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Catch Rates and Cost Effectiveness of Entrapment Gears for Asian Carp: A Comparison of Pound Nets, Hoop Nets, and Fyke Nets in Backwater Lakes of the Illinois River


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We compared three entrapment gears to determine which method was the most effective for capturing invasive Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix in terms of numbers of fish captured and labor invested. Gears were deployed concurrently in two backwater lakes of the Illinois River during the summers of 2012–2014. Overall, the nightly catch rates of all fishes, Bighead Carp, and Silver Carp were one to three orders of magnitude greater in pound nets than in either fyke nets or hoop nets. Pound nets collected larger Bighead Carp than hoop nets and fyke nets. Hoop nets were ineffective at catching Asian carp in backwater lakes. Estimation of the effort required to deploy, maintain, and remove each gear type indicated that pound nets were the most cost effective gear due to their high catch rates of Asian carp relative to the labor hours invested to collect the catch. Pound nets appear to be an effective means of removing Asian carp in backwater lake habitats of the Illinois River.
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North American Journal of Fisheries Management
ISSN: 0275-5947 (Print) 1548-8675 (Online) Journal homepage:
Catch Rates and Cost Effectiveness of Entrapment
Gears for Asian Carp: A Comparison of Pound
Nets, Hoop Nets, and Fyke Nets in Backwater
Lakes of the Illinois River
Scott F. Collins, Steven E. Butler, Matthew J. Diana & David H. Wahl
To cite this article: Scott F. Collins, Steven E. Butler, Matthew J. Diana & David H. Wahl (2015)
Catch Rates and Cost Effectiveness of Entrapment Gears for Asian Carp: A Comparison of
Pound Nets, Hoop Nets, and Fyke Nets in Backwater Lakes of the Illinois River, North American
Journal of Fisheries Management, 35:6, 1219-1225, DOI: 10.1080/02755947.2015.1091799
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Catch Rates and Cost Effectiveness of Entrapment Gears for
Asian Carp: A Comparison of Pound Nets, Hoop Nets, and
Fyke Nets in Backwater Lakes of the Illinois River
Scott F. Collins,* Steven E. Butler, Matthew J. Diana, and David H. Wahl
Illinois Natural History Survey, Kaskaskia Biological Station, 1235 County Road 1000N, Sullivan,
Illinois 61951, USA
We compared three entrapment gears to determine which method was the most effective for capturing invasive
Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix in terms of numbers of fish captured and
labor invested. Gears were deployed concurrently in two backwater lakes of the Illinois River during the summers
of 2012–2014. Overall, the nightly catch rates of all fishes, Bighead Carp, and Silver Carp were one to three orders
of magnitude greater in pound nets than in either fyke nets or hoop nets. Pound nets collected larger Bighead Carp
than hoop nets and fyke nets. Hoop nets were ineffective at catching Asian carp in backwater lakes. Estimation of
the effort required to deploy, maintain, and remove each gear type indicated that pound nets were the most cost-
effective gear due to their high catch rates of Asian carp relative to the labor hours invested to collect the catch.
Pound nets appear to be an effective means of removing Asian carp in backwater lake habitats of the Illinois River.
Bighead Carp Hypophthalmichthys nobilis and Silver Carp
H. molitrix, collec tively referred to as Asian carp, were first
introduced into the United States in the 1970s for aquaculture.
The exponential increase and expansion of populations of
these species throughout the Mississippi River and its tributar -
ies has caused concern over the effect these species have on
freshwater ecosystems (Chick and Pegg 2001; Irons et al.
2007; Sass et al. 2010). Asian carp may deplete plankton den-
sities and alter zooplankton community composition (Burke
et al. 1986; Lu et al. 2002; Sass et al. 2014), potentially com-
peting with native planktivores for food resources (Schrank
et al. 2003; Irons et al. 2007; Sampson et al. 2009). Estab-
lished populations of Bighead Carp and Silver Carp therefore
pose considerable ecological and economic threat to the Mis-
sissippi River basin and the Laurentian Great Lakes (Kolar
et al. 2007; Rasmussen et al. 2011).
Identifying sampling gears that effectively capture invasive
fishes is critical for early detection, monitoring, and control
(Basler and Schramm 2006; Diana et al. 2006; Trebitz et al.
2009). Improving the catch rates of Asian carp within invaded
watersheds throughout the Mississippi River basin has been a
high priority among state, federal, and nongovernmental institu-
tions (Conover et al. 2007; Kolar et al. 2007). Because of their
propensity for jumping, Silver Carp in particular are difficult to
capture. Thus, there is the need to evaluate how effective both
traditional and novel gears are at capturing Asian carp. Entrap-
ment gears such as hoop nets and fyke nets vary in their ability
to capture various fish species in different habitats, and may
select for different sizes of fish (Carter 1954; Muoneke et al.
1993; Lapointe et al. 2006). Although these conventional
entrapment gears have been used in large rivers and backwater
lakes to collect native fishes, there is uncertainty about their
effectiveness for Asian carp. Instead, unconventional fisheries
gears may prove to be more effective at capturing Asian carp.
Pound nets are large, stationary entrapment gears that have
long been used in coastal marine and Great Lakes fisheries
*Corresponding author email:
Received April 20, 2015; accepted September 3, 2015
North American Journal of Fisheries Management 35:1219–1225, 2015
Ó American Fisheries Society 2015
ISSN: 0275-5947 print / 1548-8675 online
DOI: 10.1080/02755947.2015.1091799
Downloaded by [University of Illinois at Urbana-Champaign] at 06:35 03 December 2015
(Chittenden 1991; Bogue 2001), although their utility for cap-
turing Asian carp in backwater lake habitats is presently
unknown. Though similar in design, pound nets are much
larger than fyke nets and are typically deployed for longer
durations. Catch is removed from a central collecting chamber
(von Brandt 1984). Pound nets tend to catch a wide range of
fish sizes and can capture large numbers of fish, making them
a potentially useful tool for Asian carp monitoring and
removal. Unfortunately, given their size, pound nets may
require additional labor to deploy and maintain relative to
other gear types.
Our goal was to compare the catch rates of Asian carp in
entrapment gears deployed in backwater lake habitats of the
Illinois River. Our objectives were to determine which entrap-
ment gears had the greatest catch rates of Asian carp in back-
water (i.e., adjacent to main-stem river) habitats, and to
compare the size distributions of Asian carp among entrap-
ment gears. Finally, we estimated the effort and cost effective-
ness (yield per labor hour) of these entrapment gears for two
different scenarios using field data to better inform manage-
ment decisions.
Study system.—The Illinois River is a tributary of the Mis-
sissippi River that flows approximately 440 km from northeast
to west-central Illinois, draining over 75,000 km
, with a mea n
daily discharge of 730.1 m
/s in the lower reaches (U.S. Geo-
logical Survey gauge 5586100; 1980–2014, Valley City, Illi-
nois). The Illinois River has numerous backwater lake habitats
that are often occupied by Asian carp. Two backwater lakes
with established populations of Asian carp were selected for
comparison of entrapment gears (LaGrange and Marseilles
navigation pools). Lily Lake (river kilometer [rkm] 133.6) is a
292-ha backwater lake located in the LaGrange Pool, where
abundances of adult Bighead Carp and Silver Carp are high
(Sass et al. 2010). The Han son Material Service pit at Morris
(rkm 423.2) is a 596-ha artificial backwater located in the Mar-
seilles Pool. Asian carp densities in the Marseilles Pool are
considerably lower than in the LaGrange Pool, although large
numbers of Asian carp have recently been captured from this
area by contracted commercial fishers (MRWG 2014).
Entrapment gears.—Three passive entrapment gears, two
conventional (hoop net and fyke net) and one novel (pound
net), were deployed in backwater habitats of the Illinois River
(Figure 1). Gears were deployed to collect fishes within the
same area and were spaced 20–40 m apart. The deployment of
gears did not block backwater lake inlets, thus allowing Asian
carp to move between main channel and backwater habitats.
The gears were positioned so that they did not block or inhibit
access to other gears. In effect, Asian carp could freely swim
in from the main channel and be collected by any of the three
gear types without concern that one gear blocked another.
Hoop nets were 1.2 m in diameter and 4.8 m in length, with
FIGURE 1. Schematics of hoop, fyke, and pound nets used during the experimental evaluation in backwater lakes of Illinois from 2012 to 2014. Note differen-
ces in scale for each gear type.
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square mesh sizes of either 3.8 or 6.4 cm. Hoop nets were set
parallel to the shoreline. Fyke nets consisted of a 0.9 £ 1.8-m
frame leading into a series of 1.2-m diameter hoops, with a
single 15 £ 1.3-m lead and 3.8-cm square mesh. Fyke nets
were set by attaching the lead to shore and stretching the net
out perpendicular to shore and anchoring the collecting cham-
ber offshore. Pound nets were constructed of 6.1 £ 3.0 £ 3.0-
m collecting chambers, with a 100-m lead that ran parallel
with the shore and two wings of adjustable length that spanned
from the opening of the collecting chamber to either shore and
effectively blocked the channel. Pound net square mes h sizes
were either 3.8 or 6.4 cm. Pound nets are much larger than
hoop and fyke nets. Our study required two boats and a three
or four person crew to deploy the pound nets. The first boat
held the pound nets and was positioned in the middle of the
channel, while the second boat pulled out the lead and king
lines parallel to the shoreline, the wings angled towards the
shorelines, and anchor lines attached to the central collecting
chamber. Once the pound nets were set, they remained in place
for a week during each sampling event. Signs directing boaters
to marked passage gaps were also installed, which allowed
recreational anglers to motor past the pound nets.
Sampling and analyses.—Average catch rates (number/net-
night) between gears were evaluated by comparing concurrent
gear deployments over 28 net-nights at Lily Lake and Morris
from 2012 to 2014. All fishes were identified to species and
measured for TL. Average catch rates between gear types
were compared using ANOVA. The mesh size of pound nets
was compared using ANOVA to determine if catch rates dif-
fered between 3.8- or 6.4-cm square sizes. Post hoc Tukey’s
highly significant difference (HSD) test was used to test differ-
ences between gears. Length-frequency histograms were gen-
erated for each species–gear combination to determine if gears
exhibited preferential size selection for either species of Asian
carp. Comparisons between gears were evaluated using the
Kruskal–Wallis test to determine whether lengths of Bighead
Carp and Silver Carp differed between gears.
Cost effectiveness.—Accounting for differences in both
catch rates and effort required to deploy and maintain the
entrapment gears provides a means of identifying the most
cost-effective (in terms of labor invested) approach to collect-
ing fish. Because management goals vary, two scenarios were
modeled to evaluate (1) cost effectiveness in terms of weekly
labor hours based on equivalent catches of fish among gears,
and (2) cost effectiveness in terms of catch per labor hour. For
both scenarios, we estimated the effort required to maintain
the gears for 1 week (Monday–Friday; Table 1). Hoop and
fyke nets were operated with a two-person crew with one boat.
For pound nets, a four-person crew with two boats was
required for the first day, then a reduced two-person crew for
the remainder of the week to maintain the gear (Table 1).
There is an initial investment of labor when deploying pound
nets due to preparing the gear in the boat (90 min) and the
time required to deploy the gear (90 min), based on our
evaluations. The effort required to deploy or collect and rede -
ploy hoop and fyke nets without time to process fish was esti-
mated to be between 5 and 9 min (Pugh and Schramm 1998).
The time required to reset a pound net varied between 45 and
83 min. Experimental effect sizes (i.e., differences in catch
rates between gears) were used to determine how many fyke
or hoop nets would be required to achieve similar catches in
relation to pound nets. Daily labor estimates, LD
, were calcu-
lated as
£ E
£ C
where G
is the number of gears of type i deployed, E
is the
daily effort required to maintain the gear in minutes, and C
the field crew size. Total labor hours were summed for the
week for each gear. For scenario 2, we considered cost effec-
tiveness by using an initial purchase cost for a pound net of
US$10,000 and then estimating the number of other gears that
could be purchased for the same amount, the total yield of fish
for each gear based on catch rates, and the effort required to
maintain the gears. Costs of gears were based on 2013 dollars
from commercial vendors of purchases made by the Illinois
Natural History Survey. Cost effectiveness was calculated as
the ratio between the numbers of fish captured relative to the
effort required to maintain the gears. Thus, a higher number
indicates a more cost-effective gear . Our models do not
account for the effort requi red to process individual fishes
(e.g., measure lengths and weights) because sampling and
monitoring programs may differ in protocols, and we assume
that the time required to handle individual fish is not depen-
dent on the gear but on the crew and therefore is not part of
the gear evaluation. Travel times between sites were not
included as these also vary by program.
Catch Rates
Catch rates of fishes were consistently higher in pound nets
than in traditional entrapment gears. The average nightly catch
of all species was, on average, 134 times greater in pound nets
than in hoop nets and five to six times greater than in fyke nets
TABLE 1. Model parameters for estimating effort between pound, fyke, and
hoop nets for the cost effectiveness analysis. Effect sizes were used from the
experimental analysis. Daily crew sizes differed between gears as pound nets
require more initial effort to deploy. M D Monday, T D Tuesday, F D Friday.
Gear Crew sizes Effort per trap (min)
Pound 4 M, 2 T–F 180 (M)
45–83 (T–F)
Fyke 2 (M–F) 5–9 (M–F)
Hoop 2 (M–F) 5–9 (M–F)
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(Figure 2a; F
3, 46
D 10.13, P < 0.01). The pattern was similar
for Asian carp, with overnight catch rates of Bighead Carp in
pound nets 113 times greater than hoop nets and 41 times
greater than fyke nets (Figure 2b; F
3, 46
D 6.31, P < 0.01).
High catch rates of Silver Carp in pound nets, coupled with
low overall catches in hoop nets, resulted in pound net catch
rates nearly 3,200 times greater than that of hoop nets (Fig-
ure 2c; F
3, 46
D 6.42, P < 0.01). Pound net catch rates of Sil-
ver Carp were 360 times greater than that for fyke nets. Catch
rates were also higher in pound nets (6 of 15 species) for fishes
common to large river ecosystems (P < 0.05; Table 2). We
detected no effect of mesh size on the catch rates of Bighead
Carp (F
1, 27
D 0.94, P D 0.33) or Silver Carp (F
1, 27
D 1.12,
P D 0.29) in pound nets.
Size Distribution
Pound nets tended to collect larger Bighead Carp relative to
hoop nets and fyke nets. The mean length § SD of Bighead
Carp was 829 § 103 mm in pound nets, 635 § 98 mm in hoop
nets, and 744 § 111 mm in fyke nets (Kruskal–Wallis: P <
0.0001). In contrast, mean length § SD of Silver Carp was
582 § 62 mm in pound nets, 593 § 87 mm in hoop nets, and
562 § 64 mm in fyke nets, and no differences were observed
between gears (Kruskal–Wallis: P D 0.27).
Effort and Cost Effectiveness
To achieve catch rates equivalent to a single pound net set
for all species would require deploying 6 fyke or 134 hoop
nets. Effort in terms of labor hours for all species was lowest
for fyke nets, intermediate for pound nets, and highest for
hoop nets (Table 3). However, to attain equal catch rates for
Bighead Carp or Silver Carp, the required labor was consider-
ably lower when using pound nets (Table 3).
With the approximate cost of a single pound net, 10 fyke or
40 hoop nets could be purchased. Based on a 5-min redeploy-
ment time for fyke nets and hoop nets, and 45 min for pound
nets, we estimated that labor would range from 8.3 to 33.3 h/
week for all gear types. Estimated yields of catch rate for all
gears ranged between 96 and 354 total individuals per week
(Table 4). Using total weekly catch of all species indicated
that fyke nets were most cost effective. However, when focus-
ing specifically on Asian carp, pound n ets were consistently
more cost effective in terms of labor hours than hoop or fyke
Overnight catch rates in pound nets were greater than in
conventional fyke and hoop nets in backwater habitats of the
Illinois River. In general, the catch rates of pound nets were
one to three orders of magnitude higher than that of hoop nets
or fyke nets when deployed concurrently. Many hoop net sets
did not collect fish, reducing catch rates and inflating the effect
size compared with pound nets. Our data suggests that the use
of pound nets in backwater habitats is a viable and eff ective
means of collecting large numbers of Asian carp.
FIGURE 2. Nightly catch rates of hoop, fyke, and pound nets for (a) all spe-
cies, (b) Bighead Carp, and (c) Silver Carp deployed concurrently in backwa-
ter lake habitats of the Illinois River. Error bars represent § SE. Letters above
columns denote differences between gears as determined by Tukey’s HSD
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Overnight catches of pound nets, like all gears, were highly
variable for Asian carp. Although tracking of movements of
Asian carp has shown that individuals select main channel bor-
ders and wing dyke habitats (i.e., manmade barriers that extend
partway into a river) over backwater habitats (DeGrandchamp
et al. 2008; Calkins et al. 2012), we observed large numbers of
Asian carp in these backwater habitats (MRWG 2014). When
conditions are appropriate, pound nets have the potential to
capture large quantities of Asian carp in backwater lakes of
large rivers. For example, during one overnight deployment of
a single pound net in the summer of 2014, 588 Asian carp
(546 Silver Carp, 42 Bighead Carp) were collected, totaling
1,058 kg (Figure 3). For perspective, that single pound net col-
lected more Asian carp in one night than all hoop and fyke
nets combined during that field season. With respect to hoop
nets, the extreme disparity in catch rates was a function of their
relative ineffectiveness in backwater habitats in our study.
However, hoop nets have been used widely with more success
for other species (Michaletz and Sullivan 2002) and may still
prove to be useful for capturing Asian carp in other habitats.
Size distributions of harvested Asian carp varied by both
gear type and species. Pound nets tended to collect larger
Bighead Carp relative to hoop nets and fyke nets. The cross-
sectional area covered by the wings and collecting chamber of
the pound net is far greater than that of fyke or hoop nets and
likely diverts more fishes and larger Bighead Carp that would
otherwise be missed by conventional sampling gears. Fyke
nets that extend perpendicularly from the shoreline can only
fish efficiently up to limited depths, and the diameter of hoop
nets can only cover so much cross-sectional area, so gear size
and positioning may limit catches of large numbers of Asian
carp. Taken together, the lar ger size distribution of Bighead
Carp in pound nets suggests that these adults are occupying
habitats away from the shoreline and higher in the water col-
umn, above the sampling area of hoop nets. Alternatively,
characteristics of each gear’s design such as the throat diame-
ter, which directs fish into the collection chamber, may also
influence catches and sizes (Shoup et al. 2003). There is the
potential that the large size of the pound net did not constrain
the size of individual fishes collected. Our findings suggest
that fyke and hoop gears may be underreprese nting the size
distributions for Bighead Carp, which demonstrated a clear
separation in size distributions between gears. No differences
were observed between mesh sizes, and adult Asian carp that
TABLE 2. Average nightly catch rates of the most common fishes in hoop, pound, and fyke nets set in backwater lakes of the Illinois River during 2012–2014.
Bold italic values indicate the highest statistically significant catch rate between gears for each species.
Hoop Fyke Pound
Common name Mean SD Mean SD Mean SD P-value
Bigmouth Buffalo Ictiobus cyprinellus 0.05 0.11 0.03 0.08 8.45 13.57 0.001
Black Buffalo Ictiobus niger 0.01 0.05 0.00 0.00 0.53 2.26 0.430
Black Crappie Pomoxis nigromaculatus 0.00 0.00 3.68 6.15 1.14 3.48 0.030
Bluegill Lepomis macrochirus 0.00 0.00 0.90 0.56 0.07 0.26 <0.0001
Common Carp Cyprinus carpio 0.00 0.00 1.03 1.05 1.52 3.87 0.065
Channel Catfish Ictalurus punctatus 0.11 0.17 0.25 0.26 2.96 4.42 0.005
Flathead Catfish Pylodictis olivaris 0.02 0.07 0.18 0.29 0.41 0.95 0.298
Freshwater Drum Aplodinotus grunniens 0.00 0.00 0.56 0.59 2.80 4.02 0.004
Grass Carp Ctenopharyngodon idella 0.00 0.00 0.00 0.00 0.36 0.90 0.150
Quillback Carpiodes cyprinus 0.00 0.00 0.03 0.09 0.34 0.77 0.002
River Carpsucker Carpiodes carpio 0.00 0.00 1.34 1.99 2.63 3.44 0.004
Smallmouth Buffalo Ictiobus bubalus 0.21 0.37 0.28 0.20 13.23 18.70 <0.0001
Shortnose Gar Lepisosteus platostomus 0.00 0.00 0.38 0.78 0.03 0.18 0.020
Shorthead Redhorse Moxostoma macrolepidotum 0.04 0.15 0.38 0.58 0.04 0.19 0.006
White Bass Morone chrysops 0.00 0.00 3.15 2.36 1.28 2.25 0.001
TABLE 3. Effort required to deploy and maintain pound nets, fyke nets, and hoop nets in Illinois River backwater lakes to achieve equivalent catch rates.
All species Bighead Carp Silver Carp
Gear Number of traps Labor hours Number of traps Labor hours Number of traps Labor hours
Pound 1 18.0–23.1 1 18.0–23.1 1 18.0–23.1
Fyke 6 5.0–9.0 41 34.2–61.5 360 300.0–540.0
Hoop 134 111.7–201.0 113 94.2–169.5 3,200
Labor hours were not calculated due to the high number of net sets required.
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were captured were typically much larger in body depth than
the mesh size of pound nets. No intermediate size-c lasses
(100–400 mm) missing from these gears were observed in
other sampling gears during a concurrent study (i.e., electro-
shocking, gill nets; S. F. Collins, personal observation); there-
fore, we cannot ascertain whether pound nets are effective at
these smaller sizes. Juveniles that were observed were small,
ranging from 30 to 70 mm, and could easily pass through the
net mesh.
Cost effectiveness of entrapment gears in terms of catch per
labor hour may be an important determinant of management
and policy decisions. Indee d, the benefits of enhanced catch
rates must be weighed against the effort needed to set and
retrieve the gears, especially when monetary, temporal, and
logistical constraints weigh heavily on decision making.
Pound nets perf ormed best in both cost effectiveness scenarios
for Asian carp. We anticipated the initial labor to set the nets
would have rendered the pound net to be cost prohibitive;
however, this was not the case. Overall, when accounting for
the added time of retrieving more fyke or hoop nets, effort rel-
ative to catch was much lower in pound nets. Estimates were
conservative by design, and it should be recognized that there
would be additional costs in terms of travel time between
gears. Thus, more gears deployed would incur more travel
time to each gear for processing. When considering the effec-
tiveness of gears in terms of initial purchase costs, pound nets
were again more cost effective in the collection of Asian carp
than were hoop and fyke nets.
Considerations and Limitations
Although pound nets had high catch rates and were cost
effective, there are some limitations to their use. Deploying
the nets successfully takes substantial effort, training, and
experience. Once they are in place, the effort decreases and
they can be fished for an extended period. Given their size, the
transport and storage of the nets is also an issue. The large size
is also an issue and limits where they can be deployed. For
instance, pound nets could be deployed in lotic habitats, but
they would be difficult to set in free-flowing areas due to
potential damage from woody debris. Connected backwater
habitats worked well, but sampling locations should consider
water level fluctuations, particularly near locks and dams or in
areas affected by strong seiche activi ty (e.g., marsh habitats of
large lakes).
TABLE 4. Estimates of projected weekly catches and cost effectiveness of entrapment gears in backwater lakes of the Illinois River based on an initial gear
budget of $10,000. Total weekly catches were estimated based on the number of traps purchased and mean catch rates for each species obtained from sampling
data collected during 2012–2014. Cost effectiveness was estimated as the ratio of the weekly catch relative to the labor hours needed to maintain the gears. BHC
D Bighead Carp, SCP D Silver Carp.
Estimated weekly catch Cost effectiveness
Gear Individual cost ($) Number of traps Estimated weekly labor (h) All spp. BHC SCP All spp. BHC SCP
Pound 10,000 1 18.0 354 51 131 19.7 2.8 7.3
Fyke 1,000 10 8.3 632 12 4 76.1 1.4 0.5
Hoop 250 40 33.3 96 16 3 2.9 0.5 0.1
FIGURE 3. A total of 588 Asian carp (546 Silver Carp, 42 Bighead Carp;
»1,058 kg) were collected in one overnight net at Lily Lake (rkm 133.6), a
backwater habitat of the Illinois River. Although catch rates such as this are
atypically high, this photo illustrates that pound nets have the capacity to catch
large quantities of Asian carp when conditions are optimal. Photo by Kevin
Irons, Illinois Department of Natural Resources.
Downloaded by [University of Illinois at Urbana-Champaign] at 06:35 03 December 2015
Bycatch mortalities of native fishes and turtles based on
anecdotal observations were low, in part, because pound nets
were attended daily. However, we did observe mortality when
pound nets collected large numbers of Asian carp, likely due
to crowding and increased stress of native fishes. Additionally,
fishes became entangl ed in the long wings of the pound net,
resulting in the mortality of both native and nonnative fishes.
Other pound net deployments, concurrent with this study in
other locations, were set for as long as 2 months. Longer sets
had problematic accumulations of woody debris and zebra
mussels Dreissena polymorpha, so consideration of site-spe-
cific biotic and abiotic conditions should be used in determin-
ing the duration of sets. Finally, based on our experience, we
strongly advocate for daily checking and maintenance to alle-
viate or lessen bycatch mortality and gear saturation.
This study was supported by the Great Lakes Research Ini-
tiative, with funding administered through the IDNR
(CAFWS-93). We thank K. Irons, M. O’Hara, D. Wyffels, J.
Mick, and V. Santucci of the IDNR for their assistance in coor-
dinating this project. In addition, we thank L. Chadderton, M.
McClelland, J. Dettmers, D. Chapman, S. Finney, and J. Gross
for initial discussions on the use of pound nets. Todd Stuth
and crews of Hickey Brothers Research made the pound nets
and provided initial training of personnel. We are grateful to
Joshua Tompkins and the numerous individuals who provided
field assistance to make this project possible, including the
graduate students and staff of the Kaskaskia and Sam Parr Bio-
logical Stations, Illinois Natural History Survey, and the Uni-
versity of Illinois.
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... We examined fish of 30 cm and greater in this study (see below), which corresponds to subadult and adult bigheaded carp of around age 1 and older . Though some size overlap occurs, bighead carp typically reach a larger body size than silver carp in this system (Collins, Butler, Diana, & Wahl, 2015;Garvey et al., 2012 ;MacNamara et al., 2016). ...
... It is unclear if the main channel depth-temperature relationships are linked to reduction of metabolic costs during periods of low prey abundance, thermoregulation, or some other factor, but nevertheless this is a potentially useful behavioural insight that can be incorporated into control efforts in flowing waters. The main channel in particular has been less of a focal area for bigheaded carp control efforts than backwaters (e.g., Collins et al., 2015;MacNamara et al., 2016), but relatively high densities can be found in the nearshore portion (DeGrandchamp et al., 2008;Calkins et al., 2012;this study). As many newly invaded or at-risk locations are heavily impounded or channelized, with little connected backwater habitat, it is prudent to develop assessment and control methods suitable for main channel habitats that can be deployed during optimal environmental conditions (i.e., low discharge and high temperature). ...
... Ongoing control efforts in the Illinois River and elsewhere have resulted in the development of novel approaches aimed at maximizing catch or detection likelihood of bigheaded carp in large rivers (e.g., Bouska, Glover, Bouska, & Garvey, 2017;Collins et al., 2015;Erickson et al., 2016), but their suitability for standardized monitoring is limited. Instead, mobile hydroacoustic surveying provides threedimensional spatial assessment of bigheaded carp (and potentially other large-bodied invasive fish species) throughout a river's macrohabitats. ...
Bigheaded carp (Hypophthalmichthys spp.) occur throughout much of the Mississippi Basin, USA. Efforts to control the spread of these invasive species require information on their spatial ecology, though sampling is hindered by their broad extent, habitat tolerances, and species‐specific behaviour. Mobile hydroacoustics was used to quantify habitat and depth use of bigheaded carp over four years in the heavily invaded Lower Illinois River, a major Mississippi tributary and potential dispersal pathway to the Great Lakes. Horizontally oriented transducers (combined with capture gear for species designation) enabled sampling of the main habitat features in this large flood plain river. Silver carp (Hypophthalmichthys molitrix) were dominant over bighead carp (Hypophthalmichthys nobilis) at all but one site, although habitat use was similar for both species. Densities were highest in lotic backwaters, followed by lentic backwaters and nearshore main channel, with lowest densities in the mid main channel. Bigheaded carp size and species composition were independent of habitat type. Depth associations were similar for both species, with average occurrence at 2.5–3.5 m in the main channel and 1–2 m in backwaters. However, depth relative to the river bed was largely similar across habitat types. Bigheaded carp density and depth use in the main channel were linked non‐linearly to river discharge and water temperature, respectively; densities were reduced during high discharge, whereas depth use became shallower at higher temperatures. Density–hydrology trends were less apparent in backwaters. These findings highlight critical aspects of bigheaded carp spatial ecology that will facilitate effective management in invaded and at‐risk ecosystems.
... Multiple gears are recommended to study bigheaded carp populations (Stancill Collins et al. 2015), which may be similar to the backwater habitats of Kentucky Lake and Lake Barkley where most bigheaded carps were collected in the present study. Collins et al. (2015) concluded that pound nets were the most cost effective entrapment gear due to their high catch rates of Silver Carp and Bighead Carp (one to three orders of magnitude higher than either fyke nets or hoop nets) when considering the time to deploy, maintain, and retrieve each gear type. ...
... Multiple gears are recommended to study bigheaded carp populations (Stancill Collins et al. 2015), which may be similar to the backwater habitats of Kentucky Lake and Lake Barkley where most bigheaded carps were collected in the present study. Collins et al. (2015) concluded that pound nets were the most cost effective entrapment gear due to their high catch rates of Silver Carp and Bighead Carp (one to three orders of magnitude higher than either fyke nets or hoop nets) when considering the time to deploy, maintain, and retrieve each gear type. Therefore, pound nets could be an appropriate alternative entrapment gear in backwater areas of Kentucky Lake and Lake Barkley. ...
The invasive Bighead Carp Hypophthalmichthys nobilis Richardson and Silver Carp H. molitrix Valenciennes (collectively referred to as bigheaded carps) were introduced to the U.S. in the 1970s to control noxious algae blooms in polyculture ponds. Fish subsequently escaped and by the 1980s bigheaded carps were widespread and established in the upper Mississippi River, lower Missouri River, and the Ohio River and some of its tributaries. In the lower reaches of the Tennessee River and Cumberland River systems, bigheaded carps were systematically sampled in 2015 and 2016 using multiple gears. Nearly 12 km of experimental gill nets captured 363 adult Silver Carp and 7 Bighead Carp. Hoop nets (n = 96) captured only 2 Silver Carp and 2 Bighead Carp. Twenty-eight hours of electrofishing collected 146 adult and 214 young-of-year (YOY) Silver Carp. Cast nets (n = 480 throws) captured 15 YOY Silver Carp. Bighead Carp and Silver Carp in Kentucky Lake and Lake Barkley reached large sizes and were long lived. The maximum total lengths (TL) and ages were 1,385 mm TL and 22 years for Bighead Carp and 1,005 mm TL and 13 years for Silver Carp. The Silver Carp populations in both reservoirs had the same strong year classes (2010, 2011, 2012, 2015) and similar growth rates which were faster than what has been reported for other populations around the globe. Silver Carp in both reservoirs were similarly robust, and more robust than Silver Carp below Barkley Dam, suggesting food resources and habitat are ideal in the reservoirs. Some YOY Silver Carp were collected 180 and 110 river kilometers upstream in Kentucky Lake and Lake Barkley, respectively, and they may represent the first evidence of natural reproduction in those reservoirs or their tributaries. The catch-per-unit-effort (CPUE) of adult Silver Carp in gill nets was similar in each reservoir, and they are already a major component of the fish assemblages vulnerable to gill nets. In electrofishing samples the CPUE of adult Silver Carp was higher in Lake Barkley but the CPUE of YOY Silver Carp was similar in each reservoir. Future efforts to control bigheaded carps in Tennessee waters should include studying the efficacy of barriers at navigation locks, determining where natural reproduction is occurring, and increasing the commercial harvest of both species.
... Multiple gears are recommended to study bigheaded carp populations (Stancill 2003;Degrandchamp et al. 2008;Wanner and Klumb 2009 (Collins et al. 2015), which may be similar to the backwater habitats of Kentucky Lake and Lake Barkley where most bigheaded carps were collected in the present study. Collins et al. (2015) concluded that pound nets were the most cost effective entrapment gear due to their high catch rates of Silver Carp and Bighead Carp (one to three orders of magnitude higher than either fyke nets or hoop nets) when considering the time to deploy, maintain, and retrieve each gear type. ...
... Multiple gears are recommended to study bigheaded carp populations (Stancill 2003;Degrandchamp et al. 2008;Wanner and Klumb 2009 (Collins et al. 2015), which may be similar to the backwater habitats of Kentucky Lake and Lake Barkley where most bigheaded carps were collected in the present study. Collins et al. (2015) concluded that pound nets were the most cost effective entrapment gear due to their high catch rates of Silver Carp and Bighead Carp (one to three orders of magnitude higher than either fyke nets or hoop nets) when considering the time to deploy, maintain, and retrieve each gear type. Therefore, pound nets could be an appropriate alternative entrapment gear in backwater areas of Kentucky Lake and Lake Barkley. ...
Technical Report
This final report is based on a thesis prepared in partial fulfillment of the Master of Science degree at Tennessee Technological University.
... Identifying effective sampling techniques of nonnative fishes is crucial to estimate their abundances, and also for feasible population control measures (Trebitz et al., 2009;Collins et al., 2015). It is known that different sampling gears can provide different estimations of the abundance of a given species even in the same location, which complicates the choice of an appropriate sampling method (Johnson et al., 2005;Brandner et al., 2013). ...
... different sampling effort, inconstant efficiency with increasing water depth, selectivity for certain species) (e.g. Fago, 1998;Diana et al., 2006;Collins et al., 2015). Although our CPUE data of electrofishing and fyke netting cannot be compared directly with statistical analysis, it was clear that in the configuration we used, electrofishing caught more individuals of both monkey goby and pumpkinseed and habitat use of both species was irrespective of the gear used (i.e. ...
Full-text available
Detailed knowledge on the habitat preference of invasive fishes and the bias of different fishing methods in determining their population dynamic parameters are essential in fisheries management, ecology and conservation. This study was conducted to determine the habitat use and length frequency distribution of the invasive monkey goby and pumpkinseed in the littoral zone of Lake Balaton (Hungary) using two different sampling methods, electrofishing and fyke netting. In general, both species preferred anthropogenically modified habitat types (rip-rap shorelines and harbours) compared with natural reed habitats with silty-sand bottom. Length frequency distribution data showed significant between-gear differences, since electrofishing resulted in the capture of larger individuals in greater proportion than fyke nets for both species. This study, which includes the first detailed data about the habitat use of the highly invasive monkey goby in lakes, suggests that invasive species may benefit from the alteration of the littoral zone. It also highlights that reliance on single gear surveys can be misleading in assessing habitat use and population structure of invasive fishes.
... We conducted a field experiment to assess whether herding fish using percussive sound or electrical stimuli can enhance catch rates and detection of bigheaded carp and other large river fishes in surfaceto-bottom gill nets. Our experiment was conducted at multiple locations along the Illinois River (Mississippi River drainage) as part of a larger study examining the most effective means of collecting and removing bigheaded carp and other invasive fishes (Collins et al. 2015(Collins et al. , 2017. Our primary objective was to identify whether catch rates in an entanglement gear could be enhanced through the use of sound or electricity and if there were differences between the two approaches. ...
... However, without the added sound or electrical stimulus, CPUE of Bighead Carp was nearly zero. This may have been due to lower abundances of Bighead Carp relative to Silver Carp at our sampling sites (Collins et al. 2015). Moreover, commercial fishers target Bighead Carp almost exclusively in shallow backwater areas where long distances ([ 1 km) of gill nets or trammel nets are often deployed. ...
Full-text available
Fish herding (driving fish into nets) is used by commercial fishers to increase harvest of invasive bigheaded carp (Hypophthalmichthys spp.), yet has not been widely adopted for fisheries monitoring purposes. We conducted an experiment to assess whether fish herding using percussive sound or electrical stimuli can enhance catch rates and detection of bigheaded carp and other fishes in surface-to-bottom gill nets. Catch rates (fish net set⁻¹) from traditional gill net sets where no herding method was applied were compared to sets combined with either sound stimuli (physical impacts to the boat hull and water surface to produce percussive sound) or electricity produced from a pulsed-DC electrofisher to manipulate fish movements. For most species, herding increased catch rates and detection probability compared to control sets. Sound stimuli increased catch rates of Silver Carp (Hypophthalmichthys molitrix) by over three times, whereas electrical stimuli increased catch rates by over six times. Catch of Bighead Carp (Hypophthalmichthys nobilis) was highest in nets paired with sound stimuli. Herding methods also reduced the number of samples required to attain target detection probabilities for bigheaded carp. Herding techniques combined with gill netting may be a valuable option for targeted bigheaded carp sampling, especially when electrofishing or netting alone is ineffective for these evasive fishes. Synergistic methods may provide a cost effective means of improving detection probabilities for bigheaded carp at their invasion front or other locations where densities are low and uncertainty of capture is high.
... 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, bigheaded 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). ...
... Consequently, the rationale for an experiment must compliment the design and any inferential limitations. The logic and design of this experiment reflects patterns observed in nature, where large numbers of bigheaded carp are imposed over native communities of fishes (Collins et al., 2015;Collins, Diana, et al., 2017;Irons, Sass, McClelland, & Stafford, 2007). Presumably, a hyperabundance of native planktivores could impart similar effects; however, such a scenario does not reflect conditions in many locations where bigheaded carp are abundant. ...
Full-text available
• 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.
... Presently, the Mississippi River and many of its larger tributaries harbor extremely high densities of bighead carps. These mobile fishes utilize both mainstem river and floodplain lake ecosystems (e.g., Sass et al. 2010;MacNamara et al. 2016) and are often the dominant fish encountered by fisheries scientists (Irons et al. 2007;Sass et al. 2010;Collins et al. 2015bCollins et al. , 2017a. As planktivores, bighead carps do not occupy a high trophic position within riverine ecosystems. ...
Pervasive environmental degradation has altered biodiversity at a global scale. At smaller scales, species extirpations, invasions, and replacements have greatly influenced how ecosystems function and interact by affecting the exchanges of energy, materials, and organisms. In this chapter, we examine how a variety of environmental stressors, and associated species losses and gains, change the exchange of resources (materials or organisms) within and among ecosystems. We specifically consider how changes that occur within an ecosystem may trigger effects that reverberate (e.g., directly, indirectly, and via feedbacks) back and forth across ecological boundaries and propagate to other ecosystems connected via exchanges of materials and organisms. Our synthesis provides cursory overviews of ecosystem “openness” as it has been addressed by community ecologists and the conceptual development of ecological frameworks used to examine resource exchanges between ecosystems. We then describe four case studies and examine how species losses and gains affect food web structure via resource exchanges between ecosystems, with particular emphasis on effects spanning land-water boundaries. Finally, we discuss the need for more complex conceptual treatment of the interconnectedness of food webs among ecosystems.
... Currently these species are abundant throughout the Illinois River and spawning has been documented as far upstream as Navigation Pool 16 (Larson et al., 2017). Where abundant, silver carp now represent a significant proportion of the total fish biomass, particularly in the Illinois River (Collins et al., 2015;Coulter et al., 2018, Fig. 6). ...
Regime shifts-persistent changes in the structure and function of an ecosystem-are well-documented for some ecosystems and have informed research and management of these ecosystems. In floodplain-river ecosystems, there is growing interest from restoration practitioners in ecological resilience, yet regime shifts remain poorly understood in these ecosystems. To understand how regime shifts may apply to floodplain-river ecosystems, we synthesize our understanding of ecosystem dynamics using an alternate regimes conceptual framework. We present three plausible sets of alternate regimes relevant to natural resource management interests within the Upper Mississippi River and Illinois River. These alternate regimes include: 1) a clear water and abundant vegetation regime vs. a turbid water and sparse vegetation regime in lentic, off-channel areas, 2) a diverse native fish community regime vs. an invasive-dominated fish community regime, and 3) a regime characterized by a diverse and dynamic mosaic of floodplain vegetation types vs. one characterized as a persistent invasive wet meadow monoculture. For each set of potential alternate regimes, we review available literature to synthesize known or hypothesized feedback mechanisms that reinforce regimes, controlling variables that drive regime transitions, and current restoration pathways. Our conceptual models provide preliminary support for the existence of alternate regimes in floodplain-river ecosystems. Quantitatively testing hypotheses contained within the conceptual model are important next steps in evaluating the model. Ultimately, the synthesis and evaluation of alternate regimes can inform the utility of resilience concepts in restoration and management on the Upper Mississippi River and Illinois River and improve our understanding of ecosystem dynamics in other large, heavily managed floodplain-river ecosystems.
... The four species have similar reproductive habits (Yi et al. 1988), but during nonbreeding periods their habitats likely differ. Bighead Carp and Silver Carp may be captured by various gears, including gill nets, hoop nets, fyke nets, pound nets, and electrofishing in backwaters and reservoirs (Collins et al. 2015;Ridgeway 2016), but behaviorally these species are filter feeders and tend to be epipelagic, unlike the Black Carp, which is usually considered benthically oriented (Nico et al. 2005). Grass Carp are morphologically similar to Black Carp but because of their largely vegetarian diet are likely to select very different habitats from the invertivorous Black Carp. ...
Black Carp Mylopharyngodon piceus are considered invasive in North America. Since the first wild capture in 2003, collection records have increased, yet information summarizing successful collection methods is lacking. Reported capture methods throughout the Black Carp's native and introduced ranges vary providing minimal aid for determining control and monitoring methods. Here, we describe the current species range and the spatial and temporal variation among captures. The size of fish can affect capture; thus, we report captured fish and gear dimensions and recommend appropriate scientific collection methods. We focus on collection data from 302 Black Carp ranging from 410 to 1,607 mm total length received from 2011 to February 2019. The reported range of Black Carp has expanded in the Cumberland, Illinois, Mississippi, Missouri, Ohio, and Tennessee rivers. Captures most frequently occurred in channel (41%), side‐channel (24%), and backwater (22%) habitat types, with increased records in May, June, and July. Most records were commercial captures, of which hoop net (51%) and gill net (26%) were most common. Results suggest that standard scientific methods for sampling fish in large rivers and standing water by hoop net and gill net may be used to monitor Black Carp, but a robust study design needs to be applied to determine gear selectivity and to determine if catch rates are density dependent or incidental.
... Electrofishing and fyke netting often provide complementary species data because together they target sedentary and active species, respectively (Ruetz et al. 2007;Eggleton et al. 2010). Though using multiple gears is advantageous, there are limits to the number of gears that can be effectively deployed (i.e., cost, time, personnel), so finding the right balance for the study area and question is required (Fischer and Quist 2014;Collins et al. 2015). In Lake Michigan, we currently use nighttime boat electrofishing, experimental gill nets, and paired fyke nets in a 40, 35, and 25% allocation, respectively. ...
Full-text available
We performed a gear comparison between three types of paired fyke nets used to monitor fish communities in the nearshore zone of Lake Michigan. Our objective was to identify a single net design that would maximize species diversity and catch. The three types of paired fyke nets included a small frame model with 3-mm bar mesh (Mini-fyke), a larger-framed model with 13-mm mesh (Fyke), and a large frame model with 13-mm mesh recommended by the American Fisheries Society (AFS-fyke). We set all three gear types in triplicate on similar nearshore littoral habitat at 16 sites in Green Bay, an embayment of Lake Michigan. Total catch was dominated by Gizzard Shad Dorosoma cepedianum, Round Goby Neogobius melanostomus, Spottail Shiner Notropis hudsonius, Trout-perch Percopsis omiscomaycus, and Yellow Perch Perca flavescens, which represented 99.3% of all individuals captured. We found that Mini-fyke nets selected for smaller individuals, caught relatively few species, and had the highest catch per unit effort; this was largely driven by high catches of Spottail Shiner and Gizzard Shad. Fyke nets captured the largest individuals, had the lowest catch per unit effort, and the greatest diversity of species. Results for AFS-fyke nets were typically intermediate between Mini-fyke and Fyke nets for most parameters. Species accumulation curves indicated that Fyke nets acquired more total species at a higher rate than the other two net types. Given the need to balance effort, gear bias, and sampling efficiency, we found that AFS-fyke nets recommended by the AFS effectively characterized the nearshore fish community of lower Green Bay, especially if used in conjunction with complementary sampling gears. Received November 28, 2016; accepted May 25, 2017Published online August 4, 2017
Full-text available
Aquatic invasive species introductions are a global environmental concern. Negative effects of invasive species are often manifested in alterations of food web structure and through competition with and predation upon native species. The Illinois River, Illinois, USA harbors invasive, planktivorous bighead, Hypophthalmichthys nobilis, and silver carp, Hypophthalmichthys molitrix, and can be a model ecosystem to test for their effects on zooplankton communities. We tested for bighead and silver carp effects on zooplankton communities pre- and post-establishment within one reach of the Illinois River and among river reaches that varied in abundances of these invasive fishes. The establishment of bighead and silver carp was associated with increased rotifer abundances, while cladoceran and copepod abundances were reduced relative to pre-establishment. Cladoceran and copepod abundance and biomass were negatively associated with bighead and silver carp abundances among reaches. Total zooplankton and rotifer abundance and biomass were positively associated with bighead and silver carp abundances. Our results suggest that bighead and silver carp have changed the zooplankton community of the Illinois River which may have implications for the food web, native species, and other ecosystems poised to be invaded, such as the Laurentian Great Lakes.
Full-text available
Invasive silver carp (Hypothalmichthys molitrix) occurs throughout much of the Mississippi River and threatens the Laurentian Great Lakes. To quantify habitat selection relative to river flow and potential phytoplankton food, 77 adult silver carp were implanted with ultrasonic transmitters during spring 2008 through spring 2009 in adjacent upstream dammed and downstream undammed reaches (48 km total) of the Mississippi River. Sixty-seven percent of the fish were located. Selection of major river habitat features (dammed vs. undammed, backwaters, channel border, wing dikes, island side channels, and the main channel) was quantified. Flow rates and chlorophyll a concentration were compared between silver carp locations and random sites. Foregut chlorophyll a concentrations plus presence of macrozooplankton and detritus of 240 non-tagged silver carp were quantified. About 30% of silver carp moved upstream into the dammed reach, where average flow was slower and chlorophyll a concentration was higher. Silver carp selected wing dike areas of moderate flow (about 0.3 m/s) and elevated chlorophyll a (about 7 μg/L) relative to random sites. No silver carp occurred in areas where flow was absent. Wing dikes were preferred while the main channel was avoided. Chlorophyll a concentrations in guts were positively related to temperature and were unrelated to flow or river chlorophyll a concentration. Macrozooplankton and detritus were rare in guts. Silver carp seek areas of low flow and successfully forage across a range of temperatures, flows, and chlorophyll a concentrations that occur in rivers and large lakes.
Full-text available
Few studies of fish assemblages have been conducted in large rivers owing to the difficulties of sampling such complex systems. We evaluated the effectiveness of six different gear types (seine nets, boat electrofishers, hoop nets, Windermere traps, trap nets, and minnow traps) in sampling the fish assemblage at 30 sites in the shallow offshore waters of the middle Detroit River in July and August 2003. A total of 2,449 fish representing 38 species in 15 families were captured by seining (1,293 fish, 29 species), boat electrofishing (398 fish, 23 species), hoop nets (524 fish, 26 species), and Windermere traps (234 fish, 14 species). Trap nets and minnow traps were not effective in sampling offshore littoral sites. Significantly higher fish species richness and abundance were obtained and more unique species were captured by seine nets than by any other gear type. When effort is constant, the highest richness and abundance are obtained by seine nets. Windermere traps produced significantly lower abundance and richness than all other gear types, but proportionally more benthic species. Total species accumulation rates were not markedly reduced when Windermere trap data were excluded. Use of additional Windermere traps at each site could increase abundance, but samples taken by Windermere traps had the lowest rarefied richness among gear types at any level of abundance. Nonmetric multidimensional scaling showed that seine-net catches, which were dominated by midwater schooling species (brook silverside Labidesthes sicculus, emerald shiner Notropis atherinoides, and mimic shiner N. volucellus), were most dissimilar from Windermere trap catches, which were dominated by centrarchids. Seine nets were the most effective gear for sampling offshore waters.
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Invasion of the round goby Neogobius melanostomus in the Great Lakes has prompted investigation into qualitative and quantitative sampling strategies. Design of an optimal sampling strategy to monitor expanding round goby populations should consider the accuracy, precision, and associated costs of gears and their deployment strategies. The goal of this study was to compare three common, low-cost, readily available gear types used to sample round goby (gill nets, minnow traps, and trotlines) in terms of catch rates, size selectivity, and bycatch. During fall assessments, baited minnow traps were the most effective at collecting round goby, followed by trotlines and monofilament gill nets. Minnow traps were more selective of small round goby, while trotlines and gill nets were more selective of larger individuals. Bycatch associated with minnow traps and trotlines was lower than that associated with gill nets. Seasonal variation in gear effectiveness was apparent: during spring, gill nets caught 216 round goby and minnow traps caught none, while during the fall only 11 round goby were captured in gill nets and 868 were captured in minnow traps. During summer assessments, diel movements were evident, as gill nets set during periods of low or no light captured more round goby than those set during the day. The cost-benefit analysis indicated that passive gears had lower scores (i.e., were more cost-effective) than active gears. The financial cost of the three gears indicated that the cost per round goby varied among gears and seasons. Our results demonstrated that baited minnow traps set overnight were the most efficient, easily deployed, cost-effective gear and exhibited less variable catch rates during late summer and fall than either gill nets or trotlines.
Because populations of channel catfish Ictalurus punctatus have been difficult to sample in small impoundments, we determined whether tandem hoop net series (three nets tied in series and baited with cheese) fished for 3 d could effectively sample these populations. In 2000 we compared seasonal catch rates (catch per unit effort (CPUE), defined as the number of fish caught per series) and length frequencies (total length (TL); mm) of channel catfish captured with two types of tandem series (long versus short bridles) and monitored the mortality of channel catfish along with the CPUE and mortality of bycatch in five lakes. Mean CPUE ranged from 12 to 194 fish/series for channel catfish and from 5 to 101 fish/series for bycatch among series types, lakes, and sampling periods. Mean CPUE for channel catfish and bycatch was similar between series types and did not consistently vary with sampling period. Length frequencies of channel catfish were usually similar between series types. Mortality was low for both channel catfish (0.3% of total catch) and bycatch (8%). In 2001, using short-bridled series, we assessed gear size bias in one lake; sampled 66 lakes that are stocked annually with channel catfish fingerlings at rates of 12, 37, or 74/ha; and estimated the sample sizes required for precise estimates of mean CPUE and accurate estimates of size structure. Hoop nets failed to capture channel catfish less than 250 mm TL in proportion to their abundance. Mean CPUE among 62 lakes ranged from 0.5 to 369.7 channel catfish/series and increased with stocking rate. Four lakes were excluded because of the high catch and mortality of turtles. Mean TL ranged from 276 to 463 mm among the lakes and decreased with stocking rate. For moderate precision (coefficient of variation (100·SE/mean) 5 0.2) of mean CPUE, from 12 to nearly 50 series were required, and length measurements from 300 fish were necessary for accurate assessments of size structure. Tandem hoop netting provided adequate samples of channel catfish in most small impoundments, but obtaining precise estimates of CPUE may be difficult; moreover, turtle mortality can be problematic in some lakes.
The effects of bighead carp Hypophthalmichthys nobilis on native planktivores in the USA is unknown. The objectives of this study were to experimentally test for competitive interactions between age-0 bighead carp and age-0 paddlefish Polyodon spathula. Differences among water chemistry variables, invertebrate densities, and relative growth of fish were assessed in mesocosms. Water chemistry variables were similar among treatments throughout the experiment and only exhibited a temporal effect. Zooplankton density declined in mesocosms after fish were introduced. In general, zooplankton densities did not differ among treatments but did differ from the control. The relative growth of paddlefish was negative in the paddlefish and paddlefish–bighead carp treatments. The relative growth of bighead carp was negative in the bighead carp treatment but positive in the paddlefish–bighead carp treatment. Age-0 paddlefish exhibited the greatest decrease in relative growth in mesocosms with bighead carp. Bighead carp exhibited the greatest increase in relative growth in mesocosms with paddlefish. These data suggest that bighead carp have the potential to negatively affect the growth of paddlefish when food resources are limited.
Procedures for sampling commercial pound-net fisheries in Chesapeake Bay are described for operations on the water and at dockside. Operations at dockside are also the same for haul-seine and gill-net fisheries. Three primary interception sites are identified for collecting biological data: (1) on the water at the individual pound net; (2) at the dock before, or as, the catch is unloaded; and (3) from the weighing scale at the dock after commercial operations sort and grade the catch by species. The latter site is recommended to intercept biological and catch-magnitude data, but advantages and disadvantages of each site are discussed. Descriptions of the commercial operations, in conjunction with published evaluations of the sources of variation in catch, can be used to help design some combination of stratified and multistage sampling surveys to characterize catches and populations of anadromous, estuarine, and coastal fishes for which little information exists.