable, but insect
Table 1.
Sedimentation
ENTOMOLOGIST
impacts on native fishes
Effect
Humans are responsible for most of the sediment that enters North American streams, including vast amounts generated by the activities of cattle (Waters 1995). Sedimentation in
excess of natural erosion is recognized as the
most prevalent and damaging pollution source
to North American streams (Waters 1995).
Sediment pollution associated with cattle production occurs primarily during heavy rains
and snowmelt when devegetation of stream
banks (Gardner 1950; Gillespie 1981; Owens
et al. 1982,1983) and compaction of riparian
AMERICAN
Examples of livestock production
•
Volume 45, Number 1
Reference
Overgrazing destroyed microhabitats frequented by
California golden trout (Onchorynchus aguabonita
[Jordan])
Matthews
(1996)
Siltation in grazed meadow streams limited the
distribution of paiute cutthroat trout
(Onchorynchus clarki se/eniris [Snyder])
KondoH (1994)
Riparian grazing reduced terrestrial insect inputs
to streams. This reduced or eliminated populations
of blacks tripe topminnows (Funda/us notatus
[Rafinesque])
McAllister
Bank trampling resulted in declines in populations of
Apache trout (Onchorynchus gi/ae apache [Miller])
Clarkson and Wilson (1995)
(1987)
15
Fig. 2. Carlson Creek, Luce Co., Michigan: (A) cattle
had unrestricted access to the stream, (8) the first year
of cattle e~clusion, (C) the second year of cattle
exclusion, and (0) the upstream forest reach.
16
AMERICAN
ENTOMOLOGIST
•
Spring 1999
commUnIties typically remain qualitatively
similar following deposition (Rabeni and Minshall 1977, Lenat et al. 1981). Brief, but intense
bouts of sedimentation, such as those that follow construction of roads, bridges, and pipelines, typically result in a decrease in standing
stocks of aquatic insects with short-term alterations of community composition (Rosenberg
and Snow 1975, Rosenberg and Wiens 1978,
Tsui and McCart 1981, Cline et al. 1982,
Ogbeibu and Victor 1989). Persistent, heavy
siltation, such as that associated with mining
near streams, can result in biomass declines
and permanent changes in insect communities
typified by the replacement of species that require silt-free substrate surfaces and interstices
with aggregations of burrowing taxa (Learner
et al. 1971, Nuttall 1972, Nuttall and Bielby
1973, Wagener and LaPierrere 1985, Quinn et
al. 1992a).
Sedimentation resulting from cattle grazing
can be heavy enough to blanket stream channels with silt, but, more commonly, it causes
spatially discrete silt accumulations on stream
beds (Quinn et al. 1992b) and a gradual decrease in the depth of pools (Sidle and Sharma
1996). Chronic, moderate siltation, such as
that experienced downstream from cattle
crossings (Armour et al. 1991), can reduce the
quality of food resources for insects that feed on
algae and other microorganisms that cover
exposed substrates (Davies-Colley et al. 1992).
It also may interfere with feeding by insects
that filter food particles from flow (Hynes
1973, Rosenberg and Wiens 1978), as has been
found for other filter-feeding invertebrates including zooplankton (McCabe and O'Brien
1983, Kirk and Gilbert 1990) and bivalves
(Ellis 1936, Aldridge et al. 1987). To test this
hypothesis, we exposed nymphs of net-spinning caddisflies, Hydropsyche betteni Ross
and Ceratopsyche sparna (Ross) (Hydropsychidae), to daily increases in fine sediments in
amounts great enough to raise suspended-sediment concentrations but light enough to preclude total habitat transformation (Strand and
Merritt 1998). Sedimentation had no effect on
nymphal growth of either species, thus indicating that the energetic costs of maintaining nets
and retreats fouled with sediment were minimal. Sediment treatments did, however, increase mortality in both experimental populations,
which
suggests
that
chronic
sedimentation can affect seemingly sedimenttolerant species.
Perhaps the most insidious component of
sedimentation is its interaction with other pollution sources to compound and prolong biotic
AMERICAN
ENTOMOLOGIST
•
Volume 45, Number 1
responses. The fate of many contaminants in
aquatic ecosystems is determined by the dynamics of sorption, storage, and transport by
sediments (Ellis 1936, Fairchild et al. 1987,
Rostad et al 1993, Taylor et al. 1994). For
example, Lemly (1982) reported that fine sediment and excrement-derived nutrients in cattle pasture runoff acted synergistically to create a situation where insects occupying
substrate surfaces of an Appalachian trout
stream became shrouded with silt-bound nutrients and thick growths of the filamentous bacterium more typically associated with sewage
lagoons. Reports of fish experiencing similar
synergisms of sedimentation
and toxins
(McLeay et a!. 1983, 1984), and pathogens
(Redding et a!. 1987), indicate that this understudied phenomenon (Waters 1995) could be a
widespread problem for insects in grazed
streams.
Excrement Input
Due to the periodic threat of drinking water
contamination with toxins and pathogenic
microorganisms, livestock excrement input to
streams is the foremost grazing-related concern to humans who live downstream from
grazed riparian habitat (Table 2). Manure and
urine input to stream water also can affect
aquatic insects through the effects of waterchemistry changes and consequent biological
responses. Livestock excrement deposited
along stream banks and directly to channels
elevates stream water concentrations of inorganic phosphorus and nitrogen (Lemly 1982,
Kownacki 1983, Mosely et al. 1993). This fertilization of stream water can result in increased production by heterotrophic and autotrophic
microbes that, when current
velocities are low, can drastically reduce dissolved oxygen concentrations (Harris et al.
1994, Fleischner 1994).
Persistent excrement addition and consumption of emergent aquatic vegetation by
cattle often results in the formation of dense
instream accumulations of the filamentous
green alga Cladophora glommerata L., a species not consumed by cattle (Armour et al.
1991,1994; Matthews et al. 1994). These conditions promote the production of some insect
species such as the Cladophora-feeding, limnephilid caddis£ly Dicosmoecus
gilvipes
(Hagen) (Tait et al. 1994). However, because
Cladophora mats tend to replace a diverse
assemblage of attached photosynthetic organisms (e.g., diatoms, protists, blue-green algae,
and green algae), many herbivorous insect
17
Table 2. Some effects of livestock grazing on water quality
Reference( s)
Effect
Giardia and Cryptisporidium
contaminated
stream water; peak levels occurred during calving
Ong et al. 1996
Fecal coliform
stream water
Faust 1982, Tiedemann et al. 1987,
Pasquarell and Boyer 1995
bacteria
Fecal streptococcus
stream water
Fecal coliform
and streams
Pathogenic
contaminated
bacteria
contaminated
bacteria contaminated
amoebae
Faust 1982
wells
Howell et al. 1995
in runoff
Sawyer 1989
Cadmium from pasture fertilizer assimilated
oysters and phytoplankton
Toxaphene cattle dip in streamwater
reptiles, and birds
by
killed fish,
Butler and Timperley 1996
Brooks and Gardner
1980
populations decline in response to Cladophora
domination of stream bed substrates (Li et al.
1994). The covering of solid surfaces by Cladophora also can result in decreased foraging
efficiency of insectivorous fish due to a switch
in prey base from relatively exposed herbivorous insects feeding on diatoms and other producers to one heavily-cased and sessile D. gilvipes larvae (Tait et ai. 1994).
When cattle excrement inputs are extremely
high, ammonia concentrations may reach levels great enough to directly harm aquatic insects. Ammonia levels in grazed streams rarely
exceed the tolerance threshold of most pasturestream inhabitants (Overcash et ai. 1983), but
sensitive insects may be displaced due to
chronic, ammonia-induced
damage to gill
membranes (Hazel et al. 1979, DeGraeve et ai.
1980). Acute ammonia toxicity (1.2-8.0 mg/l)
(Hazel et al. 1979, DeGraeve et al. 1980) also
is a potential problem for aquatic insects in
heavily grazed streams, especially during hot,
dry weather when stream flow is low and cattle
wallow for extended periods to alleviate heat
stress.
Water Temperature Change
Livestock grazing does not always cause
pronounced changes in stream water temperatures (Li et al. 1994), but it can result in increased thermal variation (Kownacki 1983,
Kauffman and Krueger 1984) and maximum
temperatures (Burcham 1988, Quinn et al.
1992b). These temperature effects are largely
the result of increased solar input that follows
vegetation removal and bank trampling
(Quinn et al. 1992b). Algal and invertebrate
production can be increased by grazing-related temperature increases (Li et al. 1994),
18
which can be further stimulated by mineral
and nutrient increases (Kownacki 1983).
Sweeney (1993) reported 2-5°C increases in
stream water temperatures attributable to riparian forest clearing in the northeastern United States. This increase may seem trivial when
compared to daily and seasonal temperature
fluctuations in terrestrial realms. However, in
the relatively constant thermal environment of
flowing water, increases as slight as 2"C can
affect the physiology and alter distributions of
sensitive species (Sweeney and Vannote 1986).
Riparian-forest clearing and subsequent pasturing also may affect aerial adult aquatic insects by eliminating shaded resting structures
that are utilized extensively and, perhaps, required by many species. Most holometabolous
aquatic insects rely on resources stored during
the larval period to complete their life cycles.
Therefore, reduction or elimination of cool,
humid resting sites could limit the reproductive
potential of aerial adults as a result of compromised conservation of resources sequestered
during the larval stage.
Paleontological Entomology:
Discovering Evidence of
Livestock Grazing Impacts
The introduction of livestock to North
America almost certainly affected insect community composition wherever grazing altered
major ecosystem attributes (e.g., soil and water temperatures, plant species composition)
(Fig. 1). However, the specific consequences of
these community changes are poorly understood due to the rarity of pre settlement survey
data and the present difficulty in establishing
well-matched comparisons of grazed and ungrazed streams. Fortunately, some evidence of
the initial impacts of livestock grazing on
aquatic insects is still recoverable through entomological examination of fragments of exoskeletons deposited in pre- and post-settlement stream-bed sediments. For example,
Schwert (1996) documented dramatic changes
in the beetle fauna of an Iowa watershed that
occurred during European-American settlement (approximately150 yrs. ago) and extensive pasturing of cattle. Abundance of scarab
beetles associated with bovid dung increased
greatly in riparian habitats, suggesting heavier grazing pressure near streams than was previously exerted by bison. Meanwhile, the instream aquatic beetle assemblage changed
from one dominated by dryopoid species (seven e1mid and three dryopid species), indicating
functional changes in stream insect communi-
AMERICAN
ENTOMOLOGIST
•
Spring 1999
a cool-water, prairie stream, to one with few
dryopoids and a newly established population
ofPeltodytes edentulusLeConte (Haliplidae),
a crawling water beetle that thrives in warm,
eutrophic waters. A similar analysis of alluvial
organic deposits in Britain revealed that intensive agrarian activities beginning nearly 3,000
years ago also displaced a rich riffle beetle
(Elmidae) fauna from the now mud-blanketed
River Avon (Osborne 1988). These studies
demonstrate how valuable the recent fossil
record can be in analyses of past land use.
When used in conjunction with insect surveys
and monitoring of abiotic conditions, knowledge gained from paleontological entomology
can offer chronological comparisons of environmental conditions that are unmatched by
habitat profiles based solely on present insect
distributions.
Aquatic Insect Communities
in Grazed and Un grazed
Riparian Habitat
Stream insect habitat is created by a combination of eroding bed material, riparian vegetation, and the plants and microorganisms that
attach to bed substrates. These variables determine the composition of aquatic insect communities and all can be affected by grazing
livestock in riparian habitat. Therefore, insect
communities in well-matched comparisons of
grazed and ungrazed stream reaches (i.e.,
same watershed but different parts of a stream
with similar velocity, depth, and width) should
reflect the effects of livestock activities. The
entomological challenge is to efficiently characterize differences among communities. Most
aquatic insects are omnivores that have
evolved morphological and behavioral adaptations to acq uire food resources of a particular
size class from a specific microhabitat (Cummins 1973, 1980; Cummins and Klug 1979;
Merritt and Cummins 1996a). For example,
several genera of chironomid midges (Diptera:
Chironomidae) have evolved adaptations for
either gathering fine particles of decomposing
organic matter deposited in pools or collecting
particles suspended in the water column. These
general associations, called functional feeding
groups (FFGs hereafter) (Cummins 1973) (Table 3), provide a proven framework for efficient analysis of the effects of livestock production on stream ecosystems (Reed et al. 1994).
The most obvious and important changes in
riverine ecology associated with livestock production involve the removal of woody riparian
vegetation and the consequent effects on solar
AMERICAN
ENTOMOLOGIST
•
Volume 45, Number 1
inputs, groundwater chemistry, channel and
bed morphology, and organic inputs. These
characteristics have enormous influences on
stream ecology by determining environmental
temperature, microbial production rates, and
the nature of spatial resources-factors
that
ultimately influence the survival, growth, and
reproductive capacities of stream insects
(Sweeney 1993). Riparian vegetation that falls
or blows into streams forms the trophic foundation for many stream ecosystems, particularly
for small streams where shading limits auto trophy or the production of energy from
within the stream itself (Cummins 1980, Vannote et al. 1980, Wallace et al. 1997). When
detritus inputs are reduced and solar inputs
increased, predictable declines occur in populations of insects that consume decomposing
leaf litter of terrestrial origin (FFG = Shredders), whereas populations of insects that
scrape algae and diatoms from stone surfaces
(FFG = Scrapers) tend to increase in proportion
to other FFGs (Merritt and Cummins 1996b;
Table 3). This general pattern has been produced experimentally (Dudgeon and Chan
1992) and confirmed by comparisons of insect
communities in grazed and ungrazed reaches
(Reed et al. 1994) and in reaches with open and
closed canopies (Behmer and Hawkins 1986).
Where livestock activities result in chronic
siltation, secondary patterns related to changes in bed morphology and disturbance regime
can cause functional changes in stream insect
communities. For example, Kownacki (1983)
reported that livestock grazing can result in
increased abundances of chironomid midges, a
family of insects with members that have a
relatively high tolerance of siltation, that are
accustomed to frequent physical disturbance of
stream-bed habitat, and an overall group with
very general feeding behaviors (FFG = Gathering- collectors). Conversely, immature insects
that filter food particles from the water column
(FFG = Filtering-collectors) are thought to be
intolerant of silt accumulation on stream beds
due to their requirement of silt-free, solid substrates and posited low tolerance for sediments
in suspension (Hynes 1973; Table 3). Livestock
grazing (Niesiolowski 1983) and deforestation
(Olejnicek 1986) have been associated with
reduced abundances of larval black flies
(Diptera: Simuliidae), but it is not certain
whether siltation, sediments in suspension, or
other landscape disturbance effects caused
these filterer decreases.
It is clear that changes in organic inputs
(Wallace et al. 1997) and stream-bed habitat
(Resh et al. 1988) can result in taxonomic and
19
Table 3.
Aquatic insect functional
Functional
Groups
feeding group categorization
and food resources (modified from Merritt
Feeding
Mechanisms
and Cummins
1996a)
Particle Size
Range of Food
Dominant Food
Resources
(mm)
Shredders
Chew conditioned or live vascular plant
tissue, or gouge wood
Decomposing (or living hydophyte)
vascular plant tissue-coarse particulate
organic matter
>1.0
Filtering-collectors
Suspension feeders-filter
particles from
water column with nets or adapted body
parts
Decomposing fine particulate organic
matter; detrital particles, algae, and
bacteria
0.01-1.0
Gathering-collectors
Deposit feeders-ingest
by gathering
sediments or brush loose surface deposits
Decomposing fine particulate organic
matter; detrital particles, associated
detritus and microflora and fauna
0.05-1.0
Scrapers
Graze mineral and organic surfaces
Periphyton-attached
algae and associated
detritus and microflora and fauna
0.01-1.0
Plant piercers
Herbivores-pierce
fluids
Macroalgae
0.01-1.0
Predators
Capture
fluids
tissues or cells and suck
and engulf prey or ingest body
ties. However, instream habitat changes may
only account for part of the differences existing
among communities in grazed and ungrazed
stream reaches. Alteration of oviposition cues
necessary for habitat recognition by aerial
adults for mate-location or dispersion flights
also may play an important role in community
change, as was demonstrated by Timm (1994)
for populations of two black fly species. After
timber was cleared from a reach of a Rhine
River tributary, the opportunistic Simulium
ornatum Meigen rapidly displaced Simulium
vernum Macquart as the dominant species.
Because there were no changes in stream bed
morphology, water chemistry, or resource
availability to account for the switch, differences in oviposition behavior (S. vernum prefers shaded riffles, S. ornatum prefers riffles
under open canopies) were indicated as the
primary cause. Many other aquatic insects use
physical cues when seeking oviposition sites
(Anderson 1974, Wallace and Anderson 1996).
Thus, it seems probable that oviposition-cue
alteration following landscape clearing could
ha ve wide-spread effects on stream insect communities.
Even insects that thrive in both forested and
pastured stream reaches can be affected by the
habitat change associated with livestock production. Taylor and Merriam (1995) reported
that the wing morphology of the damselfly
Calopteryx maculata (Beauvois)(Odonata:
Calopterygidae) differed between forest and
pasture reaches of a Canadian stream. Inhabitants in the pasture-reach had significantly
larger wings than those in the forest-reach. Individuals from both subpopulations forage in
20
>0.5
Prey-living animal tissue
forest habitat, a fact indicating that the greater
flight requirement of pasture-reach inhabitants
has resulted in directional selection toward
larger wings. In a subsequent study, Taylor and
Merriam (1996) discovered that the pasturereach C. maculata had a lower occurrence of
a protozoan pathogen than individuals from
the forest-reach. They hypothesized that the
observed lower infection rate was the result of
decreased parasite exposure for pasture-reach
individuals, a pattern that suggests a possible
benefit derived from utilizing grazed riparian
habitat.
Carlson Creek, Michigan:
A Case for Grazing Reform on
Private Lands
Much of the riparian habitat along western
rangeland streams has been altered fundamentally by livestock grazing. In many places, the
long corridors of trees and shrubs that once
wea ved through vast expanses of grassland are
now only faintly represented by small patches
dotting degraded rangeland (Minshall et al.
1989, Fleischner 1994). Relatively simple habitat restoration measures, including cattle exclusion and bank stabilization, have proved
quite successful in reversing this trend and promoting recovery of native riparian vegetation
(Rickard and Cushing 1982, Minshall et al.
1989). Vegetative recovery has, in turn, improved instream conditions for trout and their
invertebrate
prey in rangeland streams
(Tarzwell1938, Fleischner 1994). Cattle grazing also has disturbed consider able amounts of
riparian habitat in forested regions of North
AMERICAN
ENTOMOLOGIST
•
Spring 1999
America. However, the primary human disturbance in these watersheds was not always cattle introduction, but deforestation, which only
as a secondary conseq uence created pasturing
opportunities. In such cases, conditions prior to
deforestation can not be restored easily, but
insectivorous sport-fish habitat can still be
improved while cattle grazing is maintained as
a dominant land-use practice. Such is the situation in the eastern-central part of Michigan's
Upper Peninsula where wide-scale clearcutting
of old-growth white pine forests during the
1800s was followed by mixed agricultural use,
including beef and dairy cattle production.
Riparian conditions in many grazed Michigan watersheds degraded steadily during the
1900s causing consequent declines in brook
trout (Salvelinus fontinalis [Mitchell]) habitat.
This situation recently led State of Michigan
resource managers to seek funds for restoration
measures similar to those used to reclaim
rangeland riparian habitat. Several candidate
streams were selected for a since-discontinued
cooperative program involving farmers and
state and federal resource managers that provided farmers with an 80% reduction in costs
for fencing cattle out of streams and digging
wells for alternative watering sites (w. H. Taft,
personal communication). In a prerecovery
analysis of one of these overgrazed streams
(Carlson Creek, Luce Co.; Fig. 2), the first
author (Strand 1996) quantified invertebrate
abundance, diversity, and community compositions in ungrazed (forested) and grazed
stream reaches less than 1 km apart from each
other. Matched riffle-pool sites in these reaches
were sampled monthly (two sites per reach)
with drift nets and introduced rock (July-September), wood (September-November), and
leaf packs (December) during the final season
of riparian grazing. Depth, current velocity,
and water temperature were similar in forest
and pasture sites. Therefore, differences in riparian characteristics were believed to be the
most important source of variation for invertebrate abundance, diversity, and community
composition between reaches.
It is not possible to definitively assign causation from nonexperimental sampling, but
the evidence from the Carlson Creek survey is
strong in that recent human activities (i.e., deforestation and cattle production) have produced dramatic changes in the pasture-reach
invertebrate community, including markedly
reduced abundance (no. individuals per sample in forest vs. pasture = 13 vs. 9 on rocks, 51
vs. 39 on wood, 96 vs. 51 in leaf packs), taxonomic richness (44 vs 33 insect taxa; Table 4),
AMERICAN
ENTOMOLOGIST
•
Volume 45, Number 1
and reach-specific residency (44 vs. 27%; Table 4). There also were significant differences
between reaches in the proportion of taxa representing different functional-feeding groups
(Fig. 3). In the forest reach, filterers comprised
a much higher proportion of the total collection on all substrates, particularly on leaf pack
samples. Larval black flies accounted for most
of these differences, a pattern that can result
from the effects of greater availability of siltfree substrates for attachment, higher water
quality, closer proximity to the lake outlet
source of Carlson Creek, and/or altered oviposition cues for species that prefer shaded habitat (Adler and McCreadie 1997). In contrast,
gatherers were more abundant in the pasture
reach, particularly on rocks and leaf packs.
The combined patterns of filterer and gatherer
abundances produced large differences in the
filterer-to-gatherer ratio for all substrate types
(0.23 vs. 0.11), wood (0.16 vs. 0.04), and leaf
packs (2.47 vs. 0.06). This ratio reflects the
relative amounts of particulate organic matter
in transport in the water column versus deposition of fine particles into pools (Merritt and
Cummins 1996b), thus indicating that decades
of riparian grazing has increased the amount
of depositional habitat in the pasture reach
relative to that in the forest reach.
Insects that scrape algae and diatoms off of
solid substrates (i.e., scrapers) were more
abundant in the forest-reach than in the pasture
reach, due principally to differential abundances of hepatageneiid mayfly nymphs
(Ephemeroptera: Heptageniidae). This result
was somewhat surprising given the higher
rates of solar input to the pasture reach, which
typically improves the quality of food resources available for scrapers (Feminella et al.
1989, Reed et al. 1994). However, siltation
resulting from cattle activities may have countered the effects of higher insolation by scattering incoming radiation or lowering the overall
organic component of food material coating
substrates (Davies-Colley et al. 1992, Reed et
al. 1994). Insects thatfeed by piercing the cell
walls of algae and vascular hydrophytes (FFG
Plant piercers)(Table 3) were found only in
the pasture reach (Table 4; Fig. 3). This suggested that riparian grazing along Carlson
Creek may have created a situation similar to
that reported by Tait et al. (1994), where large
photosynthetic organisms flourished in response to cattle activities whereas the smaller
forms ordinarily consumed by scrapers declined.
The proportion of predators to all other invertebrates, an estimate of predator-prey ratio
=
21
Table 4.
Insect taxa from forest and pasture reaches of Carlson Creek, MI arranged by
functional feeding group"
Order
Functional Feeding
Group
Filtering-Collectors
Ephemeroptera
Trichoptera
Diptera
Gathering-Collectors
Undisturbed
Forest
Arthropleidae
Arthroplea
Polycentropodidae
Neureclipsis
Brachhycentridae
Brachycentris
Hydropsychidae
Ceratopsyche
Cheumatopsyche
Hydropsyche
Simulidae
Prosimulium
Collembolla
Baetidae
Baetis
Caenidae
Caenis
Coleoptera
Leptophlebiidae
Paraleptophlebia
Leptoceridae
Mystacides
Psychomyiidae
Psychomyia
Elmidae
Dubiraphia
Macronychus
Optioservus
Stenelmis
Diptera
Chironomidae
Scrapers
Ephemeroptera
Trichoptera
Pasture
Polycentropodidae
N eurecJi psis
Hydropsychidae
Cheumatopsyche
Hydropsyche
Simulidae
Prosimu/ium
Poduridae
Podura
Ephemeroptera
Trichoptera
Overgrazed
Ameletidae
Ameletus
Baetidae
Baetis
Caenidae
Caenis
Ephemerellidae
Ephemerella
Ephemeridae
Hexagenia
Leptophlebiidae
Paraleptophlebia
Leptoceridae
Mystacides
Psychomyiidae
Psychomyia
Elmidae
Dubiraphia
Macronychus
Optioservus
Stenelmis
Dixidae
Dixella
Chironomidae
Heptageniidae
Heptageniidae
Macdunnoa
Stenacron
Stenonema
Stenacron
Stenonema
Baetidae
Pseudocloen
Helicopsychlidae
Helicopsyche
Glossosomatidae
Glossosoma
(Merritt and Cummins 1996b; Table 3), was
much higher on forest-reach rock samples than
on pasture-reach rocks (20 vs. 10% of total
abundance). This was largely due to the presence of eight predator taxa found only in the
forest reach. Therefore, the forest community
seemingly had more narrowly defined predator niches during the summer pasturing season
and, perhaps, the frequent disturbance by cattle resulted in lower predator-prey equilibria
by favoring disturbance-tolerant prey species.
The proportion of predators to other groups
was similar between reaches on wood samples
and lower in forest-reach leaf packs. These
patterns may reflect differences in colonizers of
22
organic and inorganic substrates or seasonal
effects resulting from differences in riparian
characterstics, or they may indicate that cattle
grazing influences on predatory-prey dynamics in Carlson Creek are stronger when cattle
are present.
The evidence is convincing that Carlson
Creek invertebrate communities were altered
by land clearing and decades of grazing in riparian habitat. Cattle exclusion apparently
has started to reverse this trend and promises
ultimately to satisfy the management objectives of limiting erosion and restoring brook
trout habitat. Unfortunately, Carlson Creek is
an all-too rare example of restoration of over-
AMERICAN
ENTOMOLOGIST
•
Spring 1999
Table 4.
Order
Functional Feeding
Group
Plant-Piercers
Trichoptera
Predators
Odonata
Undisturbed
Coenagrionidae
Amphiagrion
Argia
Chromagrion
Calopterygidae
Calopteryx
Aeshnidae
Cordulegastridae
Cordulegaster
Gomphidae
Progomphus
Perlodidae
Isoperla
Corydalidae
Nigronia
Leptoceridae
Oecetis
Polycentropodidae
Paranyctiophylax
Polycentropus
Megaloptera
Trichoptera
Coleoptera
Diptera
Shredders
Ceraropogonidae
Probezzia
Chaoboridae
Chaoborus
Chironomidae
Tanypodinae
Empididae
Hemerodromia
Taeniopterygidae
Taeniopteryx
Lepidosromaridae
Lepidostoma
Limnephilidae
Plecoptera
Trichoprera
Hydatophylax
Pycnopsyche
Pyralidae
Acentria
Tipulidae
Tipula
Lepidoptera
Diptera
aInsects sampled with drift nets and introduced
substrates
grazed riparian habitat, particularly where
laws do not require farmers and ranchers to
limit impacts on riverine habitat. In Michigan,
the Water Resources Commission Act of 1929
(Figure 4) ostensibly protects against cattle
grazing damage and subsequent water pollution if it can be established that discharges of
sediment or excrement are severe enough to
negatively affect public health, wildlife condition, or fishery value. However, the law also
protects streams and ponds used to water livestock, thereby establishing grazing as an environmentally compatible and important way
to use riparian land. As with other states with
substantial fishery-based tourism revenues,
old Michigan laws that favor agricultural interests over those of tourism currently are be-
ENTOMOLOGIST
•
Forest
Overgrazed
Pasture
Hydroptilidae
Hydroptila
Plecoptera
AMERICAN
Continued
Volume 45, Number 1
Calopterygidae
Calopteryx
Polycentropodidae
Polycentropus
Dytiscidae
Ceraropogonidae
Probezzia
Chironomidae
Tanypodinae
Empididae
Hemerodromia
Lepidosromaridae
Lepidostoma
Limnephilidae
Grensia
Hydatophylax
Pycnopsyche
Tipulidae
Tipula
(rocks, wood, and leaf packs).
ing reexamined by politicians and natural resource managers. A few conflicts over stream
reaches prized for their sport fish populations
have been resolved through the simple solution
of cattle exclusion. However, aquatic insects
are not afforded the same status as game fisha reality that usually fates grazing-intolerant
insects to the growing pool of incidental environmentallosses created as byproducts of one
of the most lucrative components of the American agriculture industry.
Acknowledgments
This paper is based on research that was
supported, in part, by the United States Geological Survey, through the Michigan State
23
Fig. 3. Proportional representation of the functional feeding
groups comprising the aquatic
insect communities in undisturbed and overgrazed reaches
of a small, northern-Michigan
stream (Carlson Creek, Luce
Co.). Matched riffle-pool sites in
these reaches were sampled
monthly (two sites per reach)
with drift nets and introduced
rock (July-September), wood
(September-November), and leaf
packs (December) during the
final season of riparian grazing.
Functional feeding group compositions of the aquatic
insect communities of Carlson Creek, Michigan
Shredders
Plant Plercers
Predators
Gatherers
Fares
Pas ure
Scrapers
ROCKS
S
U
B
S
T
R
A
T
WOOD
E
LEAVES
Fig. 4. Michigan law regarding
domestic livestock grazing.
Michigan Water Resources Commission
Act of 1929
Effective August 28, 1929
323.6 Unlawful discharge into state waters
Sec.6. (1) It shall be unlawful for any person
directly or indirectly to discharge into waters
of the state any substance which is or may
become injurious to domestic, commercial,
industrial, agricultural, recreational, or other
uses which are being or may be made of such
waters; or which is or may become injurious
to the value or utility of riparian lands; or
which is or may become injurious to livestock,
wild animals, birds, fish, aquatic life, or plants
or the growth or propagation thereof be
prevented or injuriously affected; or whereby
the value of fish and game is or may be
destroyed or impaired.
University Institute of Water Research. We
would like to thank W. H. Taft, Michigan
Dept. of Environmental Quality, Surface Water Quality Division, Lansing, MI, for his support and advice on this study. We also thank
two anonymous reviewers for comments on an
earlier draft of this manuscript.
24
ReFerences Cited
Adler, P. H., and J. W. McCreadie. 1997. The hidden ecology of black flies: sibling species and
ecological scale. Am. Entomo!. 43: 153-160.
Aldridge, D. W., B. S. Payne, and A. C. Miller.
1987. The effects of intermittent exposure to
suspended solids and turbulence on three species of freshwater mussels. Environ. Pollut. 45:
17-28.
Anderson, J. R. 1974. Symposium on reproduction of arthropods of medical and veterinary
importance II. Meeting of the sexes. J. Med.
Entomo!. 11: 7-19.
Armour, C. L., D. A. Duff, and W. Elmore. 1991.
The effects of livestock grazing on riparian and
stream ecosystems. Fisheries 16: 7-11.
1994. The effects of livestock grazing on western riparian and stream ecosystems. Fisheries
19: 9-12.
Behmer, D. j., and C. P. Hawkins. 1986. Effects of
overhead canopy on invertebrate production
in a Utah stream. Freshwat. Bio!. 16: 287-300.
Berg, L., and T. G. Northcote. 1985. Changes in
territorial, gill-flaring, and feeding behavior in
juvenile coho salmon (Oncorynchus kisutch)
AMERICAN
EmOMOLOGIST
•
Spring 1999
following short-term pulses of suspended sediment. Can. J. Fish. Aquat. Sci. 42: 1410-1417.
Brooks, P. M., and B. D. Gardner. 1980. Effect of
cattle dip containing toxaphene on the fauna of
South African river. J. Limno!. Soc. South. Africa 6: 113-118.
Bryant, H. T., R. E. Blaser, and J. R. Peterson.
1972. Effect of trampling by cattle on bluegrass
yield and soil compaction of a meadowville
loam. Agron. J. 64: 331-334.
Burcham, J. 1988. Fish communities and environmental characteristics of two lowland streams
in Costa Rica. Rev. Biol.Trop. 36: 273-286.
Butler, C. A., and M. H. Timperley. 1996. Fertilized farmland as a source of cadmium in oysters. Sci. Total Environ. 181: 31-44.
Chutter, F. M. 1969. The effects of silt and sand on
the invertebrate fauna of streams and rivers.
Hydrobiologia 34: 57-76.
Ciborowski, J.J.H., P. W. Pointing, and L. D. Corkum. 1977. The effect of current velocity and
sediment on the drift of the mayfly Ephemerella
subvaria McDunnough.
Freshwat. BioI. 7:
567-572.
Clark, W. 1806. In R. G. Thwaites [ed.], Original
journals of the Lewis and Clark Expedition
1804-1806. Vol. 5, Dodd, Mead, and Co.
Clarkson, R. W., and J. R. Wilson. 1995. Trout
biomass and stream habirat relationships in the
White Mountains area, east-central Arizona.
Trans. Amer. Fish. Soc. 124: 599-612.
Cline, L. D., R. A. Short, andJ. V. Ward. 1982. The
influence of highway construction on the macroinvertebrates and epilithic algae of a high
mountain stream. Hydrobiologia
96: 149159.
Culp, J. M., F.J. Wrona, and R. W. Davies. 1986.
Response of stream benthos and drift to fine
sediment deposition versus transport. Can. J.
Zool. 64: 1345-1351.
Cummins, K. W. 1973. Trophic relations of aquatic insects. Ann. Rev. Entomol. 18: 183-206.
1980. The multiple linkages of forests to
streams, pp. 191-198. In R. H. Waring [ed.],
Forests: fresh perspectives from ecosystem
analysis. Proc. 40th Ann. BioI. colloq., Oregon
State University, Corvallis.
Cummins, K. W., and M. J. Klug. 1979. Feeding
ecology of stream invertebrates. Ann Rev. Ecol.
Syst. 10: 147-172.
Danz, H. P. 1997. Of bison and man. University of
Colorado Press.
Davies-Colley, R. J., C. W. Hickey, J. M. Quinn,
and P. A. Ryan. 1992. Effects of clay discharges
on streams 1. optical properties and epilithon.
Hydrobiologia 248: 215-234.
DeGraeve, G. M., R. L. Overcash, and H. L. Bergman. 1980. Toxicity of underground coal gasification
condenser
water
and selected
constituents to aquatic biota. Arch. Environ.
Contam. Toxico!. 9: 543-555.
Dudgeon, D., and I.K.K. Chan. 1992. An experimental study of the influence of periphytic algae
AMERICAN
ENTOMOLOGIST
•
Volume 45, Number 1
on invertebrate abundance in a Hong Kong
stream. Freshwat. BioI. 22: 445-457.
Ellis, M. M. 1936. Erosion silt as a factor in aquatic environments. Ecology 17: 29-42.
Fairchild,J. F., T. Boyle, W. R. English, and C. Rabeni. 1987. Effects of sediment and contaminated sediment on structural and functional
components of experimental stream ecosystems. Water, Air, and Soil Pollut. 36: 271-293.
Faust, M. A. 1982. Relationship between land-use
practices and fecal bacteria in soils. J. Environ.
Qua!. 11: 141-146.
Feminella, J. W., M. E. Power, and V. H. Resh.
1989. Periphyton responses to invertebrate
grazing and riparian canopy in three northern
California coastal streams. Frshwat. Biol. 22:
445-457.
Fleischner, T. L. 1994. Ecological costs of livestock
grazing in western North America. Conserv.
BioI. 8: 629-644.
Gardner, J. L. 1950. Effects of thirty years of protection from grazing in desert grassland. Ecology 31: 44-50.
Garretson, M.S. 1965. The American Bison. New
York Zoological Society.
Gillespie, P.D. 1981. Development of gully erosion
at the head of Bango Creek near Yass, New
South Wales, Australia. J. Soil Conserv. Servo
New South Wales 37: 6-12.
Harris, W. G., H. D. Wang, and K. R. Reddy. 1994.
Dairy manure influence on soil and sediment
composition: implications for phosphorous retention. J. Environ. Qual. 23: 1071-1081.
Hazel, R. H., C. E. Burkhead, and D. G. Higgins.
1979. The development of water quality criteria for ammonia and total residual chlorine for
the protection of aquatic life in two Johnson
County, Kansas streams. Off. Water Res. and
Tech., Dept. of the Interior, Washington, D.C.
Herbert, D.W.M., and J. C. Merkins. 1961. The
effect of suspended mineral solids on the survival of trout. Int. J. Air Water Pollut. 5: 46-55.
Hobbs, N. T. 1996. Modification of ecosystems
by ungulates. J. Wildl. Manage. 60: 695-713.
Hobbs, N. T., G. D. Bear, and D. C. Bowden.
1996. Ungulate grazing in sagebrush grassland: mechanisms of resource competition.
Ecol. App. 5: 207-224.
Hofstede, R.G.M. 1995. Effects of livestock farming and recommendations
for management
and conservation of Paramo grasslands. Land
Degrad. Rehab. 6: 133-147.
Howell, J. M., M. S. Coyne, and P. Cornelius.
1995. Fecal bacteria in agricultural waters of
the Bluegrass Region of Kentucky. J. Environ.
Qua!. 24: 411-419.
Hynes, H.B.N. 1973. The effects of sediment on
the biota of running water, pp. 653-663. In
Fluvial Processes and Sedimentation, Can.
Dept. Environ., Ottawa, Canada.
Kauffman, J. B., and W. C. Krueger. 1984. Livestock impacts on riparian ecosystems and
streamside management considerations: a re-
25
view.]. Range Manage. 37: 430-438.
Kirk, K. L., and]. J. Gilbert. 1990. Suspended clay
and the population dynamics of planktonic rotifers and cladocerans. Ecology 71: 17411755.
Kondolf, G. M. 1993. Lag in stream channel adjustment to livestock exclosure, White Mountains,
California.
Restoration
Ecol. 4:
226-230.
1994. Livestock grazing and habitat for threatened species: land-use decisions under scientific
uncertainty in the White Mountains, California, USA. Environ. Manage. 18: 501-509.
Kownacki, A. 1983. Stream ecosystems in mountain grassland West Carpathians, Poland 8:
benthic invertebrates. Acta Hydrobiol. 24:
375-390.
Learner, M. A., R. Williams, M. Harcup, and B. D.
Hughes. 1971. A survey of the macro-fauna of
the River Cynon, a polluted tributary of the
River Taft (South Wales). Freshwat. BioI. 1:
339-367.
Lemly, D. A. 1982. Modification of benthic insect
communities in polluted streams: combined effects of sedimentation and nutrient enrichment.
Hydrobiologia 87: 229-245.
Lenat, D. R., D. L. Penrose, and K. W. Eagleson.
1981. Variable effects of sediment addition on
stream benthos. Hydrobiologia 79: 187-194.
Leopold, A. 1923. Some fundamentals of conservation in the southwest, pp. 86-97. In S. J.
Flader, and J. B. Callicott leds.], The river of the
mother of God and other essays by Aldo Leopold (1991). Univ. Wisconsin Press, Madison.
1946. Erosion as a menace to the social and economic future of the Southwest. J. For. 44: 627633.
Li, H., G. A. Lamberti, T. N. Pearsons, C. K. Tait,J.
L. Li, and J. C. Buckhouse. 1994. Cumulative
effects of riparian disturbances along high
desert trout steams of the John Day Basin, Oregon. Trans. Am. Fish. Soc. 123: 627-640.
Matthews, B. W., L. E. Sollenberger, V.D. Nair, and
C. R. Staples. 1994. Impact of grazing management on soil nitrogen, phosphorous, potassium, and sulfur distribution. J. Environ. Qual.
23: 1006-1013.
Matthews, K. R. 1996. Habitat selection and
movement patterns of California golden trout
in degraded and recovering stream sections in
the Golden Trout Wilderness, California. N.
Amer.]. Fish. Manage. 16: 579-590.
McAllister, D. E. 1987. Status of the blackstripe
topminnow, Fudu/us notatus in Canada. Can.
Field Nat. 101: 219-225.
Crystal Clear.
The Meiji EM Series of Modular Stereo'
If you are looking for precision, durability, quality and value in a
stereo microscope, we invite you to take a closer look at Meiji's
EM Series of Stereo Microscopes.
The modular design (A wide variety of bodies, single magnification or zoom- rotatable 360°, auxiliary lenses, eyepieces,
stands, holders, etc.) gives you the freedom to create the ideal
instrument for your specific needs or application, and Meiji stands
behind every instrument with its limited Lifetime Warranty.
For more information on these economically priced stereo
microscopes, please call, FAX or write us today.
~MEIJI
L..AJTECHNO
MEIJI TECHNO AMERICA
2186 Bering Drive, San Jose, CA 95131, Toll Free Telephone: 800.832.0060
FAX: 408.428.0472, Tel: 408.428.9654
26
AMERICAN
ENTOMOLOGIST
•
Spring 1999
McCabe, G. D., and J. O'Brien. 1983. The effects
of suspended silt on feeding and reproduction
of Daphnia pulex. Am. Midland Nat. 110:
324-337.
McHugh, T. 1972. The time of the buffalo. Alfred
A. Knopf, New York.
McLeay, D. J., A. J. Knox, J. G. Malick, I. K.
Birtwell, G. F. Hartman, and G. L. Ennis. 1983.
Effects on arctic grayling (Thymal/us arcticus)
of shorr-term exposure to yukon placer mining
sediment: a laboratory study. Can. Tech. Rept.
Fisheries and Aquatic Sci. 117L
McLeay, D. J., G. L. Ennis, I. K. Birtwell, and G. F.
Hartman. 1984. Effects on arctic grayling
(Thymal/us arcticus) of prolonged exposure to
yukon placer mining sediment: a laboratory
study. Can. Tech. Rept. Fisheries and Aquatic
Sci. 124L
McNaughton, S. J. 1986. Grazing lawns: on domesticated and wild grazers. Am. Nat. 128:
937-939.
1993. Grasses, grazers, science and management. Ecol. Appl. 3: 17-2L
Merritt, R. W., and K. W. Cummins (cds.). 1996a.
An introduction to the aquatic insects of North
America (3rd cd.). KendalUHunt Publ. Co.,
Dubuque, IA.
1996b. Trophic relations of macroinvertebrates, pp. 453--474. In E R. Hauer, and G. A.
Lamberti (cds), Methods in stream ecology.
Academic Press, San Diego, CA.
Milchunas, D. G., and W. K. Lavenroth. 1993.
Quantitative effects of grazing on vegetation
and soils over a global range of environments.
Ecol. Monogr. 63: 327-366.
Minshall, G. W., S. E. Jensen, and W. S. Platts.
1989. The ecology of stream and riparian habitats of the Great Basin region: a community
profile. U.S. Fish.Wildl. Ser. BioI. Rept. 85
(7.24). Washington, D.C.
Modde, T., H. G. Drewes, and M. A. Rumble.
1986. Effects of watershed alteration on the
brook trout population of a small Black Hills
stream. Great. Basin Nat. 46: 39--45.
Mosely, J. c., T. A. Lance, J. W. Walker, D. E. Lucas, and C. M. Falter. 1993. How does grazing
affect water quality? p. 5. In D. Ortiz [ed.], Focus on renewable natural resources. Idaho For.,
Wildl., Range Exper. Stat., 1992 Ann. Rept.
Newcombe, C. 1>.,and D. D. MacDonald. 199L
Effects of suspended sediments on aquatic ecosystems. N. Am. J. Fish. Manage. 11: 72-82.
Niesiolowski, S. 1983. Stream ecosystems in
mountain grasslands West Carpathians, Poland 10: Simuliidae and Empididae, Diptera.
Acta Hydrobiol. 24: 399--404.
Nutall, P. M. 1972. The effects of sand deposition
upon the macro-invertebrate fauna of the River
Camel, Cornwell. Freshwat. BioI. 2: 181-186.
Nutall, P.M., and G. H. Bielby. 1973. The effects of
China-clay wastes on stream invertebrates. Environ. Pollut. 5: 77-86.
AMERICAN
ENTOMOLOGIST
•
Volume 45, Number 1
ENTOMOLOGISTS
Join a world-class
system for total
quality health care.
As an Army Entomologist, you will be
a vital member of the Army Health Care
Team. You could have a variety of opportunities: conducting research, performing
operational and consultative medical
entomology, or consulting with staff at
labs and preventive medical facilities.
As an Entomologist in the Army
Medical Service Corps, you will have
the rank, respect and privileges afforded
to Army officers. In addition, you will
earn 30 days of paid leave annually, and
benefit from housing and food allowances,
no-cost or low-cost medical and dental
care, post exchange and commissary
privileges, and a generous retirement
package.
To find out more, or to have an Army
Health Care Recruiter contact you, call:
1-800- USA-ARMY
www.goarmy.com
ARMY MEDICAL SERVICE CORPS.
BE ALL YOU CAN BE.
27
Ogbeibu, A. E., and R. Victor. 1989. The effects of
road and bridge construction on the bank-root
macrobenthic invertebrates of a southern Nigerian stream. Environ. Pollut. 56: 85-100.
Olejnicek, J. 1986. Influence of suspended organic
and inorganic substances in water upon the
numbers of black fly larvae (Diptera: Simuliidae). Folia Parasitol. (Prague) 33: 177-187.
Ong, C., W. Moorehead, A. Ross, and R. J. Isaac.
1996. Studies of Giardia spp. and Cryptosporidium spp. in two adjacent watersheds. Appl.
Environ. Microbiol. 62: 2798-2805.
Orodho, A. B., M. J. Trlica, and C. D. Bonham.
1990. Long-term heavy-grazing effects on soil
and vegetation in the four corners region.
Southwest. Nat. 35: 9-14.
Osborne, P.J. 1988.A late Bronze Age insect fauna
from the River Avon, Warwickshire, England:
its implication for the terrestrial and fluvial environment and for climate. J. Archaeol. Sci. 15:
715-727.
Overcash, M. R., F. J. Humenik, and J. R. Miner.
1983. Livestock waste management. Vols. I &
II. CRC Press, Boca Raton, FL.
Owens, L. B., R. W. Van Keuren, and W. M. Edwards. 1982. Environmental effects of a medium-fertility, 12-month pasture program I.
Hydrology and soil loss. J. Environ. Qual. 11:
236-240.
1983. Hydrology and soil loss from a high fertility rotational pasture program. J. Environ.
Qual. 12: 341-346.
Pasquarell, G. c., and D. G. Boyer. 1995. Agricultural impacts on bacterial water quality in karst
groundwater. J. Environ. Qual. 24: 959-969.
Quinn, J. M., R. J. Davies-Colley, C. W. Hickey, M.
L. Vickers, and P. A. Ryan. 1992a. Effects of
clay discharges on streams 2. benthic invertebrates. Hydrobiologia 248: 235-247.
Quinn, J. M., R. B. Williamson, R. K. Smith, and
M. L. Vickers. 1992b. Effects of riparian grazing and channelization on streams in Southland, New Zealand. 2. Benthic invertebrates. N.
Z. J. Mar. Freshwat. Res. 26: 259-273.
Rabeni, C. F., and G. W. Minshall. 1977. Factors
affecting the microdistribution
of stream
benthic insects. Oikos 29: 33-43.
Redding, J. M., Schreck, C. B., and F. H. Everest.
1987. Physiological effects on coho salmon
and steelhead of exposure to suspended solids.
Trans. Amer. Fish. Soc. 116: 737-744.
Reed,J. L., 1. C. Campbell, and C. E. Baily. 1994.
The relationship between invertebrate assemblages and available food at forest and pasture
sites in three southeastern Australian streams.
Freshwat. BioI. 32: 641-650.
Resh, V.H., A. V.Brown, A. P.Covich, M. E. Gurtz,
H. W. Li, G. W. Minshall, S. R. Reice, A. L. Sheldon, J. B. Wallace, and R. C. Wissmar. 1988.
The role of disturbance in stream ecology. J. N.
Am. Benthol. Soc. 7: 433-455.
Rickard, W. H., and C. E. Cushing. 1982. Recovery of streamside woody vegetation after exclu-
28
sion of livestock grazing. J. Range Manage. 35:
360-36I.
Rosenberg, D. M., and N. B. Snow. 1975. Ecological studies of aquatic organisms in the Mackenzie and Porcupine river drainages in relation
to sedimentation. Can. Fish. Mar. Servo Res.
Dev. Tech. Rep. 547.
Rosenberg, D. M., and A. P. Wiens. 1978. Effects
of sediment addition on macro benthic invertebrates in a northern Canadian river. Water Res.
12: 753-763.
Rostad, C. E., W. E. Pereira, and T.J. Leiker. 1993.
Distribution and transport of selected anthropogenic organic compounds on Mississippi
River suspended sediment (USA.), May/June
1988. J. Contaminant Hydrol. 16: 175-199.
Sawyer, T. K. 1989. Free-living pathogenic and
nonpathogenic amoebae in Maryland, USA
soils. Appl. Environ. Microbiol. 55: 10741077.
Schwert, D. P. 1996. Effects of Euro-American settlement on an insect fauna: paleontological
analysis of the recent chitin record of beetles
(Coleoptera) from northeastern Iowa. Ann.
Entomol. Soc. Am. 89: 53-63.
Servizi, J. A., and D. W. Martens. 1992. Sublethal
responses of coho salmon (Oncorynchus
kisutch) to suspended sediments. Can. J. Fish.
Aquat. Sci. 49: 1389-1395.
Sherer, B. M., J. R. Minor, J. A. Moore, and J. C.
Buckhouse. 1992. Indicator bacterial survival
in stream sediments. J. Env. Qual. 21: 591-595.
Sidle, R. c., and A. Sharma. 1996. Stream channel
changes associated with mining and grazing in
the Great Basin. J. Environ. Qual. 25: 1111112I.
Strand, R. M. 1996. Some effects of riparian habitat alteration on lotic invertebrate ecology.
Ph.D. Diss., Michigan State Univ., East Lansing,
MI.
Strand, R. M., and R. W. Merritt. 1998. Effects of
episodic sedimentation on the net-spinning
caddisflies Hydropsyche betteni and Ceratopsyche sparna (Trichoptera: Hydropsychidae).
Environ. Pollut. 98: 129-134.
Sweeney, B. W. 1993. Effects of streamside vegetation on macroinvertebrate
communities of
White Clay Creek in eastern North America.
Proc. Nat. Sci. Philadelphia 144: 291-340.
Sweeney, B. W., and R. L. Vannote. 1986. Growth
and production of a stream stonefly: influences
of diet and temperature. Ecology 67: 13961410.
Tait, C. K.,J. L. Li, G. A. Lamberti, T. N. Pearsons,
and H. W. Li. 1994. Relationships between riparian cover and community structure of high
desert streams. J. N. Am. Benthol. Soc. 13: 45-
56.
Tarzwell, C. M. 1938. Factors influencing fish
food and fish production in southwestern
streams. Trans. Amer. Fish. Soc. 67: 246-255.
Taylor, E. J., E. M. Reese, and D. Pascoe. 1994.
Mortality and drift-related response of the
AMERICAN
ENTOMOLOGIST
•
Spring 1999
freshwater amphipod Gammarus pulex (L.)
exposed to natural sediments, acidification and
copper. 29: 83-101.
Taylor, P. D., and G. Merriam. 1995. Wing morphology of a forest damselfly is related to landscape structure. Oikos 73: 43---48.
1996. Habitat fragmentation and parasitism of
a forest damselfly. Landscape Ecol. 11: 181189.
Tiedemann, A. R., D. Higgins, T. M. Quigley, H. R.
Sanderson, and D. B. Marx. 1987. Responses
of fecal coliform in streamwater to four grazing
strategies. J. Range Manage. 40: 322-329.
Timm, T. 1994. Reasons for the shift in dominance between Simulium (N.) vernum and Simulium (S.) ornatt/m (Diptera: Simuliidae) along
the continuum of an unpolluted lowland
stream. Arch. Hydrobiol. 131: 199-210.
Tsui, P.T.P., and P. J. McCart 1981. Effects of
stream-crossing by a pipeline on the benthic
macroinvertebrate
communities of a small
mountain stream. Hydrobiologia
79: 271276.
Vannote, R. L., G. W. Minshall, K. W. Cummins,J.
R. Sedell, and C. E. Cushing. 1980. The river
continuum concept. Can. J. Fish. Aquat. Sci.
37: 130-137.
Wagener, S. M., andJ. D. LaPerriere. 1985. Effects
of placer mining on the invertebrate communities of interior Alaska streams. Freshwat. Invertebr. BioI. 4: 208-214.
Wallace,J. B., and N. H. Anderson. 1996.Habitat,
life history, and behavioral adaptations of
aquatic insects, pp. 41-73. In R. W. Merritt,
and K. W. Cummins [eds.], An introduction to
the aquatic insects of North America. KendallJ
Hunt, Dubuque, IA.
Wallace, J. B., S. L. Eggert, J. L. Meyer, and J. R.
Webster. 1997. Multiple trophic levels of a forest stream linked to terrestrial litter inputs. Science 277: 102-104.
Waters, T. F. 1995. Sediment in streams. Sources,
biological effects, and control. Am. Fish. Soc.
Monogr. 7, Bethesda, MD.
Wissmar, R. c., J. E. Smith, B. A. McIntosh, H. W.
Li, G. H. Reeves, andJ. R. Sedell. 1994. A history of resource use and disturbance in riverine
basins of eastern Oregon and Washington (early 1800's-1900's). Northwest Sci. 68: 1-35.
•
Mac Strand is currently a Research Associate
in the Department of Biological Sciences at Dartmouth College in Hanover, New Hampshire. He
specializes in aquatic ecology and evolutionary
biology. Richard Merritt is Professor of Entomology and Fisheries and Wildlife at Michigan State
University in East Lansing. He studies the ecology of filter-feeding aquatic insects and the effects
of human pertubations on stream invertebrate
communities.
New items!
John W. Hock Company
www.acceleration.net/j
whock
Manufacturers of proven and reliable sampling devices for 23 years
AGRICULTURAL BACKPACK 2-CYCLE ASPIRATOR
MODEL /6/2
This unit was designed by the John W. Hock Company in response to the need for a backpackmounted aspirator for insects larger than mosquitoes and sandnies. It is used to collect resting and
flying species in row crops, on ornamentals, from turf grass, etc. This unit comes complete with
one of 2 types of collecting wand, a 2-cycle, single-cylinder gasoline engine with needle bearings
and chromed piston and cylinder wall mounted on a welded aluminum backpack frame. It is
lightweight, durable, and comfonable to use. It has been very well received by agriculture as well
as medical entomology researchers and surveyors.
Entomological Fabric (not shown). We now carry a full line of synthetic fabrics for entomological purposes- cages. nets, traps. See our web page or write, e-mail. or call for details.
The Modified CDC Backpack Aspirator (ModeI1412) (not shown) was originally designed
for the collection of resting adult mosquitoes by the U.S. Public Health Service. It is also used
to collect other resling species in row crops, etc. This unit comes complete with built-in sealed-electrolyte ballery and automatic recharger, extra screenedcollection cups, switched suction motor, and aluminum backpack frame. It is lightweight,
durable, and comfortable to use.
Insect Flight Traps (not shown): We manufacture several models. The 6-m version, designed
by Drs Gressill & Gressill, has collection heads (dry or alcohol, Models 3012 & 3112, respectively) at each end. A modified version that segregates the catch from each side is used in migration studies. A smaller, lightweight trap, developed by Dr. Henry Towns, is 2 mlong and
comes with a dry laleohol head (Model 3412).
For additional products, photos, details, and prices, sec our web page or calVe~mail for brochures
John W. Hock Company,P.O. Box 12852, Gainesville,FL 32604
(352) 378-3209 - (352) 372-/838 FAX - E-mail- [email protected]
Visa / MasterCard
AMERICAN
ENTOMOLOGIST
•
VO/llme 45, Nllmber
1
29