Invasiveness Assessment of Pumpkinseed Fish, Lepomis Gibbosus, in Albanian Freshwater Ecosystems by Using the Aquatic Species Invasiveness Screening Kit (AS-ISK)

Abstract

Pumpkinseed fish is considered to be highly invasive; it has demonstrated great variability in its environmental biology in response to environmental conditions, since its first appearance in the European waters this species has established populations in at least 28 European countries. In Albania, pumpkinseed, was introduced in 1994, even though the pathways of its introduction are not very clear. Aquatic Species Invasiveness Screening Kit (AS-ISK) risk identification screening tools was used to assess the invasiveness potential of pumpkinseed fish, Lepomis gibbosus, in Ohrid and Prespa lakes, in order to evaluate the current or future impacts of this non-native fish species. The basic AS-ISK score of 38.3 suggests the species poses a high risk of being invasive, and this risk is expected to even higher in the future, taking in consideration the potential effects of climate change (AS-ISK Climate Change Assessment = 49.7). This study was the first application of AS-ISK in Albania, and the results suggest that it can be a useful decision-supporttool for informing legislation, policy and management of potential, existing and future, undesired translocations of non-native freshwater fish species in the country.

Full text

Albanian j. agric. sci. 2022; 21 (1): 37-44 Agricultural University of Tirana
*Corresponding author: Rigers Bakiu; E-mail: rigers.bakiu@ubt.edu.al
(Accepted for publication )
ISSN: 2218-2020, © Agricultural University of Tirana
RESEARCH ARTICLE (Open Access)
Invasiveness Assessment of Pumpkinseed Fish,
Lepomis Gibbosus
, in
Albanian Freshwater Ecosystems by Using the Aquatic Species
Invasiveness Screening Kit (AS-ISK)
RIGERS BAKIU1,2*, ELVIS KAMBERI1, EDMOND HALA1
1Department of Aquaculture and Fisheries, Faculty of Agriculture and Environment, Agricultural University of Tirana, Koder-Kamez,
Tirane, Albania
2Albanian Center for Environmental Protection and Sustainable Development, Tirane, Albania
Abstract
Pumpkinseed fish is considered to be highly invasive; it has demonstrated great variability in its environmental
biology in response to environmental conditions, since its first appearance in the European waters this species has
established populations in at least 28 European countries. In Albania, pumpkinseed, was introduced in 1994, even
though the pathways of its introduction are not very clear. Aquatic Species Invasiveness Screening Kit (AS-ISK) risk
identification screening tools was used to assess the invasiveness potential of pumpkinseed fish, Lepomis gibbosus,
in Ohrid and Prespa lakes, in order to evaluate the current or future impacts of this non-native fish species. The basic
AS-ISK score of 38.3 suggests the species poses a high risk of being invasive, and this risk is expected to even higher
in the future, taking in consideration the potential effects of climate change (AS-ISK Climate Change Assessment =
49.7). This study was the first application of AS-ISK in Albania, and the results suggest that it can be a useful decision-
supporttool for informing legislation, policy and management of potential, existing and future, undesired
translocations of non-native freshwater fish species in the country.
Keywords: Biological Invasion; Risk Analyses, Non-native Species, Ohrid lake, Prespa lakes
1. Introduction
In Europe, several decision support tools have been
developed for screening aquatic organisms as a
required step in the analysis of risks posed by non-
native species (NNS) [6, 8, 9]. Risk screening is
especially required for risk assessment areas
characterized by high endemism or great biodiversity,
such as the Balkan peninsulas [35, 19], especially for
species like pumpkinseed fish (Lepomis gibbosus),
which is known to be highly invasive [41, 1] in several
countries. Invasiveness risk is particularly interesting
to conduct for inland waters of the Balkans
(Mediterranean region), where a high level of
endemism has considerably contributed to increases
the likelihood of native fish extinctions, due to their
restricted natural ranges [31].
In the Balkans, pumkinseed fish, as a popular aquarium
species, was accidentally (with a high level of
uncertainty) introduced into some trans-boundary river
systems in central North Macedonia and northern
Greece [22, 13, 18], as well as into Lake Kastoria,
Prespa (north-west Greece), River Alfios
(Peloponnesus) [14] and Lake Tavropos (central
Greece) [3].
According to [11], probably it was an accident even in
the case of Albania, while according to [34], it was
introduced in Albania in 1994. It is encountered in the

Bakiu et al., 2022
Lake of Oher and the Lakes of Big Prespa and Small
Prespa, respectively [12, 14]
The aim of the presently reported study was to assess
the current and future invasiveness potential of L.
gibbosus by using the Aquatic Species Invasiveness
Screening Kit (AS-ISK) of [42] for the first time with
aquatic species living in Albanian aquatic ecosystems.
The outputs of the presently reported study will serve
to demonstrate to environmental managers and
stakeholders in Albania the potential use of AS-ISK as
a decision-support tool for informing legislation, policy
and management (i.e. prevention, control, containment,
eradication) of potential, existing and future undesired
translocations of non-native freshwater fishes in the
country.
2. Material and Methods
The risk assessment (RA) area includes Ohrid and
Prespa lakes parts, as parts of the Albanian territory.
The Prespa and Ohrid climate is Continental/sub-
Mediterranean [29], at the transition zone between
Mediterranean and Continental climates, characterised
by warm dry summers and rather cold humid winters.
For instance Prespa average annual precipitation at lake
level reaches 763 mm and lake evaporation 833 mm
over the period 1951–2004, while open-pan
evaporation amounts to 1041 mm [40]. Popovska and
Bonacci [30] have found a statistically significant
increase in temperature variability over the period
1961–1990, with an average annual precipitation
decreased statistically significantly in Ohrid, but non-
significantly in Prespa. This freshwater ecosystem is
threatened by the dramatic fall in water level (~8 m) of
Lake Big Prespa over the past three decades, which has
been inconclusively related to climate change, water
abstraction or earthquake-induced changes to
underground karst drainage channels [27, 30]. Since
1995 water levels have remained the lowest on record,
since observations started around 1917 [5]. The Lake
of Big Prespa currently contributes about 25% of the
total inflow into Lake Ohrid through underground karst
drainage channels.
In order to identify the potential invasiveness of
L.gibbosus, the AS-ISK decision-support toolkit was
used by us. All the assessments were conducted
independently by the three authors. A direct derivative
of FISK v2 (the Freshwater Fish Invasiveness
Screening Kit [26], AS-ISK consists of 55 questions
(Qs) on the assessed species’ LHTs, invasion and
environmental biology, biogeography and history of
introduction [42]. Responses to these Qs provide a
Basic Risk Assessment (BRA) score, which is
complemented by six additional ‘climate change’
questions that ask the assessor to foretell the likely
effects of predicted future climate on the risk screening
(risks and magnitude of introduction, establishment
and dispersal). Response scores to these Climate
Change Assessment (CCA) Qs are added to the BRA
score (BRA + CCA score). To each question, the
assessor must provide a response and a justification for
their response (including bibliographic references) and
then rank their confidence in that response. The
confidence ranking categories are: 1 = low, 2 =
medium, 3 = high, 4 = very high [19]. In all cases, an
overall score < 1 assigns a status of ‘low risk’ (hence,
not likely to be invasive), whereas values ≥ 1 identify
alien species as potentially invasive and posing either a
‘medium risk’ or a ‘high risk’. Consequently the
certainty factor (CF) ranges from a minimum of 0.18
(i.e. all questions with certainty score equal to 1) to a
maximum of 1 (i.e. all questions with certainty score
equal to 4). Furthermore, it is important to identify a
‘threshold’ value for the RA area concerned by way of
a ‘calibration’ process to distinguish between species
of medium and high risk of invasiveness [6, 21].
Because there has been no calibration of AS-ISK for
(freshwater fish in) Albania, the choice of BRA and
BRA + CCA thresholds to distinguish between medium
vs high risk was based on the identified threshold
values by [19] for 24 freshwater fish species in
Balkans, the BRA threshold of 10 and BRA + CCA
threshold of 12.62, for the same set of species.
3. Results and Discussion
Based on the reference threshold score of 10, the
identified average BRA score (by the three assessors
for L. gibbosus) in Albania (38.3) falls within the ‘high
risk’ category (Fig. 1A). When the potential effects of
climate change on the risk screening responses are
taken into consideration, L. gibbosus’ BRA + CCA
score increases to 49.7 (hence well above the 12.62
threshold) reflecting an even higher risk of the species
being invasive in Albania in the future (Fig. 1A).

Albanian j. agric. sci. 2022; 21 (1): 37-44 Agricultural University of Tirana
*Corresponding author: Rigers Bakiu; E-mail: rigers.bakiu@ubt.edu.al
(Accepted for publication )
ISSN: 2218-2020, © Agricultural University of Tirana
Figure 1. Graphical presentation of the identified score values from the invasiveness assessment of pumpkinseed fish
by the three authors, expressed as (A) average score values of BRA and BRA+CCA and (B) confidence level of BRA,
BRA+CCA and CCA.
The mean confidence levels for responses to Qs
contributing to the BRA, CCA, and BRA + CCA scores
for L. gibbosus in Albania were 0.81 (± 0.05 SE), 0.75
(± 0.08 SE) and 0.80 (± 0.06 SE), respectively, which
suggests high level of confidence and furthermore a
comparability among AS-ISK groups of Qs (Fig. 1B).
Factors and traits that increased L. gibbosus’ AS-ISK
score (Fig. 2A) included a history of being invasive
elsewhere (12.7 ± 2.31 SE) and to lower level regarding
the other historical and biogeography characteristic,
represented by the high climatic match and elevated
likelihood of being illegally stocked. Regarding the
characteristics corresponding to the biology and
ecology, the undesirable (or persistence) traits (8.3) (in
case of pumpkinseed fish mainly represented by the
opportunistic foraging behaviour) represented one of
the most important traits together with likelihood high
risks posed to native threatened or protected taxa
(resource exploitation, 7.0).
Traits that reduced the overall score included
reproduction and dispersal mechanisms, though it is
known the existence of parental care and relatively
small size at maturity of this species. The average score
of tolerance attributes (3.7 ± 3.51 SE) indicate no
likelihood of hybridisation with native species, though
with a high uncertainty by the assessors. Generally, the
high score registered for the climate change factor
(11.3 ± 1.15 SE) indicate that it is likely that L.gibbosus
will continue to disperse and establish in the RA area
under current climate conditions, and more likely under
predicted future climatic conditions. In the latter case,
the risks of establishment and dispersal would increase
the species’ risk of invasiveness (Qs 50–52), and also
the magnitude of future potential impacts (Qs 53–55).

Bakiu et al., 2022
Figure 2. Graphical presentation of Score Partition of (A) Biogeography/History related factors, (B) Biology/Ecology
contributors and (C) Climate change on the invasiveness level of pumpkinseed fish in the Albanian ecosystems.
In Fig. 3 are shown the sectors affected by the
pumpkinseed fish invasiveness in the Prespa and Ohrid
ecosystems. The species (24 ± 4 SE) populating the
ecosystem due to the population nuisance traits will be
mostly affected by the presence of L. gibbosus, while
the commercial sectors (like the fisheries or tourism)
will be less affected by the potential invasiveness of
pumpkinseed fish (18 ± 2.31 SE). Generally, the
environment will suffer less than the previously
mentioned sectors by the presence of this species (12 ±
1.53 SE).
Figure 3. Graphical presentation of the impact toward different sectors close to the Prespa and Ohrid Lakes by the
presence of pumpkinseed fish.

Albanian j. agric. sci. 2022; 21 (1): 37-44 Agricultural University of Tirana
*Corresponding author: Rigers Bakiu; E-mail: rigers.bakiu@ubt.edu.al
(Accepted for publication )
ISSN: 2218-2020, © Agricultural University of Tirana
In the RA freshwater ecosystems, a strong climate
related impact on the limnology and physical
parameters including the Lake Prespa [2], is predicted
to be followed by a significant decrease in productivity,
enhanced mixing, strong decomposition and soil
erosion. For instance, future climate changes could lead
to an accelerated water-level fall and a reduction in lake
volume, then there will be substantial negative
consequences for regional water resources and global
biodiversity. The lake Prespa currently contributes
~25% of the total inflow into Lake Ohrid through
underground karst drainage channels, while it has been
observed that falling lake levels will decrease this
underground discharge [27] and the Lake Ohrid
outflow to the Drini River will decrease consequently.
Furthermore, a reduction in lake volume will
consequently bring out to an increase in pollutant
concentrations and accelerate the on-going
eutrophication of the Prespa Lakes [27]. Another
deteriorating factor is represented by the introduced
species, like L. gibbosus, which has been shown to be
highly invasive in other European countries. For the
first time in Albania, this species invasiveness potential
was assessed by identifying L. gibbosus BRA and
BRA+CCA (Fig. 1). Relative to L. gibbosus BRA and
BRA+CCA scores published for other RA areas,
except the case of Thrace and Anatolia (Turkey, [39]),
those for Albania were consistently higher than for
Poland [20], Lake Marmara (Turkey, [38]), River
Neretva catchment (Bosnia and Herzegovina, and
Croatia [19]).
Differently to Albanian freshwater ecosystems (Fig. 2),
the analysed factors and traits that increased L.
gibbosus’ AS-ISK score in the study of [20] (Poland)
included a historyof being invasive elsewhere, high
climatic match, parental care, relatively small size at
maturity, opportunistic foraging behaviour, and
elevated likelihood of being illegally stocked. Traits
thatreduced the overall score included no likelihood of
hybridisation with native species and low risksposed to
native threatened or protected taxa.
Twenty-eight taxa of fish have been identified from
Prespa and Ohrid lakes [37], mostly represented by
members of Cyprinidae and Salmonidae members,
where there are endemic species like Squalius
prespensis in Prespa and Salmo letnica together with
Salmo ohridanus in Ohrid Lake. Most of the fish
catches in Prespa lakes are represented by carp, while
in Ohrid Lake the main interest is toward the two
endemic species (authors observatons). As shown in
the graphic of Fig. 3, the presence of L. gibbosus could
deteriorate the abundance of the endemic fish species
subject of fishing activities, with a considerable impact
not only to this commercial activity, but also to tourism
related activities – strictly linked to the presence of the
endemic species. Other vertebrate and invertebrate
species population could also suffer by the presence of
the pumpkinseed fish populations, because
pumpkinseed fish is omnivorous [10, 7] and
demonstrates trophic and/or resource polymorphism.
For example, individuals in the pelagic zone appear to
be specialized for foraging on zooplankton, while those
that live in shallow littoral habitat feed primarily on
macro-invertebrates [32, 28]. With age, pumpkinseed
fish becomes increasingly predatory, and its diet may
consist of small fishes and amphibians [33, 23].
Pumpkinseed fish has also been known to consume fish
eggs and aquatic plant debris [17, 10].
However, despite the BRA and BRA + CCA scores,
which classify L. gibbosus as likely to pose a high risk
of invasiveness, the species’ known adverse impacts
are not yet fully understood for the RA area, here
represented mainly by south-eastern Albania. For
instance, studies in southern England of the species’
microhabitat and trophic interactions with native fishes
found limited or no evidence for adverse impacts [36,
24], whereas impacts have been recorded in managed
ponds in the Netherlands [41] and in natural streams of
the Iberian Peninsula [1].
4. Conclusions
Each county provides particular evidences regarding
relative impacts of pumpkinseed fish to the aquatic
ecosystem. As such, further research is needed in
Albania to assess the potential impact of L. gibbosus on
this country’s native species and ecosystems. This
could be considered as the first step followed later by
surveys and similar initiatives. Several similar studies
would be needed not only for creating an invasive alien
species strategy (including a plan of action), but also
with interest at international level (as part of
comparisons with other neighbour countries outputs).
5. Acknowledgements
This study was supported by the Albanian Center for
Environmental Protection and Sustainable
Development.
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