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13
Bull. Fish Biol. 17 (1/2)
Bulletin of Fish Biology Volume 17 Nos. 1/2 30.12.2017 13-27
Feral guppies in Germany – a critical evaluation of a citizen
science approach as biomonitoring tool
Verwilderte Guppys in Deutschland – eignet sich Citizen Science
zum Aufspüren invasiver Arten?
Juliane Lukas1,2 *, Gregor Kalinkat1, Michael Kempkes3, Udo Rose4, David Bierbach1
1Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Department of Biology
and Ecology of Fishes, Mueggelseedamm 310, D-12587 Berlin, Germany
2Humboldt University of Berlin, Faculty of Life Sciences, Invalidenstrasse 42, D-10115 Berlin, Germany
3Jenaer Weg 5, D-46397 Bocholt, Germany
4Erftverband, Am Erftverband 6, D-50126 Bergheim, Germany
*Corresponding author: contact@julianelukas.com
Summary: Biologic al invasions continue to grow at a rapid rate, fuelling the need for effective and feasible
biomonitoring approaches. Citizen science is an increasingly popular way of undertaking long-term and/
or large-scale monitoring while simultaneously engaging people with science and scientifi c issues. In tem-
perate regions, industrially created thermal pollution of freshwater systems provides suitable conditions
for (sub)tropical neobiota to survive harsh winter months and establish populations. Here, we present a
citizen science project designed to collect data on feral populations of guppies (Poecilia reticulata) and other
ornamental fi shes in Germany. So far, only one established population has been described for Germany,
residing in the thermally altered Gillbach-Erft river system near Cologne. Yet, most thermal power plants
use water as a cooling medium, thus increasing the probability that more thermally infl uenced freshwater
systems (TIFs) exist across Germany. With our large-scale approach, we were able to identify two additional
locations with non-native (sub)tropical fi sh currently established and compile more data on now extinct
populations of P. reticulata. Further, we present evidence that – as in the case of the Gillbach/Erft – these
phenomena are most likely very localized, as they are solely dependent on the presence of thermal refugia.
However, we call for continuous monitoring of these TIFs, especially in the light of disease and parasite
transmission to the native fauna.
Keywords: Thermally infl uenced freshwaters, citizen science, invasive alien species, non-native species,
aquarium trade, thermal pollution, Poecilia reticulata
Zusammenfassung: Biologische Invasionen nichteinheimischer Arten nehmen weiterhin zu und verstär-
ken damit die Notwendigkeit für effektive und praktikable Ansätze zur Überwachung und Aufzeichnung
von Invasionsereignissen und -prozessen. Wissenschaftliche Bürgerbeteiligung, besser bekannt als ‚Citizen
Science’, bietet die Möglichkeit, langfristige und/oder groß angelegte Monitoringstudien durchzuführen und
gleichzeitig Mitbürger in wissenschaftliche Themen und Problematiken einzubeziehen. In den gemäßigten
Breiten führt das Einleiten von industriell erzeugtem warmem Abwasser in Flüsse und Bäche dazu, dass
sich nichtheimische (sub)tropische Neobiota trotz der oftmals harschen Wintertemperaturen dauerhaft
ansiedeln können. Hier präsentieren wir ein Citizen-Science-Projekt, das dazu entwickelt wurde, Daten
über das Vorkommen von wilden Populationen von Guppys (Poecilia reticulata) und anderen Zierfi schen in
Deutschland zu sammeln. Bisher war nur eine Guppypopulation in Deutschland beschrieben, die sich im
thermisch belasteten Gillbach-Erft-Flusssystem in der Nähe von Köln etabliert hat. Allerdings nutzen viele
Kraftwerke Wasser als Kühlmedium und somit ist die Wahrscheinlichkeit hoch, dass mehr solcher thermisch
belasteten Süßwassersysteme (TIFs) innerhalb Deutschlands existieren. Im Laufe des Projekts konnten wir
zwei weitere Gebiete mit etablierten (sub)tropischen Fischen identifi zieren und zusätzliche Daten über bereits
ausgestorbene Populationen zusammentragen. Nach unserer Einschätzung sind solche Refugien – wie im
14
Falle des Gillbachs – höchstwahrscheinlich nur lokal begrenzte Phänomene, da sie von der stetigen Warm-
wassereinleitung abhängen. Dennoch fordern wir eine kontinuierliche Überwachung solcher Systeme, vor
allem angesichts der Tatsache, dass die Übertragung von Erkrankungen und Parasiten auf die einheimische
Fauna bereits vereinzelt nachgewiesen worden konnte.
Schlüsselwörter: Thermisch belastete Süßwassersysteme, wissenschaftliche Bürgerbeteiligung, invasive
fremde Arten, nichteinheimische Arten, Zierfi schhandel, thermische Belastung, Poecilia reticulata
rare organisms, such as newly-arrived neobiota
(e.g. ‘Check, Clean, Dry’, Invasive Tracers,
SeaLifeTracker, AquaInvaders; see appx. 1)
and disappearing native species (e.g. ‘The Lost
Ladybug Project’; see appx. 1).
The aquarium trade has been recognized as
an important source for species introductions
on a global scale (PADILLA & WILLIAMS 2004;
DUGGAN et al. 2006; GERTZEN et al. 2008; COPP
et al. 2010; STRECKER et al. 2011; MACEDA-VEIGA
et al. 2013; KALOUS et al. 2015; SEEBENS et al.
2016; ZIERITZ et al. 2016; LUKAS et al. 2017).
A study investigating main pathways of intro-
ductions of freshwater non-natives in Europe
showed that the release of pets was only second
to aquaculture in terms of biological introduc-
tions caused (NUNES et al. 2015). Most released
aquarium species have (sub)tropical origins and
thus are unable to survive winter temperatures in
temperate regions, such as Germany. However,
as these thermal constraints start to diminish
with climate change, the likelihood for non-
natives to persist, establish and eventually spread
increases (RIXON et al. 2005). In fact, some
freshwaters already experience increases in water
temperatures that are consistent with climate
change projections due to thermal pollution
(e.g. Rivers Mississippi, Rhine and Weser; RAP-
TIS et al. 2016). In the case of the River Rhine,
richness and abundance of non-native species
has increased continuously since the early 20th
century (LEUVEN et al. 2009; PANOV et al. 2009).
Nevertheless, water temperatures in the Rhine
can drop to below 4 °C in winter (e.g. January
2017 near Düsseldorf-Flehe; LANUV 2017) and
thus most non-natives of (sub)tropical origin do
not survive. Some often overlooked areas, where
non-native species might survive the harsh win-
ter months, are thermally infl uenced freshwater
systems (TIFs, also termed thermally altered
1. Introduction
Invasive species are drivers of global environ-
mental change (SALA et al. 2000; CLAVERO &
GARCIA-BERTHOU 2005; SCHRÖTER et al. 2005;
SHVIDENKO et al. 2005; BUTCHART et al. 2010),
which in its course is likely to drive even more
new invasions (WALTHER et al. 2002; PARMESAN
& YOHE 2003; RIXON et al. 2005; HICKLING et
al. 2006; BRITTON et al. 2010). When managing
non-native species, one of the top issues identi-
fi ed is a general lack of awareness and education
(CAFFREY et al. 2014; PIRIA et al. 2017). In fact,
some non-native species remain undetected
or are detected only after their successful es-
tablishment (e.g. GELLER et al. 1997; LOHRER
2001). Control measures are most effective
when intervening at an early stage of invasion,
thus a timely detection and rapid response are
pivotal to the success of most management
actions (BAX et al. 2001; CAMBRAY 2003; COPP et
al. 2005a, b; VERBRUGGE et al. 2014). Monitoring
efforts increase the chance of early detection
(MYERS et al. 2000; BAX et al. 2001; LODGE et al.
2006) and the collection of spatial and temporal
information of species’ ranges – native and non-
native alike – are integral to this feat (RICCIARDI
et al. 2000). Yet, the intensity of biomonitoring
approaches is often limited by the availability of
funding and staff. Volunteer-based monitoring
may be the only practical way to achieve the
reach relevant to species’ range shifts. Over the
past decade, this type of citizen science (see
ROY et al. 2012 for defi nition) has contributed
greatly to the wealth of information available
on spatial variation in colonization/extinction
events (e.g. ROCHA-CAMARERO & DE TRUCIOS
2002; STOHLGREN et al. 2006; ERAUD et al. 2007;
DELANEY et al. 2008; CROWL et al. 2008). In that,
citizen science has proven effective in fi nding
15
Bull. Fish Biol. 17 (1/2)
aquatic systems (TAAS)). These systems are
either heated by natural geothermal sources (e.g.
SPECZIÁR 2004; PETUTSCHNIG et al. 2008; PIAZZINI
et al. 2010; MILENKOVIC et al. 2013; O’GORMAN
et al. 2012, 2014; SAS-KOVACZ et al. 2015) or due
to anthropogenic activities (LANGFORD 1990; SI-
MARD et al. 2012; KLOTZ et al. 2013; COHEN et al.
2014; HUSSNER 2014; JOURDAN et al. 2014; EMDE
et al. 2016; MULHOLLEM et al. 2016; LUKAS et al.
2017). Despite Germany’s Renewable Energy
Sources Act (“Energiewende”), thermal power
stations fuelled by black and brown coal or nu-
clear energy are still abundant. Water is the stan-
dard cooling medium in thermal power plants,
which take it in from nearby rivers and streams
and in a once-through system return it to the
natural environment at a higher temperature.
Maximum discharge temperatures are assigned
with the operation permit and are often based
on recommended best practices. However, the
prescribed maximum temperature difference of
3 K between water upstream and downstream
of the discharge can be – and often is – exceeded
due to permit exceptions (ROSE, pers. communi-
cation 2017). Within their thermal range, these
systems can provide suitable conditions for (sub)
tropical neobiota year-round.
While TIFs exist throughout Germany, most
studies analysing the distribution of non-native
species exempt TIFs from their surveys (e.g. WOL-
TER & RÖHR 2010). So far, the stream Gillbach in
the Rhine/Erft catchment is the only TIF with
established non-natives in Germany that has been
described in the scientifi c literature (KEMPKES et
al. 2009; KLOTZ et al. 2013; JOURDAN et al. 2014;
EMDE et al. 2016; LUKAS et al. 2017). The Gillbach
is exclusively fed by a power plant’s coolant water
discharge and has received attention due to its
established non-native species assemblage (e.g.
Vallisneria spiralis, Neocaridina davidi, Macrobrachium
dayanum, Poecilia reticulata, Amatitlania nigrofasciata,
Oreochromis sp., Pelmatolapia mariae, Ancistrus sp.;
HÖFER & STAAS 1998; KEMPKES et al. 2009;
KLOTZ et al. 2013; JOURDAN et al. 2014; EMDE
et al. 2016; LUKAS et al. 2017). Among them are
species like the guppy and several cichlids, all of
which have a long invasion history all over the
world (WELCOMME 1988; CANONICO et al. 2005;
DEACON et al. 2011). The guppy exhibits parti-
cularly high propagule pressure (LINDHOLM et al.
2005) seeing that only one pregnant female is
needed to establish a whole population (DEACON
et al. 2011). Nevertheless, the Gillbach has been
identifi ed as a rather localized phenomenon with
its (sub)tropical invaders being constrain ed by the
temperature gradient, which is only maintained
over a short distance (KLOTZ et al. 2013; JOURDAN
et al. 2014; LUKAS et al. 2017). However, there
are ecological consequences for the native fl ora
and fauna (e.g. introduction of non-native para-
sites; EMDE et al. 2016) that call for continuous
monitoring of the Gillbach and similar systems.
Outside of the scientifi c community, infor mation
of (sub)tropical species are circulating – whether
it is the sensationalism of piranhas being landed
by anglers capturing the headlines of local press
(ANONYMOUS 2007) or fi sh enthusiasts sharing
video observations of feral aquarium fi sh found
in local creeks (see appx. 2). Also, the aquarium
magazine ‘DATZ – Die Aquarien- und Terrari-
enzeitschrift’ pub lished several articles about the
Gillbach (KEMPKES 2002, 2005, 2011; MENDAX
2011; ROSE 2012).
Given the novelty of the idea that thermally
infl uenced freshwaters serve as hotspots for
non-native species (GOLLASCH & NEHRING 2006;
EMDE et al. 2016) and the scarcity of knowledge
we have about them, this study was designed to
(1) investigate whether more thermal refuges
for warm-adapted freshwater fi sh exist (or have
previously existed) throughout Germany. This
spatial and temporal baseline data could then be
used to further instigate long-term monitoring
efforts and management decisions. Further, we
wanted to engage the public and (2) raise aware-
ness for the issue of petfi sh release by aquarium
hobbyists and its consequences.
2. Material and Methods
According to POCOCK et al. (2014a, b) citizen s
are motivated to participate in science through
interest, curiosity, fun or concern. Local natu-
ralists and conservation organisations (e.g. The
Nature and Biodiversity Conservation Union
‘NABU’) can easily be engaged, because they
16
already have a strong interest in invasive non-
native species and the management thereof.
Aquarium fi sh clubs and associations are equally
aware of the subject. Ornamental trade is a main
introduction pathway for non-natives (PADILLA
& WILLIAMS 2004; EMDE et al. 2016; LUKAS et
al. 2017), so many clubs are educating their
members that aquarium releases can be harmful
to the local fl ora and fauna and are prohibited
by Germany’s animal welfare laws (§3 Abs. 3,
4 TIERSCHG). Further, some aquarists harbour
a great curiosity for novelty strains, such as
feral populations of guppies (fi g. 1) and other
ornamental fi sh, making them a great resource
in terms of biomonitoring.
To reach our identifi ed target audience, we
approached four of the most widely distributed
aquarium magazines in Germany with a pro-
posal for a citizen science project. Our project
was met with enthusiasm and three out of the
four editors contacted published a small article
stating our objectives and means of contact in
their upcoming issues. Within a span of three
months, our letter to the readership was printed
in the ‘Aquaristik Fachmagazin’ [Oct/Nov 2016
(LUKAS & BIERBACH 2016a)], ‘Amazonas’ [Sep/
Oct 2016 (LUKAS & BIERBACH 2016b)] and the
‘DATZ – Die Aquarienzeitschrift’ [Aug 2016 (LU-
KAS & BIERBACH 2016c)]. Each of these magazines
has a print run of approximately 20,000, 15,000
and 3,500 copies, respectively. Additionally, our
article was published in the newsletters of three
aquarium fi sh societies [Association of German
Clubs for Aquarium and Terrarium Care (VDA),
German Society for Livebearers (DGLZ) and
viviparos – the German Livebearer Working
group]. We chose the guppy (Poecilia reticulata
Peters, 1859) as an ambassador for our message
Fig. 1: Specimens of feral guppies retrieved from the Gillbach population in 2016. Both females (A) and
males (B) show a great variation in live coloration, typical for fi sh of the ornamental trade.
Abb. 1: Guppys, die im Jahr 2016 aus dem Gillbach entnommenen wurden. Weibchen (A) und Männchen
(B) zeigen ein großes Farbspektrum, typisch für Fische aus dem Aquarienhandel.
17
Bull. Fish Biol. 17 (1/2)
(also referred to as ‘fl agship species’; VERÍSSIMO
et al. 2011; KALINKAT et al. 2017), seeing that the
species is very popular with aquarists, which is
directly linked to its invasion success worldwide
(FROESE & PAULY 2017). As a visual stimulus, we
included a picture of a pair of feral guppies ob-
tained from the Gillbach in the letter. We quickly
summarized the research previously conducted at
the Gillbach and its implications for research on
climate change and biological invasions. Further,
we stated our objective to gather information
about similar systems, which harbour non-native
species in Germany. As a call to action, we asked
readers to send in any information they might
have on feral populations of guppies and other
(sub)tropical fi sh via a mail address specifi cally
activated for the project, associated with the
Leibniz-Institute of Freshwater Ecology and
Inland Fisheries. To further motivate readers and
incentivise reporting, we advertised a prize draw
of the popular aquarist books “Die Guppys”
volumes 1 and 2 by Michael KEMPKES (2010a, b).
Participants were considered in the price draw,
when their information was submitted to us via
mail by November 30th, 2016.
3. Results
In total, we received eight replies – fo ur were
sub mitted before the end of the deadline and
four additional reports were sent in afterwards
(as of August 2017; see tab. 1) –, all of which
varied greatly in detail and quality. We received
GPS coordinates to two extant guppy popula-
tions in Germany: a thermal spring in Baden-
Württemberg and a former coalmine in the
Saarland, which has been turned into a water
garden for tourism (see fi g. 2). The site now
includes a geothermal plant, whose discharge
heats the water garden before being returned to
the nearby creek at a more ambient temperature.
Two participants verifi ed the establishment of
guppies in the Gillbach-Erft-system (see fi g.
1). Another writer provided us with historical
information of two sites: Wölfersheimer See
and a power plant outlet near Kornwestheim. In
the former, guppies and other neozoans such as
goldfi sh, clown loaches, cichlids, suckermouth
armoured catfi sh and turtles could be found
until the early 1990s. Further, we did receive
information of guppy occurrences in Australia
Tab . 1 : Summary of feral guppy populations recorded in Germany. Adapted from observations compiled
by KEMPKES (2010a). Information received as a result of citizen science are indicated (CS).
Tab . 1 : Zusammenfassung der in Deutschland aufgezeichneten, wilden Guppypopulationen. In Anlehnung
an Ausführungen von KEMPKES (2010a). Informationen, die im Zuge der Citizen-Science-Studie gewonnen
wurden, sind gekennzeichnet (CS).
18
(1980s), Tanzania (1998) and Puerto Rico (cur-
rent). Notably, one participant did specifi cally
point out that no (sub)tropical fi sh species had
established populations in any water bodies of
Lower Saxony.
4. Discussion
The enactment of the legislation on the “Pre-
venti on and management of the introduction
and spread of invasive alien species” (EUROPEAN
UNION 2014) poses an important milestone in
the prevention of their establishment. Yet, the
surveillance needed has to occur at spatial scales
beyond the reach of ordinary research efforts.
Citizen science provides the potential to collect
data across much larger spatio-temporal extents
than would otherwise be feasible. Rising in
prominence (SILVERTOWN 2009; DICKINSON et al.
2012), citizen science covers a wide range of taxa
(see DICKINSON et al. 2010 for review). Among
the most successful are targeted monitoring
projects, where species are prioritized based
on their taxonomy, endemic status, sensitivity
to threats and/or public interest (YOCCOZ et al.
2001). For example, citizen science data have
enabled researchers to identify areas harbou-
ring non-native birds in the continental United
States and Hawaii (STOHLGREN et al. 2006; CROWL
et al. 2008). In Europe, thermally infl uenced
freshwaters have been identifi ed as hotspot for
non-native fi sh species of (sub)tropical origin
(SPECZIÁR 2004; PIAZZINI et al. 2010; PETUTSCH-
NIG et al. 2008; MILENKOVIC et al. 2013; JOURDAN
et al. 2014; SAS-KOVACZ et al. 2015; LUKAS et al.
2017). By engaging the public and asking people
to participate in scientifi c research, our aim was
to investigate how frequent these ‘hotspots’
are in Germany. When comparing print ratios
(ranging from 3,500 to 20,000 copies) to the
feedback we received (n = 8), the results of the
survey were slightly puzzling. Several questions
immediately arose:
(i) Are there no other sites with established
(sub)tropical fi sh species? Judging by the amount
of power plants currently employed that use
water as a cooling medium, it is highly likely that
more TIFs exist throughout Germany. In fact,
the cooling ponds of some power plants are
used commercially, rearing fi sh such as sturgeon,
carp, tench, pike and pikeperch to take advantage
of the elevated temperatures (e.g. power plants
Jänschwalde and Biblis [closed 2009]; KLUG
2009). However, the likelihood of (sub)tropical
fi sh persisting remains low, seeing that a species
must pass through a variety of environmental
fi lters to become successfully established in a
new habitat (e.g. VERMEIJ 1996; WILLIAMSON &
FITTER 1996; WILLIAMSON 2006; THEOHARIDES &
DUKES 2007). In aquarium fi sh, the display of
certain traits such as aggressive behaviour, rapid
Fig. 2: Map of Germany and the identifi ed sites cur-
rently harbouring feral populations of (sub)tropical
non-native fi sh. A total of four TIFs with extant
populations of P. reticulata and other (sub)tropical
fi sh taxa were identifi ed (gray; tab.1). Further, popula-
tions that are known to be extinct (†) or whose status
is unknown/could not be verifi ed (?) are indicated.
Abb. 2: Deutschlandkarte und identifi zierte Standor-
te, die derzeit wilde Populationen von gebietsfremden,
(sub)tropischen Fischen beherbergen. Es konnten
gegenwärtig vier thermisch belastete Gewässer mit
Populationen von P. reticulata und anderen (sub)
tropischen Fischarten identifi ziert werden (grau; Tab.
1). Ferner sind ausgestorbene Populationen (†) und
solche, deren Status unbekannt ist/nicht verifi ziert
werden konnte (?), aufgezeigt.
19
Bull. Fish Biol. 17 (1/2)
reproduction, large size or illness increases the
likelihood for intentional release by their owners
(PADILLA & WILLIAMS 2004; DUGGAN et al. 2006;
GERTZEN et al. 2008). Especially the former two
can assist the success of establishment, but to
survive fi sh must tolerate the environmental
conditions at the introduction site. Even within
a thermally infl uenced system, water quality can
be an issue for stenoecious species. Further, they
must succeed in acquiring critical resources and
surviving interactions with natural predators and
competitors. For example, the guppy population
of the Zerkwitzer Kahnfahrt near Cottbus in
Eastern Germany (tab. 1) persisted for about
ten years before it broke down due to a combi-
nation of high predation pressure (most likely
European chub (Squalius cephalus), established
convict cichlids (Amatitlania nigrofasciata) and
several avian predators) and an accident that
caused the nearby power plant to shut down
temporarily (PAEPKE & HEYM 2002). In contrast,
the reported population in the Saarland appears
to be thriving (see appx. 2) and experience only
moderate predation (introduced convict cichlids
(Amatitlania nigrofasciata)). While this too seems
to be a very localized system, we do recommend
continuous monitoring due to its connectivity
to a natural creek and the consequential threat
of disease and parasite transmission.
(ii) Seeing that some TIFs harbour (sub)
tropical fi sh populations, why did they not get
reported? BLACKMORE et al. (2013) recommend-
ed in their Common Cause for Nature report
to not only communicate the objective (why?)
and methodology (how?) of a project, but also
the consequences of the cause (then what?).
Without a clear statement, organisers and vo-
lunteers might pursue different agendas (NER-
BONNE & NELSON 2004), e.g. participants may
expect actions that are beyond the scope of the
project or, in contrast, may face a scenario they
fi nd unacceptable. In light of pan-European
bans for popular but invasive genera such as
the apple snails Pomacea sp. (EUROPEAN UNION
2012) or the marbled crayfi sh Procambarus fallax
f. virginalis (EUROPEAN UNION 2016), participants
may fear that a detection of feral populations
of aquarium fi sh will provoke similar legislative
acts. As a matter of fact, the fact that we receiv-
ed a curious reply solely stating the absence
of any feral fi sh populations in Lower Saxony
may further support this hypothesis. Another
potential explanation is that sites harbouring
guppies are not easily accessible by the public.
While many non-native species tend to invade
highly modifi ed habitats and thus end up in
close proximity to the potential observer, on
average, people are less likely to spend time
around power plants for recreational purposes
such as bathing or hiking. On top, power plant
grounds are often enclosed by security fences,
thus obstructing the access to TIFs that po-
tentially contain non-native species. However,
TIFs can be quite popular among anglers (e.g.
SPIGARELLI 1974). An additional problem is that
potential catchers such as motivated aquarists
are legally hindered on catching fi sh without
a valid fi shing license and thus could only en-
counter potential feral populations of guppies
as by-catch when seeking for natural feed for
their pets (e.g. “Tümpelfutter”).
Ideally, a trigger (= event prompting involve-
ment) should neither be too common nor too
rare to avoid participants feeling overwhelmed
or disengaged (POCOCK et al. 2014a,b). In our
case, while spectacular, the trigger was most
likely too rare, so that most people in our target
audience simply did not possess the desired
information. Lastly, motivation for the project
could be lacking or the audience we engaged
with was too narrow (see GROVE-WHITE et al.
2007). Successful projects may resonate with
people for various reasons (see POCOCK et al.
2014a,b) and in our letter to the readership we
attempted to appeal to people’s sense of place
(“my area”), their pre-existing interest in fi sh
(especially aquarium fi sh) as well as their sense
of discovery (“I had no idea that feral guppies
existed in Germany”) and jeopardy (“My river
might be under threat”).
With hindsight comes insight, so (iii) how
could we improve and structure future projects?
Conservation enthusiasts and organisations
with similar interests (e.g. naturalist societies,
angling associations) have previously expressed
concerns about sightings of invasive non-native
20
species, so could easily be engaged with record-
ing them. Angling associations are already invol-
ved in citizen science, monitoring fi sh catches
and stocking efforts (e.g. ‘Besatzfi sch’, ‘Digitaler
Fischartenatlas’; see appx. 1), as well as assessing
invertebrate abundance and water quality (e.g.
‘Riverfl y Monitoring Intiative’; see appx. 1).
There may be potential for tapping into this,
seeing that anglers regularly visit fi shing spots
and are often well informed about the species
they encounter. Due to the licensing process,
anglers are trained to identify common fi sh
taxa that are of local interest and thus would be
able to identify non-native species more quickly
than laypeople. Furthermore, they often keep
extensive and detailed records, allowing us to
also access historical data. While reports of
anglers landing tilapia and even piranhas in the
Gillbach-Erft river system have made headlines
before, they are, however, unlikely to notice
smaller cichlids (e.g. Amatitlania nigrofasciata,
Hemichromis bimaculatus) or small livebearers such
as guppies, mollies and swordtails. National citi-
zen science project databases (e.g. ‘Portal Bee’,
see appx. 1) can also be useful in widening the
audience, allowing motivated people seeking a
worthy cause to get involved. Further, collabo-
rations with already existing programs can help
to successfully combine engagement and data
gathering to answer a question of shared interest
(see ‘Check, Clean, Dry’). One particularly inter-
esting candidate would be the ‘Ventus’ project
(see appx. 1) that gathers information on power
plants worldwide. They primarily map locations,
but also request other information concerning
carbon dioxide emission via simple form fi lling.
Adding a few questions about the surrounding
water bodies, their fl ora and fauna as well as
their temperature regime could provide valuable
insight for our mission. But even with abundant
data, new issues such as data verifi cation, stor-
age and security arise. For example, an internet
source had reported a feral guppy population in
the thermal springs of Kaiserstuhl near Freiburg
(tab. 1), yet we were unable to verify this infor-
mation. One possible strategy is applied by the
North American Breeding Bird Survey, which
only codes a species “absent” when data on
other parameters or non-focal species has been
submitted for this site. In our case, the status
of this population remains unknown, but many
other TIFs could be eliminated if parameters
such as the water temperature or occurrence of
native species were recorded instead.
(iv) How feasible is such an effort in this
particular case? It is noteworthy, that citizen
science is not free. To make a project successful,
it requires investment in recruiting, motivating
and retaining volunteers, as well as managing and
analysing the data that are produced. Germany’s
goal is to switch off all of its nuclear reactors by
2022 (FEDERAL GAZETTE 2011). In its mission to
signifi cantly reduce greenhouse gas emis sions,
the German government aims to generate 80%
of its electricity from renewables by 2050 (BMWI
2016). Further, many stakeholders call for stricter
regulations on thermal pollution in light of cli-
mate change and recent ecological assessments
(BUND 2009). Current proposals would force
many power plants to return their coolant water
at a temperature equal to the point of collection.
With the future of German TIFs unknown, a
comparison with a similar scenario that occurred
after the German reunifi cation suggests itself.
In the years subsequent to 1989, many Eastern
German power stations were unable to compete
and either went offl ine or where substituted by
newer models that were more effi cient and water
conserving. Consequently, guppy and swordtail
populations that had inhabited outlets of these
power plants (e.g. Lübbenau, Trattendorf; tab.
1) all broke down shortly after. The population
of Lake Wölfersheim met a similar fate as the
power plant Wölfersheim stopped its operations
in 1991. In view of previous developments,
thermal refuges and their non-native inhabitants
are likely to be impacted by the German energy
revolution. With anthropogenic TIFs becoming
increasingly scarcer (WIKIPEDIA 2017), the basis
for the survival of fi sh species from warmer
regions may no longer be a given.
5. Conclusion
With the newest EU legislatio n concerning the
regulation and management of invasive species
21
Bull. Fish Biol. 17 (1/2)
(EUROPEAN UNION 2014), the obligation has
been placed on EU member states to assess key
introduction pathways and develop action plans
for preventive measures. Yet, among the top
challenges faced by this endeavour are insuffi ci-
ent funding and a lack of awareness (CAFFREY et
al. 2014). Citizen science can be a powerful tool
to improve community awareness of biological
invasions and support biomonitoring efforts.
To be successful, however, each project needs
to be carefully tailored to the specifi c issues and
audience it is designed to address. In addition
to the array of studies that have employed
citizen science successfully, several guidelines
and manuals exist that can provide detailed
recommendations and assist in putting projects
into practice (see ROY et al. 2012; TWEDDLE et
al. 2012; POCOCK et al. 2014a, b).
We believe that our study not only high-
lights some of the strengths and limitations
of a citizen science approach, but also gives
more insight to an often overlooked refuge
for (sub)tropical neobiota. Our data – while
sparse – do further support the assumption
that these systems are very localized pheno-
mena (KLOTZ et al. 2013; JOURDAN et al. 2014;
LUKAS et. al. 2017). Historical records of feral
guppies provided us with new examples of
population collapses after thermal pollution
ceased (tab. 1). In light of Germany’s energy
revolution and stricter regulations on thermal
pollution, this seems to be a likely future
scenario for the feral guppy population of
the Gillbach. In place of thermal pollution,
however, climate change might become the
main driver of species’ range shifts and adap-
tive responses. Thus, we call for continuous
monitoring to allow for a timely reaction if
new invaders or detrimental impacts to the
native fl ora and fauna are detected. Further,
we want to encourage more research to take
advantage of these systems, which provide
a unique opportunity to study the impacts
of climate change and species invasion on a
small geographical scale. Lastly, we hope our
efforts could contribute in raising awareness
for the ongoing threat of pet releases and its
implication for the endemic fl ora and fauna.
Acknowledgement
First and fo remost, the authors would like to
thank all the participants, who have contributed
to the study. Further, we express our gratitude
to the editors and aquarium fi sh associations
for supporting the project and publishing our
request. We are grateful to Hans-Joachim PAEP-
KE and Holm ARNDT for their detailed records
and invaluable comments. Lastly, we thank the
anonymous reviewers for their careful reading
and insightful suggestions to our manuscript.
This study received funding by the Gesellschaft
für Ichthyology e.V. (German Ichthyological
Society).
Literature
ANONYMOUS. 2007, Jan 31. Pira nhas aus Rhein-Ne-
benfl uss gefi scht. Focus. Retrieved from http://
www.focus.de /panorama/welt/ueberraschung_
aid_123738.html (Accessed on 31-08-2017).
ARNOLD, A. 1987. Zur Biologie von Koboldkärpfl -
ing, Gambusia affi nis und Guppy, Poecilia reticulata
(Poeciliidae) in europäischen Freilandgewässern.
Aquarien Terrarien 34, 128-131 & 167-170.
ARNOLD, A. 1990. Eingebürgerte Fischarten. Die
Neue Brehm-Bücherei, Bd. 602. A. Ziemsen
Verlag, Wittenberg Lutherstadt.
BAX, N., CARLTON, J.T., MATHEWS-AMOS, A., HAE-
DRICH, R.L., HOWARTH, F.G., PURCELL, J.E., RIESER,
A., & A. GRAY. 2001. The control of biological
invasions in the world’s oceans. Conservation
Biology 15, 1234-1246.
BECKER, W. 1983. Guppys trotz Eis und Schnee.
DGLZ-Rundschau 10, 66-68.
BERND, A. 2003. Neues vom „Guppybach“ bei Köln.
DGLZ-Rundschau 30, 59-63.
BLACKMORE, E., UNDERHILL, R., MCQUILKIN, J., & R.
LEACH. 2013. Common cause for nature: fi nding
values and frames in the conservation sector. Pub-
lic Interest Research Centre, Machynlleth, Wales.
BRITTON, J.R., CUCHEROUSSET, J., DAVIES, G.D.,
GODARD, M.J., & G.H. COPP. 2010. Non-native
fi shes and climate change: predicting species re-
sponses to warming temperatures in a temperate
region. Freshwater Biology 55, 1130-1141.
BMWI – Bundesministerium für Wirtschaft und En-
ergie. 2016. Fifth “Energy Transition” Monitoring
Report The Energy of the Future 2015 Reporting
Year – Summary. Federal Ministry for Econom-
22
ic Affairs and Energy. Retrieved from http://
www.bmwi.de/Redaktion/EN/Publikationen/
monitoring-report-2016-summary.pdf?__blob=-
publicationFile&v=14 (Accessed on 31-08-2017)
BUND – Bund für Umwelt und Naturschutz
Deutschland. 2009. Abwärmelast Rhein. Retrie-
ved from http://cms.bund-hessen.de/hessen
/presse/2009/pm_20090630_bund_waerme_
lang_bild.pdf (Accessed on 31-08-2017)
BUTCHART, S.H., WALPOLE, M., COLLEN, B., VAN STRI-
EN, A., SCHARLEMANN, J.P., ALMOND, R.E., BAILLIE,
J.E., BOMHARD, B., BROWN, C., BRUNO, J., & K.E.
CARPENTER. 2010. Global biodiversity: indicators
of recent declines. Science 328(5982), 1164-1168.
doi:10.1126/science.1187512
CAFFREY, J.M., BAARS, J.-R., BARBOUR, J.H., BOETS, P.,
BOON, P., DAVENPORT, K., DICK, J.T.A., EARLY, J.,
EDSMAN, L., GALLAGHER, C., GROSS, J., HEINIMAA,
P., HORRILL, C., HUDIN, S., HULME, P.E., HYNES,
S., MACISAAC, H.J., MCLOONE, P., MILLANE, M.,
MOEN, T.L., MOORE, N., NEWMAN, J., O’CONCHUIR,
R., O’FARRELL, M., O’FLYNN, C., OIDTMANN, B.,
RENALS, T., RICCIARDI, A., ROY, H., SHAW, R., VAN
VALKENBURG, J.L.C.H., WEYL, O., WILLIAMS, F.,
& F.E. LUCY. 2014. Tackling invasive alien spe-
cies in Europe: the top 20 issues. Management
of Biological Invasions 5, 1-20. http://dx.doi.
org/10.3391/mbi.2014.5.1.01
CAMBRAY, J.A. 2003. Impact on indigenous species
biodiversity caused by the globalisation of alien
recreational freshwater fi sheries. Hydrobiologia
500, 217-230.
CANONICO, G.C., ARTHINGTON, A., MCCRARY, J.K., &
M.L. THIEME. 2005. The effects of introduced tila-
pias on native biodiversity. Aquatic Conservation:
Marine and Freshwater Ecosystems 15, 463-83.
CLAVERO, M.,, & E. GARCÍA-BERTHOU. 2005. Invasive
species are a leading cause of animal extinctions.
Trends in Ecology & Evolution 20(3), 110. doi:
10.1016/j.tree.2005.01.003.
COHEN, A.E., DUGAN, L.E., HENDRICKSON, D.A., MAR-
TIN, F.D., HUYNH, J., LABAY, B.J., & M.J. CASAREZ.
2014. Population of variable platyfi sh (Xiphophorus
variatus) established in Waller. The Southwestern
Naturalist 59, 413-419.
COPP, G.H., WESLEY, K.J., & L. VILIZZI. 2005a. Pathways
of ornamental and aquarium fi sh introductions into
urban ponds of Epping Forest (London, England):
the human vector. Journal of Applied Ichthyology
21, 263-274. doi: 10111/j.1439-0426.2005.00673.x
COPP, G.H., BIANCO, P.G., BOGUTSKAYA, N., ERŐS, T.,
FALKA, I., FERREIRA, M.T., FOX, M.G., FREYHOF,
J., GOZLAN, R.E., GRABOWSKA, J., KOVÁČ, V.,
MORENO-AMICH, R., NASEKA, A.M., PEŇÁZ, M.,
POVŽ, M., PRZYBYLSKI, M., ROBILLARD, M., RUS-
SELL, I.C., STAKĖNAS, S., ŠUMER, S., VILA-GISPERT,
A., & C. WIESNER. 2005b. To be, or not to be, a
non-native freshwater fi sh? Journal of Applied
Ichthyology 21, 242-262. doi: 10111/j.1439-
0426.2005.00679.x
COPP, G.H., VILIZZI, L. & R.E. GOZLAN. 2010. The
demography of introduction pathways, propagule
pressure and occurrences of non-native fresh-
water fi sh in England. Aquatic Conservation:
Marine and Freshwater Ecosystems 20, 595-601.
http://dx.doi. org/10.1002/aqc.1129
CROWL, T.A., CRIST, T.O., PARMENTER, R.R., BE-
LOVSKY, G., & A.E. LUGO. 2008. The spread of
invasive species and infectious disease as drivers
of ecosystem change. Frontiers in Ecology and
the Environment 6, 238-46.
DEACON, A.E., RAMNARINE, I.W., & A.E. MAGURRAN.
2011. How reproductive ecology contributes to
the spread of a globally invasive fi sh. PLoS One
6(9), e24416.
DELANEY, D.G., SPERLING, C.D., ADAMS, C.S. & B.
LEUNG. 2008. Marine invasive species: validation
of citizen science and implications for national
monitoring networks. Biological Invasions 10,
117-28.
DICKINSON, J.L., ZUCKERBERG, B., & D.N. BONTER.
2010. Citizen science as an ecological research
tool: challenges and benefits. The Annual
Review of Ecology, Evolution, and Systematics
41, 149-72.
DICKINSON, J.L, SHIRK, J., BONTER, D., BONNEY, R.,
CRAIN, R.L., MARTIN, J., PHILLIPS, T., & K. PURCEL.
2012. The current state of citizen science as a tool
for ecological research and public engagement.
Frontiers in Ecology and the Environment 10,
291-97.
DUGGAN, I.C., RIXON, C.A.M. & H.J. MACISAAC. 2006.
Popularity and propagule pressure: Determinants
of introduction and establishment of aquarium
fi sh. Biological Invasions 8, 377-82.
ENGELHARDT, A. 1993. Eine Guppypopulation im
Raum Cottbus. Die Aquarien- und Terrarienzeit-
schrift 46, 454-457.
EMDE, S., KOCHMANN, J., KUHN, T., DÖRGE, D.D. ,
PLATH, M., MIESEN, F.W., & S. KIMPEL. 2016. Cool-
ing water of power plant creates “hot spots” for
tropical fi shes and parasites. Parasitology Research
115, 85-98. doi: 10.1007/s00436-015-4724-4
ERAUD, C., BOUTIN, J.-M., ROUX, D., & B. FAIVRE. 2007.
Spatial dynamics of an invasive bird species assessed
using robust design occupancy analysis: the case of
23
Bull. Fish Biol. 17 (1/2)
the Eurasian collared dove (Streptopelia decaocto) in
France. Journal of Biogeography 34, 1077-1086.
EUROPEAN UNION (2012) 2012/697/EU: Commis-
sion Implementing Decision of 8 November
2012 as regards measures to prevent the intro-
duction into and the spread within the Union
of the genus Pomacea (Perry) (notifi ed under
document C(2012) 7803). Offi cial Journal of the
European Union. Retrieved from http://data.
europa.eu/eli/dec_impl/2012/697/oj (Accessed
on 31-08-2017)
EUROPEAN UNION. 2014. Regulation (EU) No
1143/2014 of the European Parliament and of
the Council of 22 October 2014 on the prevention
and management of the introduction and spread
of invasive alien species. Offi cial Journal of the
European Union. Retrieved from http://data.
europa.eu/eli/reg/2014/1143/oj (Accessed on
31-08-2017)
EUROPEAN UNION. 2016. Commission Implementing
Regulation (EU) 2016/1141 of 13 July 2013 adopt-
ing a list of invasive alien species of Union concern
pursuant to Regulation (EU) No 1143/2014 of the
European Parliament and of the Council. Offi cial
Journal of the European Union. Retrieved from
http://data.europa.eu/eli/reg_impl /2016/1141/
oj (Accessed on 31-08-2017)
FROESE, R. & D. PAULY (eds.). 2017. Fishbase 2017,
version (June, 2017). World Wide Web electronic
publication. Retrieved from http://www.fi sh base.
org (Accessed on 31-08-2017)
FEDERAL LAW GAZETTE. 2011. Dreizehntes Gesetz
zur Änderung des Atomgesetzes. Deutsches
Bundesgesetzblatt Nr 43: 1704-05 Retrieved
from https://www.bgbl.de/xaver/bgbl/start.xav?
start=%2F%2F*%5B%40attr_id%3D›
bgbl111s1704.pdf›%5D#__bgbl__%2F%2F
*%5B%40attr_id%3D%27bgbl111s1704.
pdf%27%5D__1488384033647 (Accessed on
31-08-2017)
FUNDA, K.-H. 1979. Der Guppy im Spreewald. Aqua-
rien Terrarien 26, 104.
GELLER, J.B., WALTON, E.D., GROSHOLZ, E.D., & G.M.
RUIZ. 1997. Cryptic invasions of the crab Carcinus
detected by molecular phylogeography. Molecular
Ecology 6, 901-906.
GERTZEN, E., FAMILIAR, O. & B. LEUNG. 2008. Quan-
tifying invasion pathways: fi sh introductions from
the aquarium trade. Canadian Journal of Fisheries
and Aquatic Sciences 65, 1265-1273.
GOLLASCH, S., & S. NEHRING. 2006. National checklist
for aquatic alien species in Germany. Aquatic
Invasions 1, 245-69.
GROVE-WHITE, R., WATERTON, C., ELLIS, R., VOGEL,
J., STEVENS, G., & B. PEACOCK. 2007. Amateurs as
experts: harnessing new networks for biodiversity.
Lancaster University, Lancaster.
HICKLING, R.R.B., ROY, J., HILL, K., FOX, R., & C.D.
THOMAS. 2006. The distributions of a wide range
of taxonomic groups are expanding polewards.
Global Change Biology 12, 450-455.
HÖFER, S & S. STAAS. 1998. Bericht zur fi scherei-
biologischen Untersuchung des Gillbaches im
Bereich Bergheim/Auenheim (Okt./Nov. 1998).
Zoologisches Institut der Universität zu Köln,
Abt. Allgemeine Ökologie und Limnologie,
Köln.
HUSSNER, A. 2014. Long-term macrophyte map-
ping documents a continuously shift from native
to non-native aquatic plant dominance in the
thermally abnormal River Erft (North Rhine-
Westphalia, Germany). Limnologica 48, 39-45.
JOURDAN, J., MIESEN, F.W., ZIMMER, C., GASCH, K.,
HERDER, F., SCHLEUCHER, E., PLATH, M., & D.
BIERBACH. 2014. On the natural history of an
introduced population of guppies (Poecilia reticulata
Peters, 1859) in Germany. BioInvasions Records 3
(3), 175-184. doi:10.3391/bir.2014.3.3.07
KALINKAT, G., CABRAL, J. S., DARWALL, W., FICETOLA, G.F.,
FISHER, J.L., GILING, D.P., GOSSELIN, M.-P., GROSSART,
H.-P., JÄHNIG, S.C., JESCHKE, J.M., KNOPF, K., LARSEN,
S., ONANDIA, G., PÄTZIG, M., SAUL, W.-C., SINGER,
G., SPERFELD, E., & I. JARIĆ. 2017. Flagship umbrella
species needed for the conservation of overlooked
aquatic biodiversity. Conservation Biology, 31, 481-
485. doi:10.1111/cobi.12813
KALOUS, L., PATOKA, J., & O. KOPECKÝ. 2015. Eu-
ropean hub for invaders: Risk assessment of
freshwater aquarium fi shes exported from the
Czech Republic. Acta Ichthyologica et Piscatoria
45, 239-45.
KEMPKES, M. 2002. „Rheinische“ Guppys. Die Aquari-
en- und Terrarienzeitschrift (DATZ) 55 (3), 12-13.
KEMPKES, M. 2005. Neues von den „rheinischen“
Guppys. Die Aquarien- und Terrarienzeitschrift
(DATZ) 58 (9), 64-68.
KEMPKES, M. 2010a. Die Guppys, Band 1. Westarp
Wissenschaften-Verlagsgesellschaft mbH, Ho-
henwarsleben.
KEMPKES, M. 2010b. Die Guppys, Band 2. Westarp
Wissenschaften-Verlagsgesellschaft mbH, Ho-
henwarsleben.
KEMPKES, M. 2011. Guppys in der Erft. Die Aquari-
en- und Terrarienzeitschrift (DATZ) 64 (8), 8-9.
KEMPKES, M., ROSE, U., & F. BUDESHEIM. 2009. Etho-
ecological observations of a guppy population
24
(Poe cilia reticulata Peters, 1859) in a thermally pol-
luted stream in Germany. Westarp Wissenschaf-
ten, BrehmSpace.
KLOTZ, W., MIESEN, F.W., HÜLLEN, S., & F. HERDER.
2013. Two Asian fresh water shrimp species found
in a thermally polluted stream system in North
Rhine-Westphalia, Germany. Aquatic Invasions
8, 333-339.
KLUG, M. 2009. Karpfen und Aale unter Kühltür-
men. Potsdamer Neueste Nachrichten (PNN).
Retrieved from http://www.pnn.de/havel-
spree/152068/ (Accessed on 31-08-2017)
LANUV – Landesamt für Natur, Umwelt und
Verbraucherschutz Nordrhein-Westfalen. 2017.
Hydrologische Rohdaten Online: Messstation
Düsseldorf-Flehe. Retrieved from http://luadb.
it.nrw.de/LUA/hygon/ (Accessed on 31-08-2017)
LANGFORD, T.E. 1990. Ecological effects of thermal
discharges. Springer Science & Business Media,
Luxemburg, Heidelberg & Berlin.
LEUVEN, R.S.E.W, VAN DER VELDE, G., BAIJENS, I.,
SNIJDERS, J., VA N DER ZWART, C., LENDERS, H.J.R., &
A. BIJ DE VAATE. 2009. The River Rhine: A global
highway for dispersal of aquatic invasive species.
Biological Invasions 11, 1989-2008. doi: 10.1007/
s10530-009-9491-7
LINDHOLM, A.K., BREDEN, F., ALEXANDER, H.J., CHAN,
W.-K., THAKURTA, S.G., & R. BROOKS. 2005. Inva-
sion success and genetic diversity of introduced
populations of guppies Poecilia reticulata in Aus-
tralia. Molecular Ecology 14, 3671-3682.
LODGE, D.M., WILLIAMS, S., MACISAAC, H.J., HAYES,
K.R., LEUNG, B., REICHARD, S., MACK, R.N.,
MOYLE, P.B., SMITH, M., ANDOW, D.A., CARLTON,
J.T., & A. MCMICHAEL. 2006. Biological invasions:
recommendations for U.S. policy and manage-
ment. Ecological Applications 16, 2035.
LOHRER, A.M. 2001. The invasion by Hemigrapsus
sanguineus in eastern North America: a review.
Aquatic Invaders 12, 1-11.
LUKAS, J. & D. BIERBACH. 2016a. Wer weiß, wo die
Guppys sind? Aquaristik Fachmagazin 251.
LUKAS, J. & D. BIERBACH. 2016b. Wer weiß, wo die
Guppys sind? Amazonas 67(12), 7.
LUKAS, J. & D. BIERBACH. 2016c. Wer weiß, wo die
Guppys sind? Die Aquarienzeitschrift (DATZ)
69 (8), 13.
LUKAS, J.A.Y., JOURDAN, J., KALINKAT, G., EMDE, S.,
MIESEN, F.W., JUENGLING, H., COCCHIARARO, B., &
D. BIERBACH. 2017. On the occurrence of three
non-native cichlid species including the fi rst record
of a feral population of Pelmatolapia (Tilapia) mariae
(Boulenger, 1899) in Europe. Royal Society Open
Science 4, 170160. http://dx.doi.org/10.1098/
rsos.170160
MACEDA-VEIGA, A., ESCRIBANO-ALACID, J., DE SOSTOA,
A., & E. GARCÍA-BERTHOU. 2013. The aquarium
trade as a potential source of fi sh introductions
in southwestern Europe. Biological Invasions 15,
2707-2716.
MENDAX, F. 2011. Erfolgreiche Winterfütterung von
Fischen im Freiland. Die Aquarien- und Terrari-
enzeitschrift (DATZ) 64 (4), 22-23
MEYER, M.K., WISCHNATH, L., & W. FOERSTER. 1985.
Lebendgebärende Zierfische. Mergus Verlag,
Melle.
MILENKOVIĆ, M., ŽIKIĆ, V., STANKOVIĆ, S.S., & S.
MARIĆ. 2013. First study of the guppy fi sh (Poecilia
reticulata Peters, 1859) occurring in natural thermal
waters of Serbia. Journal of Applied Ichthyol ogy
30, 160-163.
MULHOLLEM, J.J., COLOMBO, R.E., & D.H. WAHL.
2016. Effects of heated effl uent on Midwestern
US lakes: implications for future climate change.
Aquatic Sciences, 1-11. doi: 10.1007/s00027-
016-0466-3
MYERS, J.H., SIMBERLOFF, D., KURIS, A.M., & J.R.
CAREY. 2000. Eradication revisited: dealing with
exotic species. Trends in Ecology & Evolution
15, 316-320.
NERBONNE, J.F., & K.C. NELSON. 2004. Volunteer
macroinvertebrate monitoring in the United States:
resource mobilization and comparative state struc-
tures. Society & Natural Resources 17, 817-839.
NUNES, A.L., TRICARICO, E., PANOV, V.E., CARDOSO,
A.C., & S. KATSANEVAKIS. 2015. Pathways and gate-
ways of freshwater invasions in Europe. Aquatic
Invasions 10 (4), 359-70.
O’GORMAN, E.J., PICHLER, D.E., ADAMS, G., BEN-
STEAD, J.P., COHEN, H., CRAIG, N, GISLASON, G.M.,
GUDMUNDSDOTTIR, R., HAWCZAK, A., HOOD, J.M.,
HUDSON, L.N., JOHANSSON, L., JOHANSSON, M.P.,
JUNKER, J.R., LAURILA, A., MANSON, J.R., MAVRO -
MATI, E., NELSON, D., OLAFSSON, J.S., PERKINS,
D.M., PETCHEY, O.L., PLEBANI, M., REUMAN, D.C.,
RALL, B.C., STEWART, R., THOMPSON, M.S.A., & G.
WOODWARD. 2012. Impacts of Warming on the
Structure and Functioning of Aquatic Communi-
ties. Individual- to Ecosystem-Level Responses.
Advances in Ecological Research 47, 81-176.
O’GORMAN, E.J., BENSTEAD, J.P., CROSS, W.F., FRIBERG,
N., HOOD, J.M., JOHNSON, P.W., SIGURDSSON, B.D.,
& G. WOODWARD. 2014. Climate change and geo-
thermal ecosystems: Natural laboratories, sentinel
systems, and future refugia. Global Change Biol-
ogy 20, 3291-3299.
25
Bull. Fish Biol. 17 (1/2)
PADILLA, D.K., & S.L. WILLIAMS. 2004. Beyond bal-
last water: aquarium and ornamental trades as
sources of invasive species in aquatic ecosystems.
Frontiers in Ecology and the Environment 2 (3),
131-138.
PAEPKE, H.-J., & W.-D. HEYM. 2002. Guppys in der
Niederlausitz. Die Aquarien- und Terrarienzeit-
schrift (DATZ) 55 (3), 14-15.
PANOV, V.E., ALEXANDROV, B., ARBACIAUSKAS, K.,
BINIMELIS, R., COPP, G.H., GRABOWSKI, M., LUCY,
F., LEUVEN, R.S., NEHRING, S., PAUNOVIĆ, M., &
V. SEMENCHENKO. 2009. Assessing the risks of
aquatic species invasions via European inland
waterways: the concepts and environmental in-
dicators. Integrated Environmental Assessment
and Management 5, 110-126.
PARMESAN C., & G. YOHE. 2003. A globally coher-
ent fi ngerprint of climate change impacts across
natural systems. Nature 421(6918), 37-42.
PETUTSCHNIG J., HONSIG-ERLENBURG W., & R. PEKNY.
(2008) Zum aktuellen Flusskrebs- und Fischvor-
kommen des Warmbaches in Villach. Carinthia II
198 (118), 95-102.
PIAZZINI, S., LORI, E., FAVILLI, L., CIANFANELLI, S.,
VANNI, S., & G. MANGANELLI. 2010. A tropical
fi sh community in thermal waters of Southern
Tuscany. Biological Invasions 12, 2959-2965.
PIRIA, M., COPP, G.H., DICK, J.T.A, DUPLIĆ, A., GROOM,
Q., JELIĆ, D., LUCY, F.E., ROY, H.E., SARAT, E.,
SIMONOVIĆ, P.,TOMLJANOVIĆ,T., TRICARICO, E., WEIN-
LANDER, M., ADÁMEK, Z., BEDOLFE, S., COUGHLAN,
N.E., DAVIS, E., DOBRZYCKA-KRAHEL, A., GRGIĆ, Z.,
KĪRANKAYA, S.G., EKMEKÇI, F.G., LAJTNER, J., LUKAS,
J.A.Y., KOUTSIKOS, N., MENNEN, G.J., MITIĆ, B.,
PASTORINO, P., RUOKONEN, T.J., SKÓRA, M.E., SMITH,
E.R.C., ŠPREM, N., SERHAN TARKAN, A., TREER, T.,
VARDAKAS, L., VEHANEN, T., VILIZZI, L., ZANELLA, D.,
& J.M. CAFFREY. 2017. Tackling invasive alien species
in Europe II: threats and opportunities until 2020.
Management of Biological Invasions 8 (3), 273-286.
doi:10.33991/mbi.2017.8.3.02
POCOCK, M.J.O., CHAPMAN, D.S., SHEPPARD, L.J., &
H.E. ROY. 2014a. A strategic framework to sup-
port the implementation of citizen science for
environmental monitoring. Final Report to SEPA.
Centre for Ecology & Hydrology, Wallingford,
Oxfordshire.
POCOCK, M.J.O., CHAPMAN, D.S., SHEPPARD, L.J., &
H.E. ROY. 2014b. Choosing and Using Citizen
Science: a guide to when and how to use citizen
science to monitor biodiversity and the environ-
ment. Centre for Ecology & Hydrology, Walling-
ford, Oxfordshire.
RAPTIS, C.E, VAN VLIET, M.T.H., & S. PFISTER. 2016.
Global thermal pollution of rivers from thermo-
electric power plants. Environmental Research
Letters 11(10), 104011. doi:10.1088/1748-
9326/11/10/104011
RICCIARDI, A., MACK, R.N., STEINER, W.M., & D. SIM-
BERLOFF. 2000. Toward a global information sys-
tem for invasive species. BioScience 50, 239-244.
RIXON, C.A., DUGGAN, I.C., BERGERON, N.M., RIC-
CIARDI, A., & H.J. MACISAAC. 2005. Invasion risks
posed by the aquarium trade and live fi sh markets
on the Laurentian Great Lakes. Biodiversity and
Conservation 14, 1365-1381.
ROCHA-CAMARERO, G., & S.H. DE TRUCIOS. 2002. The
spread of the collared dove Streptopelia decaocto
in Europe: colonization patterns in the west of the
Iberian Peninsula. Bird Study 49, 11-16.
ROGNER, M. 1981. Freilebende Guppys und Schwertträ-
ger in Heinsberg. Tetra Informationen (TI) 55, 42.
ROSE, U. 2012. Neobiota in einem thermisch anor-
malen Fluss in NRW. Die Aquarienzeitschrift
(DATZ) (8), 26-29.
ROY, H.E., POCOCK, M.J.O., PRESTON, C.D., ROY, D.B.,
SAVAG E, J., TWEDDLE, J.C., & L.D. ROBINSON. 2012.
Understanding citizen science & environmental
monitoring. Final Report on behalf of UK-EOF.
NERC Centre for Ecology & Hydrology and
Natural History Museum, 10-11.
SALA, O.E., CHAPIN, F.S., ARMESTO, J.J., BERLOW, E.,
BLOOMFIELD, J., DIRZO, R., HUBER-SANWALD, E.,
HUENNEKE, L.F., JACKSON, R.B., KINZIG, A., &
R. LEEMANS. 2000. Global biodiversity scenarios
for the year 2100. Science 287(5459), 1770-1777.
SAS-KOVACS, I., TELCEAN, I.C., & S.D. COVACIU-
MARCOV. 2015. A non-native fish assemblage
in geothermal waters of Romania. Journal of
Applied Ichthyology 31 (1), 211-213.
SCHRÖTER, D., CRAMER, W, LEEMANS, R., PRENTICE,
I.C., ARAÚJO, M.B., ARNELL, N.W., BONDEAU, A.,
BUGMANN, H., CARTER, T.R., GRACIA, C.A., &
C. ANNE. 2005. Ecosystem service supply and
vulnerability to global change in Europe. Science
310 (5752), 1333-1337.
SEEBENS, H., BLACKBURN, T.M., DYER, E., GENOVESI,
P., HULME, P.E., JESCHKE, J.M., PAGAD, S., PYŠEK,
P., WINTER, M., ARIANOUTSOU, M., BACHER, S.,
BLASIUS, B., BRUNDU, G., CAPINHA, C., CELESTI-
GRAPOW, L., DAWSON, W., DULLINGER, S., FUENTES,
N., JÄGER, H., KARTESZ, J., KENIS, M., KREFT, H.,
KÜHN, I., LENZNER, B., LIEBHOLD, A., MOSENA,
A., MOSER, D. NISHINO M., PEARMAN, D., PERGL,
J., RABITSCH W., ROJAS-SANDOVAL, J., ROQUES, A.,
RORKE, S., ROSSINELLI, S., ROY, H.E., SCALERA, R.,
26
SCHINDLER, S., ŠTAJEROVÁ K., TOKARSKA-GUZIK,
B., VAN KLEUNEN, M., WALKER, K., WEIGELT, P.,
YAMANAKA, T., & F. ESSL. 2016. No saturation
in the accumulation of alien species worldwide.
Nature Communications, 1-9.
SHVIDENKO A., BARBER C.V. & R. PERSSON. 2005 Forest
and woodland systems. Proceedings from Ecosys-
tems and Human Well-being: Current State and
Trends. Island Press, Washington D.C., 585-621.
SILVERTOWN, J. 2009. A new dawn for citizen science.
Trends in Ecology & Evolution 24, 467-471.
SIMARD, M.A., PAQUET, A., JUTRAS, C., ROBITAILLE, Y.,
BLIER, P.U., COURTOIS, R., & A.L. MARTEL. 2012.
North American range extension of the invasive
Asian clam in a St. Lawrence River power station
thermal plume. Aquatic Invasions 7, 81-9.
SPECZIÁR, A. 2004. Life history pattern and feeding
ecology of the introduced eastern mosquitofi sh,
Gambusia holbrooki, in a thermal spa under temper-
ate climate, of Lake Hévíz, Hungary. Hydrobio-
logia 522, 249-60.
SPIGARELLI, S.A. 1974. Behavioral responses of Lake
Michigan fi shes to a nuclear power plant discharge.
IAEA Symposium Proceedings: Environmental Ef-
fects of Cooling systems at nuclear power plants; In-
ternational Atomic Energy Agency, Vienna, 479-498.
STOHLGREN, T.J., BARNETT, D., FLATHER, C., FULLER,
P., PETERJOHN, B., KARTESZ, J., & L.L. MASTER.
2006. Species richness and patterns of invasion
in plants, birds, and fi shes in the United States.
Biological Invasions 8, 427-47.
STRECKER, A.L., CAMPBELL, P.M., & J.D. OLDEN. 2011.
The aquarium trade as an invasion pathway in the
Pacifi c Northwest. Fisheries 36 (2), 74-85.
THEOHARIDES, K.A., & J.S. DUKES. 2007. Plant inva-
sion pattern and process: factors affecting plant
invasion at four spatio-temporal stages. New
Phytologist Journal 176, 256-273.
TIERSCHUTZGESETZ (TIERSCHG). German Animal
Welfare Act in the version of the promulgation
of 18 May 2006 (Federal Law Gazette [BGBI.]
Part I pp. 1206, 1313), most recently amended by
Article 4 (87) of the Act of 18 July 2016 (Federal
Law Gazett [BGBI.] Part I p. 1666). Available at
http://www.gesetze-im-internet.de/tierschg /
BJNR012770972.html (Accessed on 31-08-2017)
TWEDDLE, J, ROBINSON, L, ROY, H., & M. POCOCK.
2012. Guide to Citizen Science. Nature Neuro-
science, 1-36.
VERBRUGGE, L.G., LEUVEN, R., VAN VALKENBURG, J.,
& R. VAN DE BORN. 2014. Evaluating stakeholder
awareness and involvement in risk prevention of
aquatic invasive plant species by a national code
of conduct. Aquatic Invasions 9, 369 -381.
VERÍSSIMO, D., MACMILLAN, D.C., & R.J. SMITH. 2011.
Toward a systematic approach for identifying
conservation fl agships. Conservation Letters
4, 1-8.
VERMEIJ, G.J. 1996. An agenda for invasion biology.
Biological Conservation 78, 3-9.
WALTHER, G.R., POST, E., CONVEY, P., MENZEL, A.,
PARMESAN, C., BEEBEE, T.J., FROMENTIN, J.-M.,
HOEGH-GULDBERG, O., & F. BAIRLEIN. 2002.
Ecological responses to recent climate change.
Nature 416 (6879), 389-395.
WELCOMME, R.L. 1988. International introductions
of inland aquatic species. FAO fi sheries technical
paper 294. Food and Agriculture Organisation of
the United Nations, Rome.
WIKIPEDIA. 2017, Feb 19. Liste stillgelegter Kraftwer-
ke in Deutschland. In: Wikipedia, Die freie En-
zyklopädie. Retrieved from: https://de.wikipedia.
org/w/index.php?title=Liste_stillgelegter
_Kraftwerke_in_Deutschland&oldid=162795383
(Accessed on 31-08-2017)
WILLIAMSON, M. 2006. Explaining and predicting
the success of invading species at different
stages of invasion. Biological Invasions 8,
1561-1568.
WILLIAMSON, M., & A.FITTER. 1996. The varying suc-
cess of invaders. Ecology 77, 1661-1666.
WOLTER, C., & F. RÖHR. 2010. Distribution history
of non-native freshwater fi sh species in Germany:
how invasive are they? Journal of Applied Ichthy-
ology 26, 19-27.
YOCCOZ, N.G., NICHOLS, J.D., & T. BOULINIER.
2001. Monitoring of biological diversity in
space and time. Trends in Ecology & Evolu-
tion 16, 446.
ZIERITZ, A., GALLARDO, B., BAKER, S.J., BRITTON, J.R.,
VAN VALKENBURG, J.L.C.H., VERREYCKEN, H., &
D.C. ALDRIDGE. 2016. Changes in pathways and
vectors of biological invasions in Northwest
Europe. Biological Invasions, 1-14. doi: 10.1007/
s10530-016-1278-z
Received: 20.07.2017
Accepted: 31.08.2017
27
Bull. Fish Biol. 17 (1/2)
Appendix 1: Table of the aforementioned citizen science projects.
Anhang 1: Aufl istung der genannten Citizen-Science-Projekte.
Appendix 2: List of public video observations of feral populations of (sub)tropical fi sh in Germany. All
videos were accessed on 31-08-2017.
Anhang 2: Liste mit öffentlichen Videoaufnahmen von wilden, (sub)tropischen Fischpopulationen in
Deutschland. Alle Quellen wurden am 31.08.2017 eingesehen.
28
