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Management of a highly unlikely native fish: The case of arctic charr Salvelinus alpinus from the Southern Alps

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1. Because of ancient introductions, some alien species can be erroneously considered native. Salvelinus alpinus survived as a post glacial relict in the northern European Alps, whereas documented ancient introductions question its native status in a few mountain lakes from the southern Alps (Trentino Alto Adige, Italy). Regardless of its uncertain autochthony, management and alleged conservation actions allowed its recent expansion across the southern Alps (introduced in >170 lakes, mainly originally fishless high-altitude lakes). 2. The present study is a review on the origin of S. alpinus in the southern Alps and on the appropriateness of the above-mentioned management/conservation actions. 3. The autochthony of S. alpinus in this region is rejected by multiple lines of evidence and historic introductions are the most likely hypothesis explaining this presence. Only the origin of two populations occurring at lower altitude is uncertain as they could be native. 4. Residual uncertainty makes it difficult to evaluate the conservation status and value of the Italian populations of S. alpinus, but it does not prevent to highlight several errors in the past and current management of this species. 5. Past and present introductions altered the original genetics of the historical introduced populations and contributed to the invasion of mountain aquatic habitats by modern domestic fish. Time has come to consider the negative ecological consequences of fish stocking, but many introductions of S. alpinus are associated with a misleading conservation rhetoric, which likely provides wrong educational messages to people and relevant stakeholders, and which divertes resources intended for biodiversity conservation. 6. A nonintervention approach (i.e. do not stock or fish S. alpinus) would have been the wiser strategy to preserve the ancient populations, their putative conservation value, and their actual cultural value. Even now, the same strategy is probably the best option, while planning hopefully definitive researches.
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Management of a highly unlikely native fish: The case of arctic
charr Salvelinus alpinus from the Southern Alps
Rocco Tiberti
|Andrea Splendiani
Dipartimento di Scienze della Terra e
dell'Ambiente, Università di Pavia, Pavia, Italy
Department of Life and Environmental
Sciences, Università Politecnica delle Marche,
Ancona, Italy
Rocco Tiberti, DSTA, Università di Pavia, Via
Ferrata 9, 27100, Italy.
1. As a result of ancient introductions, some alien species are erroneously considered
native. Salvelinus alpinus (Linnaeus, 1758) is hypothesized to have survived as a
postglacial relic in the northern European Alps, although documented ancient intro-
ductions contradict its native status in a few mountain lakes from the southern Alps
(Trentino Alto Adige, Italy). Regardless of its uncertain origin, its recent expansion
across the southern Alps (introduced into >170, mainly originally fishless, high
altitude lakes) was the result of management and alleged conservation actions.
2. The present study is a review of the origin of S. alpinus in the southern Alps, and of
the appropriateness of management and conservation actions.
3. The autochthony of S. alpinus in this region is rejected by multiple lines of evidence
and its presence is most likely the result of historical introductions. Only the origin
of two populations occurring at lower altitude is uncertain, as they may be native.
4. Residual uncertainty makes it difficult to evaluate the conservation status and value
of the Italian populations of S. alpinus, but it does not prevent the highlighting of
several errors in the past and the present management of this species.
5. Past and present introductions have altered the original genetics of the ancient
populations and have contributed to the invasion of montane aquatic habitats by
modern domestic fish. Although it is now timely to consider the adverse ecological
consequences of fish stocking, the many introductions of S. alpinus are associated
with a misleading conservation rhetoric, providing ambiguous educational mes-
sages to people and relevant stakeholders, and probably diverting resources
intended for biodiversity conservation.
6. A nonintervention approach (i.e. not to stock or fish S. alpinus) would have been
the wiser strategy to preserve ancient populations, their supposed conservation
value, and their actual cultural value. Even now, this strategy is probably the best
option, while planning definitive research.
ancient introductions, biogeography, high mountain lakes, fish stocking, Trentino Alto Adige,
Received: 31 January 2018 Revised: 16 August 2018 Accepted: 12 November 2018
DOI: 10.1002/aqc.3027
Aquatic Conserv: Mar Freshw Ecosyst. 2019;19. © 2019 John Wiley & Sons, 1
In recent times, the problems related to invasive alien species have
increased substantially, becoming an important issue of conservation
and socioeconomic concern (International Union for Conservation
of Nature (IUCN), 2000); however, the original distribution of many
species has been altered by many, albeit infrequent, ancient introduc-
tions. Possibly in no other part of the world are ancient introductions
so common as in Mediterranean countries. Here, 9000 years of human
civilization have modified and destroyed the original landscapes and
biota (Gippoliti & Amori, 2006). How conservation biology should
address the issue of ancient introductions is an open and complex
question. These introductions often predate the first species invento-
ries and are no longer present in collective memory. The risk of con-
founding introduced species with native species is real, as is the risk
of diverting efforts and resources intended for biodiversity conserva-
tion (Clavero, Nores, KuberskyPiredda, & CentenoCuadros, 2016;
Gippoliti & Amori, 2006). Speciesspecific studies can overcome
uncertainties concerning the native status of many species through
various approaches. Palaeontology, archaeology, philology, biogeogra-
phy, and molecular phylogenetics provide an interdisciplinary frame-
work to test the autochthony of uncertain native taxa (Clavero et al.,
2016). One of these taxa is the arctic charr, Salvelinus alpinus
(Linnaeus, 1758), from the southern Alps.
Salvelinus alpinus has a wide Holarctic distribution (Klemetsen
et al., 2003) with some isolated southerly populations, such as in the
European Alps, where they persisted as a relic of the last Pleistocene
glacial event (Kottelat & Freyhof, 2007). Owing to high morphological
and genetic variability, the taxonomy of S. alpinus is debated and
authors either refer to S. alpinus as a species complex or they split
the complex into several separate species. According to Kottelat and
Freyhof (2007), the alpine populations should be attributed to a differ-
ent species, the Alpine charr, Salvelinus umbla (Linnaeus, 1758),
highlighting the relevance of intraspecific or intragroup diversity for
conservation and management purposes. The original distribution of
S. alpinus in the Alps is restricted to the northern rim (Switzerland,
France, Austria, and Germany), with the exception of a few Italian
populations from the Trentino Alto Adige (Trentino AA, henceforth)
region, which are commonly reported as the only native populations
of the southern Alps (Freyhof & Kottelat, 2008; Machino, 1999).
Above all, this claim is supported by several lines of historical evidence
documenting the presence of S. alpinus in Trentino AA in the 16
tury (Pincio, 1546; Salviani, 1554). The finding that fish stocking across
the Alps may be even older (Pechlaner, 1984), however, challenged
the native status of S. alpinus populations in Italy (Bianco et al.,
2013; Machino, 1999; Piccinini, Nonnis Marzano, & Gandolfi, 2004).
Contrary to the northernmost populations of S. alpinus, which can be
anadromous and thrive in riverine habitats, southern and alpine
S. alpinus are rarely found in rivers and essentially live in lakes
(Klemetsen et al., 2003).
Able to survive in extremely cold climates, S. alpinus is also a val-
ued game species in the Alps. As with other salmonid species, S. alpinus
is widely used to stock originally fishless, highaltitude mountain lakes
(Machino, 1995, 1999); however, high mountains are extremely imper-
meable to fish colonization (Adams, Frissell, & Rieman, 2001). Most
alpine aquatic biota have developed in the absence of fish and are par-
ticularly sensitive to their introduction (Ventura et al., 2017). There-
fore, the recent spread of S. alpinus across the lakes of the Alps
represents a problem for the conservation of native invertebrates
and semiaquatic vertebrates (Ventura et al., 2017).
This ecological perspective contrasts with current fish manage-
ment in the Alps, where fish stocking is commonly accepted as an eco-
logically harmless and economically beneficial management measure
that supports the recreational angling industry as well as many local
microeconomies. More specifically it contrasts with the management
and conservation measures undertaken in favour of S. alpinus in Italy,
which have produced an extensive expansion of the range of this
The spread of S. alpinus across the southern Alps has been
sustained regardless of the uncertainties concerning its autochthony
in Italy and of the lack of data about the conservation status of the
Italian populations (Bianco et al., 2013). A better understanding of
the real conservation status and original distribution of S. alpinus in
Italy represents the essential background for preventing serious errors
on the part of management and conservation authorities. The main
objectives of the present article are: (i) to assess the present and his-
torical distribution of S. alpinus in the Italian southern Alps; (ii) to
review the current knowledge on its origin and biogeography in Italy;
and (iii) to evaluate the conservation policies adopted to manage
S. alpinus in light of its taxonomic and conservation status.
2.1 |Historical and archaeozoological approaches
For centuries the only known populations of S. alpinus inhabiting the
Italian Alps coincided with the historical sites of occurrence
(Canestrini, 1872; Figure 1; Appendix S1). In the last two centuries,
its range has expanded in the large prealpine lakes and in dozens (per-
haps hundreds) of highaltitude lakes of the southern Alps by means of
several introductions using wild and domestic fish from both the
Italian or the northernmost alpine and boreal populations (Tortonese,
1970). Information on the history of fish introductions in the Alps is
scarce, scattered in many archives and grey literature, or simply non
existent. This study used a variety of sources such as scientific and
technical literature, historical documents, and fishstocking reports to
draw a map of the current distribution of S. alpinus in Italy (Figure 1;
Appendix S1). Salvelinus alpinus is present throughout the Italian Alps
in more than 170 lakes, and its range expansion is still sustained by
many institutional stocking programmes.
The first documented evidence of the presence of S. alpinus in the
southern Alps dates back to the Middle Ages, and is limited to a few
low and high mountain lakes (8232400 m a.s.l.) of the Trentino AA,
Italy (Pincio, 1546; Salviani, 1554; Appendix S1). These very old occur-
rence data currently provide the main argument in favour of the
autochthony of S. alpinus in Italy. Although there is evidence that fish
translocations across mountain ranges are much older than commonly
believed (HuitfeldtKaas, 1918; Miró, 2011; Pechlaner, 1984), possibly
dating back to Neolithic times (e.g. in Norway and the Pyrenees;
Sønstebø, Borgstrøm, & Heun, 2007; Miró & Ventura, 2013), in most
mountain areas across the Northern Hemisphere there are no data
supporting the presence of fish in mountain lakes before the late
century (Ventura et al., 2017). This circumstance probably deter-
mined the common belief that fish introductions in mountain areas are
limited to the modern age and that older fish populations should
therefore be native. According to this inaccurate view, the length of
time that elapsed following the first observations of S. alpinus in
Trentino AA was considered a clear proof of the native status of
ancient populations. At least some ancient Italian populations of
S. alpinus were introduced, however: the first documented fish intro-
ductions in the mountain lakes of the Alps precede this evidence,
and were carried out at the time of the Holy Roman Empire (during
the kingdom of Maximilian I, 14861519) in Tyrol (a historical region
in the Eastern Alps, including both Austrian and Italian territories, i.e.
the provinces of Trento and Bolzano; Figure 1). In the Italian Tyrol,
several lakes were stocked with S. alpinus in the 16
and 17
ries, i.e. lakes in the Ultentald'Ultimo, ShnalstalSenales, and
PustertalPusteria valleys, Bolzano in the 16th century (Machino,
1999; Stolz, 1936; von Wolkenstein, Stolz, & Kramer, 1936), and Lake
Ledro (Trento, 655 m a.s.l.) in the 17
century (Bernardi, 1953, 1956).
The statement ancient presence is equal to natural presenceshould
be evaluated cautiously, especially when sound congruencies with
other scientific disciplines are lacking (see below).
An alternative view is given by the archaeozoological data, which
represent a valuable source of information for understanding the orig-
inal distribution of species. A 6millionyearold charr fossil, Salvelinus
oliveroi Gaudant, 1987, was discovered in the southern Alps (Cavallo &
Gaudant, 1987), but 6 million years ago was a period of intense alpine
orogenesis, unrelated to the postglacial events determining the cur-
rent distribution of S. alpinus. Although scarce, archaeozoological data
fail to place the origin of the Italian S. alpinus populations in the early
Holocene or before the first mediaeval introductions. The absence of
S. alpinus bones from prehistoric remains is not proof of its nonnative
status, but is a noteworthy fact, especially considering that the few
studies analysing prehistoric fish remains in the Italian Alps were car-
ried out in the Italian Tyrol, which is the supposed glacial refuge area
for S. alpinus (Albertini & Tagliacozzo, 2004; Bazzanella, Betti, &
Wierer, 2007). Archaeozoological remains and palaeosoils could also
represent a good opportunity for studying ancient species composi-
tion (i.e. Splendiani et al., 2016; Stager, Sporn, Johnson, & Regalado,
2015). Searching for S. alpinus environmental DNA in the
palaeosediments of alpine lakes hosting putative native populations
could provide further data to resolve the issue of the native origin of
S. alpinus in Italy.
2.2 |Biogeographic approach
The limited capacity of freshwater fish to disperse across terrestrial or
marine barriers limits fish dispersal across catchments. As a conse-
quence, there is often a close match between the geological history
of river basins and the fish species and lineages that originally
inhabited them (Waters & Wallis, 2000). The geomorphology of alpine
valleys and the large longitudinal and altitudinal extent of the Alps
limit fish dispersal at both a catchment scale and a regional scale (i.e.
across the Alps). As all of the historical sites of occurrence of S. alpinus
were covered by the ice sheet during the last glacial maximum
(26.519.0 ka BP; Figure 1), postglacial geological events should be
regarded as the likely origin of their putative colonization. The natural
colonization of the southern Alps depends on the ability of S. alpinus
to cross the Alps when glaciers retreated, as alternative colonization
routes via the Mediterranean Sea seem impossible to support and are
not contemplated, i.e. no traces of S. alpinus can be found along the
Mediterranean coasts, such as other relic populations or fossil remains.
With the exceptions of a few regions where some fish species are
able to climb waterfalls and steep watercourses (e.g. Sicyopterus
stimpsoni Gill, 1860 from the Hawaiian archipelago and some galaxiid
fish from the Australasian realm; Blob et al., 2008; Hardie, Jackson,
Barmuta, & White, 2006), the systematic presence of barriers to
upstream movement has led to the natural absence of fish from most
FIGURE 1 Current distribution of Salvelinus alpinus in the Italian Alps and Trentino Alto Adige in relation to its native range (northern Alps) and
other biogeographical, political, and historical cartographic layers. For a list of the sites of occurrence, see Appendix S1
mountain areas across the world (Adams et al., 2001; Knapp,
Matthews, & Sarnelle, 2001; Pechlaner, 1984; Reissig, Trochine,
Queimalinos, Balseiro, & Modenutti, 2006). Many salmonid species
are strong swimmers, able to live in fast waters and to take remarkable
leaps (estimates of the maximum jump height for most salmonids are
often about 1 m; Kondratieff & Myrick, 2006), but they do not possess
any adaptation to climb and were therefore originally absent from high
mountains. Most of the supposedly native Italian populations of
S. alpinus (all but the ones of Lakes Tovel and Molveno) inhabit high
altitude lakes (>1700 m a.s.l.) located in four catchments (Sarca, Noce,
Brenta, and Avisio; see Appendix S1), well above several insurmount-
able barriers to fish colonization. As commonly observed in the Alps,
many of these barriers originated when Pleistocenic glaciers retreated,
and remain despite the erosive action of running water (Pechlaner,
1984). The putative native status of S. alpinus in these lakes implies
the recognition of an extraordinary exception, enabling S. alpinus to
reach the high mountain lakes in several valleys of Trentino AA, but
not in other mountain ranges or elsewhere in the Alps. Fish may have
bypassed upstream barriers through zoochory, anemochory, and head-
water stream captures (occurring when a river is diverted from its own
bed and flows instead down the bed of a neighbouring river; Waters &
Wallis, 2000). Although theoretically possible, the probability of a fish
population becoming established in even one high mountain lake
through one of these dispersal routes appears negligible, and at pres-
ent there is no scientific evidence for most of these mechanisms
(Schmidt, 2013). Such an unlikely circumstance suggests that the
autochthony of S. alpinus in the high mountain historical sites of occur-
rence is at least unreliable, and that the debate on the autochthony of
S. alpinus in Italy should be restricted only to the ancient populations
situated at lower altitudes (Molveno and Tovel). Salvelinus alpinus is
consistently considered a mountain species only in Italy and Austria,
where historical introductions in mountain lakes have occurred. In
the rest of its original perialpine range (e.g. France and Switzerland),
however, it is considered a species typical of lowland prealpine lakes,
because in the absence of ancient introductions in mountain lakes it
was restricted to lowlands until recent times (Keith, Persat, Feunteun,
& Allardi, 2011).
At a regional biogeographic scale, the Alpine chain was already
well formed during the Pleistocene and, thanks to its transverse orien-
tation, represented an important vicariant barrier between the
Mediterranean and European ichthyofauna (Bianco, 1995). The effi-
cacy of the Alps as a barrier to fish colonization is demonstrated by
the existence of several endemic species of the PadanoVenetian bio-
geographic district (Bianco, 1995), as well as by the genetic divergence
between the native fish populations inhabiting the northern and
southern rims of the Alps (Sušnik, Snoj, & Dovč, 2001). This genetic
divergence can be regarded as indirect evidence of the separated bio-
geographic history of these populations and sometimes challenges
their real taxonomic status as a single transalpine species (Šlechtová,
Bohlen, Freyhof, Persat, & Delmastro, 2004). The role of the eastern
Alps as a barrier to Italian and Adriatic freshwater fish has been clearly
established for several taxa, e.g. agnates (Meraner & Gandolfi, 2012),
cyprinids (Stefani, Galli, Crosa, Zaccara, & Calamari, 2004; Perea
et al., 2010 and reference therein), sculpin (Cottus gobio Linnaeus,
1758; Lucek, Keller, Nolte, & Seehausen, 2018), southern pike (Esox
cisalpinus Bianco & Delmastro, 2011 or Esox flaviae Lucentini et al.,
2011, as synonymous; Gandolfi et al., 2017), and several salmonids,
such as the marble trout, Salmo marmoratus Cuvier, 1829, the Adriatic
haplotypes of the brown trout, Salmo trutta Linnaeus, 1758, complex
and the European grayling, Thymallus thymallus (Linnaeus, 1758)
(Bernatchez, 2001; Meraner, Cornetti, & Gandolfi, 2014). As well as
S. alpinus, the Danubian haplotypes (DA lineages) of the brown trout
and European grayling can be found in both the Austrian and Italian
Tyrol, and were used in ancient (S. trutta, at least) and recent stocking
campaigns (Splendiani et al., 2016, and references therein). The pres-
ence of these DA lineages in the Italian Tyrol can be explained by
ancient introductions from Austria or by ancient river captures
(Meraner, Baric, Pelster, & Dalla Via, 2007). The presence of the
T. thymallus DA lineage in the Italian Tyrol, however, has been related
to a mediaeval introduction, based on an estimated divergence time of
116 generations and placing its origin close to the ruling period of the
Austrian monarch Maximilian I (Meraner et al., 2014). Historical intro-
ductions that occurred in the 16
century provide a plausible scenario
for explaining the present distribution of several game fish (i.e.
S. alpinus,S. trutta DA lineage, and T. thymallus DA lineage) in the
Southern Alps.
An interesting contribution to solving the problem might come
from a comparison of the biogeographic histories of transalpine game
versus nongame fish, such as the sculpin (C. gobio), i.e. a species that
is at presently economically insignificant and, when compared with
cooccurring game species (e.g. S. alpinus,S. trutta, and T. thymallus),
has presumably suffered fewer translocations for fishing purposes
(Lucek et al., 2018). In addition to many other freshwater fish, the exis-
tence of a deeply divergent Adriatic clade of C. gobio from the T icino
drainage (southern Alps, Switzerland) indicates a separated biogeo-
graphic history between the populations from the northern and south-
ern rims of the Alpine barrier (Lucek et al., 2018). However, Šlechtová
et al. (2004) found that some C. gobio populations from the Adriatic
basin originated from a recent invasion from the Danubian drainage
area. Although this might be explained by one or more stream captures
(according to Šlechtová et al., 2004), human translocations should also
be taken into account to explain these uncommon phylogenetic pat-
terns. Indeed, small fish are commonly used as live bait for fishing,
and their distribution can be altered by anglers (Jørgensen et al.,
1999; Miró & Ventura, 2015). There is also evidence of similar range
modifications for C. gobio (Jørgensen et al., 1999), and the assumption
that nongame species are immune to human translocations should be
considered with caution in this case.
Headwater stream captures are commonly called into question to
explain the presence of S. alpinus in the southern Alps (Tortonese,
1970). Stream captures are a rare geomorphological event, but numer-
ous phylogeographic studies have inferred river capture as a coloniza-
tion mechanism in freshwater fish (Waters & Wallis, 2000). In the case
of S. alpinus, the river capture would have occurred somewhere along
the border between the northern and southern Alps. As fish are not
able to naturally colonize high mountains, this river capture would
have occurred at relatively low altitudes, i.e. through Alpine passes
connecting Austria and Italy. A focused geomorphological study
involving the main Alpine passes of this area might also give some
indications on the possibility of a similar event.
2.3 |Phylogenetic approach
Alpine populations of S. alpinus have a low genetic mitochondrial DNA
(mtDNA) diversity, which is regarded as a consequence of a single
postglacial colonization 10 00020 000 years ago (Brunner, Douglas,
& Bernatchez, 1998). If S. alpinus is native in Italy, however, some
degree of genetic distinctiveness between the Italian and Austrian
populations should remain visible as an effect of the Alpine barrier,
i.e. a distinct mtDNA lineage or, at least, some private Italian haplo-
types. There is only one phylogenetic study that included Italian
S. alpinus specimens (Colli et al., 2010), which was based on mtDNA
and amplified fragment length polymorphism (AFLP) analyses. That
study provided contradictory results on the origin of S. alpinus, but it
showed that the Italian populations are affected by a strong genetic
admixture. This is a likely consequence of past and present introduc-
tions and may have hindered the possibility of understanding the phy-
logenetic history of the Italian S. alpinus populations. Most mtDNA
haplotypes observed in the Italian populations by Colli et al. (2010)
belonged to the socalled Atlantic lineageand had already been
observed in Austrian populations (Brunner et al., 1998; Brunner,
Douglas, Osinov, Wilson, & Bernatchez, 2001). Their presence in Italy
could represent the effect of fish translocations carried out in the
Middle Ages. However, a new haplotype (hereafter referred to as
the Trentino haplotype) was also observed in a high mountain lake
(Lake Erdemolo, 1994 m a.s.l.; Appendix S1), but its genetic distance
from haplotypes already detected appears surprisingly low. AFLP anal-
yses indicate that the specimens from this lake are hybrids between
populations from different geographic regions, although it is not clear
if these are from the northern Alps or from Northern Europe. The find-
ing of a new haplotype in a hybrid population makes any attempt at
classifying its origin very difficult. Based on the outcomes of AFLP
analyses, Colli et al. (2010) maintain that at least three populations
from Trentino AA (the lakes Lagorai Maggiore, Corvo Maggiore, and
Bombasel) should be considered native, but this result contrasts with
mtDNA analyses, which indicate that the same populations belonged
to the Atlantic lineage. Unfortunately, none of these nucleotide
sequences were deposited in a public database nor provided to us
when requested, limiting the possibility of further phylogenetic analy-
ses or a reevaluation of the Trentino haplotype. It would be very
interesting, however, to backcalculate the number of generations
passed since the separation from Austrian haplotypes, as has already
been performed for the T. thymallus DA haplotypes from the Italian
Tyrol (Meraner et al., 2014).
2.4 |Overview
Overall, a parsimonious approach suggests that historical introduction
is the most likely hypothesis for the origin of S. alpinus in the southern
Alps. The hypothesis concerning its native status lacks sound congru-
encies among the different research approaches. These are: (i) histor-
ical evidence of ancient introductions; (ii) arguments excluding the
natural colonization of high mountain lakes by this species; (iii) only
speculative biogeographic and phylogenetic arguments; and (iv) no
archaeozoological evidence in favour of autochthony. Thus, S. alpinus
should be considered an old introduced species in all of the high
altitude historical sites of occurrence, and its autochthony in historical
sites at lower altitudes (lakes Molveno and Tovel) seems highly
unlikely. This small margin of uncertainty might be filled by transpar-
ent and comprehensive studies using molecular techniques.
3.1 |Conservation status and conservation and
cultural value
Even if the recognition of the alpine populations of S. alpinus as mem-
bers of a separate species (i.e. S. umbla sensu Kottelat & Freyhof,
2007) is not universally accepted, their distinctiveness from boreal
populations highlights the importance of recognizing intraspecific
and intragroup diversity to define rational conservation units. Work
at a level below that of species is an element of conservation that is
growing in recognition and, in partial support of this approach, the
IUCN assessed the conservation status of S. alpinus at a panAlpine
scale. According to the IUCN criteria, the alpine populations of
S. alpinus fall within the Least Concern category of the Red List of
Threatened Species (Freyhof & Kottelat, 2008). Habitat destruction
and interactions and hybridization with alien species such as Salvelinus
fontinalis (Mitchill, 1814), and with boreal S. alpinus, are the main
threats for the species (Englbrecht, Schliewen, & Tautz, 2002; Freyhof
& Kottelat, 2008; Keith et al., 2011).
A rigorous evaluation of the conservation status of the Italian
populations of S. alpinus is hampered definitively by its uncertain clas-
sification as a native or an introduced species. Despite this, S. alpinus
populations have long been managed as a conservation unit, and the
species was included on the list of Italian fish of conservation interest
(Zerunian, 2003). Although the Italian S. alpinus populations were clas-
sified as Data Deficient under the IUCN national Red List of Endan-
gered Species (because of the lack of information concerning
population trends; Bianco et al., 2013), their recent spread across
the Alps would mean that their conservation status would not raise
any particular concern in Italy (Figure 1). However, the authors
claiming the existence of a native Italian genetic lineage contend that
the few residual native Italian populations are in a critical conservation
state exacerbated by hybridization with northern populations (Colli
et al., 2010).
If overwhelming evidence were to emerge of the autochthony of
S. alpinus from the low mountain lakes of Molveno and Tovel, these
populations, as well as some historically or recently introduced
populations bearing more or less intact native genotypes, would
assume a very high conservation value. These populations could be
used as ex situ populations with conservation value, e.g. pure S. trutta
belonging to the Danubian haplotype are threatened in Austria
because of the introgression with domestic lineages, but ancient pop-
ulations introduced in high mountain lakes are currently valued as a
conservation resource (Weiss, Schlötterer, Waidbacher, & Jungwirth,
2001). For the reasons mentioned above, a similar scenario is very
unlikely for the Italian S. alpinus. This situation does not prevent the
attribution of a historical and cultural value to the ancient Italian pop-
ulations, however, including the fact that they are a very old testimony
of ancient wildlife management, and that they are part of the gastro-
nomic tradition of Trentino AA. Fortunately, S. alpinus lives in isolated
habitats and does not expand autonomously, which would create a
conflict between the need to preserve its cultural value while still tak-
ing care of the ecological integrity of alpine waters.
3.2 |An assessment of the management practices in
3.2.1 |What has been done so far
Fishing and stocking have generally been allowed regardless of the
presence of ancient S. alpinus populations, and the ancient population
of Lake Molveno became extinct in 1952 owing to the construction of
a hydroelectric plant (but it was subsequently restocked with individ-
uals from Lake Iseo, which, in turn, probably came from Lake
Molveno). Ancient populations were affected by fishing and competi-
tion with other recently introduced fish (Appendix S1), and were
therefore sustained by means of several stocking campaigns using
S. alpinus from various origins (i.e. from other historical sites, from
the northern Alps, and maybe from the boreal regions; Appendix S1).
In more recent times, from 2000 to 2016, S. alpinus was introduced
into 29 lakes of the Provincia Autonoma di Trento (PAT, the local
administrative structure including all of the putative native popula-
tions of S. alpinus in Italy). At least 14 of these lakes did not previously
contain S. alpinus, and one of them was still fishless (see Appendix S1
and references therein). On at least two occasions, the introduction of
S. alpinus was associated with the introduction of minnows,
Phoxinus sp., to provide highquality food for S. alpinus (Cavallar,
2013). In recent times, S. alpinus from PAT rapidly became an impor-
tant aquaculture resource (Camera di Commercio, Industria,
Artigianato e Agricoltura di Trento (CCIAA), 2015), granted the
Protected Geographical Indication (PGI) EU quality logo (Council of
the European Communities, 2013), and used in territorial marketing
to attract fisheryrelated and gastronomic tourism (Ciutti, Merati,
Mirto, Coller, & Benedetti, 2006). In the last few years, despite the
very dubious native status of the Italian populations of S. alpinus and
their genetic admixture, an ex situ action has been undertaken to pre-
serve part of the residual original genetic diversity of the ancient pop-
ulations. Several domestic strains have been isolated in the hatchery
of Molveno, based on the lake of origin of their founder individuals,
and these have been used for stocking many mountain lakes in the
3.2.2 |What went wrong?
So far, the management of S. alpinus has produced several undesirable
effects both in terms of conservation of the historical populations and
in terms of protection of high mountain aquatic habitats. The distribu-
tion of S. alpinus in Italy (Figure 1) and the genetic composition of its
ancient populations have been changed by means of its long history
of stocking (Colli et al., 2010), despite recent attempts to preserve
their residual original genetic diversity. The establishment of some
ex situ populations indicates that management authorities recognized
the importance of preserving intraspecific diversity. The founders of
domestic populations already had admixed genotypes, however, and
their descendants were incautiously used to stock many lakes. At
the same time, the management and misguided conservation of S.
alpinus increased the invasion potential of alien fish in high mountain
lakes (i.e. with introductions of S. alpinus and associated Phoxinus sp.).
As in the rest of the Italian Alps, fish stocking in mountain lakes is also
authorized in PAT, with scarce consideration of: (i) the negative eco-
logical implications; (ii) the international legislation prohibiting the
introduction of species that are nonnative to a particular territory
(Council of the European Communities, 1993, 2014, 2016); and (iii)
the conservation constraints at some sites of introduction, i.e. many
lakes that are stocked with S. alpinus are located within the Natura
2000 network and are designated as special areas of conservation
and special protection areas(Council of the European Communities,
1992, 2010), and Lake Tovel is protected under the Ramsar Conven-
tion on Wetlands of International Importance (UNESCO, 1971). How-
ever, using the supposed native status of S. alpinus in some lakes of
PAT, its introduction has been promoted as a conservation measure,
illustrated by the fact that a protected area also took part in these
alleged conservation actions (Parco Naturale Adamello Brenta (PNAB),
2011). Salvelinus alpinus stocking is often associated with an inappro-
priate use of the language typical of conservation efforts, which is
likely to provide misleading educational messages to relevant stake-
holders, such as recreational anglers, anglers' associations, and conser-
vation associations, and diverting resources intended for biodiversity
conservation. Several examples of this misleading communication
can be found not only in the local press as part of territorial marketing
(Ciutti et al., 2006), but also in scientific reports and settings (Betti,
2006; PNAB, 2011). The same rhetoric is sometimes also used outside
PAT in several fishstocking projects from disparate regions of the
southern Alps, where the use of S. alpinus instead of other salmonids
is communicated as an ecologically friendly option. Moreover, the
introduction of minnows to provide food for S. alpinus increases the
invasion potential of a species that is causing serious ecological dam-
age in many boreal and alpine habitats (Miró, Sabás, & Ventura,
2018). To the best of our knowledge, this is the first case where min-
now introduction was mediated by a public authority. In general, man-
agement and conservation authorities never rule out fish stocking as
the main management tool, incurring some irreversible errors and
unnecessarily expensive strategies (e.g. the ex situ production of
S. alpinus fry for lake stocking).
3.2.3 |What should have been done?
We contend the systematic use of introductions as a primary means of
conservation and management. Cheaper and more effective measures
ought to be used instead, such as in situ conservation of ancient pop-
ulations. Nonintervention management would have been the best
option, representing a costeffective approach that can free resources
for higher priority conservation actions or sound research. Most of the
aforementioned undesired effects could have been avoided if the his-
torical populations had been protected, i.e. not subjected to fishing (or
at least overfishing, requiring periodic restocking), and not subjected
to the introduction of competitor fish (e.g. trout). This would have
allowed the preservation of the genetic integrity of the ancient
S. alpinus populations, without significantly affecting angling opportu-
nities (fishing would only have been banned in a few lakes). In the
same way, the scientific value of the historical populations would also
have been preserved, because stocking bans would have avoided
genetic admixture, which is currently one of the main obstacles to
understanding the origin of the historical populations using modern
molecular techniques.
3.2.4 |What to do now
There are now two priorities: stop the invasion of introduced fish in
the Alps and reach an unambiguous stance on the native or introduced
state of Italian S. alpinus. Limiting fish stocking (including S. alpinus and
several other species) is probably the best option for stopping and
reversing fish invasion (Armstrong & Knapp, 2004), and for ensuring
a better adherence to international legislation. In this regard, the
senseless rhetoric of the conservation value of S. alpinus introductions
should be definitively abandoned, putting a stop to the broadcasting
of noneducational messages in an already conflictive context.
Resources destined for stocking campaigns would become available
for wiser management and conservation priorities or for definitive
research into the native or introduced status of S. alpinus. Research
priorities include a new comprehensive and transparent phylogenetic
study, or new archaeozoological or palaeoecological evidence, proving
or not that S. alpinus was present before the historical introduc-
tions in the 16
century, possibly in much earlier prehistoric times.
Some molecular techniques (i.e. a phylogenetic study including more
samples from Austria, or the study of ancient environmental DNA
(eDNA) in palaeosediments) could represent a valuable tool to thor-
oughly understand the origin of Italian populations. In addition, the
inclusion of the domestic S. alpinus from the Molveno hatchery in a
phylogenetic study would provide indispensable information before
their use as a conservation and management tool. If the likely non
native status of S. alpinus in Italy were to be confirmed, the rationale
for maintaining the domestic strain should also be reevaluated.
We thank Giovanni del Mastro and the personnel of the Ufficio Caccia
e Pesca (Provincia Autonoma di Bolazano) for providing original data
on the distribution of S. alpinus, and two anonymous reviewers for
their constructive comments. We also thank Laura Bodé for her care-
ful linguistic revision.
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How to cite this article: Tiberti R, Splendiani A. Management
of a highly unlikely native fish: The case of arctic charr Salvelinus
alpinus from the Southern Alps. Aquatic Conserv: Mar Freshw
Ecosyst. 2019;19.
... The results presented here support the hypothesis that the extant normal charr of Lake Constance over the years may have had the potential to both displace and hybridize with endemic charr and pass on their faster growth trait (Tiberti and Splendiani 2019). An alternative hypothesis, that the observed difference in growth in normal charr might reflect a diet shift (Malmquist et al. 1992) towards piscivory (Klemetsen et al. 2003, Eloranta et al. 2011, 2015, has to be rejected, as the data presented here indicate a switch in feeding preference from macrozoobenthos during the 1970s (Dörfel 1974) to pelagic zooplankton today. ...
... In the present case, it appears that stocking offers the most likely explanation for the observed morphological and genetic traits in extant populations of Lake Constance charr, and not introgressive hybridization between endemic forms or rapid adaptation after re-oligotrophication. Many studies of Arctic charr in other lakes have identified stocking as a relevant factor driving change in the genomic biodiversity of endemic populations (Brunner et al. 1998, Savary et al. 2017, Tiberti and Splendiani 2019 and stocking with allochthonous fish has been common practice in most pre-alpine and alpine lakes for over 100 years (Englbrecht et al. 2002). Conservation practitioners must often act without full knowledge of the factors at play in a given setting but inferences about the integrity of endemic species based solely on recent genetic data without accounting for possible confounding factors like stocking (Vonlanthen et al. 2012) may lead to a false presumption, e.g. that the endemic normal charr of Lake Constance still exist in large numbers. ...
In the welcome circumstance that species believed extinct are rediscovered, it is often the case that biological knowledge acquired before the presumed extinction is limited. Efforts to address these knowledge gaps in particular to assess the taxonomic integrity and conservation status of such species can be hampered by a lack of genetic data and scarcity of samples in museum collections. Here we present a proof-of-concept case study based on a multidisciplinary data evaluation approach to tackle such problems. The approach was developed after the rediscovery, 40 years after its presumed extinction, of the enigmatic Lake Constance deep-water charr Salvelinus profundus. Targeted surveys led to the capture of further species and additional sympatric normal charr, Salvelinus cf. umbla. Since the lake had been subject to massive stocking in the past, an evaluation of the genetic integrity of both extant forms was called for in order to assess possible introgression. A two-step genomic approach was developed based on restriction site associated DNA (RAD). Diagnostic population genomic (SNP) data was harvested from contemporary samples and used for RNA bait design to perform target capture in DNA libraries of archival scale material, enabling a comparison between extant and historic samples. Furthermore, life history traits and morphological data for both extant forms were gathered and compared with historical data from the last 60-120 years. While extant deep-water charr matched historical deep-water specimens in body shape, gill raker count and growth rates, significant differences were discovered between historical and extant normal charr. These resulted were supported by genomic analyses of contemporary samples, revealing the two extant forms to be highly divergent. The results of population assignment tests suggest that the endemic deep-water charr persisted in Lake Constance during the eutrophic phase, but not one of the historical genomic samples could be assigned to the extant normal charr taxon. Stocking with non-endemic charr seems to be the most likely reason for these changes. This proof-of-concept study presents a multidisciplinary data evaluation approach that simultaneously tests population genomic integrity and addresses some of the conservation issues arising from rediscovery of a species characterized by limited data availability.
... The most common stocked fish species in alpine lakes of the Alps are Arctic Charr (Salvelinus alpinus L.) and Brown Trout (Salmo trutta L.) (Pechlaner, 1966(Pechlaner, , 1984Tiberti and Splendiani, 2018). The later species is described as an opportunistic feeder preying on aquatic and terrestrial invertebrates, but after reaching large size, piscivorous feeding is also commonly observed (Klemetsen et al., 2003;Kottelat and Freyhof, 2007;Jensen et al., 2012). ...
... Sympatric populations of S. trutta in lakes are usually piscivorous and even sometimes cannibalistic (L' Abée-Lund et al., 1992;Meeuwig and Peacock, 2017). An exception appears to be when they live in sympatry with Arctic charr Salvelinus alpinus (L.) (Cavalli et al., 1998;Sánchez-Hernández and Amundsen, 2015), another common stocked fish species in alpine lakes of the Alps (Tiberti and Splendiani, 2018). Otherwise, in oligotrophic alpine and subarctic lakes, S. trutta seems to follow a generalistic and opportunistic feeding behavior that includes benthic, zooplanktonic and pleustonic resources (Table 1). ...
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The introduction of fish into mountain lakes typically leads to profound ecological changes within the food web, but its consequences depend on the dietary preferences of fish and on the resistance of prey organisms against predation. Here we used stable isotopes and fatty acid analyses in combination with the traditional stomach content analysis to examine the diet of an allopatric population of Salmo trutta, which has originally been stocked during the Middle Ages in an alpine lake, and to identify what components of the food web are more affected. The results from stable isotopes and fatty acids indicated that planktonic and benthic food sources, in particular chironomids larvae, were the most important prey items all year round. Airborne terrestrial insects made most of the stomach content during the ice-free period, but their stable isotope and fatty acids values did not match up with those in fish, suggesting a minor role for fish nutrition. Copepods were relevant as fish diet only during the ice-covered period. In contrast to the stable isotope values of the fish muscle tissue, those of the liver, which reflect potentially short-term changes in diet, were significantly different between the ice-covered and ice-free period. Fatty acid analysis revealed that polyunsaturated fatty acids contents of chironomids, copepods, and chydorids contributed similarly to fish diet. Overall, our results suggest that the introduction of this fish species has decreased the lake-to-land resource transfer by reducing the abundance of emerging midges and that the population is food-limited as indicated by its low condition factor. This field study eventually acts as a reference for possible future reintroduction efforts, as this population is one of few existing in Europe with pure Danubian origin.
... To address this conservation issue, it is a basic requirement to have reliable distribution data on introduced fish (Radomski & Goeman, 1996;Mir o & Ventura, 2013). However, such data are usually scarce, lacking, not updated, and scattered in local archives and, therefore, inaccessible for many montane regions (Ventura et al., 2017;Tiberti & Splendiani, 2019). Given the situation, it would be beneficial for available data to be collated and published by fish management authorities and kept up to date. ...
... Cottus gobio; Fam. Cottidae; Pastorino et al., 2019;Tiberti & Splendiani, 2019). However, the fact that false absences by VES were recorded for all the species, but only when they lived at low densities, suggests that the population density, not the species-specific features, is the main factor influencing fish detectability. ...
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Introduced fish are a widespread ecological threat in originally fishless high mountain lakes. However, basic distribution data are largely missing for most high mountain regions. Using time‐consuming standard methods (e.g. Nordic standard fishing nets) to assess fish distribution and relative densities at a relevant spatial scale can be impracticable, because of the large number of high mountain lakes. To overcome this problem, alternative rapid monitoring methods would be helpful. Visual encounter survey (VES) is a candidate method that enables observing fish from the shoreline. It takes only minutes to implement and is already widely used for amphibian monitoring in high mountain lakes and ponds. VES was evaluated as a method for monitoring introduced salmonids and cyprinids (the most widespread fish families) in 52 high mountain lakes. The probability of detecting both families by VES rapidly approaches 100% as the relative densities of fish increase, and false absences are restricted to populations living at low relative densities. VES also provides simple indications about fish relative densities, distinguishing between high‐density and low‐density populations. As VES usually does not enable fish species identifications, we propose VES as a useful method to describe large fish distribution inventories, not needing high taxonomic detail, but necessary for planning large‐scale conservation measures.
... The rate of warming is a major concern, but many other environmental stressors are likely to affect arctic charr population dynamics in alpine lakes and should not be neglected (Champigneulle and Gerdeaux, 1995;Gerdeaux, 2011;Caudron et al., 2014;Tiberti and Splendiani, 2019). While habitat degradation, habitat loss and lack of thermal refugia are critical abiotic pressures, biotic interactions are equally important but receive less attention in a multiple stressors framework. ...
... The past decade has seen investigators start questioning management practices (Brannon et al., 2004), even though when carried out carefully, stocking can help populations recover to a certain extent. A recently published review on the current status of arctic charr in Italian Alps (Tiberti and Splendiani, 2019) suggests that we reevaluate the conservation value of the species at this latitude -especially in lakes where the charr was introduced -and re-think our approach to conservation. Prior to decision-making, a holistic approach integrating life-history, physiological performance and information on the genetic background of populations, remains essential. ...
In a warming climate, the capacity of species to adopt effective strategies to cope with temperature increase will be key to their persistence in hostile environments. Furthermore, elevated temperatures are likely to modulate the effects of other environmental pressures on biota.The Arctic charr (Salvelinus alpinus) is a cold water adapted stenotherm, found essentially below the Arctic circle. In Europe, the Southernmost edge of its native distribution range is located in the Alps where the species remained following the glacier retreat after the last glaciation. As alpine and peri-alpine lakes are deemed particularly vulnerable to warming, these isolated populations can be considered as sentinels of climate change and constitute an interesting study system to investigate i) local adaptation to thermal habitat and ii) population response to multiple environmental stressors.Using a common garden experimental design, we first reared embryos originating from four lakes along an altitudinal gradient to an optimum temperature (5°C) or to a temperature close to the thermal tolerance limit of arctic charr embryos (8.5°C). We measured fitness-related traits in hatched larvae and at near emergence and investigated the evolutionary processes underlying population divergence using a QST-FST approach. Results revealed contrasted thermal reaction norms with effects of temperature affecting survival, body size and timing of hatching, that reflected genetic divergence among populations. However, pairwise population comparisons showed that quantitative trait divergence could often be explained by drift and homogenous selection. Results also indicated that neutral genetic diversity was relatively high, but adaptive potential to warming was limited in populations managed by supportive breeding, suggesting a negative effect of local management practices on populations.A second study investigated the combined effects of temperature and fine sediment, a stressor that affects strongly oxygen availability and habitat quality of salmonids. Results revealed that temperature can decrease the tolerance of arctic charr early life stages to fine sediment. Exposure to a gradient of fine sediment under stressful thermal conditions during egg incubation had dramatic effects on embryonic life-history traits, with temperatures strongly exacerbating the impacts of sediment loads that did not exert any detrimental effects at cold.Finally, a third study showed that co-exposure to temperature and fine sediment during embryo development can lead to different trade-offs between size at hatching, yolk conversion efficiency and timing of hatching among wild populations. As a confirmation of the previous study, temperature and sediment did affect early life traits interactively, although the effects were essentially sublethal and temperature was dominant. This indicated that wild populations were more resistant than the previously studied captive stock, certainly due to natural exposure to sediment, but the observed reduction in size and increased energy expenditure might have critical consequences in later life stages.Overall, this work showed that wild arctic charr populations exhibit adaptive divergence in response to temperature to a certain extent, but the history of anthropogenic disturbances in alpine lakes (inappropriate stocking practices, allochthonous fish introductions, overfishing) is likely to hinder their capacity to respond and adapt to future temperature elevations. This work also highlighted that the reevaluation of common stressors in freshwaters (e.g. fine sediment deposition) under different thermal scenarios while taking into account population specificities is necessary.
... On the other hand, there is ample evidence of salmonid introductions in old historical times from outside Italy. Domestication practices and translocations of freshwater fishes, even across mountain ranges, go back to the Middle Ages and possibly to the Neolithic, seamlessly continuing through to the 18th and 19th century, before the onset of the fishculture industry [10,[116][117][118][119]. Non-native trouts with "brown-trout" dotted coloration patterns could have been introduced in northern Italy from adjacent areas such as the orographic right tributaries of the Po River, or even beyond the Alpine Divide, e.g., from the Danube basin, such as the common carp Cyprinus carpio L. in the Roman Period [10,120]. ...
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During the last 150 years, the trout-culture industry focused on enhancing trout populations by stocking, in response to the growing anglers’ demand and the habitat degradation associated to the rapid urbanization and hydropower development. The industrialized north of Italy, home to the Italian Alpine and subalpine trout populations, is the source of most of the revenues of the national trout-culture industry. Its rapid growth, and the massive introduction of non-native interfertile trouts eroded the genetic diversity of native lineages, leading to harsh confrontations between scientists, institutions, and sportfishing associations. We review here the state of the art of the taxonomy and distribution of the northern Italian native trouts, presenting both scientific results and historical documentation. We think the only native trouts in this region are Salmo marmoratus, widespread in this region, plus small and fragmented populations of S. ghigii, present only in the South-western Alps. We strongly recommend the interruption of stocking of domesticated interfertile non-native trouts in this area, and recommend the adoption of Evolutionary Significant Units for salmonid fishery management. We further propose future research directions for a sustainable approach to the conservation and ecosystem management of the fishery resources and inland waters of northern Italy.
... On the other hand, there is ample evidence of salmonid introductions in old historical times from outside Italy. Domestication practices and translocations of freshwater fishes, even across mountain ranges, go back to the Middle Ages and possibly to the Neolithic, seamlessly continuing through to the 18th and 19th century, before the onset of the fishculture industry [10,[116][117][118][119]. Non-native trouts with "brown-trout" dotted coloration patterns could have been introduced in northern Italy from adjacent areas such as the orographic right tributaries of the Po River, or even beyond the Alpine Divide, e.g., from the Danube basin, such as the common carp Cyprinus carpio L. in the Roman Period [10,120]. ...
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During the last 150 years, the trout-culture industry focused on enhancing trout populations by stocking, in response to the growing anglers’ demand and the habitat degradation associated to the rapid urbanization and hydropower development. The industrialized north of Italy, home to the Italian Alpine and subalpine trout populations, is the source of most of the revenues of the national trout-culture industry. Its rapid growth and the massive introduction of non-native interfertile trouts eroded the genetic diversity of native lineages, leading to harsh confrontations between scientists, institutions, and sportfishing associations. We review here the state of art of the taxonomy and distribution of the northern Italian native trouts, presenting both scientific results and historical documentation. We think the only native trouts in this region are Salmo marmoratus, widespread in this region, plus small and fragmented populations of S. ghigii, present only in the Southwestern Alps. We strongly recommend the interruption of stocking of domesticated interfertile non-native trouts in this area, and recommend the adoption of Evolutionary Significant Units for salmonid fishery management. We further propose future research directions for a sustainable approach to the conservation and ecosystem management of the fishery resources and inland waters of northern Italy.
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The golden-striped salamander is a streamside species endemic to the northwestern corner of the Iberian Peninsula. In the first half of the twentieth century, an undisclosed number of individuals of this species were reportedly captured in Buçaco, Central Portugal, and deliberately introduced in Sintra Mountains, 170 km south of its native distribution range. The discovery of a breeding population of this salamander in Sintra during 2015 prompted this work: we used neutral genetic markers, the mitochondrial DNA cytochrome b (cytb), and seven microsatellite loci to elucidate on the relict/human-introduced nature of Sintra population, identify the potential source population, and infer the severity of founder effect. Our results support a human-mediated introduction. First, sequencing analysis of cytb showed the presence of a unique haplotype (h31) in Sintra, which was detected only in Buçaco and in two additional populations located close to Mondego river. Second, microsatellite analysis showed that Sintra is more closely related to populations in between Douro and Mondego rivers (Central Portugal), instead of its geographically closest populations (southernmost), as would be expected if Sintra was a relict population isolated in an interglacial refuge. Third, Sintra presents both reduced levels of genetic variability and effective population size when compared to native populations, particularly to those of Central Portugal. Consistent with an isolated population funded by a small number of individuals (inferred herein to be ca. 10–11 salamanders), Sintra forms a geographically coherent genetic unit that is significantly differentiated from the extant native C. lusitanica populations. Although our data provide supporting evidence for Buçaco as a likely source population, as documented in the literature, overall, we cannot unequivocally exclude other populations close to Mondego river as a potential source of the introduced individuals in Sintra.
The peninsular trout, commonly referred to as the “Mediterranean brown trout” and here classified as Salmo ghigii, has an important role in the ongoing conflict on fish stocking. The Italian law defines as autochthonous species or differentiated populations that are part of the original flora or fauna of a certain area, or that arrived there without human intervention. It defines as allochthonous species or differentiated populations that are not a part of the original flora or fauna of a certain area, but arrived there due to intentional or accidental human intervention. In Italy, the law defines as “parautochthonous” those species that are not a part of the original flora or fauna of a certain Italian territory, but were here introduced and naturalised before 1500, or were introduced elsewhere before 1500 and arrived in Italy without human intervention. This concept is presently only applied, by law, to homeotherms (mammals and birds). The only autochthonous and widely distributed salmonid in the Alpine and subalpine Italian region is the marble trout (S. marmoratus). There is strong scientific evidence that S. ghigii is autochthonous only in the South-western Alps (Maritime and Cottian Alps), and that the introduction of stocked “Mediterranean brown trout” of variable origin in other areas of this region implies high risks of introgressive hybridization with S. marmoratus. Such introductions also risk compromising future attempts of better understanding the phylogeographic history of native Italian and Alpine salmonids. For these reasons, we propose to dedicate to native populations of S. ghigii the utmost attention and caution, when utilising it for stocking activities. In general, Italian salmonid populations should always be managed as Evolutionary Significant Units, at the basin and sub-basin scales. Biologia Ambientale, 36: 24-44.
Mountain lakes are the most affected by climate change; however, few of these lakes are regularly sampled because of their remoteness. We discussed limnological data (e.g. water temperature, light transparency, and plankton diversity) of Lake Campo (1944 m above sea level, Adamello Mountains, Italy) scattered over almost forty years in the light of climate change. Specifically, occasional samplings in 1980, 1988, 2016, 2017, and 2018 and more extensive surveys in 1997 and 2015 were carried out. Among the investigated years, 2015 was the warmest. Inter-year variability in water temperature was quite marked in Lake Campo. Water temperature profiles of July (1980, 1997, 2015) showed increased surface warming, while the deeper layers (> 15 m) were always isothermal at around 5 °C. Hypolimnetic dissolved oxygen never decreased below 50 % saturation. Secchi disk depth was not substantially different among years. Summer profiles of light transparency showed discontinuous light attenuation, which was tentatively attributed to algae located in deeper layers. In cluster analysis of phytoplankton and zooplankton data, differences between seasons but not years were found. The autumn decline of Bacillariophyta and the increase of mixotrophic Cryptophyta was linked to decreasing silica concentrations towards autumn. Apart from this general pattern, several observations (e.g. high abundance of Tovellia sanguinea, requiring warmer temperatures and thermal stratification to compete with Bacillariophyta; a spatially extended metalimnetic oxygen maximum in July 2015) showed the effects of particularly warm conditions of 2015 compared to 1997. The continuous presence of crustacean males and first generation of rotifers (Polyarthra f. aptera) hatching from sexual eggs indicated the importance of sexual reproduction in the lake. Length measurements of Daphnia gr. longispina before (1997) and after (2015) non-native fish removal and Arctic char introduction were similar and indicated no apparent change in predation pressure. Studies like this, despite scattered data, can provide valuable insights into the changes mountain lakes undergo through time.
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Stocking game fish into originally fishless mountain systems is a major threat for high-altitude lakes and the inhabiting native species. The adoption of stocking and fishing bans and the implementation of eradication actions have proven to be effective in stopping this biological invasion. However, there is still little appetite for such measures/actions in fishery management in European mountains and protected areas probably because of their possible, negative, socio-economic implications. Here, we briefly present; i) the ecological costs of this general inaction and ii) the reasons for embracing a conservation-minded approach to the management of fish resources in mountain areas, adopting appropriate measures and actions (i.e. fish eradications).
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High mountain lakes are mostly naturally fishless ecosystems that have received numerous trout introductions over the world. Extensive studies mostly developed in west North America have shown a large negative effect of these introductions on amphibians, although no extensive studies are available from other continents such as Europe. Fish were also introduced extensively in the Pyrenees (southern Europe), mainly trout for angling and minnows for their use as live bait for fishing trout. We studied the effect of non-native trout and minnows on the occurrence of amphibian species inhabiting Pyrenean lentic habitats. Chi-square tests and Generalized Additive Models were applied on a dataset of 12 environmental descriptors from 1739 water bodies surveyed from 2006 to 2016. After accounting for environmental characteristics we found a large negative effect of non-native trout and minnows on Pyrenean amphibians. Trout was negatively associated with four of the six studied species. Since minnows were only introduced in trout present lakes, they were only significant for Rana temporaria, the most distributed amphibian in the area. None of the palatable amphibians have been able to recolonise the lakes where minnow remain as the only fish species indicating a strong negative effect. Minnow is the non-native fish with a higher introduction rate in the mountain range indicating that it might be a threat for other species in the future. Therefore, the control of trout stocking and minnow release in high mountain lakes is necessary to preserve European and worldwide amphibian populations in these ecosystems.
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High mountain lakes are originally fishless, although many have had introductions of non-native fish species, predominantly trout, and recently also minnows introduced by fishermen that use them as live bait. The extent of these introductions is general and substantial often involving many lakes over mountain ranges. Predation on native fauna by introduced fish involves profound ecological changes since fish occupy a higher trophic level that was previously inexistent. Fish predation produces a drastic reduction or elimination of autochthonous animal groups, such as amphibians and large macroinvertebrates in the littoral, and crustaceans in the plankton. These strong effects raise concerns for the conservation of high mountain lakes. In terms of individual species, those adapted to live in larger lakes have suffered a higher decrease in the size of their metapopulation. This ecological problem is discussed from a European perspective providing examples from two study areas: the Pyrenees and the Western Italian Alps. Species-specific studies are urgently needed to evaluate the conservation status of the more impacted species, together with conservation measures at continental and regional scales, through regulation, and at local scale, through restoration actions, aimed to stop further invasive species expansions and to restore the present situation. At different high mountain areas of the world, there have been restoration projects aiming to return lakes to their native fish-free status. In these areas autochthonous species that disappeared with the introduction of fish are progressively recovering their initial distribution when nearby fish-free lakes and ponds are available.
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Esox flaviae represents the native esocid species of the Italian peninsula at present potentially highly threatened by the diffusion of exotic E. lucius. Here, we present a novel mtDNA (N = 272) and microsatellite (N = 275) dataset including 13 test and 3 reference samples, aimed to delineate the distribution of the native as well as the exotic species and to unravel potential introgressive hybridisation between the two species in Northern Italy. We highlight a complex mosaic distribution of both species, with contrasting occurrence even between neighbouring sites. Significant genetic substructure is still observed within E. flaviae, while the dispersal of the invader seems to be promoted by restocking actions. In addition, we prove the existence of introgressive hybridisation between native and exotic pikes. Here, gender-biased hybridisation is suggested, with native E. flaviae constituting the predominant ‘mother species’ in the hybridisation process. Finally, we underline the need for a revision of fisheries management regulations, for which a nation-wide and exhaustive genetic screening in the near future should build the scientific basis.
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In this pilot study for the first time, ancient DNA has been extracted from bone remains of Salmo trutta. These samples were from a stratigraphic succession located in a coastal cave of Calabria (southern Italy) inhabited by humans from upper Palaeolithic to historical times. Seven pairs of primers were used to PCR-amplify and sequence from 128 to 410 bp of the mtDNA control region of eleven samples. Three haplotypes were observed: two (ADcs-1 and MEcs-1) already described in rivers from the Italian peninsula; one (ATcs-33) belonging to the southern Atlantic clade of the AT Salmo trutta mtDNA lineage (sensu Bernatchez). The prehistoric occurrence of this latter haplotype in the water courses of the Italian peninsula has been detected for the first time in this study. Finally, we observed a correspondence between frequency of trout remains and variation in haplotype diversity that we related with ecological and demographic changes resulting from a period of rapid cooling known as the Younger Dryas.
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Environmental, climate and historical factors are important to explain patterns of freshwater biodiversity and population dynamics in the Mediterranean area. This region is one of the most important areas for the maintenance of native lineages for brown trout. The aim of this study was the identification of the main drivers for the spread and the distribution of genetic introgression between alien brown trout and two native Mediterranean salmonids (brown and marble trout). Estimates of mitochondrial and nuclear introgression were from both the literature and original data and were used as dependent variables in a multivariate framework, correlating them to a suite of environmental and climate parameters. The last glacial maximum appeared as an important factor explaining the geographic pattern of alien brown trout genes throughout the Alps. Here, native populations of Mediterranean salmonids persisted in former refugia. Throughout the Italian Peninsula and major islands, geological setting of catchment and current climate conditions are key factors for securing the persistence of native trout populations. The reevaluation of genetic data regarding the spread of alien brown trout lineage into Mediterranean salmonids populations with a landscape approach allowed us to reveal the role of important factors implicated with the current pattern of distribution of remnant native populations of salmonids. This information provides new insights for improving conservation strategies and management of taxa threatened by the incipient global climate changes.
Ecological speciation and adaptive radiation are key processes shaping northern temperate freshwater fish diversity. Both often involve parapatric differentiation between stream and lake populations and less often, sympatric intralacustrine diversification into habitat‐ and resource‐associated ecotypes. However, few taxa have been studied, calling for studies of others to investigate the generality of these processes. Here, we test for diversification within catchments in freshwater sculpins in a network of peri‐Alpine lakes and streams. Using 8,047 and 13,182 restriction site associated (RADseq) SNPs respectively we identify three deeply divergent phylogeographic lineages associated with different major European drainages. Within the Aare/Rhine catchment, we observe populations from geographically distant lakes to be genetically more similar to each other than to populations from nearby streams. This pattern is consistent with two distinct colonization waves, rather than by parapatric ecological speciation after a single colonization wave. We further find two distinct depth distribution modes in three lakes of the Aare catchment, one in very shallow and one in very deep water, and significant genome‐wide differentiation between these in one lake. Sculpins in the Aare catchment appear to represent an early stage adaptive radiation involving the evolution of a lacustrine lineage distinct from parapatric stream sculpins, and the repeated onset of depth‐related intralacustrine differentiation. This article is protected by copyright. All rights reserved.