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Relative leaping abilities of native versus invasive cyprinids as criteria for selective barrier design


Abstract and Figures

Restoration of river connectivity favors the spread of native but also of exotic invasive populations, mainly freshwater fish. This has rarely been studied, and never between migrating cyprinids. To harmonize both objectives, the feasibility of a selective leaping barrier for migratory cyprinids is studied through the measurement of fish leaping capabilities while freely migrating at a weir in the Guadiana River of southwest Spain. A cross-population analysis provided the cost-benefit outcomes of completely blocking the invasive Carassius auratus while allowing negotiation for most of the native Luciobarbus sp. populations. Larger fish reached higher leap heights, the highest being attained by the native barbel species. Barbels reached up to four times its total length and a maximum height of approximately 150 cm, while the figures for the invasive goldfish were double total length with a maximum of approximately 80 cm. The selective obstacle height (SOH) for goldfish was 81.2 cm, the estimated maximum height that the tip of a jumping goldfish could reach. Facility designs (whether culvert, weir or fish pass) with this SOH criterion guarantees complete migration failure of goldfish. Also, most (95–99%) of the barbels migrating populations will surpass the SOH regardless of body length; only the less capable or those in poor condition will be blocked. Advice on SOH utility to evaluate existing instream structures—and their position within the cost-benefit balance—is provided.
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Relative leaping abilities of native versus invasive cyprinids
as criteria for selective barrier design
R. Mora
´pez .O. Uceda Tolosa
Received: 30 May 2016 / Accepted: 7 November 2016
ÓSpringer International Publishing Switzerland 2016
Abstract Restoration of river connectivity favors
the spread of native but also of exotic invasive
populations, mainly freshwater fish. This has rarely
been studied, and never between migrating cyprinids.
To harmonize both objectives, the feasibility of a
selective leaping barrier for migratory cyprinids is
studied through the measurement of fish leaping
capabilities while freely migrating at a weir in the
Guadiana River of southwest Spain. A cross-popula-
tion analysis provided the cost-benefit outcomes of
completely blocking the invasive Carassius auratus
while allowing negotiation for most of the native
Luciobarbus sp. populations. Larger fish reached
higher leap heights, the highest being attained by the
native barbel species. Barbels reached up to four times
its total length and a maximum height of approxi-
mately 150 cm, while the figures for the invasive
goldfish were double total length with a maximum of
approximately 80 cm. The selective obstacle height
(SOH) for goldfish was 81.2 cm, the estimated
maximum height that the tip of a jumping goldfish
could reach. Facility designs (whether culvert, weir or
fish pass) with this SOH criterion guarantees complete
migration failure of goldfish. Also, most (95–99%) of
the barbels migrating populations will surpass the
SOH regardless of body length; only the less capable
or those in poor condition will be blocked. Advice on
SOH utility to evaluate existing instream structures—
and their position within the cost-benefit balance—is
Keywords River connectivity Invasive species
Selective barrier Migratory fish Leap height
Facility design
Intense modifications for water flow and longitudinal
connectivity have driven a sizeable and continuously
incrementing number of artificial barriers (Sabater
et al. 2009), a trend which climate change will most
probably exacerbate (Xenopoulos et al. 2005). Artifi-
cial barrier prevalence in turn stimulates the study of
the biological and ecological consequences of con-
nectivity loss (e.g. Mora
´pez et al. 2012), which
have shown reduced recruitment success, altered fish
assemblages, and the local extinction of fish popula-
tions in Europe and elsewhere (Mueller et al. 2011;
R. Mora
´pez (&)
Area of Zoology, Department of Anatomy, Cellular
Biology and Zoology, Science Faculty, University of
Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
O. Uceda Tolosa
SIGnatur – Innovative Solutions for Nature Management,
C/Vicente Rodero 8, 5°B, 06300 Zafra (Badajoz), Spain
Biol Invasions
DOI 10.1007/s10530-016-1328-6
Branco et al. 2012). Also, invasive species represent
an important pressure that prevents the achievement of
good ecological status, through the alteration of biotic
communities and ecological function. Migration and
jumping behaviours are also present in introduced
species, and these abilities promote the dispersion of
invasive populations (Holthe et al. 2005). Restoring
connectivity for the native species while preventing
further spread of the exotics can be a difficult task, for
which new knowledge and technologies are in great
Knowledge of the swimming and leaping capabil-
ities of fish can lead to the development of improved,
more permeable barriers and less selective fish
passage facilities for native species (Roscoe and
Hinch 2010; Bunt et al. 2012; Katopodis and Williams
2012; Nooman et al. 2012). But there remains
substantial research to be done. To date, most jumping
performance studies use hatchery-reared or wild
captured fish under laboratory conditions (Kondratieff
and Myrick 2005; Mueller et al. 2008; Lauritzen et al.
2010; Ficke et al. 2011); studies of fish in their natural
environments are conversely scarce (Ombredane et al.
1987; Lauritzen et al. 2005,2010). Laboratory control
and experimental designs provide high quality data,
but at the cost of using fish with potentially inferior
capabilities (McDonald et al. 1998; Kondratieff and
Myrick 2006; Pedersen et al. 2008; Bestgen et al.
2010). Also, it increases the uncertainty of whether the
results can be transferred to naturally occurring
conditions, which are more complex (Ovidio et al.
2007). Salmonids are the best known group studied; a
few studies include less economical or recreationally-
valued fish such as potamodromous cyprinids (Holthe
et al. 2005; Ficke et al. 2011). However, Cyprinidae is
the largest family of freshwater fishes with over 2000
species naturally distributed in Eurasia, Africa and
North America (Moyle and Cech 2004).
Invasive species superimpose an added threat factor
to habitat degradation for migratory and other fish
(Holthe et al. 2005; Northcote 2010). In these cases,
obstacles provide positive outcomes (Kondratieff and
Myrick 2005), with a number of obstacles being used
to restrict upstream movement of introduced or
undesirable native cyprinids such as the Asian carp
or minnows (see Table 4 in McLaughlin et al. 2013).
When compared to studies on non-jumping species
´lez-Espino et al. 2011), even rarer are studies that
design selective dispersion barriers of invasive species
based on their leaping abilities (either by weirs or
fishways; Brandt et al. 2005; Holthe et al. 2005; Stuart
et al. 2006). To the best of our knowledge, no study
examines the differential leaping performance of
native versus invasive cyprinids, for the knowledge
and to the benefit (i.e. management and conservation)
of native cyprinids and other coarse fish species, in
their natural ranges.
In this study, we analyse the leaping capabilities of
three cyprinids—one invasive, and two native spe-
cies—freely migrating into the artificial waterfall of an
impassable weir in the Guadiana River of southwest
Spain. We hypothesized that there are differences in
maximum leaping capabilities associated to fish size.
We also hypothesized that there are differences in
maximum leaping capabilities associated to popula-
tions nativeness of these sympatric cyprinid taxa. Our
prediction is that these differences would allow to
determine the height of a waterfall barrier able to
block all invasive populations while allowing the
negotiation for most of the native jumping ones. This
new knowledge on the leaping capabilities and the
comparison between species and taxonomic groups is
discussed, along with its application to optimize weirs
and fish pass facility designs.
Materials and methods
Study area and species
The Granadilla weir is located about 6.5 km upstream
of the Spanish–Portuguese border in the middle
Guadiana (38°51042.500N7°0100200W), the main river
of the fourth largest basin in the Iberian Peninsula
(67,000 km
; Fig. 1). The Guadiana River has a low
gradient and a Mediterranean regime with most of the
precipitation occurring from November to March
(80% of total annual rainfall), then descending
throughout a dry and hot summer (Gasith and Resh
1999; Mora
´pez et al. 2006). There are dams and a
number of differently designed weirs installed in the
main river and its tributaries to regulate this flow.
The Granadilla’s weir is more than 400 m long and
3 m high, and is located in the middle section of the
Guadiana River, at 166 m.a.s.l. Flow follows a semi-
natural regime with a mean annual discharge of
63.5 m
, although the monthly discharge ranges
from 7.3 to 885.2 m
(Guadiana Hydrographic
R. Mora
´pez, O. Uceda Tolosa
Confederation). The weir was equipped with two
fishways prior to this study, both having very low
efficiency and being species- and size-selective for
both native and invasive species (GIC 2008).
As is typical for the Iberian Peninsula, the Guadi-
ana’s native freshwater fish community is species-
poor yet highly endemic with mostly cyprinids, and is
rife with invasive species (Cabral et al. 2005; Doadrio
et al. 2011). Concerning native cyprinids, only one out
of five small sized species migrate and none jump, all
these species being mostly or totally restricted to
tributaries (Doadrio et al. 2011; our own data). And
five out of six large sized species migrate and of these,
four out of five jump, all these species occupying the
Guadiana River and major tributaries (Doadrio et al.
2011; our own data). All native jumping migrants are
barbel (Luciobarbus sp.) species; the southern
straight-mouth nase (Pseudochondrostoma willkom-
mii) has never been observed displaying such
behaviour in the study area. We noted that while the
nase population is declining downstream of the
Granadilla weir, two barbel species still maintain
abundant migrating populations that try to negotiate
the Granadilla weir through leaping: the Iberian long-
snout barbel (Luciobarbus comizo) and the Iberian
small-head barbel (L. microcephalus).
Thirteen exotic species have been cited in the
Guadiana basin, with ten of them in the study area
(Doadrio 2001; Doadrio et al. 2011; preliminary
observations). Of those in our area of interest, three
cyprinids (Alburnus alburnus,Carassius auratus, and
Cyprinus carpio) and two non-cyprinids (Esox lucius
and Sander lucioperca) are partial or total migrants,
and we found only the cyprinids goldfish (C. auratus)
and common carp (C. carpio) displaying jumping
behaviour. We observed that while the latter have less
abundant migrant populations and only display occa-
sional jumping behaviour, the former has large
populations concentrated downstream of the Grana-
dilla weir that repeatedly try to negotiate the obstacle
through leaping.
Data collection and analysis
Data on jumping behaviour were collected through
video images taken downstream from the right margin
of the Granadilla weir (Fig. 1), in April 26, 2011 at
12:45 CET (Central European Time). Because the
weir is impassable by leaping and no juveniles were
observed with this behaviour, data correspond to adult
fish leaping to their maximum capabilities under
presumably optimal conditions of temperature (water
temperature: 21 °C). These data are within the max-
imum frequency of cyprinid jumping behaviour
observed in decadal (2007–2016), seasonal (January
to July), and daily (dawn to dusk) time scales: a long
term monitoring scheme showed that the seasonal
maximum number of barbels jumps per minute in the
Fig. 1 Inset of the south-
western Iberian Peninsula,
with the study area indicated
(arrow). The Granadilla
weir (in black) is retrofitted
with two fishways located at
the right (A) and left
(B) margins of the Guadiana
River (C). The study site
was located at the edge of
the right margin (D).
Direction of flow and
migrating fish are indicated
with black and white arrows,
Relative leaping abilities of native versus invasive cyprinids as criteria
37 m stretch nearest to the right margin of the
Guadiana River was 150 in 2011, while the decade
mean maximum was 55.1 ±93.3 (unpublished
results). Therefore, the data corresponds to carefully
selected conditions, where the selection of the year,
site, date, and horary of data collection represent fish
highly motivated to jump; such accessibility to high
quality data on free-ranging leaping fish is not known
elsewhere in the Guadiana basin. For comparative
purposes, we also collected capture data from the river
immediately downstream the weir using nets; total fish
length was measured on these migrating fish species.
A SONY DCR-SR290E digital camera with a video
rate of 25 frames s
, a focal distance of 25.9 mm
(35 mm equivalent ca. 200 mm), and a maximum
aperture of f/1.8 was used. Zoom level was adjusted to
cover a field of view of approximately 7 94 m, which
included the first six metres of water falling adjacent to
the margin; this was a compromise between horizontal
amplitude of spatial coverage of the obstacle and fish
size on the images. The field of view also covered parts
of the facility immediately adjacent to the waterfall;
their known dimensions allowed us to scale image
pixels to absolute metric measures in a Cartesian
coordinate system. The fall height (h) was measured
on the images as the vertical distance from the abrupt
drop of water at the crest of the weir to the downstream
pool water surface. As the latter level is somewhat
imprecise because of the fluctuating standing wave,
the mean level of emergence of a sample of leaping
fish was used (h =1.62 m, n =67). The depth of the
plunge pool within the video frame was measured at
six locations using a metre stick at the standing wave,
which varied from 0.85 to 1.05 m. As these values
were double the mean fish size of the larger migrating
populations (barbel mean ±S.D., 44.8 ±7.9 cm,
n=71), the depth of the water was considered
enough to not limit maximum leaping performance
of the fish (Powers and Osborn 1985; Lauritzen et al.
Individual video frames of 1024 9576 pixels were
extracted for complete fish trajectories using VLC
media player (version 2.1.5). ImageJ version 1.46
(Schneider et al. 2012) was used to set abscissa and
ordinate origins at pool water level and weir margin,
respectively, within which water develops the fall.
Microsoft Excel 97–2003 was used to convert the
spatial scale of images from pixels to centimetres.
Total fish length was measured in the image using the
upper height (when the fish was near zero velocity)
with the fish’s straightest posture (i.e. not C- or
S-bent); trajectories clearly departing from these
criteria were excluded from further analysis. In
addition, absolute horizontal and vertical coordinates
of fish were registered in the frame when and where it
reached its absolute maximum height. The tip of the
snout was used as it reached the maximum height in all
occasions, as it is a more accurate measure of fish
position in the videos (Shih and Techet 2010), and it is
a useful indicator of the height of an impassable
Precision was estimated throughout repeated mea-
sures of a 500 mm static portion of the infrastructure
in a number of random video frames (CV =1.7%;
n=30); in addition, a free falling 239 mm diameter
ball was filmed and measured as aforementioned on
repeated occasions (CV =4.6%; n =68). These
measures indicated that a certain combination of the
objects’ size and velocity influenced the precision of
the measurements taken in the images, but remained
within a tolerable range of around 2.3% above or
below the true measure for moving fishes (approxi-
mately 1 cm in a barbel of average length). Measure-
ment errors for coordinates taken in the images have
no expected bias because their random nature causes
them to average. On the contrary, actual total fish
length measurements are prone to underestimation
bias, since fish may have a variable non-normal body
angle with respect to the camera. We used a barbel
total length (TL) conversion coefficient (Lauritzen
et al. 2005) of 1.22, developed from the size distribu-
tion of migrating barbel captured downstream the
weir, and applied it to the size distribution of a sample
of jumping fish on the video images (n =260); a
similar coefficient of variation for total fish length
from both data sources (respectively, 17.5% vs.
16.4%) support their use within the same migrating
population. The same method was used for goldfish
(conversion coefficient =1.02; respectively, n =93
vs. n =110 and CV =6.5% vs. 10.4%).
Sex determination was not possible from the videos
(e.g., Lauritzen et al. 2005), though sex differences in
leaping capabilities are not to be expected (Kondrati-
eff and Myrick 2006). Nor was it possible to distin-
guish between the two barbel species or to identify
individuals within the video frames (e.g., Mueller et al.
2008). Nevertheless, comparable contributions were
found between the two barbel species in migrating
R. Mora
´pez, O. Uceda Tolosa
population size, individual size distribution, and sex
ratio in both data from captures downstream the weir
(L. comizo 46.4%; L. microcephalus 53.6%; n =71)
and photographs of leaping individuals taken at the
weir (L. comizo 57.4%; L. microcephalus 42.6%;
n=169; unpublished data). Therefore, hereafter we
refer to the barbel species group, which is still
representative of the native leaping fish community,
and remains useful for management and conservation
applications. Multispecies approaches have demon-
strated utility in quantitative assessments for conser-
vation management (Bonn and Schro
¨der 2001;
Dallimer et al. 2009; Schwenk and Donovan 2011;
´pez et al. 2016).
Prior to the following analyses, normality of the
variables leap height (LH), fish TL, and relative LH to
total length (LH/TL) were checked using the Kol-
mogorov–Smirnov test. Relationships between LH
and TL were measured using Pearson product moment
correlation analyses by species. Within species, leap-
ing capabilities are described through basic statistics;
for comparative purposes, barbels were characterized
both along its own range of TL and within the range of
the goldfish TL. Between species comparisons of
height distribution were made through a Ttest both
within the same range and for the whole range of TLs.
The height of a barrier exceeding the invasive
goldfish, but not the native barbel leaping capabilities
(hereinafter called selective obstacle height, SOH)
was graphically determined using relative cumulative
frequency distribution curves (RCFD). These curves,
), were approximated by plotting the value of the
LH by species i(i=Cfor Carassius or i=Lfor
Luciobarbus) against the relative number of leaps up
to a given height xis reached. The ordinate axis of the
plot is given by:
where LHxiis the number of leaps up to a given height
xis reached by species i, and Nis the total number of
cases. Therefore, the relative number of leaps is the
number of leaps up to a given height divided by the
total number of leaps of any height. The abscissa axis
of the plot is given by:
where LH is the variable of interest, leap height. The
horizontal axis on the resulting RCFD curves covers
the entire range of LHs observed in any species, and
the vertical axis encompasses all negotiation attempts
(0–100%). Assuming invasive species have inferior
leaping capabilities compared to native species, the
vertical line located at the 100% limit of the goldfish
curve fulfils:
ðxCÞmax ¼ðxLÞSOH
where (X
is the SOH for goldfish that barbels
have to negotiate. This limit will show: (a) the height
of an obstacle that completely blocks negotiation
attempts by the invasive species [(x
]; and (b), the
fraction of unsuccessful leaps by the native species at
that height [f(x
]. For security reasons, the SOH
must add the aforementioned error term of 2.3%.
The cost of the SOH to native species was studied
through two analyses. In the first, assuming that any
individual fish may reach the SOH in one out of
several negotiation attempts, TL distribution of bar-
bels reaching the SOH versus the whole jumping
population were compared using a Ttest. These data
do not correspond to individuals but to whole leaping
samples which were, thus, analysed at the population
level (similar to use-availability designs in habitat
selection studies; Manly et al. 1993).
In the second analysis, a cross-population approach
was used to estimate the fraction of native migrating
barbel populations that would be blocked by the SOH
(Kondratieff and Myrick 2006). A least square
regression model was developed to relate barbel LH
to TL. Then, the model was applied to the TL
distribution from capture data, and the number of
individuals and their sizes under the SOH were
calculated. The fraction of unsuccessful negotiation
attempts according to the SOH was also calculated.
Kolmogorov–Smirnov tests showed LH (d =0.5429;
p[0.20), TL (d =0.4838; p[0.20), and LH/TL
(d =0.0553; p[0.20) to be normally distributed.
There was a general positive correlation between LH
and TL (r
=0.48; p\0.01), which was significant in
barbels (r
=0.30; p\0.01) but not in goldfish
=0.28; p=0.06). Smaller barbels achieved
greater relative LH (r
=-0.28; p\0.01). There
was a significant difference in mean LH between
Relative leaping abilities of native versus invasive cyprinids as criteria
goldfish and barbels within the range of TL of the
former (tvalue =-5.10; p\0.00); where the gold-
fish reached LH =79.4 cm while the barbels reached
LH =138.7 cm. These differences increased when
the whole range of barbels TL was included in the
analysis (tvalue =21.24; p\0.01); where the leap-
ing capabilities were clearly superior in the barbels
than in the goldfish both in absolute and relative terms
(Table 1).
The RCFD curves for goldfish and barbels showed
that 50% of the leaps reached at most 32.2 and 94.1 cm
height, respectively (Fig. 2). At 100% RCFD, leaps
were (x
=79.4 cm and (x
=150.7 cm
(Fig. 2). Thus, the SOH for goldfish is 79.4 cm;
adjusting for errors in LH measurement results in a
SOH of 81.2 cm. The intersection between the SOH
for goldfish [(x
] and the cumulative leap fre-
quency curve of barbels [(x
] shows that f(x
=34.3% of barbel leaps do not exceed the SOH
for goldfish. Note that this number of leaps corre-
sponds most probably to a smaller number of individ-
uals from the barbel populations, for it is reasonable to
expect that any individual will make repeated jumps
against an impassable obstacle.
There was no difference in TL between those
barbels exceeding the SOH compared to the whole
jumping population (tvalue =-1.5190; p=0.13).
Therefore, TL difference in barbels does not affect
their ability to reach the SOH. Our regression model
revealed that a TL of 34.0 cm is the estimated
minimum length required for barbels to cross the
SOH of goldfish, hereafter referred to as threshold size
(Fig. 3). However, this model explained very low
variance (R
=0.087), which indicates that there is a
large variation in LH for fish of the same TL. This is an
expected result when individuals make multiple
negotiation attempts, with some higher or lower than
The very low variance explained by our regression
model is particularly informative for proper interpre-
tation of the cross-population estimate of the fraction
of barbel individuals that would be blocked by the
SOH for goldfish. The sample of n =71 barbels
captured contained 5.6% individuals under the thresh-
old size. These individuals were the youngest migrat-
ing, sexually mature (TL [30 cm; no juveniles in the
sample), and mainly male (sex ratio 3:1) barbels.
Based on the model, such fish would be blocked by the
SOH for goldfish. However, Fig. 3clearly shows that a
fraction of filmed barbels under the threshold size can
and do actually surpass the SOH. Therefore, the very
low variance explained by the regression model
indicates that the 34.3% of the native species leaps
(not individuals) estimated to be blocked by the SOH,
is a result that corresponds in terms of native
populations with a number well below the estimated
5.6% of the younger, mainly male, breeding individ-
uals (not leaps) while still maintaining 100% blockage
Table 1 Descriptive
statistics for fish leaping
capabilities in absolute (cm)
and relative (leap height to
total length) terms
Results are presented for all
sizes of the populations as
well as by comparable size
classes (note that the
goldfish do not reach the
barbels higher length class)
LH leap height, LH/TL
relative leap height to total
Species Valid N Mean Minimum Maximum SD
Absolute (LH)
Luciobarbus sp. 260 92.4 27.1 150.7 25.3
\35 cm 20 79.6 30.7 137.7 29.0
35–45 cm 114 86.4 27.1 144.2 25.6
[45 cm 126 99.8 44.6 150.7 22.1
Carassius auratus 110 36.8 10.1 79.4 16.4
\35 cm 27 45.1 26.7 79.4 14.5
35–45 cm 20 53.2 27.9 79.2 13.4
Relative (LH/TL)
Luciobarbus sp. 260 2.1 0.7 4.1 0.6
\35 cm 20 2.5 1.0 4.1 0.9
35–45 cm 114 2.2 0.7 3.5 0.6
[45 cm 126 2.0 1.0 3.0 0.5
Carassius auratus 47 1.4 0.7 2.4 0.4
\35 cm 27 1.4 0.8 2.4 0.4
35–45 cm 20 1.4 0.7 2.1 0.4
R. Mora
´pez, O. Uceda Tolosa
of the invasive species. Moreover, any observed
(filmed or captured) native barbel individual could
exceed the SOH for the invasive goldfish according to
its size (TL [30 cm) and demonstrated capabilities
(Fig. 3). Therefore, the native population blocked with
the SOH for the invasive species approaches zero.
Non-physical barriers to deter fish movements have
limited potential even when used as a component of an
integrated system for invasive species restriction
(Noatch and Suski 2012). Seasonally operated phys-
ical barriers and fishways may be an unsuccessful
approach when migration phenologies overlap
between the targeted and non-targeted native species
´lez-Espino et al. 2011). A potentially useful
alternative is the use of leaping capabilities (Rahel
2013), as leaping barriers can be true selective
barriers. But empirical comparative studies of native
versus invasive species are extremely rare. In one
Fig. 2 Relative cumulative frequency distribution (RCFD)
curves of leap height for goldfish (grey) and barbels (black).
The abscissa axis represents the leap height in millimetres, and
the ordinate axis represents the relative cumulative fraction
(percentage) of leaps reaching that height. Vertical lines
indicate the height reached by 50% (dotted vertical lines) and
100% (dashed vertical lines) of leaps for each species. The
selective obstacle height (SOH) is indicated with the arrowed
line, and connects the maximum leap height of any goldfish
(100% cumulative frequency) with the cumulative frequency of
barbel leaps under this height (SOH =79.4 mm). Other
acronyms used are CARAUR for Carassius auratus, LUCSPP
for Luciobarbus sp., and LH for leap height
Fig. 3 Scatterplot of total length (TL) against leap height (LH)
for barbels (dots). The lines represent the regression model
relating LH to barbel TL (dotted line), and SOH for goldfish
(grey line). The vertical,black line indicates the TL where the
barbel model intersects the SOH for goldfish (TL =34.0 cm):
this line discriminates between the barbels not capable (left)
versus capable (right) of exceeding the SOH for goldfish due to
the barbels’ leaping abilities, which is associated with their total
length. Note that barbels smaller than 34 cm would not be
capable of exceeding the SOH in this model, but observed data
(LHobs) indicates that they indeed can and do
Relative leaping abilities of native versus invasive cyprinids as criteria
study, the leaping capabilities of the invasive Euro-
pean minnow (Phoxinus phoxinus) and the native
brown trout (Salmo trutta) were simultaneously mea-
sured with the aim of constructing suitable waterfall
barriers to prevent further dispersal of the invasive
while allowing passage for the native species (Holthe
et al. 2005). In another, the leaping behaviour of the
common carp (C. carpio) has been used to separate
this invasive species from native Australian fishes
lacking this behaviour (Stuart et al. 2006). To the best
of our knowledge, there are no more studies available
on selective leaping barriers for fish, and particularly
none about cyprinids.
In the taxa studied here, larger fish reached higher
LHs, with the highest being attained by the native
barbel species and the younger barbels showing
greater relative leaping capabilities. The invasive
goldfish clearly showed inferior leaping capabilities
compared to the barbels, even when the same size
range was considered. These differences provide an
opportunity to develop and design criteria for a
selective barrier to fully restrain further spread of the
invasive cyprinid and/or its population control—to the
extent that access is limited to habitats needed to
complete its life cycle (Rahel 2013)—while maintain-
ing most or all the connectivity for native cyprinids.
This SOH for goldfish was set to 81.2 cm, which
represents the estimated maximum height that the tip
of the snout of a goldfish could reach. Since the centre
of mass of the fish remains below the SOH, it
guarantees complete migration failure for goldfish
leaping under an obstacle of such vertical dimension.
Concerning the native barbels, the most of its
population has the capability to exceed the SOH for
goldfish, as most of the variation in LH was associated
with variables outside of TL. The large variability in
the LH compared to TL observed has several, non-
incompatible explanations: (a) the length–height rela-
tionship varies in a non-linear way, with smaller fish
having superior relative capabilities (as it was in the
case of Kondratieff and Myrick 2006); (b) two indi-
viduals of the same TL can have inherently different
stamina and/or conditions (Ovidio and Philippart
2002; Kondratieff and Myrick 2006); (c) the same
individual may reach different heights during separate
jumping instances due to occasionally underpowered
jumps, or simply because repeating a manoeuvre in a
plunge pool with mixed hydrodynamic signals from
multidirectional flows is very difficult (Lauritzen et al.
2005; Ovidio et al. 2007). Therefore, leap distance to
the weir, takeoff angle, and thrust probably vary both
within and between individuals of similar size,
suggesting that fish size is neither the only nor
necessarily the main factor determining LH. These
considerations promote support for the results
obtained in this study, in contrast to length–height
rigid capability rules (Kondratieff and Myrick 2006).
Moreover, the lack of a rigid length–height rule is a
fortunate result as it reflects the barbels’ capability to
surpass the SOH for a wide range of fish sizes, which
likely encompasses the great majority ([99%) of
native jumping populations downstream the Grana-
dilla weir. Only the smallest (mainly non-migrant)
fish, the less capable or the ones in poor condition
would be blocked. Furthermore, the younger barbels
showed greater relative leaping capabilities—as it is
the case for Salvelinus fontinalis (Kondratieff and
Myrick 2006)—making them capable of exceeding
the SOH for goldfish from TL [30 cm onwards. This
guarantees that an obstacle using the SOH will not
impose substantial artificial selection pressures to the
native barbels.
Barbel leaping capabilities are comparable to those
observed in different salmonid species. Barbels
demonstrated inferior absolute leaping capabilities
compared to: larger species such as the Chinook
salmon (Oncorhynchus tshawytscha); species of sim-
ilar size such as steelhead (O. mykiss) or coho salmon
(O. kisutch); and with smaller species such as the
sockeye salmon (O. nerka; Table 3 in Reiser et al.
2006). In contrast, the capabilities of these barbels
exceeded those of the similarly-sized chum salmon (O.
keta) and the smaller pink salmon (O. gorbuscha;
Table 3 in Reiser et al. 2006). In relative terms
however, of all of these species, only O. mykiss is
superior to Luciobarbus sp. (4.79 vs. 4.08, respec-
tively). Their absolute capabilities are similar to Salmo
salar (1.5 m) but superior to S. trutta (1.1 m) or
Thymallus thymallus (0.85 m; Ovidio and Philippart
2002); Luciobarbus sp. have also superior relative
leaping capabilities to all these species along all the
length classes studied (Table 1). The variation in
leaping capabilities amongst species may provide
opportunities to control invasive populations through
selective barriers where cyprinids and salmonids
collide. For example, the brook trout (S. fontinalis)
is an invasive species introduced in several continents
and is also included in the Spanish catalogue of exotic
R. Mora
´pez, O. Uceda Tolosa
invasive species (Royal Decree 630/2013 2013). In the
event that the barbels and the brook trout exist
sympatrically, Luciobarbus sp. surpass the leaping
capability of the salmonid, which can jump during
migration up to 4.7 body lengths when small in size
(approximately TL =15 cm), and 3–4 body lengths
(73.5 cm) when larger (TL C20 cm; Kondratieff and
Myrick 2006). This provides further applied examples
on the potential use of jumping abilities as design
criteria of selective barriers for deliberate fragmenta-
tion (Fausch et al. 2009).
To the best of our knowledge, there are no
published studies on the leaping performance of
cyprinid species comparable to the size of adult
Luciobarbus sp. Holthe et al. (2005) found European
minnows of TL =50–110 mm forced waterfall bar-
riers up to 27 cm at 14.0–16.5 °C. Ficke et al. (2011)
studied the North American cyprinid brassy minnow
(Hybognathus hankinsoni) and the common shiner
(Luxilus cornutus), and found leaping capabilities of
15 cm at 25 °C and 10 cm at 17.5 °C, respectively.
Geeraerts et al. (2007) cite the non-systematic obser-
vation of roach (Rutilus rutilus), an infrequent obstacle
leaper, jumping at least 15 cm—the species being
introduced in the Guadiana basin (Doadrio et al.
2011). All these species are small cyprinids
(TL \30 cm) with obvious, inferior leaping capabil-
ities than the larger Luciobarbus sp.
(TL =30–70 cm).
Our results indicate that a barrier designed to
prevent the upstream movement of the goldfish (C.
auratus), while allowing the negotiation of native
barbels (Luciobarbus sp.), should be at least
81.2 cm in height. An upward safety factor of
10% would likely be appropriate, setting the SOH
figure at approximately 90 cm. A lower height will
also meet the selective barrier criterion as long as a
lesser plunge pool depth limits the leaping capability
of the fishes, but larger native fishes like barbels
will also be negatively affected. The use of such a
design will provide population control of the
invasive species, by disrupting the connectivity
between habitats needed for the species to complete
its life cycle, and by preventing them from colonis-
ing further tributaries within the river network
where it is allochthonous (isolation management in
Rahel 2013). A selective barrier would also be
useful in the control of invasive exotics by incor-
porating a structure for the capture of jumping fish,
as it was in the case of traditional fishing (Brandt
1984). This selective capture system could be
retrofitted to the current weir, so the invasive fish
are guided by it to the margin where they can be
For non-jumping native species, a selective fish
pass should be retrofitted as a complementary mea-
sure. Data on Luciobarbus sp. leaping capabilities can
also be useful in optimising designs of the pool-and-
weir fishways, which are often used to mitigate the
effects of dams and weirs (Clay 1995), similar to
culverts retrofitted to road crossings (Maitland et al.
2015). Fish passes provide further opportunities for
the control of invasive species populations using them,
as it is in Australia for carp control (Stuart et al. 2006),
and could be the case of the goldfish in Iberia and
Finally, the SOH for goldfish criterion found in this
study apply to the abiotic conditions (temperature,
flow, plunge pool depth, etc.) and taxa involved in the
study. The transferability of these results to other
native species or environments should be tested,
because of the limitations on the observation period,
spatial scale, and number of species studied. Future
studies including more years, more obstacles, and
more species will improve our understanding of the
differential leaping capabilities between native and
invasive cyprinids, and its utility for selective barrier
Acknowledgements ChristopherMyrick and three anonymous
referees provided useful comments to the manuscript.
Compliance with ethical standards
Conflict of interest The authors declare that they have no
conflict of interest.
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Relative leaping abilities of native versus invasive cyprinids as criteria
... Nevertheless, Branco et al. (2017) studied the movements of Iberian barbel Luciobarbus bocagei in a river segment affected by the presence of small weirs and concluded that 11% of the tagged individuals moved between segments, negotiating the weirs either by swimming or jumping. Furthermore, Morán-López and Tolosa (2017) reported on the great ability of barbel (Luciobarbus spp.) to jump a maximum height of approximately 150 cm when trying to negotiate the Granadilla weir, located in the Guadiana River, 6.5 km upstream of the Spanish-Portuguese border. Thus, these studies seem to demonstrate that if suitable hydraulic conditions are found directly downstream of obstacles, potamodromous cyprinids may individually adapt their passage behaviour (swimming vs. jumping) to the local hydrodynamic scenario in their attempts to overcome barriers to reach upstream essential habitats Lucas & Frear, 1997;Morán-López & Tolosa, 2017;Ovidio & Philippart, 2002). ...
... Furthermore, Morán-López and Tolosa (2017) reported on the great ability of barbel (Luciobarbus spp.) to jump a maximum height of approximately 150 cm when trying to negotiate the Granadilla weir, located in the Guadiana River, 6.5 km upstream of the Spanish-Portuguese border. Thus, these studies seem to demonstrate that if suitable hydraulic conditions are found directly downstream of obstacles, potamodromous cyprinids may individually adapt their passage behaviour (swimming vs. jumping) to the local hydrodynamic scenario in their attempts to overcome barriers to reach upstream essential habitats Lucas & Frear, 1997;Morán-López & Tolosa, 2017;Ovidio & Philippart, 2002). ...
... This result is, in a way, in agreement with the expected passage behaviour for barbel, because potamodromous cyprinids are considered by some authors as a "non-jumping species" (Baudoin et al., 2014;Doadrio et al., 2011). However, although jumping is not the passage behaviour most frequently used by these species to negotiate obstacles (Baudoin et al., 2014), most cyprinids when confronted with higher barriers to overcome, or high turbulence, are able to modify their individual passage behaviour increasing their attempts to pass by jumping (Baudoin et al., 2014;Morán-López & Tolosa, 2017) and being successful in passing by this means, as found in this study. a standing wave (Powers & Orsborn, 1985;Stuart, 1962), higher energy dissipation of the plunging jet, more turbulence downstream of the obstacle, and more air entrainment (Baudoin et al., 2014;Pasternack, Ellis, Leier, Valle, & Marr, 2006;Wyrick & Pasternack, 2008), are conditions that limit the upstream successful passages of fish (see Amaral et al., 2016) and proved to be an influencing factor in barbel switching passage behaviour from swimming to jumping. ...
Physical stressors, such as man-made obstacles, are considered one of the main causes that negatively affect freshwater fish. Even small weirs may impact fish populations, including potamodromous cyprinids, by partially or totally blocking upstream migratory movements. Some studies have addressed the effect of key hydraulic parameters on upstream movements past small weirs, but little is known on how these parameters interact to induce swimming or jumping behaviour in negotiating such obstacles. This study aims to evaluate the passage behaviour (swimming vs. jumping) of Iberian barbel (Luciobarbus bocagei), a potamodromous species, over an experimental small broad-crested weir, considering the effect of different plunge pool depths (D), waterfall heights (H), and weir discharges (Q). Results revealed that passage behaviour was highly dependent on combinations of plunge pool depths and waterfall heights. Barbel navigated most configurations by swimming (overall outcomes: 81.5% swimming vs. 18.5% jumping), except the ones with the higher waterfall heights (25 cm) tested. Therefore, higher waterfalls proved to be preponderant in the switching of passage behaviour from swimming to jumping. Regarding the discharge over the 1-m-wide weir (overall outcomes: 85% swimming vs. 15% jumping), contrary to what was expected, there was no evidence that passage behaviour was discharge-related, for the range of discharges tested (25–100 L/s). These results are useful to identify potential migration obstacles and should be taken into consideration in river restoration projects and when designing fishways for potamodromous cyprinids.
... Isolating populations makes them more vulnerable to extinction due to inbreeding depression and stochastic environmental events (Hilderbrand and Kershner, 2000;Fagan, 2002). Vertical barriers have been designed that can successfully allow passage of native fish by exploiting the inferior leaping behaviour of invasive species (Holthe et al., 2005;Morán-López and Tolosa, 2017). For Frontiers in Ecology and Evolution | ...
... Also, selective barrier designs that have worked under laboratory conditions can fail when tested in the field (e.g., Zielinski and Sorensen, 2015). Targeting traits to allow selective passage may be relatively straightforward in low diversity communities (Holthe et al., 2005;Morán-López and Tolosa, 2017) but is likely to be increasingly difficult in more biodiverse tropical communities. Overall, research on selective passage is in its infancy and more innovative solutions are required. ...
Full-text available
Aquatic invasive species (AIS) are one of the principal threats to freshwater biodiversity. Exclusion barriers are increasingly being used as a management strategy to control the spread of AIS. However, exclusion barriers can also impact native organisms and their effectiveness is likely to be context dependent. We conducted a quantitative literature review to evaluate the use of barriers to control animal AIS in freshwater ecosystems worldwide. The quantitative aspect of the review was supplemented by case studies that describe some of the challenges, successes, and opportunities for the use of the use of AIS exclusion barriers globally. Barriers have been used since the 1950s to control the spread of AIS, but effort has been increasing since 2005 (80% of studies) and an increasingly diverse range of AIS taxa are now targeted in a wide range of habitat types. The global use of AIS barriers has been concentrated in North America (74% of studies), Australasia (11%), and Europe (10%). Physical barriers (e.g., weirs, exclusion screens, and velocity barriers) have been most widely used (47%), followed by electric (27%) and chemical barriers (12%). Fish were the most targeted taxa (86%), followed by crustaceans (10%), molluscs (3%) and amphibians (1%). Most studies have been moderately successful in limiting the passage of AIS, with 86% of the barriers tested deterring >70% of individuals. However, only 25% of studies evaluated barrier impacts on native species, and development of selective passage is still in its infancy. Most studies have been too short (47% < 1 year, 87% < 5 years) to detect ecological impacts or have failed to use robust before-after-control-impact (BACI) study designs (only 5%). Hence, more effective monitoring is required to assess the long-term effectiveness of exclusion barriers as an AIS management tool. Our global case studies highlight the pressing need for AIS control in many ecoregions, and exclusion barriers have the potential to become an effective tool in some situations. However, the design and operation of exclusion barriers must be refined to deliver selective passage of native fauna, and exclusion barriers should only be used sparingly as part of a wider integrated management strategy.
... As an increase in water levels brings new opportunities to obtain resources, it may also be considered an indication that migration could be beneficial, i.e., that there are favourable conditions in other habitats. As some species may have limited ability to overcome obstacles 31 , increasing water levels in reservoirs may signal suitable conditions for spread. However, data on what is triggering the migration of fish currently widespread in the reservoir are still very scarce. ...
Full-text available
Reservoirs interrupt natural riverine continuity, reduce the overall diversity of the environment, and enhance the spread of non-native fish species through suitable environments. Under favourable conditions, invasive species migrate to tributaries to benefit from local resource supplies. However, the changes in physical conditions in reservoirs that motivate fish species to migrate remain poorly understood. We analysed migration between a reservoir and its tributary in three non-native (asp Leuciscus aspius, ide Leuciscus idus, and bream Abramis brama) and two native (chub Squalius cephalus and pike Esox lucius) species equipped with radio tags. This 5-year study revealed that an increasing day length was the most general predictor of migration into the tributary in all observed species except E. lucius. Only L. aspius responded to the substantially increasing water level in the reservoir, while the migration of L. idus and S. cephalus was attenuated. Abramis brama and S. cephalus occurred more frequently in tributaries with an increase in temperature in the reservoir and vice versa, but if the difference in temperature between the reservoir and its tributary was small, then A. brama did not migrate. Our results showed that migration from the reservoir mainly followed the alterations of daylight, while responses to other parameters were species specific. The interindividual heterogeneity within the species was significant and was not caused by differences in length or sex. Our results contribute to the knowledge of how reservoirs can affect the spread of non-native species that adapt to rapid human-induced environmental changes.
... Across all of the study sites, Silver Carp traversed great distances (482.34 cm) and heights (276.06 cm), which is comparable to the performance of other species including Brook Trout Salvelinus fontinalis, barbels Luciobarbus sp., and Goldfish Carassius auratus (Kondratieff and Myrick 2006;Moran-Lopez and Tolosa 2017). Considering the variation in leaping ability within and between study sites, managers and barrier designers must consider the maximal capabilities of Silver Carp rather than their average performance abilities. ...
Full-text available
Measuring burst speeds of fish has long been problematic due to the lack of in‐situ measurements. Using boat‐mounted cameras, we recorded video of invasive Silver Carp Hypophthalmichthys molitrix, in the field leaping from the water and measured their leap height, horizontal distance, angle of escape, and estimated their escape velocity. Leap characteristics, fish morphometrics, and environmental data were measured from populations of carp in Mississippi, Missouri, and Illinois. Mean leap height and distance (± SE) across all study areas were 125 ± 5.54 and 209 ± 9.10 cm, respectively. Maximum leap height recorded was 276.08 cm (Ramsey Creek, Missouri) and maximum distance was 482.34 cm (DeSoto Lake, Mississippi), both more than double the mean values. The majority of carp (66.1%) leaped at angles between 46 and 65°. Mean water escape velocities (WEV) varied across the three study sites. Velocities in Missouri, 628.4 ±31.6 cm*s‐1, were significantly higher than in Mississippi, 471.2 ± 16.9 cm*s‐1 or in Illinois, 551.7 ± 20.6 cm*s‐1. Maximum measured escape velocity was 771 cm*s‐1 but maximum estimated WEV was substantially higher at 1280 cm*s‐1. Larger Silver Carp were captured at lower latitudes: 54.79 ± 0.74 cm in Illinois, 60.86 ± 0.75 cm in Missouri, and 73.09 ± 1.03 cm in Mississippi. Regression analysis indicated that leap distance and height were correlated with fish size, escape velocity, and angle of escape, and that escape velocity was correlated with streamflow velocity, fish size, and water temperature. This study provides first time quantification of Silver Carp leap characteristics and escape velocities, which we believe approximates maximum burst swim speeds. As such, these data can be used to develop or refine effective vertical and hydraulic barriers to Silver Carp dispersal. Data also demonstrate that leaping and high‐speed swimming capabilities of Silver Carp are greater than previously assumed.
... Sex differences in leaping capabilities are not to be expected (Kondratieff and Myrick, 2006). Captures and photographs made at the weir showed the two species to be comparable in population size, length distribution, and sex ratio (Morán-López and UcedaTolosa, 2017a). Thus we considered them together as the barbel species group because multispecies approaches have a demonstrated utility in quantitative assessments for conservation management (Bonn and Schröder, 2001;Dallimer et al., 2009;Schwenk and Donovan, 2011;Morán-López et al., 2017). ...
Understanding freshwater fish population ecology is a pre-requisite for their conservation, management, and exploitation. Many populations of cyprinids, the largest family of freshwater fish, undertake potamodromous migrations. This has important implications for the conservation and management of their stocks. Habitat and connectivity loss are the main factors threatening these stocks. The fine-scale routes (i.e., banks vs. midchannel) of cyprinid spawning migrations in generally turbid rivers are largely unknown, contrary to other taxa such as salmonids, shads, and eels. In this work, we studied the fine-scale leaping behavior of two cyprinid taxa (Luciobarbus sp., barbels) which support commercial and recreational fisheries. We used fish size and leap distance to the margin as indicative of fine-scale spawning migration routes following the river banks vs. midchannel. The results support the idea that these cyprinids migrate close to the banks, and that the larger adults migrate nearer the banks than the smaller ones. This marks a difference between cyprinids and salmonids, showing that knowledge of cyprinid migration routes can help fisheries managers develop improved, more permeable, barriers and less selective fish pass facilities. Particularly, this behavior of cyprinid species can be applied to optimize the design of fish pass facilities: first, by installing fish passes on each bank of wide rivers, where the large lateral distance may make a single facility difficult to find; and second, by using either a single wider entrance or several narrower entrances distributed over a greater distance from the margins so as to cover the more distant stretch used by the younger adults.
To evaluate volleyball players' sports activities using the author's own video recording system. They tested 28 volleyball players in four games for the Polish Volleyball League Plus and the Federation of Europe. Record data were analyzed for groups in matches given the average total distance covered by the volleyball players in different meetings' specialties. The research programs that extend the finals' players' distance set indicate these individual meetings' long-term trend. It is crucial to monitor the training load to essential the state together to prevent unnecessary changes. Knowledge of these variables during the volleyball season is still lacking—objective: To describe competitive volleyball players' training load and recovery status during the monitoring season. The purpose of this research is to describe and explore professional volleyball players throughout the season for Internal Training Load (ITL), recovery and body distribution. Recipe: 15 professional male Brazilian volleyball players participated. The target's three-dimensional position monitoring technology is beneficial for analysis and professional understanding of volleyball games. Still, many factors make any change in the rate of sports volleyball tracking. This article describes the image processing technology combined with 3D space matching technology. It features a particle filter, effectively enhancing volleyball tracking accuracy, tracking a game system's structure. Second, the proposed similarity prediction method is based on the properties of volleyball itself, mainly to solve supercomputing in real-time monitoring based on the similarity prediction of alkali and HSV color spaces. Finally, the simulation test results show that this method can significantly improve the tracking success rate—high efficiency and high accuracy dynamic video game tracking properties unexpected value development value volleyball.
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Barrier removal is a recognized solution for reversing river fragmentation, but restoring connectivity can have consequences for both desirable and undesirable species, resulting in a connectivity conundrum. Selectively passing desirable taxa while restricting the dispersal of undesirable taxa (selective connectivity) would solve many aspects of the connectivity conundrum. Selective connectivity is a technical challenge of sorting an assortment of things. Multiattribute sorting systems exist in other fields, although none have yet been devised for freely moving organisms within a river. We describe an approach to selective fish passage that integrates ecology and biology with engineering designs modeled after material recycling processes that mirror the stages of fish passage: approach, entry, passage, and fate. A key feature of this concept is the integration of multiple sorting processes each targeting a specific attribute. Leveraging concepts from other sectors to improve river ecosystem function may yield fast, reliable solutions to the connectivity conundrum.
Worldwide river fragmentation by infrastructures is altering essential ecological processes including fish migrations. Unlike laboratory approaches, field methods and biophysical models have the potential to provide realistic representations of interacting fish-obstacle systems, furthering insights in behavioural and biomechanics science, and allowing better bioinspired engineering. We developed a new field, image-based method that integrates a biophysical mechanistic model to describe the swimming and leaping biomechanics of wild populations of fish in the non-lab ecological context where their reproductive migration takes place. A weir obstacle in natural riverine conditions where fish freely migrate upstream to their breeding grounds was filmed. A biophysical model including the relevant biomechanical and hydraulic forces and their interactions was parametrised and calibrated with the spatial coordinates of fish trajectories. The method was validated with independent empirical data under field conditions. The distribution of fish initial velocities and angle of emergence of the sample of filmed leaps were reliably quantified in field conditions. The distribution of burst swimming velocities underwater was differentiated from that of the initial leaping velocities associated with the thrust of hydraulic forces; fish behaviour while emerging from water was described. Fish approximated the optimum angle to negotiate the waterfall but did not reach the minimum velocity needed to negotiate the obstacle. The method demonstrated the ability to provide realistic, accurate and precise ecological data on field-based fish interactions with challenge zones during upstream reproductive migrations. The method is cost-effective as it is based on general purpose digital cameras, image analysis, and modelling equations in spreadsheets; all inexpensive and readily available. This new approach can be directly applied to solve scientific problems and bioengineering challenges in any freshwater ecosystem that has natural or artificial obstacles and migratory fish with leaping behaviour.
Disruption of movement patterns due to alterations in habitat connectivity is a pervasive effect of humans on animal populations. In many terrestrial and aquatic systems there is increasing tension between the need to simultaneously allow passage of some species while blocking the passage of other species. We explore the ecological basis for selective fragmentation of riverine systems where the need to restrict movements of invasive species conflicts with the need to allow passage of species of commercial, recreational, or conservation concern. We develop a trait‐based framework for selective fish passage based on understanding the types of movements displayed by fishes and the role of ecological filters in determining the spatial distributions of fishes. We then synthesize information on trait‐based mechanisms involved with these filters to create a multi‐dimensional niche space based on attributes such as physical capabilities, body morphology, sensory capabilities, behavior, and movement phenology. Following this, we review how these mechanisms have been applied to achieve selective fish passage across anthropogenic barriers. To date, trap‐and‐sort or capture‐translocation efforts provide the best options for movement filters that are completely species selective, but these methods are hampered by the continual, high cost of manual sorting. Other less effective methods of selective passage risk collateral damage in the form of lower or higher than desired levels of passage. Fruitful areas for future work include using combinations of ecological and behavioral traits to passively segregate species; using taxon‐specific chemical or auditory cues to direct unwanted species away from passageways and into physical or ecological traps while attracting desirable species to passageways; and developing automated sorting mechanisms based on fish recognition systems. The trait‐based approach proposed for fish could serve as a template for selective fragmentation in other ecological systems. This article is protected by copyright. All rights reserved.
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Although there is increasing evidence for the effects on wildlife of primary infrastructure (paved roads and human settlements), the effect of secondary infrastructure (tracks and isolated buildings) is generally assumed to be low in sparsely developed areas. We hypothesized that secondary infrastructure may have a negative effect similar to that of primary infrastructure, and hence may be the source of extended impacts in landscapes that are otherwise relatively undisturbed. We studied multi-year breeding site data for a community of large birds (raptors and storks) in the Monfragüe Biosphere Reserve, in the south-west Iberian Peninsula. Using a bootstrap model selection approach we modelled the distribution of breeding sites, using as predictors measures of habitat accessibility (relief, hydrography) and various types of infrastructure (primary and secondary) at different scales. Distance effect functions were developed. Secondary infrastructure exerted a negative effect on breeding sites that was equivalent to that of primary infrastructure, in terms of both transport (track vs road) and dwellings (scattered vs aggregated). The negative effect was distance (rather than density) mediated, and remained within the 1 km scale. The potential impact of secondary infrastructure is greater than that of primary infrastructure as it occupies more extensive areas and includes richer communities, with significant proportions of threatened populations. Our results contradict common assumptions about the negligible impact of secondary infrastructure on biodiversity, reveal new challenges for biodiversity conservation, and provide insights relevant for the spatial planning of isolated buildings and tracks in sparsely developed areas with species of conservation interest.
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1. Stream crossing structures are an increasingly prevalent anthropogenic feature on North American riverscapes, particularly in watersheds affected by industrial resource development in sensitive boreal environments. If improperly managed, stream crossings have the potential to alter fish habitat and impede fish movement. 2. This study assessed instream habitat characteristics and fish communities from 33 culverted, bridged, and reference streams in an industrializing region of the boreal forest in west-central Alberta. Mixed-effects modeling and multivariate analysis were used to determine impacts of stream crossings at three scales: whole-stream scale, within-stream scale, and the interaction of scales. 3. Instream habitat characteristics such as mean depth, water velocity, percent fines, turbidity, water temperature, and dissolved oxygen showed significant between- as well as within-stream differences among stream crossings. The majority of fish species exhibited significantly lower densities (n·m -2) in upstream habitats as compared to downstream habitats, including a significant reduction in Slimy Sculpin densities in culverted streams. Multivariate tests corroborated these results, showing that fish assemblages differ as a function of stream type. 4. This study suggests industrial stream crossings influence abiotic habitat characteristics in freshwater ecosystems, restrict biotic connectivity, and impact fish community structure at the whole-stream and within-stream scales. Alterations to stream ecosystems associated with stream crossings may be driving large-scale changes in stream fish communities in the boreal forest. With expanded development expected in much of North America’s boreal region, mitigation measures which limit impacts from stream crossings are needed to ensure proper ecosystem function in freshwater systems.
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Summer rainfall shortage and low or no flows in Mediterranean rivers make it difficult for fish to attain their final preferenda and hinder the assembling of fish communities. We investigated in this study the degree to which large-scale features of the watersheds and reach-scale habitats correlated with a non-random structure of fish species' richness, composition and distribution under these conditions by intensively sampling a river system during summer and using Geographical Information Systems data. The results of multivariate ordination and association analyses showed that multi-scale factors were hierarchically related and that they correlated with non-random fish distributions and assemblage structure. They also highlighted large-scale factors shaping reach-scale water availability for fish during summer. Fish species' richness, composition and distribution varied along a gradient of water shortage and connectivity loss which were more severe with the smaller drainage area into the reaches upstream. Fish species' distributions along these gradients were strongly correlated with both life-history traits (adult size) and biogeographical origin (native vs. exotic). The results for the summer environmental segregation of exotic versus small endemic richness characteristics indicate strong species' interactions forcing the latter into the upstream, harsher seasonal habitats. Special fitness costs are to be expected in drought years, in regulated rivers, and in general, in a climate change scenario in Mediterranean river networks. The study emphasizes that the conservation of the threatened Mediterranean freshwater fish faunas requires operating at the proper spatial scale. In particular, reach-scale habitat improvements are adequate but not enough during the summer in fragmenting river networks, unless there is proper watershed-scale management of the flow regimes.
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For centuries, humankind has constructed dams on rivers to control flooding, provide for irrigation and utilize potential energy for power, but generally dams had no or little provision for fish passage. Thus, they often blocked or impeded fish migrations. Empirical observations and “trial and error” approaches that characterized historical efforts to develop passage systems for upstream migrating fish often did not work. The first concerted efforts to develop scientifically based fishways for upstream migrant fish began in the early 1900s in Europe with field and laboratory testing of different fishway designs. These were followed by extensive efforts beginning in the 1940s in North America. Scientifically based testing of configurations for fishways for downstream migrant fish began in the 1950s. Nearly all early efforts were directed at salmonid species, with smaller efforts on shad. Recent species at risk legislation in the U.S.A., Canada, and Europe places renewed emphasis on fish passage for all migratory species, and efforts have also begun to develop successful passage strategies for migratory species in other countries worldwide. This has led to renewed efforts to develop effective passage systems and to try creative solutions using natural materials in addition to concrete or metal used in standard technical fishways. Regardless of the type of structures built, history has shown that the most effective means to develop successful installations has occurred when engineers and biologists worked together systematically to design passage structures based on the ability and willingness of fish to seek and accept the hydraulic conditions presented to them.
Adult roach Rutilus rutilus (L.) (N = 24; 19.9–36.1 cm FL) from three highly fragmented Belgian rivers were tagged with surgically implanted radio transmitters. Their seasonal movements were observed from March to August 2004 (circum reproduction period) in river stretches delimited by two physical barriers. In the three rivers, roach displayed similar patterns of movements which were mainly influenced by the date of observation (movements increased in late April–May) and water temperature (travel distances were more important when water temperature ranged between 10°C and 14°C). Roach sometimes cleared physical obstacles. The mean distances travelled in each river were relatively short (max. 2.5 km) and mainly influenced by the length of the study reach, which was delimited by physical barriers.
Publisher Summary This chapter highlights that Iberian rivers are naturally rich in terms of their biota. The biological richness in Iberian inland waters is under threat because of the high number of biological invasions. For example, the river Ebro has been invaded by the molluscs D. polymorpha and C. fluminea, but also by the fishes S. glanis and Ictalurus melas in its lower course. These invasions have resulted in a decrease in habitat diversity and in the number of native species. Water transfer between basins is a constant issue in the different hydrological plans that the governments develop to satisfy the high water demands and which would increase the possibility for species invasion. The management of rivers and their associated disturbance regimes has a cultural or societal component. The human presence and management of watercourses may have very different affects depending on the cultural perception of rivers. People in arid and semi-arid regions have the least respect toward rivers since the rivers are often dry or have catastrophic floods and are, therefore, viewed more as a danger than as a natural resource to be preserved. Moreover, there is a well-rooted perception that any water that reaches the sea is wasted. The chapter suggests that this perception being difficult to change, the progressive implementation of the Water Framework Directive (WFD) in the different basins will hopefully force a change in attitude toward the rivers as well as the required administrative steps to secure their conservation and sound management.
In an attempt to restore the connectivity of fragmented river habitats, a variety of passage facilities have been installed at river barriers. Despite the cost of building these structures, there has been no quantitative evaluation of their overall success at restoring fish passage. We reviewed articles from 1960 to 2011, extracted data from 65 papers on fish passage efficiency, size and species of fish, and fishway characteristics to determine the best predictors of fishway efficiency. Because data were scarce for fishes other than salmonids (order Salmoniformes), we combined data for all non‐salmonids for our analysis. On average, downstream passage efficiency was 68.5%, slightly higher than upstream passage efficiency of 41.7%, and neither differed across the geographical regions of study. Salmonids were more successful than non‐salmonids in passing upstream (61.7 vs. 21.1%) and downstream (74.6 vs. 39.6%) through fish passage facilities. Passage efficiency differed significantly between types of fishways; pool and weir, pool and slot and natural fishways had the highest efficiencies, whereas Denil and fish locks/elevators had the lowest. Upstream passage efficiency decreased significantly with fishway slope, but increased with fishway length, and water velocity. An information‐theoretic analysis indicated that the best predictors of fish passage efficiency were order of fish (i.e. salmonids > non‐salmonids), type of fishway and length of fishway. Overall, the low efficiency of passage facilities indicated that most need to be improved to sufficiently mitigate habitat fragmentation for the complete fish community across a range of environmental conditions.
Maintaining or restoring connectivity in aquatic systems can enhance migratory fish populations; maintain genetic diversity in small, isolated populations; allow organisms to access complementary habitats to meet life-history needs; and facilitate recolonization after local extirpations. However, intentional fragmentation may be beneficial when it prevents the spread of nonnative species or exotic diseases, eliminates hybridization between hatchery and wild stocks, or stops individuals from becoming entrapped in sink environments. Strategies for fragmenting aquatic systems include maintaining existing natural barriers, taking advantage of existing anthropogenic features that impede movement, severing artificial connectivity created by human actions, and intentionally creating new barriers. Future challenges for managing fragmentation include maintaining hydrologic connectivity while blocking biological connectivity in water development projects; identifying approaches for maintaining incompatible taxa, such as sport fishes and small nongame species; and developing selective barriers that prevent the passage of unwanted species while allowing normal life-history movements of other species.