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Size-specific effects of bighead carp predation across the zooplankton size spectra



• Bigheaded carp (Cyprinidae: Hypophthalmichthys spp.) were brought to North America for aquaculture and eventually escaped captivity. Since their liberation, they have dispersed northward through the Mississippi River Basin and its tributaries. Although bigheaded carp are omnivorous filter‐feeding planktivores, their predatory effects on zooplankton are of principal concern because many native fishes feed on planktonic invertebrates during some phase of their life history. The aim of our study was to quantify the magnitude of effect of bighead carp (Hypophthalmichthys nobilis) on zooplankton body size and daily secondary production across a range of body lengths. • We conducted an experiment where we compared responses of zooplankton in the presence of a native fish assemblage (control, n = 5 ponds) and a native fish assemblage plus bighead carp (invaded, n = 5 ponds). The experiment lasted 3 months (June–September, 2014) and was conducted in clay‐lined ponds (0.04 ha. wetted area; 1.5–1.75 m water depths). We quantified the predatory effects of bighead carp on overall changes to the size structure of zooplankton assemblages, body lengths of zooplankton taxa and taxa‐specific changes to standing crop biomass and daily secondary production. • The size structure of zooplankton assemblage shifted towards smaller invertebrates in the presence of bighead carp. Bighead carp reduced the individual body sizes of Diaphanosoma (Sididae) (−19%) and Daphnia (Daphniidae) (−9%) after 3 months. Moreover, the standing crop biomass (−92% to 98%) and daily production (−65% to 74%) of Diaphanosoma, Daphnia and Calanoida were reduced in the presence of bighead carp. Bighead carp reduced immature copepod nauplii by 75% when compared to controls and may have affected recruitment to the adult stage. • Our experiment indicated that the magnitude of predation by bighead carp increased with zooplankton body size, although rotifers and nauplii were exceptions to this pattern. The combined effects of reduced body sizes of some taxa and direct predation on immature and adult life stages of larger taxa suggest that bighead carp may be affecting zooplankton demographics through additional mechanisms such as reduced egg production, mate limitation, and recruitment.
Size-specific effects of bighead carp predation across the
zooplankton size spectra
Scott F. Collins
David H. Wahl
Kaskaskia Biological Station, Illinois Natural
History Survey, Sullivan, IL, USA
Scott F. Collins, Kaskaskia Biological Station,
Illinois Natural History Survey, Sullivan IL,
Funding information
Illinois Natural History Survey; Great Lakes
Research Initiative; Illinois Department of
Natural Resources, Grant/Award Number:
1. Bigheaded carp (Cyprinidae: Hypophthalmichthys spp.) were brought to North
America for aquaculture and eventually escaped captivity. Since their liberation,
they have dispersed northward through the Mississippi River Basin and its tribu-
taries. Although bigheaded carp are omnivorous filter-feeding planktivores, their
predatory effects on zooplankton are of principal concern because many native
fishes feed on planktonic invertebrates during some phase of their life history.
The aim of our study was to quantify the magnitude of effect of bighead carp
(Hypophthalmichthys nobilis) on zooplankton body size and daily secondary pro-
duction across a range of body lengths.
2. We conducted an experiment where we compared responses of zooplankton in
the presence of a native fish assemblage (control, n= 5 ponds) and a native fish
assemblage plus bighead carp (invaded, n= 5 ponds). The experiment lasted
3 months (JuneSeptember, 2014) and was conducted in clay-lined ponds
(0.04 ha. wetted area; 1.51.75 m water depths). We quantified the predatory
effects of bighead carp on overall changes to the size structure of zooplankton
assemblages, body lengths of zooplankton taxa and taxa-specific changes to
standing crop biomass and daily secondary production.
3. The size structure of zooplankton assemblage shifted towards smaller invertebrates
in the presence of bighead carp. Bighead carp reduced the individual body sizes of
Diaphanosoma (Sididae) (19%) and Daphnia (Daphniidae) (9%) after 3 months.
Moreover, the standing crop biomass (92% to 98%) and daily production (65%
to 74%) of Diaphanosoma,Daphnia and Calanoida were reduced in the presence of
bighead carp. Bighead carp reduced immature copepod nauplii by 75% when com-
pared to controls and may have affected recruitment to the adult stage.
4. Our experiment indicated that the magnitude of predation by bighead carp
increased with zooplankton body size, although rotifers and nauplii were excep-
tions to this pattern. The combined effects of reduced body sizes of some taxa
and direct predation on immature and adult life stages of larger taxa suggest that
bighead carp may be affecting zooplankton demographics through additional
mechanisms such as reduced egg production, mate limitation, and recruitment.
Asian carp, Hypophthalmichthys, invasive species, planktivory, size-specific predation
Accepted: 20 March 2018
DOI: 10.1111/fwb.13109
Freshwater Biology. 2018;19. ©2018 John Wiley & Sons Ltd
Human activities have greatly expedited the rate of species introduc-
tions across the globe (Ricciardi, Steiner, Mack, & Simberloff, 2000;
Ruiz & Carlton, 2003; Vitousek, Mooney, Lubchenco, & Melillo,
1997). Although many invasions are rather benign in terms of overall
impacts to the environment (Williamson & Fitter, 1996), others
involve species whose presence is characterised by disproportionate
alterations to food-web structure and function (Mack et al., 2000;
Moyle & Light, 1996; Vitousek et al., 1997). Bigheaded carp (Cyprini-
dae: Hypophthalmichthys spp.) are known for their ability to effi-
ciently control plankton (Chapman & Hoff, 2011; Kolar et al., 2007;
Smith, 1985). Consequently, these planktivorous cyprinids have been
transported across the globe for aquaculture applications. As is often
the case, those bigheaded carp that were brought to North America
eventually escaped captivity (Chick & Pegg, 2001; Naylor, Williams,
& Strong, 2001). Since their liberation, bighead (Hypophthalmichthys
nobilis) and silver carp (Hypophthalmichthys molitrix) have dispersed
northward through the Mississippi River Basin and its tributaries
towards the Laurentian Great Lakes of North America (Chick & Pegg,
2001; Naylor et al., 2001). During this period of expansion, big-
headed carp populations have increased substantially and have
become one of the predominant fish encountered in many locations
(Collins, Butler, Diana, & Wahl, 2015; Collins, Diana, Butler, & Wahl,
2017; MacNamara, Glover, Garvey, Bouska, & Irons, 2016; Sass
et al., 2010).
Bigheaded carp are filter-feeding planktivores that have been
shown to reduce zooplankton and thus pose a substantial ecological
threat to many native fishes that rely on zooplankton during larval,
juvenile and adult life stages (Chapman & Hoff, 2011; Kolar et al.,
2007; Sass et al., 2014). These cyprinids use comb-like gill rakers
and epibranchial organs (i.e., accessory feeding structures that accu-
mulate food particles) to feed on planktonic invertebrates and phyto-
plankton (Callan & Sanderson, 2003; Kolar et al., 2007). Filter-
feeding planktivores consume many prey at once, often in propor-
tion to prey densities (Lazzaro, 1987), although some prey are better
adapted to avoid consumption (Drenner, de Noyelles, & Kettle,
1982). Moreover, some prey populations may also benefit from a
competitive release from other species experiencing enhanced pre-
dation pressure (Neill, 1975). The magnitude of predation across the
size spectrum of prey may be an abrupt (i.e., sigmoidal pattern) tran-
sition between readily exploited and unexploited prey, with potential
compensatory increases by those less exploited prey populations. In
contrast, the magnitude of predation may scale with body size (i.e.,
linearly) as larger, longer-lived and less abundant prey are dispropor-
tionately affected and slower to recover (Drenner, Mummert, de
Noyeiles, & Kettle, 1984).
Most often, the top-down effects of these planktivores are char-
acterised via changes to prey densities (e.g., Collins, Nelson,
Deboom, & Wahl, 2017; Cooke, Hill, & Meyer, 2009; Sass et al.,
2014). Other prey responses, such as plastic changes to body length
and alterations to energy flow via secondary production, are seldom
assessed. The threat of predation can affect prey body size by influ-
encing prey feeding activity and growth (e.g., Peckarsky et al., 2008;
Tollrian & Dodson, 1999), which has implications for egg and clutch
sizes and fitness (Green, 1956; Lynch, 1977). Predators also affect
prey recruitment, particularly when early life stages are susceptible
to predation (e.g., Gaines & Roughgarden, 1987). The culmination of
direct and indirect predator effects on prey populations should
ultimately affect the accumulation of new prey biomass (i.e., energy
flow via secondary production) within the ecosystem. Thus, know-
ledge of each is needed to better characterise the effects of invasive
bigheaded carp in freshwater ecosystems.
Here, we conducted an experiment to quantify the magnitude of
effect of bighead carp on zooplankton body size and daily secondary
production across a range of body lengths. Specifically, we examined
the predatory effects of bighead carp on (1) overall changes to the
size structure of zooplankton assemblages, (2) body lengths of zoo-
plankton taxa and (3) taxa-specific changes to standing crop biomass
and daily secondary production. Finally, we tested whether the rela-
tionship between the magnitude of predation by filter-feeding big-
head carp and prey body size was linear or sigmoidal. Because
strong predation effects on larger taxa can also influence interactions
within the zooplankton assemblage, we considered that smaller taxa
with faster population turnover (i.e., egg to adult) may be released
from regulatory constraints (e.g., predation, competition) and, in turn,
their populations may increase or dampen predation effects (Collins,
Detmer, Nelson, Nannini, & Wahl, 2018; Cooke et al., 2009; Sass
et al., 2014).
Experimental design
We tested our hypothesis with an additive experiment, which is rec-
ommended for evaluating the effects of non-native fishes because it
hold all factors equal except for the invader (Fausch, 1998). Additive
experimental designs have an inherent logical limitation which pre-
cludes separating the effect of an invader from simply having more
individuals within a treatment (Collins, Nelson, et al., 2017). Conse-
quently, the rationale for an experiment must compliment the design
and any inferential limitations. The logic and design of this experi-
ment reflects patterns observed in nature, where large numbers of
bigheaded carp are imposed over native communities of fishes (Col-
lins et al., 2015; Collins, Diana, et al., 2017; Irons, Sass, McClelland,
& Stafford, 2007). Presumably, a hyperabundance of native plankti-
vores could impart similar effects; however, such a scenario does
not reflect conditions in many locations where bigheaded carp are
We compared responses of zooplankton in the presence of a
native fish assemblage (control, n=5 ponds) and a native fish
assemblage plus bighead carp (invaded, n=5 ponds; Table 1). The
experiment lasted 3 months (JuneSeptember, 2014) and was con-
ducted in clay-lined ponds (0.04 ha. wetted area; 1.51.75 m water
depths) at the Sam Parr Biological Station, Kinmundy, IL, USA. Ten
ponds were filled 5 weeks prior to start of the experiment, at ran-
dom, with filtered water (300-lm sieve to remove larval fishes) from
Forbes Lake (UTM: 38.726, 88.779) to ensure similar inoculums of
zooplankton assemblages. Water temperatures (average SD) were
21.9 1.1°C during the experiment and did not differ between
treatments (ANOVA, F
1, 9
=0.44, p=.76).
All 10 ponds were stocked with juvenile native fishes with func-
tional traits representative of large riverfloodplain ecosystems and
included representative taxa of the Illinois River and the upper Mis-
sissippi River. Native fishes encompassed a range of functional traits,
including a benthic predator (channel catfish, Ictaluridae: Ictalurus
punctatus), a planktivore (golden shiner, Cyprinidae: Notemigonus
crysoleucas) and taxa that forage on both benthic and pelagic inver-
tebrates (red shiner, Cyprinidae: Cyprinella lutrensis; largemouth bass,
Centrarchidae: Micropterus salmoides); see Table 1 for experimental
densities. Field surveys by Illinois Natural History Survey biologists
determined that juvenile bigheaded carp comprised a large compo-
nent of fish assemblages in floodplain lakes of the Illinois River (Col-
lins, Diana, et al., 2017). Five ponds were randomly stocked with
juvenile bighead carp so that their densities comprised 58% of the
fish assemblage and 84% of the fish biomass. Juvenile bighead carp
(H. nobilis, 7.62 1.78 g) were obtained from a regional commercial
hatchery (Osage Catfisheries Inc., Osage Beach, MO, USA).
Zooplankton sampling and analyses
Zooplankton samples were collected monthly at three random loca-
tions (11.5 m depths) within each pond with a depth-integrated
tube sampler. Samples were filtered through 20-lm-mesh sieve to
collect zooplankton (Chick, Levchuk, Medley, & Havel, 2010) and
then stored in Lugols solution. Zooplankton samples were counted
and identified to genera when possible (Thorp & Covich, 2010).
Because predation by fishes can affect invertebrate recruitment (e.g.,
Gaines & Roughgarden, 1987) and bighead carp are capable of con-
suming small invertebrates, we examined their potential effect on
copepod recruitment from immature to adult life stages by
comparing densities of copepod nauplii (i.e., free-swimming larvae).
Subsets of 50 individuals were measured using an optical microme-
tre to determine body length (mm). Taxa-specific body lengths were
used as input in lengthmass regressions to obtain biomass (dry
mass; McCauley, 1984). To characterise the impact of bighead carp
on the size spectra of planktonic invertebrates, histograms (columns
represent average counts SE;n=5) were generated for invaded
and control ponds. We used ANCOVA to test whether treatment
(categorical factor) influenced the slope of the line between counts
(dependent variable) and length size bins (independent variable).
Secondary production is an integrative measurement of energy
flow through an ecosystem (Dolbeth, Cusson, Sousa, & Pardal,
2012). Despite calls for production-based approaches to aquatic-
and fisheries-related issues, inferences pertaining to production rely
heavily on changes to standing crop biomass. Zooplankton secondary
production was calculated with a regression model for the produc-
tion of freshwater invertebrates (R
=.79; Plante & Downing, 1989).
Estimates of annual production were then converted to daily produc-
tion by dividing each estimate by the number of experimental days
(g m
). Regression-based production models have been used
to contrast differences in ecological systems (e.g., Kelly, Solomon,
Weidel, & Jones, 2014), but estimates can differ from classical
approaches (Morin, Mousseau, & Roff, 1987; Stockwell & Johanns-
son, 1997). For instance, production estimates of larger-bodied cope-
pods can be inflated when compared to other production
approaches (i.e., egg ratio method; Stockwell & Johannsson, 1997).
Nevertheless, we reason that the environmental characteristics (e.g.,
temperature, inoculum sources) were similar between experimental
units and any biases would be consistent across controls and treat-
ments. To assess the effects of bighead carp on zooplankton body
lengths, we analysed responses in the last sample date of the experi-
ment using a one-way analysis of variance (ANOVA), with treatment
as the fixed factor. Similarly, daily secondary production was an inte-
grative metric that encompassed the whole duration of the experi-
ment and was analysed with a one-way ANOVA with treatment as
the fixed factor. Standing crop biomass was analysed using a
repeated-measures ANOVA, where the effect of treatment, time and
their interaction was assessed. For all statistical tests, p-values <.05
were considered significant. All response variables were log
formed to correct for any non-normality of residuals and
heteroscedasticity. All ANOVAs were conducted using SAS v.9.3
(SAS Institute, Cary, North Carolina, USA).
The magnitude of experimental effect was determined for
ANOVA main effect means via GlasssD[(Average
vaded) SDcontrol
]. GlasssDwas used because the metric is con-
strained by the variability (SD, standard deviation) of prey
populations in the experimental control (Ferguson, 2009). Effect
sizes for responses (dependent variables: GlasssDstanding crop bio-
mass and daily production) were examined along the zooplankton
body length spectra (independent variable) to determine whether the
pattern was linear, quadratic or sigmoidal (Logistic 3 parameter, Pro-
bit 4 parameter). Positive values indicate reductions in prey biomass
and production by bighead carp, whereas negative values would
TABLE 1 Average individual body weight (g SD), standing crop
biomass (g/m
SD) and density (# m
SD) of fishes added to
native (control, n=5) and invaded (treatment, n=5) ponds during
the 3-month experiment (JuneSeptember 2014)
Treatment Species Body weight Biomass Density
Control Channel catfish 6.24 2.19 0.32 0.03 0.05
Golden shiner 0.78 0.21 0.10 0.01 0.12
Largemouth bass 1.31 0.94 0.13 0.01 0.10
Red shiner 2.11 0.79 0.08 0.01 0.04
Invaded Bighead carp 7.62 1.78 3.19 0.07 0.42
Channel catfish 6.24 2.19 0.30 0.02 0.05
Golden shiner 0.78 0.21 0.09 0.02 0.12
Largemouth bass 1.31 0.94 0.13 0.01 0.10
Red shiner 2.11 0.79 0.08 0.01 0.04
indicate potential compensatory increases for respective metrics. We
fit and contrasted models using a corrected Akaike information crite-
ria (AICc) model selection approach (Burnham & Anderson, 2003).
The model with the smallest AICc value was considered the best fit.
If the models were within D2 AICc, we determine them to be
equally informative (Burnham & Anderson, 2003). Finally, effect sizes
of standing crop biomass and daily production were regressed to
determine whether effects scaled proportionately or departed from a
1:1 relationship (linear regression: adj. R
, RMSE, F,p).
The size structure of the zooplankton assemblage shifted towards
smaller individuals in ponds invaded by bighead carp, whereas the
zooplankton size structure in ponds with only native fishes had a
higher frequency of large-bodied individuals (ANCOVA: treat-
ment 9length bin, F=7.17, p=.01; Figure 1). Shifts towards smal-
ler size distributions were influenced, in small part, by a reduction in
individual body lengths of Diaphanosoma (Family: Sididae) and Daph-
nia (Family: Daphniidae) in ponds where bighead carp were present
(Table 2; Figure 2a). Average (SD) body lengths of Diaphanosoma
decreased by 19% and Daphnia decreased by 9% in the presence of
bighead carp, relative to controls.
The strongest driver of changes to the size distribution of zoo-
plankton assemblage was the direct effect of predation by bighead
carp on the standing crop biomass and secondary production of zoo-
plankton. Larger zooplankton (>0.55 mm) exhibited stronger reduc-
tions in standing crop biomass and daily production when bighead
carp were present (Table 2, Figure 2b,c). For instance, Cyclopoida
standing crop biomass and daily production were reduced by 79%
and 47%, respectively. Diaphanosoma,Daphnia and Calanoida all
responded similarly, with biomass reduced from 92% to 98% and
daily production by 6574%. Calanoida standing crop biomass also
varied through time, which differed between treatments (time:
F=26.31, p<.001; time 9treatment: F=16.11, p<.001). Con-
trary to our predictions, we detected no compensatory increases by
smaller invertebrates. Bighead carp had no effect on the biomass
and daily production of small-bodied Bosmina (Family: Bosminidae),
Ostracoda and Ceriodaphnia (Family: Daphniidae; Table 2, Figure 2b,
c). Although rotifers were smaller than bosminids and ostracods,
their standing crop biomass and daily production were reduced in
ponds with bighead carp (Table 2, Figure 2b,c). Densities of imma-
ture copepod nauplii, which were similar in size to rotifers, were
75% lower in ponds invaded by bighead carp (F
1, 9
p=.002; Figure 3).
The magnitude (GlasssD) of bighead carp predation on zoo-
plankton was best characterised as a linear relationship with prey
body length (Table 3). Standing crop biomass (adj. R
RMSE =1.08, F
1, 7
=4.61, p=.07; biomass effect =1.0069 +
5.56359 9body length) and secondary production (adj. R
RMSE =1.90, F
1, 7
=6.5, p=.04; production effect =2.1908 +
11.5757 9body length) were generally related to prey body length
(Figure 4a). In general, effect sizes increased with body size and the
strength of this relationship was stronger for daily production. Fur-
thermore, relationship between standing crop biomass and sec-
ondary production effect sizes was not proportional (adj. R
RMSE =0.51, F
1, 7
=42.0, p=.0006; biomass effect =0.0351 +
0.47747 9production effect). Instead, top-down effects of bighead
carp were skewed towards greater impacts on secondary production
Body length (mm)
0 – 0.1
0.1 – 0.2
0.2 – 0.3
0.3 – 0.4
0.4 – 0.5
0.5 – 0.6
0.6 – 0.7
0.7 – 0.8
0.8 – 0.9
0.9 – 1
1 – 1.1
1.1 – 1.2
Count (±SE)
FIGURE 1 Average count (SE) of planktonic invertebrates
within specific body length bins (mm). Black columns represent the
zooplankton size spectra of ponds invaded (n=5) by bighead carp
Hypophthalmichthys nobilis and white columns represent controls
(n=5) with only native fishes
TABLE 2 Statistical responses (F-value, p-value) examining the
effects of bighead carp on the body length (mm; one-way ANOVA),
standing crop biomass (g/m
; rmANOVA) and daily secondary
production (g m
; one-way ANOVA) of zooplankton and
rotifers from a 3-month experiment (JuneSeptember, 2014). In all
cases, bighead carp had a negative effect on a response variable
when a significant effect was detected (indicated with bold). For the
repeated-measures ANOVA of standing crop biomass, both time and
time 9treatment interactions were non-significant for all taxa
(p>.05), except Calanoida (time: F=26.31, p<.001;
time 9treatment: F=16.11, p<.001)
Body length
Standing crop
biomass Daily production
FpF pF p
Rotifera 2.13 .18 5.46 .04 11.01 .01
Ostracoda 0.13 .74 0.94 .35 <0.001 .98
Bosmina 0.35 .58 1.26 .29 4.07 .07
Ceriodaphnia 0.03 .87 1.32 .28 1.35 .27
Cyclopoida 0.09 .77 8.62 .01 26.43 <.001
Calanoida 0.10 .75 107.6 <.001 83.48 <.001
Diaphanosoma 19.44 .002 62.12 <.001 112.3 <.001
Daphnia 6.35 .05 15.28 .004 29.45 <.001
rather than the more common metric of standing crop biomass (Fig-
ure 4b).
Our findings indicate intense predation by bighead carp reduced the
body size of individuals, shifted community size structure towards
smaller individuals, reduced the biomass and daily production of zoo-
plankton and reduced immature copepod nauplii. Although filter-fee-
ders can consume many prey at a time, we did not detect an abrupt
threshold between exploited and unexploited prey. Our experiment
indicated that the magnitude of predation increased linearly with
prey body size such that the strongest effects were observed for the
largest prey taxa. Findings from our experiment align with patterns
from the Illinois River (La Grange reach), where densities of Clado-
cerans and Copepods were 9.8 and 26.3 times lower, respectively,
following the invasion of bighead and silver carp (Sass et al., 2014).
Filter-feeding planktivores typically consume more slower prey and
fewer evasive prey like copepods (Drenner et al., 1982; Lazzaro,
1987). Yet, bighead carp had the strongest effect on copepod bio-
mass and daily production, perhaps because of strong negative
effects on immature and less mobile nauplii. Interestingly, filter-feed-
ing bighead carp imparted size-specific changes to the zooplankton
assemblage, producing patterns similar to particulate feeding plankti-
vores (e.g., Brooks & Dodson, 1965; Greene, 1983), despite the fact
that bighead carp do not visually select individual prey. Because big-
head carp are planktivorous throughout their life (Kolar et al., 2007),
feeding on zooplankton as both juveniles and adults, we expect
effects between life stages to be similar. However, such comparisons
Body length (mm)
Standing crop biomass (g/m2)
Daily production (g/m2/day)
FIGURE 2 Effects of invaded (black circles) and native (white
circles) fish assemblages on zooplankton: (a) average individual body
length (mm); (b) standing crop biomass (g/m
); (c) daily secondary
production (g m
). Error bars represent 1SE (n=5)
Control Invaded
Copepod nauplii (# L–1)
FIGURE 3 Average density of immature copepod nauplii in
ponds with native fishes (control) and ponds with native fishes and
bighead carp (invaded). Error bars represent 1SE (n=5)
TABLE 3 Models selected under AICc model selection to explain
relationships between taxa-specific effect sizes (metrics: standing
crop biomass, g/m
; secondary production, g m
) in relation
to prey body length at the end of the 3-month experiment. Each
point represents the effect of bighead carp on a specific
zooplankton taxon. P =parameter
Metric Model AICc DAICc AICc weight BIC
Biomass Linear 33.76 0.85 27.99
Logistic 3P 37.76 4.00 0.11 24.74
Quadratic 40.02 6.26 0.04 27.00
Probit 4P 56.07 22.31 0.00 26.47
Production Linear 42.70 0.90 36.94
Quadratic 48.00 5.30 0.06 34.98
Logistic 3P 48.89 6.19 0.04 35.88
Probit 4P 66.18 23.47 0.00 36.58
require further evaluation because other factors such as metabolic
requirements and differences in habitat associations between life
stages may also influence overall effects.
The magnitude of predation by bighead carp scaled positively
with prey body size, except for rotifers. Effect sizes were generally
greater for daily production than for standing crop biomass, suggest-
ing inferences based solely on standing crop biomass may
underrepresent the top-down effect of predation and associated
impacts to energy flows within the planktonic food web. The bio-
mass and production of five zooplankton taxa declined in the pres-
ence of bighead carp. Overall, these effects are consistent with
others demonstrating reduced densities or standing crop biomass of
zooplankton by bigheaded carp (e.g., Fukushima et al., 1999; Sass
et al., 2014; Shao, Xie, & Zhuge, 2001). Our findings indicate that
predation by bighead carp affect zooplankton populations through
multiple mechanisms. Larger and more susceptible zooplankton taxa
such as Calanoida, Daphnia and Diaphanosoma appear to be
exploited faster than their populations (i.e., generation times) could
resupply adults (Gillooly, 2000; Sanoamuang, 1993); thus, their popu-
lations could not overcome predation by bighead carp. For smaller
taxa, the weaker effects observed may have been dampened by fas-
ter population turnover or because they were less abundant and
encountered less often. For such minor differences, the functional
consequences, such as changes to the volumes of water filtered by
suspension-feeding taxa, may be minimal when compared to greater
effects on larger suspension-feeding taxa (e.g., Collins et al., 2018).
We present evidence that bighead carp reduced the body size of
zooplankton at the end of our 3-month experiment. Body lengths of
Diaphanosoma and Daphnia experienced a 919% reduction in body
size, presumably from reduced activity, foraging and growth (e.g.,
Lind & Cresswell, 2005; OBrien, 1987; Van Buskirk & Yurewicz,
1998). In a companion study, we documented a trophic cascade
resulting in increased phytoplankton (Collins & Wahl, 2017), which
indicates that there was abundant food for these zooplankton. Zoo-
plankton will phenotypically reduce body size and age at maturation,
which also reduces clutch size (Green, 1956; Havel & Dodson, 1987;
Lynch, 1977). Despite being smaller, Diaphanosoma and Daphnia
remained susceptible to predation by bighead carp. Based on these
findings, such plastic reductions were inconsequential because stand-
ing crop biomass and daily production of both Diaphanosoma and
Daphnia were reduced.
Fish predation can reduce the recruitment of early life stages of
invertebrates into the population by altering the reproductive output
of adults and by enhancing mortality of larval nauplii (Sebastidae:
Sebastes spp., Gaines & Roughgarden, 1987; Salmonidae spp., Sar-
nelle & Knapp, 2004). Findings from our study suggest juvenile big-
head carp may negatively affect copepod recruitment by reducing
numbers of immature stages, yet the observed pattern may have
been influenced by direct and indirect mechanisms. Copepod nauplii
were similar in size to rotifers, and yet densities of nauplii were
more strongly affected by bighead carp. Both nauplii and rotifers are
readily consumed by bighead carp, based on diet assessments from
the Illinois River, USA (Sampson, Chick, & Pegg, 2009), so direct pre-
dation is an important factor. Additionally, indirect predation effects
may also influence nauplii densities. For instance, numbers of nauplii
depend on the reproductive success of adults and the presence of
egg-bearing females from the population. Finally, carp may have
altered processes that influence the contribution of eggs to the sedi-
ments or survival from egg to naupliar stage. Although we cannot
distinguish direct from indirect influences, our findings suggest that
Body length (mm)
Effect size: production
Effect size
Effect size: biomass
0.0 0.2 0. 4 0.6 0.8
FIGURE 4 Experimental effect sizes (GlasssD;
) of bighead carp on the
(a) standing crop biomass (linear regression: adj. R
RMSE =1.08, F
1, 7
=4.61, p=.07; biomass
effect =1.0069 +5.56359 9body length) and daily secondary
production (linear regression: adj. R
=.44, RMSE =1.90, F
1, 7
p=.04; production effect =2.1908 +11.5757 9body length) of
zooplankton taxa in relation to average body length (mm). (b) The
relationship between experimental effect sizes (GlasssD) for each
zooplankton taxa was plotted to determine whether bighead carp
predation effects on standing crop biomass and daily secondary
production scaled in a 1:1 relationship (linear regression: adj.
=.85, RMSE =0.51, F
1, 7
=42.0, p=.0006; biomass
effect =0.0351 +0.47747 9production effect)
alterations to copepod recruitment limited the production of new
copepod tissue and, ultimately energy flow through the planktonic
environment, as evidenced in their daily secondary production. The
effects of bighead carp on these life history processes are unknown
and warrant further exploration because of the implications for the
dynamics of invertebrate populations and for the flow of energy
through freshwater food webs.
Planktonic rotifers play a significant role in carbon transfer
between the microbial food web and higher trophic levels (Arndt,
1993) and are often an underrepresented component of aquatic
food webs (Chick et al., 2010). By altering the size structure of prey
communities, predators further influence competitive interactions
among prey (Collins et al., 2018; H
ulsmann, Rinke, & Mooij, 2011).
Although we anticipated compensatory increases by rotifers (Collins
et al., 2018), the removal of large zooplankton did not release roti-
fers from regulatory constraints. Instead, densities of rotifers
declined, indicating these small invertebrates were suppressed during
our experiment. The reduced biomass of rotifers in our experiment
is consistent with several studies (e.g., Fukushima et al., 1999; Shao
et al., 2001), but opposite of others (e.g., Sass et al., 2014), suggest-
ing compensation by rotifer assemblages does vary and the reasons
remain elusive. Similar responses have been observed by other inva-
ders such as zebra mussels (Dreissenidae: Dreissena polymorpha),
which reduced rotifer numbers in the Hudson River, USA (Pace,
Findlay, & Fischer, 1998). Despite their small size, these inverte-
brates are an important component of the diets of bighead and silver
carp in the wild (Sampson et al., 2009; Williamson & Garvey, 2005).
Owing to their short generation times and rapid biomass turnover,
these small invertebrates may provide an efficient pathway of
energy flow to bigheaded carp through the aquatic food web (Nel-
son, Collins, Sass, & Wahl, 2017), particularly if native fishes are
poorly suited to exploit rotifers.
Moving forward, ecologists need to identify the habitats that
supply zooplankton inoculums to mainstem habitats of riverflood-
plain ecosystems (Wahl, Goodrich, Nannini, Dettmers, & Soluk,
2008) and to determine whether bigheaded carp are present within
these habitats and whether their predatory impacts alter zooplank-
ton similarly. If bigheaded carp regulate zooplankton recruitment, or
disparities are observed between taxa, the varied effects on zoo-
plankton may be far reaching, both spatially and temporally. What
are the long-term ramifications of intense exploitation of zooplank-
ton by bigheaded carp? Consumption of females may impact the via-
bility of ephippial and parthenogenetic eggs during digestion (e.g.,
Conway, McFadzen, & Tranter, 1994). Do bigheaded carp reduce the
supply of zooplankton eggs to seed banks in the sediments of large
riverfloodplain ecosystems and are ephippia resistant to digestion
(e.g., Mellors, 1975)? Moreover, how might these impacts affect the
resilience of zooplankton communities in the coming decades (e.g.,
Hairston, 1996; Jarnagin, Kerfoot, & Swan, 2004)? Pervasive preda-
tion on nauplii may adversely affect recruitment, limiting the num-
bers of individuals that survive to adulthood, potentially causing
depensation within populations (e.g., Liermann & Hilborn, 2001).
Experimental evaluations, including our own, largely focus on the
immediate or seasonal effects of these invasive planktivores. Future
studies will require examining population dynamics of wild popula-
tions of zooplankton at longer timescales.
We thank M. Diana, S. Butler and M. Nannini for their logistical and
intellectual contributions. Additionally, we thank B. Diffin for his
technical assistance in processing zooplankton samples. Partial sup-
port was provided by the Illinois Natural History Survey and the
Great Lakes Research Initiative, administered through the Illinois
Department of Natural Resources (CAFWS-93). Finally, we thank
members of the Kaskaskia, Ridge Lake and Sam Parr Biological Sta-
tions of the Illinois Natural History Survey, as well as graduate stu-
dents from the University of Illinois for their intellectual discussions
and feedback. Institutional Animal Care and Use Committee
(#14069) approval was obtained before commencement of the
study. All fishes were acquired, retained and used in compliance with
federal, state and local laws and regulations.
SFC and DHW conceived and designed the experiment. SFC per-
formed the experiment. SFC analysed the data and wrote the manu-
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... nobilis] and Bighead Carp combined up to 80% fish biomass; Coulter, MacNamara, et al., 2018). For example, native planktivores are negatively impacted by invasive Bighead Carps (Fritts et al., 2018;Tristano et al., 2019) and plankton assemblages are altered (e.g., Collins & Wahl, 2018). The Illinois Waterway has been a focal point for Bighead Carp management because this waterway connects the Mississippi River Basin to the valuable fisheries resources of the Laurentian Great Lakes via man-made canal systems. ...
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... Asian carp are not universally welcome and have faced severe rejection from consumers (Collins and Wahl 2018;Kočovský et al. 2018;Lu et al. 2020;B Li et al. 2021). Asian carp, like many other cyprinids, are bony and have numerous intermuscular bones (IBs) or pin bones embedded within the fillets (Freeman 1996;Sahu et al. 2014;Coad and Mcallister 2020). ...
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... In contrast, the response of microplankton like rotifers has been more mixed. Mesocosm experiments show BHC planktivory selectively favors some taxa of smaller bodied rotifers while concurrent field studies find the density of rotifers is either unaffected by or even elevated where BHC abundance is highest (Sass et al., 2014;Collins and Wahl, 2018;Chará-Serna and Casper, 2021). The characteristic of rotifers that appears responsible for this response is reproduction; rotifers have shorter generation times than the majority of macroplankton (Lu et al., 2002;Lair, 2006). ...
The invasion of silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) or “bigheaded carps” has caused extensive ecological and economic harm throughout the Mississippi River and its tributaries. To prevent their continued spread upstream toward the Great Lakes, intense commercial harvest was implemented on the Illinois River, a large tributary that connects the Mississippi River to Lake Michigan. Since implementation, harvest has reduced densities at the invasion front while also presenting an opportunity to generate a synthesis on ecosystem resilience in the face of accelerating invasion. Resilience, the ability of an ecosystem to recover after perturbation, was observed at local scales and within some taxa but has yet to manifest at a river-wide scale and often co-varied with abiotic environmental or seasonal factors. Thus, while intensive harvest has limited further spread of bigheaded carps, and evidence of additional secondary ecosystem benefits exists, opportunities remain to identify potential pathways that could spread such ecosystem benefits even farther.
... Bigheaded carps can be highly invasive owing to their high consumption rates of plankton, rapid growth rates, large sizes (up to 130 cm and 50 kg), and high fecundities (0.6-2.0 million eggs/female) as well as the paucity of predators on adult carp (Williamson and Garvey 2005;Kolar et al. 2007;Hayer et al. 2014;Zhang et al. 2016). Several studies have shown that at high population densities, BHC consumption can cause shifts in size and abundance of plankton communities (Zhang et al. 2006;Cooke et al. 2009;Sass et al. 2014;Li et al. 2017;Tumolo and Flynn 2017;Collins and Wahl 2018). For example, in the lower Illinois River, BHC biomass has reached 45-78% of the total fish biomass (Coulter et al. 2018). ...
Bigheaded carps (BHCs; Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis) are economically and culturally important in Asia and Europe but are considered highly invasive throughout the Mississippi River watershed and pose a threat to the food web and fisheries of the Laurentian Great Lakes. We used the Ecopath with Ecosim model framework to evaluate potential risk of BHC population growth and food web effects in four Great Lakes habitats, including mesotrophic waters of Saginaw Bay (Lake Huron) and Lake Erie and the oligotrophic main basins of Lakes Michigan and Huron. We simulated BHC population growth and food web effects under different scenarios of BHC production rates, prey vulnerability to BHCs, and availability of age‐0 BHCs to predation by salmonines. In the main basins of Lakes Michigan and Huron, the projected BHC population growth was low or negative, with a projected final BHC biomass of 0.5–1.1 times the initial introductory biomass (2% of total fish biomass for each BHC species), and BHCs had negligible effects on most food web groups across all scenarios. In contrast, in Saginaw Bay and Lake Erie, the projected BHC biomass was 2.5–12.5 times higher than the initial biomass across all scenarios, and the largest increases occurred under scenarios of high prey vulnerability to BHCs and high BHC production rates. High projected BHC biomass in Saginaw Bay and Lake Erie had negative effects on zooplankton and planktivorous fish groups and mixed effects on piscivores but had relatively negligible effects on most other food web groups across all scenarios. Our results are consistent with reported BHC effects on food webs in the Mississippi River and its tributaries and inform efforts to prevent BHC invasion of the Great Lakes.
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Invasive Silver Hypophthalmichthys molitrix and Bighead Carp H. nobilis (collectively bigheaded carp) regularly alter zooplankton communities in lentic systems but dynamics in lotic systems are less understood. Here, we investigated trends in zooplankton communities, densities, and biomass in pools 14–20 of the Upper Mississippi River (UMR) across a gradient of bigheaded carp presence and relative abundance during 2016–2018. We explored the effects of bigheaded carp presence on zooplankton communities using non-metric multidimensional scaling (NMDS) and assessed taxa-specific relationships with bigheaded carp relative abundance using ordinary least-squares regression with an indicator variable for bigheaded carp presence. Zooplankton communities in the UMR were dominated by rotifers and crustacean zooplankton densities were low, making up only 2% of the community density. Zooplankton communities differed where bigheaded carp were present. Density and biomass of cladocerans and copepods were both reduced where bigheaded carp were present but copepods increased with bigheaded carp relative abundance. Ostracod biomass increased in the presence of bigheaded carp whereas rotifers declined with bigheaded carp relative abundance. Low crustacean zooplankton densities in the UMR may limit larval/juvenile fish growth and recruitment regardless of bigheaded carp, but further declines in the crustacean community due to expanding bigheaded carp populations are concerning.
Bigheaded carp (Bighead Carp, Hypophthalmichthys nobilis and Silver Carp, Hypophthalmichthys molitrix) are invasive species in the US and have spread throughout much of the Mississippi River Basin. Population abundance upstream of Lock and Dam 19 (LD19) on the Upper Mississippi River (UMR) has likely been limited by the high‐head dam at this location, which restricts all upstream fish passage to the lock chamber. We measured otolith (lapillus) stable isotope composition and elemental microchemistry of 146 Silver Carp (n = 77 females and n = 69 males) and 141 Bighead Carp (n = 76 females and n = 65 males) to determine early‐life environments of adult bigheaded carp captured upstream of LD19 at the invasion front, in an area of intense management (Pools 16‐19). Otolith oxygen isotope ratios (δ18O) and elemental ratios (Sr:Ca and Ba:Ca) were compared to values of isotope and elemental ratios in water from putative early‐life environments to assign early‐life environment for each fish. Most Bighead Carp (68.8%) and Silver Carp (54.1%) collected upstream of LD19 had otolith core signatures consistent with early‐life environments downstream of LD19. Nineteen percent of Bighead Carp and 34% of Silver Carp could not be classified. The sex ratios of bigheaded carp (Pools 17‐19 combined) with otolith core signatures downstream of LD19 did not differ from 1:1. Our results when compared to Whitledge et al. (2019) suggest low but stable recruitment above this population pinch‐point dam in the UMR and that targeting removal of bigheaded carp downstream of LD19 or inhibiting their movement upstream through the lock there might be effective as part of integrated control efforts.
1) Recent evidence shows that in lotic, physically‐dominated ecosystems like large rivers, zooplankton can develop spatially structured assemblages and fulfill functionally important roles. While refuting the long‐standing notion that riverine zooplankton communities are numerically depauperate and spatially homogeneous, this also shows that the importance of abiotic and biotic drivers and the consistency of ecological patterns are still poorly understood for these communities. 2) We collected zooplankton along 300 km of the Illinois River for 5 years to test the influence of a suite of biotic and abiotic variables on zooplankton density, biomass, and diversity. We hypothesized abiotic variables such as temperature, turbidity, and velocity would be predominant predictors, with biotic variables like planktivory becoming important when physical factors do not constrain them. 3) Results showed basin‐wide declines in zooplankton taxonomic richness as planktivory from the invading silver carp (Hypophthalmichthys molitrix) increased. In contrast, density and biomass were explained by abiotic factors at the basin scale, with velocity, turbidity, and pH driving biomass and velocity driving density. We also found that both the driving factors and the plankton responses varied among the upper, middle, and lower sections of the Illinois River. 4) We conclude that while zooplankton communities of the Illinois River are highly structured in space, the driving forces behind their distribution patterns are not simple. Instead, there is a complex spatio‐temporal template of biological, chemical, and hydraulic factors shaping these communities in the Illinois River. Along with emphasizing the importance of spatial heterogeneity in large river ecosystems, these results also support a growing view that invasive species interactions can supersede the well‐established role of abiotic factors in explaining global freshwater diversity losses. This also highlights the importance of including long‐term zooplankton sampling in ecological monitoring programs in diverse and productive large river systems like the Illinois.
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Ecosystem level effects of common (Cyprinus carpio) and bighead carp (Hypophthalmichthys nobilis) have generally focused on adult life stages. The objective of our mesocosm study was to investigate and contrast the roles of juvenile common and bighead carp in structuring planktonic invertebrate assemblages, with focus on rotifers. We examined whether predation by juvenile carp was indiscriminate or size-selective with respect to prey size. Furthermore, we examined how changes to large and small prey influenced the potential for compensatory increases of some taxa within prey assemblages. Both species of juvenile carp reduced large zooplankton taxa. However, rotifer responses were variable depending on the taxon and predator combination. Juvenile common carp enhanced abundance for Polyartha and Squatinella, but most taxa were unaffected. Juvenile bighead carp had a more varied effect on rotifer abundance, having no effect on most, reducing Keratella and enhancing Anuraeopsis. We also estimated net filtration volume of the zooplankton community for each of the treatments and found partial compensation in net filtration because of the increased abundance of a few rotifer taxa, but this reduction did not match the depletion of macrozooplankton. Rotifers that benefitted from the presence of fish predators likely responded positively because of reduced predation by mesopredators, because of their short generation times, and/or from reduced competition.
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Communities of organisms are shaped by a complex suite of positive and negative species interactions. Ecological phenomena like biological invasions typically evoke notions of negative effects on native communities. Yet, negative effects within specific food-web components can also have positive feedbacks that manifest elsewhere within the food web. We designed an experiment to evaluate the direct and indirect effects of invasive bighead carp (Hypophthalmichthys nobilis: Cyprinidae) on planktonic and benthic invertebrates and the growth and survival of juvenile bluegill sunfish (Lepomis macrochirus: Centrarchidae). Our experiment indicated that the presence of bighead carp indirectly facilitated bluegill growth and survival. The underlying processes driving predator-predator facilitation stemmed from a combination of indirect interactions occurring through invertebrates in planktonic and vegetated habitats. Individual bluegill consumed more cladocerans and predatory macroinvertebrates in the presence of bighead carp. The presence of bighead carp appears to have indirectly influenced interactions among cladocerans, invertebrate predators, and bluegill. Understanding the cumulative direct and indirect effects of bigheaded carp on aquatic ecosystems requires the documentation of both negative and positive effects. Although one taxon benefitted from the presence of an invader, our findings demonstrate that this response occurred because bigheaded carp caused imbalances within the food web. We urge that future studies consider a priori how positive and negative interspecific interactions shape the structure of food webs.
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Ecological theory has long recognised the importance of positive and negative species interactions as drivers of food web structure, yet many studies have only focused on competition. Because competitive and facilitative mechanisms operate simultaneously, but through different food web pathways, the balance of their combined effects can produce complex and variable responses. We used a response-surface experimental design to assess the roles of negative (e.g. intra-, interspecific competition) and positive (e.g. facilitation) interactions between native and invasive juvenile fishes. We tested whether these interactions alter the densities of planktonic and benthic invertebrates to evaluate the magnitude and mechanism(s) influencing the acceptance or resistance of biological invaders. Interactions between bighead carp (Hypophthalmichthys nobilis) and bluegill (Lepomis macrochirus) or common carp (Cyprinus carpio) were evaluated in mesocosms. Intraspecific interactions were 1.5-2.4 times stronger than interspecific interactions between carp species. The only instance of interspecific competition resulted in bighead carp reducing the daily growth of bluegill, whereas the reciprocal interaction resulted in facilitation. Facilitation occurred when bluegill increased the daily growth of low density bighead carp treatments, despite increased numbers of fishes. Bighead carp also increased densities of benthic Chironomidae larvae, which were subsequently consumed by bluegill, but did not result in enhanced bluegill growth. These suites of interactions were not observed between common and bighead carp. Our response-surface design proved useful for comparing the relative magnitude of intra- vs. interspecific competition, identifying facilitation among species, and tracing attendant effects on invertebrate communities. By accounting for the directionality of interactions within our experimental framework and tracking responses of prey at lower trophic levels, we provide a clearer understanding of how competitive effects and stressed consumers alter prey communities and influence facilitation. plain language summary is available for this article.
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Bighead carp (Hypophthalmichthys nobilis) are an invasive planktivore that can greatly deplete planktonic resources. Due to the inefficient conversion of food into fish tissue, large portions of consumed materials are egested and shunted to benthic habitats. We explored how bighead carp alter pools of organic matter between planktonic and benthic habitats, and across ecosystem boundaries. Here, we report evidence from a manipulative experiment demonstrating that bighead carp greatly reapportion pools of organic matter from planktonic to benthic habitats to such a degree that additional effects propagated across ecological boundaries into terrestrial ecosystems. Strong direct consumption by bighead carp reduced filamentous algae, biomass and production of zooplankton, and production of a native planktivorous fish within planktonic habitats. Reduced herbivory indirectly increased phytoplankton (chlorophyll a). Direct consumption of organic matter by bighead carp supported high carp production and concomitant losses of materials due to egestion. Perhaps in response to organic matter subsidies provided by fish egestion, ponds having bighead carp had higher standing crop biomass of Chironomidae larvae, as well as cross-boundary fluxes of their adult life stage. In contrast, we detected reduced cross-boundary fluxes of adult Chaoboridae midges in ponds having bighead carp. Consideration of bighead carp as mediators of organic matter exchanges provides a clearer framework for predicting the direct and extended impacts of these invasive planktivores in freshwater ecosystems. The perception of bighead carp must evolve beyond competitors for planktonic resources, to mediators and processors of nutrients and energy within and across ecosystems.
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Effective management and monitoring programs require confidence regarding basic biological sampling. Gear comparisons are often required to determine the most effective techniques. Such is the case for populations of invasive Asian carps Hypophthalmichthys spp., which have recently occurred in large numbers throughout sections of the Mississippi River basin. We tested five gears (mini-fyke nets, beach seine, purse seine, pulsed-DC electrofishing, and gill net) that targeted juvenile (age 0) Silver Carp H. molitrix at sites along the Illinois River during 2014 and 2015 to determine the most effective ones for age-0 Silver Carp. We considered the most cost-effective gear to be the one that provided the largest catch at a minimal expenditure of labor. Mini-fyke nets were the most effective at collecting large numbers of age-0 Silver Carp, followed in decreasing order by beach seines, pulsed-DC electrofishing, purse seines, and gill nets. The smallest Silver Carp were caught in beach seines and the largest were caught in gill nets, and there was considerable variation in size distributions among gears. However, when we considered cost-effectiveness in terms of labor hours for each gear, both beach seines and mini-fyke nets had similar and overlapping labor expenditures. Gill nets and purse seines were not cost-effective, as they required more labor and had lower overall catch rates. Received May 23, 2016; accepted September 19, 2016
The 3e of Ecology and Classification of North American Freshwater Invertebrates continues the tradition of in-depth coverage of the biology, ecology, phylogeny, and identification of freshwater invertebrates from the USA and Canada. This edition is in color for the first time and includes greatly expanded classification of many phyla and a downloadable set of references for all chapters. - Contains extensive and detailed classification keys for identification of diverse freshwater invertebrates. - Many drawings and color photographs of freshwater invertebrates. - Single source for a broad coverage of the anatomy, physiology, ecology, and phylogeny of all major groups of invertebrates in inland waters of North America, north of Mexico. "Thank you for the opportunity to comment on the latest edition of Thorp and Covich. I have admired prior editions of this superb book for its comprehensive coverage of freshwater invertebrates. The current edition improves upon the high standard set by prior editions through the use of color and greater taxonomic specificity. Authored by an outstanding collection of experts, individual chapters provide comprehensive coverage of morphology, physiology and ecology, as well as methods for collecting, rearing and preserving freshwater invertebrates. Together with chapters on ecology and habitats of inland waters, this carefully edited volume provides the central knowledge of freshwater invertebrates that every student and researcher will find invaluable. I highly recommend this superb new edition of Thorp and Covich - it is a must-own volume that every student and researcher of freshwater invertebrates will find invaluable." J. David Allan, Ph.D. Professor and Acting Dean School of Natural Resources and Environment The University of Michigan *** "This 3rd edition contains a wealth of information, which has expanded its utility beyond the earlier editions. Thorp and Covich gathered the recognized experts in North America to compile the full extent of current knowledge on this diverse group of aquatic fauna. The color plates are amazing and add tremendous value to both the learner and learned of the invertebrate biologists." Michael T. Barbour, PhD Director, Center for Ecological Studies Tetra Tech, Owings Mills, Maryland *** "At last, after half a century, this new edition of Thorp and Covich is a worthy successor to Edmondson's (1957) classic second edition of Ward and Whipple's Freshwater Biology. It brings us up to date on the amazing advances in the biology of freshwater invertebrates, the keys are detailed, and the illustrations as beautiful as they are useful." Nelson G. Hairston, Jr. Frank H.T. Rhodes Professor of Environmental Science Department of Ecology and Evolutionary Biology Cornell University *** "The 3rd edition of Thorp and Covich has been extensively revised. The chapters are written by experts who present up-to-date reviews on the structure, function, ecology, and systematics of each invertebrate group. The biggest change from the 2nd edition is an expansion of the taxonomic keys to allow identifying many of the taxa to the species level. References to more-detailed monographs and web sites allow users to quickly gain a fuller perspective on particular groups of interest. The book should continue to be a vital resource for research labs and as a classroom text." John E. Havel, Ph.D. Professor of Biology Missouri State University "The 3rd edition of Ecology and Classification of North American Freshwater Invertebrates continues the tradition of in-depth coverage of the biology, ecology, phylogeny, and identification of freshwater invertebrates from the USA and Canada. This edition is in color for the first time and includes greatly expanded classification of many phyla and a downloadable set of references for all chapters."--GrrlScientist's Maniraptora blog on "This third edition ensures that this work will remain the most up-to-date and comprehensive information source on freshwater invertebrate animals in the US and Canada. Numerous color photographs and some diagrams now brighten more than half of the new chapters. Fifty coauthors contributed, a 35 percent increase from the second edition.. Highly recommended."--CHOICE