PRIMARY RESEARCH PAPER

Associations between stream habitat characteristicsand native and alien crayfish occurrence

Martin Weinlander • Leopold Fureder

Received: 20 January 2012 / Revised: 19 April 2012 / Accepted: 24 April 2012 / Published online: 11 May 2012

� Springer Science+Business Media B.V. 2012

Abstract Human mediated introductions of non-

indigenous crayfish species (NICS) are responsible for

their rapid colonisation of European freshwaters. The

introduction of North American crayfish is further-

more linked to the spread of crayfish plague and the

decline of indigenous crayfish species (ICS). As the

management of ICS and NICS have become neces-

sary, a detailed knowledge on their distribution and

ecological requirements is needed. We studied the

current range of native noble crayfish Astacus astacus

and stone crayfish Austropotamobius torrentium, as

well as alien signal crayfish Pacifastacus leniusculus

in Carinthia (Austria) and evaluated environmental

and physical habitat features in streams with and

without crayfish. Meanwhile, the loss of many ICS

populations was recorded and alien P. leniusculus was

found to be widespread in this region. Most of the

habitat features of streams having crayfish differed

significantly from sites lacking crayfish for at least one

investigated native or alien species. Furthermore,

multivariate and regression analyses showed specific

differences in the habitat use of the investigated

crayfish. Our results showed that the presence of alien

P. leniusculus was associated with larger and

smoother sloped lowland rivers, while the occurrence

of the two native species was confined to smaller

streams either at higher altitudes and with distinct

physical habitat conditions (A. torrentium) or with

moderate water temperatures (A. astacus). This study

helps to identify potential refuge areas for the

endangered native species and to predict the further

spread of the most common non-native crayfish

species in European streams.

Keywords Threatened crayfish � Astacus astacus �Austropotamobius torrentium � Invasive species �Pacifastacus leniusculus � Stream habitat use

Introduction

Human activities accelerate the spread of aquatic alien

species all over the world (e.g. Gherardi, 2007;

Strayer, 2010) and among them especially non-

indigenous crayfish species (NICS) have been shown

to colonise new freshwater habitats within a short time

(e.g. Gherardi et al., 2008). Stockings, escapes,

releases and discards from aquaria or fisheries are

the main factors for the rapid spread of NICS in

Europe (Peay, 2009). While crayfish are generally

directly and/or indirectly affecting their habitats and

coexisting organisms (e.g. Creed, 1994; Statzner et al.,

2000; Stenroth and Nystrom, 2003), especially NICS

have shown negative effects on both indigenous

Handling editor: Sonja Stendera

M. Weinlander (&) � L. Fureder

Alpine Stream Ecology and Invertebrate Biology, Institute

of Ecology, University of Innsbruck, Technikerstrasse 25,

6020 Innsbruck, Austria

e-mail: martin.weinlaender@student.uibk.ac.at

123

Hydrobiologia (2012) 693:237–249

DOI 10.1007/s10750-012-1125-x

crayfish species (ICS) and functioning of aquatic

ecosystems (Nystrom, 1999; Rodriguez et al., 2006;

Gherardi & Acquistapace, 2007).

Hence, introductions of NICS have had major

consequences for aquatic ecosystems and the survival

of ICS in Europe (Holdich et al., 2006a, 2009). In

particular the transmission of the crayfish plague

caused by Aphanomyces astaci Schikora, with North

American crayfish species acting as potential vectors,

cause mass mortalities in European ICS populations

(Holdich et al., 2006a; Fureder, 2009). A potential

carrier of the crayfish plague is the signal crayfish

Pacifastacus leniusculus (Dana), which is native to the

western region of the United States and South-west

Canada. In the last century, this species was intro-

duced into Europe to boost stocks of native crayfish,

became invasive and is today the most widespread

NICS in Europe (Holdich et al., 2009). In the early

1970s, P. leniusculus was also illegally introduced to

the Austrian region Carinthia (Spitzy, 1973), where a

further spread of this alien species was recorded in the

following decades (Wintersteiger, 1985; Honsig-

Erlenburg & Schulz, 1996; Petutschnig, 1997, 2002;

Weinlander & Fureder, 2009). The expansion of

P. leniusculus consequently led to the extinction of

most of the native noble crayfish Astacus astacus (L.)

and stone crayfish Austropotamobius torrentium (Sch-

rank) populations in Carinthia (Weinlander & Fureder,

2009).

In Europe, as these two ICS are threatened by e.g.

crayfish plague, NICS and habitat loss (Fureder &

Souty-Grosset, 2005; Holdich et al., 2006a; Fureder,

2009), A. torrentium and A. astacus are protected by

national as well European laws (Fureder, 2009;

Edsman et al., 2010; Fureder et al., 2010). Due to

their size and economic interest, the ecology and

habitat requirements of A. astacus and P. leniusculus

are well studied, whereas only a scattered knowledge

of the small sized A. torrentium exists (Holdich et al.,

2006a; Fureder et al., 2006; Fureder, 2009). Astacus

astacus and P. leniusculus are known to have similar

habitat requirements and inhabit lentic as well lotic

waters of any size (Fureder et al., 2006; Holdich et al.,

2006a), while A. torrentium is predominantly found in

smaller mountain streams having distinct physical and

chemical habitat requirements (Machino & Fureder,

2005). In running waters, native A. astacus and

A. torrentium are mostly associated to natural stream

sections with heterogeneous substrate composition

offering plenty of refuges and their presence is often

indicating good water quality and functioning of the

aquatic ecosystem (Fureder et al., 2006; Fureder,

2009; Parvulescu et al., 2011). Contrary to them,

P. leniusculus can also be found in obstructed rivers

with adverse environmental conditions and water

qualities (Holdich et al., 2006a; Weinlander &

Fureder, 2009).

As conservation measures are immediately needed

to support the sustainability of the remaining A. astacus

and A. torrentium populations in Europe, a detailed

knowledge of their current existence, distribution and

habitat requirements is essential. Furthermore, the

survival of ICS is strongly dependent on the colonisa-

tion success or failure of NICS in new freshwater

habitats. Most of the studies dealing with habitat

associations and distribution patterns of ICS and NICS

in Europe mainly focus on the endangered Austropot-

amobius pallipes (Lereboullet) and Procambarus

clarkii (Girard) as the native and alien species,

respectively (e.g. Smith et al., 1996; Naura & Robin-

son, 1998; Gil-Sanchez & Alber-Tercedor, 2002;

Favaro et al., 2010). Although some recent studies

provided useful information on the habitat require-

ments of native A. astacus and A. torrentium in lotic

waters (e.g. Zuther et al., 2005; Holdich et al., 2009;

Vlach et al., 2009a, Weinlander & Fureder, 2010;

Parvulescu et al., 2011), no publication considered the

habitat use of native A. astacus and A. torrentium, as

well as alien P. leniusculus at a larger scale. However,

as P. leniusculus is the most common NICS and the

main threat to ICS in Europe (Holdich et al., 2009), this

kind of study is crucial to identify suitable refuge areas

for ICS and to predict the further spread of NICS.

The objective of our study was to determine the

current distribution and habitat use of ICS and NICS in

selected catchments in Carinthia (Austria). Habitat

features in streams with as well as without crayfish were

associated to the presence/absence of native A. astacus

and A. torrentium, as well as alien P. leniusculus. We

hypothesise that the spread of P. leniusculus should be

limited by geographical and environmental features, such

as steep slopes, higher altitudes and therefore lower water

temperatures. We expect that the existence of ICS is

related to natural stream sections with various substrates

offering a lot of shelters, while the presence of alien P.

leniusculus is associated with a broader range of certain

environmental conditions, making this species an advan-

tageous competitor.

238 Hydrobiologia (2012) 693:237–249

123

Materials and methods

Study area

The study was carried out in the Central European

region of Carinthia (46�220–47�080N; 12�390–15�040E), a southern province of Austria adjacent to

northern Italy and Slovenia with an area of 9,536 km2

(Fig. 1). This region is located in the temperate zone,

influenced by Mediterranean climate and harbours

about 1,270 lakes (Sampl 1976). Elevation ranges

from 348 m above sea level (a.s.l.) in the South-east to

3,798 m a.s.l. in the North–west, with mean annual

rainfalls ranging from 750 to 2,000 mm. Flooding

events appear after the snow melt in spring or after

thunder storms during the summer. The total stream

length in Carinthia is about 8,000 km, where most of

the streams drain into the biggest river of Carinthia,

the Drau (Honsig-Erlenburg & Petutschnig, 2002).

This 7th order stream is a tributary of the Danube and

also the geological border of Carinthia, where primary

rocks (granite, gneiss, mica schist) are dominating in

the North and limestone in the South. While chemical

pollution in Carinthian waters can be neglected today,

especially the channels of the rivers Drau and Glan

were altered in the last century (Honsig-Erlenburg &

Petutschnig, 2002).

Stream survey

From June to November in 2008 and 2009, the crayfish

absence or presence was recorded in selected stream

sites within the catchments of the rivers Drau, Gurk,

Glan and Lavant, where native A. astacus and A.

torrentium as well as alien P. leniusculus have their

main distributions in Carinthia (Petutschnig, 2002).

Hand sampling was applied from first- to third-order

streams, where the water level was low enough and

Fig. 1 Investigation area of Carinthia with its main water

bodies and its location in Austria and Europe. Symbols represent

all sites investigated in this study in Eastern Carinthia, including

historical crayfish sites (Petutschnig, 2002) and the additionally

investigated sites. Symbols may overlap, showing one symbolfor several sites

Hydrobiologia (2012) 693:237–249 239

123

visibility reached the bottom. Crayfish were collected

by stone turning for at least 30 min during night and/or

day, while from fourth- to seventh-order streams three

baited ‘‘pirate traps’’ (Bock-As Ky, Finland: L: 61 cm,

W: 31.5 cm, H: 25 cm, mesh sieve: 2.5 9 1 cm) were

set at each sampling site overnight (14 h). In any case,

a river stretch of 100 m was investigated. As the

investigated first- to third-order streams had a mean

width of 1.7 m and the effective sampling area of one

baited trap is 56 m2 (Acosta & Perry, 2000) both

methodologies are quite comparable (in both cases ca.

170 m2 were sampled). Petutschnig (2002) recorded

19 stream sites with A. astacus, 33 with A. torrentium

and 31 with P. leniusculus in the river systems in

question. In our study, these were visited again and in

addition 115 sites in vicinity of the formerly recorded

sites were investigated (Fig. 1). In some of these, even

crayfish were recorded by fishery authorities between

the years 2003 and 2007. They were also considered in

the analysis as historical records.

To identify the factors responsible for the crayfish

presence or absence in streams, 17 habitat features

were evaluated and recorded on a presentable 50 m

stream stretch of the investigated stream sites

between July and August 2009. At every site,

altitude (m a.s.l.), slope (in % measured from the

sampling site to the confluence of the next main

river), stream order (Strahler), width (m), depth

(cm), velocity (m s-1), water temperature (�C), the

presence or absence of bryophytes and macrophytes,

the relative percentage of woody debris, shelters and

stones in different grain sizes (classes defined

according to ONORM M 6232 (1995): megalithal

([400 mm), macrolithal ([200–400 mm), mesoli-

thal ([60–200 mm), microlithal ([20–60 mm), akal

([2–20 mm), sand and mud (\2 mm) were evalu-

ated. Stream order, altitude and slope were obtained

in Geographical Information System (GIS, ArcView

9.3.1). For all three species, separate equipment

(boots, buckets, etc.) was used to avoid the potential

transfer of crayfish plague from P. leniusculus sites

to the streams having native crayfish. Furthermore,

all equipment was disinfected with 4 % formalde-

hyde after each trapping session.

Statistical analyses

To detect differences between historical and/or current

crayfish sites and sites without crayfish, a t test or

Mann–Whitney U-test (for data with normal and non-

normal distribution, respectively) was conducted with

each habitat feature in the crayfish streams against

sites without crayfish. Multivariate analyses were

performed in Canoco 4.5 with the measured environ-

mental variables (Table 1) for a better illustration of

their variation in the sites with ICS and NICS. As the

Preliminary Detrended Correspondence Analysis

(DCA) resulted in lengths of gradients with values

below 1.3, Redundancy Analysis (RDA) is required

instead of Canonical Correspondence Analysis (Leps

& Smilauer, 2003). After computing RDA with all the

habitat features, a stepwise forward selection of

environmental variables was used to identify the

parameters explaining the highest proportion of var-

iance in the species data. The significance (P \ 0.05)

of axes and variables were tested with Monte Carlo

permutation tests and Bonferroni corrections. In order

to clearly separate sites with crayfish presence from

sites without logistic regressions were performed in

SigmaPlot 9.0, as these provide a sigmoid model

producing a real number in the range of 0 and 1 and

returns species occurrence probability with greater

robustness. Hosmer & Lemeshow (2000) suggested a

procedure of building multivariate logistic regressions

where single logistic regressions are followed by

multivariate models. First we analysed single logistic

regression for each parameter (Table 1), where only

the significant variables (P \ 0.05, Wald test) were

considered for further analyses. We added these

variables one by one into a multivariate model

analysing the effect of its addition on the significance

of all other variables already in the model. The best

subset of these significant variables was then com-

puted in a multivariate logistic regression for each

crayfish species. The choice of the final models was

based on maximum likelihood ratio tests (G test) and

associations between variables were tested with odds

ratios (W), where a value above 1.0 indicates positive

and W \ 1.0 negative association.

Results

Compared to earlier crayfish mapping activities in the

investigation area (Petutschnig, 2002), an extensive

loss of ICS stream populations was found, while the

alien P. leniusculus is now the dominant crayfish

species (Fig. 2). Assumingly, one reason for the

240 Hydrobiologia (2012) 693:237–249

123

decline of ICS might be caused by the spread of the

NICS, as 48 additional, not yet recorded stream sites

with P. leniusculus were found. Also interestingly, no

ICS were found anymore, where just a few years ago

one of the two species was recorded (A. astacus:

n = 18, A. torrentium: n = 21). This was especially

apparent in sites at lower altitudes, with warmer water

temperatures and smooth slopes (Fig. 3). Steeper and

cooler sites at higher elevations having A. torrentium

remained more unaffected, where additional six new,

not yet recorded stone crayfish populations were

detected in isolated headwaters. Furthermore, in our

survey, A. torrentium was found in one site, where

A. astacus was falsely recorded in previous studies,

whereas P. leniusculus was now found in four sites,

where A. astacus or A. torrentium were recorded

earlier. At one site having A. torrentium, the habitat

disappeared completely (is now a dry and filled up

bypass of a hydropower plant). This resulted in a total

of 201 sites, 39 sites with historical records (with no

crayfish evidence today), 100 sites with crayfish and

62 sites lacking crayfish (Fig. 2; Table 1).

Habitat features of ICS and P. leniusculus sites

differed significantly (P \ 0.05) from sites without

crayfish for at least one of the investigated crayfish

species, except for mesolithal and macrophytes

(Table 1). Compared to sites without crayfish,

historical A. astacus sites were found in lower

stream orders, smaller widths, depths, lower veloc-

ities and higher water temperatures. These sites had

also lower proportions of megalithal, macrolithal

and bryophytes, but higher fractions of sand and

mud and microlithal. The historical and current A.

torrentium sites were mostly situated in headwaters

with lower stream orders, steeper slopes, smaller

widths, depths and lower velocities than sites

lacking crayfish. These sites having A. torrentium

had furthermore higher fractions of woody debris

and refuges, but lower proportions of megalithal.

Sites having P. leniusculus differed from sites

without crayfish in terms of lower slopes and

altitudes, but higher water temperatures and higher

fractions of sand and mud and akal.

The RDA based on presence/absence data of the

three species and the environmental variables detected

distinct differences in the habitat use of native and

alien crayfish (Monte Carlo test for all canonical axes,

F = 35.99, P = 0.002). The first two axes explained

Table 1 Mean values (±SD) of recorded environmental parameters with results of Mann–Whitney U-tests and t tests, respectively

of habitat features of individual crayfish species (historical and current records) against sites without crayfish

ASA (n = 18) AUT (n = 42) PAL (n = 79) NCF (n = 62) U-values (P values)

Mean ± SD Mean ± SD Mean ± SD Mean ± SD

Altitude (m a.s.l.) 537.7 ± 116.0 572.0 ± 162.6 485.4 ± 90.5 545.9 ± 138.2 4999 (PAL*)

Slope (%) 1.8 ± 1.5 5.3 ± 5.3 0.7 ± 0.8 1.7 ± 3.2 2942 (AUT***), 5009.5 (PAL*)

Stream order (Strahler) 2.1 ± 1.6 2.0 ± 1.0 4.0 ± 1.9 3.7 ± 1.7 408.5 (ASA***), 1447 (AUT***)

Width (m) 8.4 ± 28.4 2.1 ± 2.2 31.7 ± 85.1 47.2 ± 156.3 369 (ASA***), 1350 (AUT***)

Depth (cm) 37.0 ± 58.2 20.4 ± 10.4 76.4 ± 78.8 61.5 ± 84.6 483.5 (ASA**), 1382.5 (AUT***)

Velocity (m s-1) 0.3 ± 0.2 0.4 ± 0.2 0.4 ± 0.2 0.5 ± 0.3 467.5 (ASA**), 1800.5 (AUT**)

Temperature (�C) 19.3 ± 3.4 16.3 ± 1.8 17.8 ± 2.9 16.5 ± 2.7 467.5 (ASA**), 3690.5 (PAL**)

Megalithal (%) 1.7 ± 3.8 5.0 ± 5.6 7.6 ± 6.9 9.8 ± 14.0 408 (ASA***), 1877 (AUT*)

Macrolithal (%) 8.6 ± 8.7 16.0 ± 9.8 16.2 ± 10.0 18.5 ± 13.0 472 (ASA**)

Mesolithal (%) 21.9 ± 10.3 26.1 ± 10.7 23.2 ± 11.1 22.9 ± 9.5 n.s.

Microlithal (%) 28.6 ± 14.3 23.1 ± 11.4 20.1 ± 9.4 19.9 ± 10.4 941.5 (ASA*)

Akal (%) 18.1 ± 7.7 14.8 ± 7.1 17.3 ± 9.0 15.7 ± 12.1 4061.5 (PAL*)

Sand and mud (%) 10.3 ± 13.2 2.4 ± 6.1 5.9 ± 8.9 4.0 ± 10.9 947.5 (ASA*), 3851 (PAL*)

Woody debris (%) 10.8 ± 3.5 12.7 ± 5.9 9.7 ± 5.6 9.2 ± 6.1 2607.5 (AUT**)

Macrophytes (0/1) 0.0 ± 0.0 0.0 ± 0.2 0.1 ± 0.3 0.3 ± 1.3 n.s.

Bryophytes (0/1) 0.1 ± 0.3 0.5 ± 0.5 0.3 ± 0.5 0.5 ± 0.5 530 (ASA*)

Refuges (%) 24.4 ± 11.5 42.5 ± 13.9 30.6 ± 14.0 29.6 ± 14.6 2818.5 (AUT***)

*** P \ 0.001, ** P \ 0.01, * P \ 0.05, n.s. not significant. ASA A. astacus, AUT A. torrentium, PAL P. leniusculus, NCF no

crayfish sites

Hydrobiologia (2012) 693:237–249 241

123

40.4 % of the variance in species data (eigenvalue axis

1 = 0.32, axis 2 = 0.084). The variable slope had the

strongest correlation to axis 1, while macrolithal to

axis 2 (Fig. 4). The presence of A. torrentium was

associated with sites having steep gradients, refuges,

but also altitude, the presence of bryophytes and

woody debris were important predictors (Fig. 4). In

contrast, the presence of A. astacus was related to

warmer water temperatures and sites having higher

percentages of microlithal, sand and mud (Fig. 4).

Sites with the alien P. leniusculus were linked to

stream order, depth, megalithal, velocity, macrophytes

and stream width (Fig. 4). The triplot of the RDA also

showed an overlap of the habitat range of P. lenius-

culus and the two native crayfish species, especially

with A. astacus (Fig. 4). A stepwise forward selection

of variables identified the parameters slope explaining

22 % (F = 38.13, P = 0.002), stream order 7 %

(F = 13.55, P = 0.002), refuges 3% (F = 6.03, P =

0.002) and microlithal 2 % (F = 3.38, P = 0.038) of

the variation in the species data.

Single logistic regression was applied for each

variable and crayfish species, where the significant

parameters were used in a forward stepwise selection

regression (Table 2). The best subset of the most

significant variables for every crayfish species were then

computed in multiple logistic regressions (Table 3).

The presence of A. astacus in streams was best predicted

by the logistic regression model: Logit PASA =

-2.440 - (0.713 9 streamorder) ? (0.212 9 temper-

ature) - (1.762 9 bryophytes). This model predicted

the presence or absence of noble crayfish correctly in

84 % of the cases, where temperature positively and

stream order as well bryophytes negatively affected its

presence. In 78 % of the cases, the presence or absence of

A. torrentium was correctly predicted by: Logit

Fig. 2 Investigated stream sites with native A. astacus and A.torrentium, as well as alien P. leniusculus and streams without

crayfish in the catchments of the Drau, Gurk, Glan and Lavant in

Eastern Carinthia (Austria). Historical = historical records

(Petutschnig, 2002 and fishery authorities), this study has no

crayfish evidence. Symbols may overlap, showing one symbol

for several sites

242 Hydrobiologia (2012) 693:237–249

123

PAUT = 0.895 - (0.686 9 stream order) - (3.159 9

velocity) ? (0.0529 9 refuges). Refuges were posi-

tively related to the presence of A. torrentium, while

stream order and velocity negatively affected its distri-

bution. The logistic regression model Logit PPAL =

-2.183 - (0.461 9 slope) ? (0.169 9 temperature)

predicted the presence or absence of P. leniusculus

correctly in 67 % of the cases, where steep slopes

negatively and warmer water temperatures positively

affected the presence of signal crayfish.

Discussion

We found that P. leniusculus has become the most

dominant crayfish by occurrence in the Carinthian

main rivers and also inhabits most of their tributaries

in the lowland. Once established in a favourable

freshwater habitat, P. leniusculus can extend its range

very fast, where active dispersal capacities of P.

leniusculus can range between 4 km upstream and

24 km downstream per year (Hudina et al., 2009;

Weinlander & Fureder, 2009). Therefore, an expan-

sion of alien P. leniusculus and the exposure to loss of

native A. astacus and A. torrentium populations was

visible in the investigated Carinthian streams. Com-

pared to the study of Petutschnig (2002), all A. astacus

and 50 % of the A. torrentium stream sites might have

disappeared, assumingly due to the spread of P.

leniusculus and the associated crayfish plague. In spite

of these findings, only two sites, where A. astacus has

been previously recorded as well as two sites with A.

torrentium occurrence recently harboured P. lenius-

culus. A simple presence of P. leniusculus in nearby

waters seemed to have led to the extinction of ICS

populations, as fish stockings and contaminated fish-

ing equipment can act as vectors for the transmission

of crayfish plague (Oidtmann et al., 2002). Consider-

ing the short time in the shift of crayfish species

composition in Carinthia, it might take time for plague

carrying P. leniusculus to reach the sites with former

ICS occurrence. In only one case habitat loss was

detected to have caused the disappearance of

A. torrentium, as this stream completely disappeared.

All other investigated stream sites with historical

crayfish occurrence and where ICS are absent today,

were assumed to be appropriate habitats for crayfish

occurrence, as these sites had heterogeneous habitat

characteristics providing a lot of refuges and chemical

water quality is good in Carinthia (Honsig-Erlenburg

& Petutschnig, 2002). Therefore, crayfish plague

seems to be the most likely reason for the disappear-

ance of ICS sites in Carinthia. However, most of the

habitat features of confirmed and historical crayfish

300350400450500550600650700750800850900950

1000105011001150

altit

ude

[m a

.s.l.

]

ASA

AUT

PAL

1112131415161718192021222324252627

wat

er t

empe

ratu

re [

o C]

ASA

AUT

PAL

-2

0

2

4

6

8

10

12

14

16

18

20

22

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85

slop

e [

%]

number of sites

ASA

AUT

PAL

Fig. 3 Number of visited crayfish sites (ASA A. astacus, AUT A.torrentium, PAL P. leniusculus) against altitude, water temper-

ature and slope in the investigation area. Blackened symbolsindicate historical records of ICS (Petutschnig, 2002 and fishery

authorities), whose presence could not be confirmed by the

present study

Hydrobiologia (2012) 693:237–249 243

123

sites and sites without crayfish showed distinct

differences, indicating certain physical and ecological

requirements of the individual native and alien

crayfish species. Sites with confirmed historical and

current ICS discriminated from sites without crayfish

in most of the variables, where stream size, water

temperature and substrate composition seemed to be

crucial for their distribution. In the Mann–Whitney

U-tests the historical and confirmed ICS sites had

significantly lower stream orders, widths, depths,

velocities and percentages of megalithal than sites

without crayfish. Sites having alien P. leniusculus

differed significantly from sites without crayfish in

terms of altitude, slope, water temperature and stones

in smaller grain sizes. These patterns were also

supported by multivariate analyses, where additional

refuges, woody debris and slope (A. torrentium) were

identified to play a crucial role in crayfish distribution.

Sites with the alien P. leniusculus clearly discrimi-

nated from sites having native crayfish species, but

also showed an overlap within the range of ICS,

especially with A. astacus. This was not surprising, as

A. astacus and P. leniusculus are known to have

similar habitat requirements (Fureder et al., 2006;

Holdich et al., 2006a). These two species inhabit both

lentic and lotic waters to the same extent (Holdich

et al., 2006a), while A. torrentium is rarely found in

lake habitats (Fureder et al., 2006). Most of the lakes in

Carinthia are now having P. leniusculus instead of A.

astacus and are the source of migrations into streams

(Weinlander & Fureder, 2009). Only a few smaller and

isolated lakes with low anthropogenic impacts (e.g.

fishery, recreation) remained unaffected, still func-

tioning as refuge sites for A. astacus.

Since its introduction P. leniusculus has continued

to colonise wide parts of the investigated catchments

in Carinthia thereby overcoming considerable altitu-

dinal differences. This has dramatic consequences for

the stream populations of A. astacus, as its main

distribution is found at lower altitudes in Carinthia

(Petutschnig, 2002). A similar situation was found in

the A. torrentium stocks, where the population loss

was also more apparent at lower altitudes, while

isolated headwaters with steep gradients were spared

from population decline. In the present study, A. tor-

rentium was found from 370 to 1,100 m a.s.l. and

therefore occupying the highest situated sites in the

investigation area. This crayfish species is reported to

naturally occur up to 1,700 m a.s.l. in Europe (Mach-

ino & Fureder, 2005). This may be beneficial to

prevent or at least slow down future signal crayfish

invasions in A. torrentium habitats. In Europe A. asta-

cus is mainly found in lowlands and hills below 800 m

a.s.l, but in exceptional cases it was introduced in

altitudes up to 1,700 m a.s.l. in Switzerland (Fureder

et al., 2006). In Austria, the highest situated estab-

lished population is found above 1,500 m a.s.l, where

it was stocked in a lake (Patzner et al., 2005), although

1.0-1.0

1.0

-1.0

ASA

AUTPAL

altitude

slope

stream order

widthdepth

velocity

temperature

megalithal macrolithal

mesolithal

microlithal

akal

sand and mud

woody debris

macrophytes

bryophytes

refuges

SPECIES

ENV. VARIABLES

SAMPLES

ASA

AUT

PAL

Fig. 4 Redundancy

analysis (RDA) triplot (first-

and second-axes) showing

the distribution of the

investigated crayfish species

and sampling sites (ASAA. astacus, AUT A.torrentium, PAL P.leniusculus) in relation to

the measured habitat

features. Axis 1 is explaining

32 % of the variance in the

species data, while 8.4 % is

explained by axis 2

244 Hydrobiologia (2012) 693:237–249

123

Table 2 Significant habitat features detected from single logistic regression for each crayfish species with Wald statistics and

maximum likelihood ratio test (G)

Coefficient SE Wald P G P

Astacus astacus

Constant 0.81 0.628 1.664 0.197

Stream order -0.744 0.239 9.69 0.002 14.211 \0.001

Constant 0.199 0.557 0.128 0.72

Velocity -3.729 1.395 7.151 0.007 8.643 0.003

Constant -6.3 1.681 14.041 \0.001

Temperature 0.287 0.0918 9.743 0.002 11.002 \0.001

Constant -0.247 0.352 0.492 0.483

Megalithal -0.246 0.0851 8.351 0.004 16.449 \0.001

Constant -0.166 0.422 0.156 0.693

Macrolithal -0.0831 0.0308 7.258 0.007 9.955 0.002

Constant -2.659 0.66 16.247 \0.001

Microlithal 0.0597 0.0236 6.405 0.011 7.138 0.008

Constant -0.724 0.305 5.647 0.017

Bryophytes -1.95 0.792 6.063 0.014 8.569 0.003

Austropotamobius torrentium

Constant -1.118 0.286 15.247 \0.000

Slope 0.249 0.0746 11.153 \0.001 18.352 \0.001

Constant 2.091 0.565 13.718 \0.001

Stream order -0.91 0.205 19.643 \0.001 30.909 \0.001

Constant 1.046 0.384 7.43 0.006

Width -0.397 0.117 11.495 \0.001 31.976 \0.001

Constant 2.189 0.601 13.244 \0.001

Depth -0.0938 0.0227 17.028 \0.001 33.399 \0.001

Constant 0.745 0.475 2.461 0.117

Velocity -2.724 1.058 6.625 0.01 7.722 0.005

Constant 0.0945 0.283 0.111 0.739

Megalithal -0.0722 0.0326 4.901 0.027 6.604 0.01

Constant -1.494 0.464 10.364 0.001

Woody debris 0.102 0.038 7.19 0.007 8.546 0.003

Constant -2.707 0.663 16.681 \0.001

Refuges 0.0638 0.0166 14.835 \0.001 18.878 \0.001

Pacifastacus leniusculus

Constant 2.609 0.82 10.127 0.001

Altitude -0.0046 0.00155 8.764 0.003 9.446 0.002

Constant 0.733 0.239 9.399 0.002

Slope -0.498 0.185 7.291 0.007 11.604 \0.001

Constant -3.024 1.203 6.322 0.012

Temperature 0.191 0.0704 7.378 0.007 8.621 0.003

Constant 0.547 0.219 6.243 0.012

Bryophytes -0.823 0.357 5.298 0.021 5.387 0.02

Hydrobiologia (2012) 693:237–249 245

123

also here the main distribution of this species is found

at much lower altitudes (Fureder, 2009). In the recent

study, however, A. astacus was found in streams from

350 to 800 m a.s.l., while it was stocked in lentic

waters up to 1,100 m a.s.l. in Carinthia (Petutschnig,

2002). Although P. leniusculus exists in lakes at

1,900 m a.s.l. in North America (Abrahamsson &

Goldman, 1970), the highest situated P. leniusculus

population in Europe as far as we know is reported

from Carinthia, where it was stocked in a lake at nearly

1,400 m a.s.l. (G. Vogel, pers. comm.). In the present

study, P. leniusculus was found in streams from 340 to

nearly 700 m a.s.l.

Even though water temperature is correlated with

altitude it seems that it plays a more important role in

limiting crayfish distribution than altitude. In our

study, A. astacus and P. leniusculus were associated to

moderate water temperatures. During the summer

months, A. astacus needs a water temperature of at

least 15 �C (Hager, 1996) and P. leniusculus is also

predicted to be absent in streams with summer water

temperatures below 14.5 �C (Usio et al., 2006). In

Carinthia, P. leniusculus was found in streams with

summer water temperatures of 13.1 �C, but in 90 % of

the cases water temperatures exceeded 15 �C with a

maximum at 26 �C. Abrahamsson & Goldberg (1970)

showed that female signal crayfish did not hatch at

average water temperatures of 6.8 �C. This study

identified cold water temperatures as a biological limit

for the reproduction success of P. leniusculus, which

should be relevant in a mountainous region like

Carinthia. According to these findings A. torrentium

should be more protected due to its occurrence in

cooler streams with steep gradients at higher altitudes

(Machino & Fureder, 2005). Although these authors

identify A. torrentium as a rheophilic crayfish species

in general, other studies showed that the stone crayfish

prefers areas with the lowest velocities in streams

(Streissl & Hodl, 2002; Vlach et al., 2009a; Weinlan-

der & Fureder, 2010). In our study, A. torrentium

Table 3 Logistic regression models for native and alien crayfish in Carinthia derived from the best subset selections on all

significant variables from single logistic regression with Goodness-of-fit tests

Coefficient SE Wald P Odds ratio

Astacus astacus

Constant -2.440 1.922

Stream order -0.713 0.241 8.758 0.003 0.490

Temperature 0.212 0.0997 4.514 0.034 1.236

Bryophytes -1.762 0.861 4.193 0.041 0.172

Pearson Chi-square statistic: 101.984 (P = 0.021)

Likelihood ratio test statistic: 29.007 (P B 0.001)

Hosmer–Lemeshow statistic: 17.525 (P = 0.025)

Austropotamobius torrentium

Constant 0.895 1.037

Stream order -0.686 0.209 10.813 \0.001 0.504

Velocity -3.159 1.602 3.888 0.049 0.0425

Refuges 0.0529 0.0192 7.568 0.006 1.054

Pearson Chi-square statistic: 93.385 (P = 0.640)

Likelihood ratio test statistic: 43.063 (P B 0.001)

Hosmer–Lemeshow statistic: 11.713 (P = 0.164)

Pacifastacus leniusculus

Constant -2.183 1.231

Slope -0.461 0.187 6.115 0.013 0.63

Temperature 0.169 0.0709 5.666 0.017 1.184

Pearson Chi-square statistic: 144.341 (P = 0.317)

Likelihood ratio test statistic: 18.004 (P B 0.001)

Hosmer–Lemeshow statistic: 15.432 (P = 0.051)

246 Hydrobiologia (2012) 693:237–249

123

showed negative associations to high velocities, which

often results in patchy distribution patterns in streams

(Machino & Fureder, 2005). This is similar to A.

pallipes, which also prefers to inhabit stretches with

lower velocities (Souty-Grosset et al., 2006).

While A. astacus and P. leniusculus were mostly

associated to moderate water temperatures, the pres-

ence of A. torrentium was more closely related to a

heterogeneous stream morphology, which relates to

the presence of shelters (Streissl & Hodl, 2002;

Weinlander & Fureder, 2010). Laboratory experi-

ments showed that A. torrentium is more dependent on

the presence of refuges and prefers different substrates

than P. leniusculus (Vorburger & Ribi, 1999a, b).

These authors showed that mud is also used as shelter

by P. leniusculus, by burrowing in this soft substrate,

while A. torrentium prefers stones if available. This

might be a reaction caused by their occurrence in more

turbulent streams (Machino & Fureder, 2005), where

soft substrates are often rare (Weinlander & Fureder,

2010; present study). In the investigated A. torrentium

sites, mud was only present in 19 %, while it was

present in 48 % of the P. leniusculus sites. An

exception was found by Vlach et al. (2009b), who

showed that in rare cases mud can be the main

substrate in A. torrentium streams, which is also the

preferred substrate of juvenile stone crayfish (We-

inlander & Fureder, 2010). Holdich et al. (2006b)

showed that A. pallipes is able to colonise muddy

streams in numbers, when submerged roots from the

riparian vegetation act as shelters.

Austropotamobius torrentium was positively and

alien P. leniusculus negatively associated to higher

altitude sites with steep gradients. This is in accor-

dance with other studies, which showed that

P. leniusculus is more likely to occur in low gradient

streams (Light, 2003) with moderate water tempera-

tures (Usio et al., 2006). However, Light (2003) also

showed that established signal crayfish populations

were not able to colonise stream sections upstream of

natural and artificial barriers. Surprisingly, we found

one juvenile signal crayfish on the top of a weir, which

proved that this kind of obstacles cannot really stop

upstream movements of P. leniusculus.

In conclusion, our results suggest that alien P.

leniusculus is an opportunistic crayfish species and can

exist in a wider range of stream habitats and physical

conditions than both ICS. These ecological advantages

together with superior biological traits and aggressive

dominance of P. leniusculus over both ICS will further

increase the invasiveness of the alien and the decline

of endangered A. astacus and A. torrentium. As

P. leniusculus is a potential carrier of the crayfish

plague (Oidtmann et al., 2002), it is urgently necessary

to gain knowledge about its ecological and biological

distribution limits in Europe. This information is

essential to establish further conservation and reintro-

duction plans for the remaining ICS populations

(Souty-Grosset & Reynolds, 2009), as the complete

eradication of established NICS populations is impos-

sible up to now and even their control is difficult to

achieve (Freeman et al., 2010). The identification of

refuge areas, where gene pools of native crayfish

species can be established, seems to be the only

possibility to preserve the remaining ICS populations

in Europe and Carinthia. In addition information from

the fishery authorities, fishermen and general public is

needed, to reveal the threats, which are associated to

crayfish plague and its transmission with alien crayfish

species. The present study provided important infor-

mation on the associations between the distribution of

native A. astacus and A. torrentium, as well as alien

P. leniusculus and stream habitats. These results can

be used to identify suitable refuge areas for the

imperiled ICS and to predict the potential range of the

alien P. leniusculus in streams. Reintroductions in

appropriate stream habitats, isolated from NICS and

with low anthropogenic impact, could function as

protection areas. For the Carinthian situation, an

identification of potential refuge sites and threats on

a landscape level considering habitat suitability of

native and alien crayfish species, fragmentation and

land use is currently carried out.

Acknowledgments This study was financially supported by the

University of Innsbruck (PhD scholarship) and the Natural Science

Association of Carinthia (NWV), Austria. We thank especially

Jurgen Petutschnig, Wolfgang Honsig-Erlenburg and the numerous

fishery authorities for providing information on historical and

current crayfish distribution and the Carinthian government

(Abt.20: Landesplanung, UAbt.Raumordnungskataster—KAGIS,

Abt. 18: Wasserwirtschaft) for GIS-layers. We are grateful to

Brigitte Weinlander and Josef Weinlander sen. and jun. for their

assistance during field work.

References

Abrahamsson, A. A. & C. R. Goldman, 1970. Distribution,

density and production of the crayfish Pacifastacus

Hydrobiologia (2012) 693:237–249 247

123

leniusculus Dana in Lake Tahoe, California, Nevada.

Oikos 21: 83–91.

Acosta, C. A. & S. A. Perry, 2000. Effective sampling area: a

quantitative method for sampling crayfish populations in

freshwater marshes. Crustaceana 73: 425–431.

Creed, R. P., 1994. Direct and indirect effects of crayfish grazing

in a stream community. Ecology 75: 2091–2103.

Edsman, L., L. Fureder, F. Gherardi & C. Souty-Grosset, 2010.

Astacus astacus. In IUCN 2011. IUCN Red List of

Threatened Species. Version 2011.1 [available on internet

at http://www.iucnredlist.org 09 August 2011].

Favaro, L., T. Tirelli & D. Pessani, 2010. The role of water

chemistry in the distribution of Austropotamobius pallipes(Crustacea Decapoda Astacidae) in Piedmont (Italy).

Comptes Rendus Biologies 333: 68–75.

Freeman, M. A., J. F. Turnbull, W. E. Yeomans & C. W. Bean,

2010. Prospects for management strategies of invasive

crayfish populations with an emphasis on biological con-

trol. Aquatic Conservation: Marine and Freshwater Eco-

systems 20: 211–223.

Fureder, L. & C. Souty-Grosset, 2005. European native crayfish

in relation to land-use and habitat deterioration with a

special focus on Austropotamobius torrentium. Bulletin

Francais de la Peche et de la Pisciculture 376–377:

487–848.

Fureder, L., L. Edsman, D. M. Holdich, P. Kozak, Y. Machino,

M. Pockl, B. Renai, J. D. Reynolds, H. Schulz, D. Sint, T.

Taugbøl & M. C. Trouilhe, 2006. Indigenous crayfish

habitat and threats. In Souty-Grosset, C., D. M. Holdich,

P. Y. Noel, J.D. Reynolds & P. Haffner (eds), Atlas of

Crayfish in Europe. Museum national d’ Histoire naturelle,

Patrimoines naturels 64, Paris, France: 25–48.

Fureder, L., 2009. Flusskrebse: Biologie-Okologie-Gefahrdung.

Folio, Wien/Bozen und Naturmuseum Sudtirol, Austria/

Italy.

Fureder, L., F. Gherardi & C. Souty-Grosset, 2010. Austropot-amobius torrentium. In IUCN 2011. IUCN Red List of

Threatened Species. Version 2011.1 [available on internet

at http://www.iucnredlist.org 09 August 2011].

Gherardi, F., 2007. Biological invaders in inland waters: pro-

files, distribution and threats. Springer, Dordrecht.

Gherardi, F. & P. Acquistapace, 2007. Invasive crayfish in

Europe: the impact of Procambarus clarkii on the littoral

community of a Mediterranean lake. Freshwater Biology

52: 1249–1259.

Gherardi, F., S. Bertolino, M. Bodon, S. Casellato, S. Cianfa-

nelli, M. Ferraguti, E. Lori, G. Mura, A. Nocita, N. Ric-

cardi, G. Rossetti, E. Rota, R. Scalera, S. Zerunian & E.

Tricarico, 2008. Animal xenodiversity in Italian inland

waters: distribution, modes of arrival, and pathways. Bio-

logical Invasions 10: 435–454.

Gil-Sanchez, J. M. & J. Alba-Tercedor, 2002. Ecology of the

native and introduced crayfishes Austropotamobius palli-pes and Procambarus clarkii in southern Spain and

implications for conservation of the native species. Bio-

logical Conservation 105: 75–80.

Hager, J., 1996. Edelkrebse: Biologie, Zucht, Bewirtschaftung.

Leopold Stocker, Graz-Stuttgart, Austria/Germany.

Holdich, D. M., P. Haffner, P. Noel, J. Carral, L. Fureder, F.

Gherardi, Y. Machino, J. Madec, M. Pockl, P. Smietana, T.

Taugbøl & E. Vigneux, 2006a. Species Files. In Souty-

Grosset, C., D. M. Holdich, P. Y. Noel, J. D. Reynolds &

P. Haffner (eds), Atlas of Crayfish in Europe. Museum

national d’ Histoire naturelle, Patrimoines naturels 64,

Paris, France: 49–131.

Holdich, D. M., S. Peay, J. Foster, P. D. Hiley & J. H. Brickland,

2006b. Studies on the white-clawed crayfish (Austropot-amobius pallipes) associated with muddy habitats. Bulletin

Francais de la Peche et de la Pisciculture 380–81:

1055–1078.

Holdich, D. M., J. D. Reynolds, C. Souty-Grosset & P. J. Sibley,

2009. A review of the ever increasing threat to European

crayfish from non-indigenous crayfish species. Knowledge

and Management of Aquatic Ecosystems 394–395: 11.

Honsig-Erlenburg, W. & N. Schulz, 1996. Die Flußkrebse des

Lavanttales. In Wieser, G. (ed.), Die Gewasser des La-

vanttales. Naturwissenschaftlicher Verein fur Karnten,

Klagenfurt: 91–95.

Honsig-Erlenburg, W. & W. Petutschnig, 2002. Fische, Neun-

augen, Flusskrebse, Großmuscheln. Sonderreihe des Na-

turwissenschaftlichen Vereins fur Karnten, Klagenfurt.

Hosmer, D. W. & S. Lemeshow, 2000. Applied logistic regres-

sion. Wiley-Interscience Publication, Wiley, New York.

Hudina, S., M. Faller, A. Lucic, G. Klobucar & I. Maguire, 2009.

Distribution and dispersal of two invasive crayfish species

in the Drava River basin, Croatia. Knowledge and Man-

agement of Aquatic Ecosystems 394–395: 09.

Leps, J. & P. Smilauer, 2003. Multivariate Analysis of Eco-

logical Data Using Canoco. Cambridge, UK.

Light, T., 2003. Success and failure in a lotic crayfish invasion:

the roles of hydrologic variability and habitat alteration.

Freshwater Biology 48: 1886–1897.

Machino, Y. & L. Fureder, 2005. How to find a stone crayfish

Austropotamobius torrentium (Schrank, 1803): a biogeo-

graphic study in Europe. Bulletin Francais de la Peche et de

la Pisciculture 376–377: 507–517.

Naura, M. & M. Robinson, 1998. Principles of using river

habitat survey to predict the distribution of aquatic species:

an example applied to the native white-clawed crayfish

Austropotamobius pallipes. Aquatic Conservation: Marine

and Freshwater Ecosystems 8: 515–527.

Nystrom, P., 1999. Ecological impact of introduced and native

crayfish on freshwater communities: European perspec-

tives. In Gherardi, F. & D. M. Holdich (eds), Crayfish in

Europe as Alien Species. Crustacean Issues 11. AA Balk-

ema, Rotterdam, Netherlands: 63–86.

Oidtmann, O., D. Heitz, D. Rogers & R. W. Hoffmann, 2002.

Transmission of crayfish plague. Diseases of Aquatic

Organisms 52: 159–167.

ONORM M 6232, 1995. Richtlinien fur die okologische Un-

tersuchung und Bewertung von Fließgewassern. Osterrei-

chisches Normungsinstitut, Wien.

Parvulescu, L., O. Pacioglu & C. Hamchevici, 2011. The

assessment of the habitat and water quality requirements of

the stone crayfish (Austropotamobius torrentium) and

noble crayfish (Astacus astacus) species in the rivers from

the Anina Mountains (SW Romania). Knowledge and

Management of Aquatic Ecosystems 401: 03.

Patzner, R. A., S. Langmaier, S. Schacherl, A. Strasser &

D. Zick, 2005. Distribution of crayfish in Salzburg, Austria.

Bulletin Francais de la Peche et de la Pisciculture 376–377:

539–546.

248 Hydrobiologia (2012) 693:237–249

123

Peay, S., 2009. Invasive non-indigenous crayfish species in

Europe: recommendations on managing them. Knowledge

and Management of Aquatic Ecosystems 394–395: 03.

Petutschnig, J., 1997. Die Flusskrebsvorkommen. In Honsig-

Erlenburg, W. & G. Wieser (eds), Die Gurk und ihre Sei-

tengewasser. Naturwissenschaftlicher Verein fur Karnten,

Klagenfurt: 108–112.

Petutschnig, J., 2002. Flusskrebse. In Honsig-Erlenburg, W. &

W. Petutschnig (eds), Fische, Neunaugen, Flusskrebse,

Großmuscheln. Sonderreihe des Naturwissenschaftlichen

Vereins fur Karnten, Klagenfurt: 167–185.

Rodriguez, C. F., E. Becares & B. Fuertes, 2006. Comparison of

the impact of the freshwater decapod species Austropot-amobius pallipes (indigenous) and Procambarus clarkii(non-indigenous), on the submerged vegetation of two

Mediterranean wetlands. Freshwater Crayfish 15:

166–175.

Sampl, H., 1976. Die Natur Karntens. Heyn, Klagenfurt.

Smith, G. R. T., M. A. Learner, F. M. Slater & J. Foster, 1996.

Habitat features important for the conservation of the

native crayfish Austropotamobius pallipes in Britain. Bio-

logical Conservation 75: 239–246.

Souty-Grosset, C., D. M. Holdich, P. Y. Noel, J. D. Reynolds &

P. Haffner, 2006. Atlas of Crayfish in Europe. Museum

national d’ Histoire naturelle, Patrimoines naturels 64,

Paris, France.

Souty-Grosset, C. & J. D. Reynolds, 2009. Current ideas on

methodological approaches in European crayfish conser-

vation and restocking procedures. Knowledge and Man-

agement of Aquatic Ecosystems 394–395: 01.

Spitzy, R., 1973. Crayfish in Austria, history and actual situa-

tion. Freshwater Crayfish 1: 8–14.

Statzner, B., E. Fievet, J. Y. Champagne, R. Morel & E. Her-

ouin, 2000. Crayfish as geomorphic agents and ecosystem

engineers: biological behavior affects sand and gravel

erosion in experimental streams. Limnology and Ocean-

ography 45: 1030–1040.

Stenroth, P. & P. Nystrom, 2003. Exotic crayfish in a brown

water stream: effects on juvenile trout, invertebrates and

algae. Freshwater Biology 48: 466–475.

Strayer, D. L., 2010. Alien species in freshwaters: ecological

effects, interactions with other stressors, and prospects for

the future. Freshwater Biology 55: 152–174.

Streissl, F. & W. Hodl, 2002. Habitat and shelter requirements of

the stone crayfish Austropotamobius torrentium Schrank.

Hydrobiologia 477: 195–199.

Usio, N., H. Nakajima, R. Kamiyama, I. Wakana, S. Hiruta & N.

Takamura, 2006. Predicting the distribution of invasive

crayfish (Pacifastacus leniusculus) in a Kusiro Moor marsh

(Japan) using classification and regression trees. Ecologi-

cal Research 21: 271–277.

Vlach, P., D. Fischer & L. Hulec, 2009a. Microhabitat prefer-

ences of the stone crayfish Austropotamobius torrentium(Schrank, 1803). Knowledge and Management of Aquatic

Ecosystems 394–395: 15.

Vlach, P., L. Hulec & D. Fischer, 2009b. Recent distribution,

population densities and ecological requirements of the

stone crayfish (Austropotamobius torrentium) in the Czech

Republic. Knowledge and Management of Aquatic Eco-

systems 394–395: 13.

Vorburger, C. & G. Ribi, 1999a. Aggression and competition for

shelter between a native and an introduced crayfish in

Europe. Freshwater Biology 42: 111–119.

Vorburger, C. & G. Ribi, 1999b. Pacifastacus leniusculus and

Austropotamobius torrentium prefer different substrates.

Freshwater Crayfish 12: 696–704.

Weinlander, M. & L. Fureder, 2009. The continuing spread of

Pacifastacus leniusculus in Carinthia (Austria). Knowl-

edge and Management of Aquatic Ecosystems 394–395:

17.

Weinlander, M. & L. Fureder, 2010. The ecology and habitat

requirements of Austropotamobius torrentium (Schrank,

1803) in small forest streams in Carinthia (Austria).

Freshwater Crayfish 17: 221–226.

Wintersteiger, M. R., 1985. Flußkrebse in Osterreich: Studie zur

gegenwartigen Verbreitung der Flußkrebse in Osterreich

und zu den Veranderungen ihrer Verbreitung seit dem

Ende des 19. Jahrhunderts – Ergebnisse limnologischer

und astacologischer Untersuchungen an Krebsgewassern

und Krebsbestanden. PhD thesis, Salzburg University,

Austria.

Zuther, S., H. K. Schulz, A. Lentzen-Godding & R. Schulz,

2005. Development of a habitat suitability index for the

noble crayfish Astacus astacus using fuzzy modeling.

Bulletin Francais de la Peche et de la Pisciculture 376–377:

731–742.

Hydrobiologia (2012) 693:237–249 249

123