It.J.Fresh.Ichthyol., 2014(1): 244-248.

Italian Journal of Freshwater Ichthyology, 2014 vol. 1
Atti XIII Congresso Nazionale Associazione Italiana Ittiologi Acque Dolci – Sansepolcro (Ar)
It.J.Fresh.Ichthyol.
2014(1) : 244-248.
NEW DATA ON DISTRIBUTION OF POTAMON FLUVIATILE (DECAPODA,
BRACHYURA) IN SICILY (SOUTHERN ITALY)
DALILA GIACOBBE1 & SALVATORE RESTIVO2
1 Salita vecchia Granatari – 98164, Torre Faro, Messina. [email protected]
2 Via S. Giovanni 1 – 98155, Castanea delle Furìe, Messina. [email protected]
Corresponding author: [email protected], [email protected]
Riassunto
Unico Crostaceo Brachiuro presente nelle acque interne italiane, il Granchio di fiume
Potamon fluviatile (Herbst, 1785), sta subendo una notevole rarefazione e riduzione in
abbondanza delle sue popolazioni, fino alla scomparsa da alcuni fiumi in cui era storicamente
presente.
In Sicilia non sono ancora disponibili dati precisi ed aggiornati sullo status e sull’areale
occupato dalla specie. Le segnalazioni puntuali e gli UTM 10x10Km già noti per il granchio
di fiume, consultabili sul database CKmap e sulla ridotta letteratura scientifica disponibile,
risultano non rappresentativi dell’attuale distribuzione di P. fluviatile in Sicilia. Inoltre i dati
disponibili spesso si riferiscono a pubblicazioni risalenti a più di 90 anni fa. Pertanto è stata
avviata un’indagine sulla presenza di questo Brachiuro nei corsi d’acqua della Sicilia orientale
per accertarne la distribuzione attuale, confrontarla quando possibile con dati storici e
bibliografici e raccogliere informazioni sulle popolazioni individuate.
I sopralluoghi sono stati effettuati dal 2006 al 2010 e la presenza di P. fluviatile nei siti
indagati è stata rilevata tramite l’avvistamento diretto, il rinvenimento di esuvie o resti di
individui e la presenza di tane. È stato tenuto conto delle testimonianze di terzi solo quando
supportate da un’adeguata documentazione. Inoltre sono stati annotati dati di carattere
biologico ed ecologico, oltre alle misure morfometriche di esemplari raccolti ed
immediatamente rilasciati. Infine, in alcuni casi sono stati prelevati campioni di tessuto per lo
studio della struttura genetica di popolazione.
Confrontando i risultati ottenuti con i dati di distribuzione desunti dalla bibliografia, si
evidenzia un importante incremento dell’areale occupato dalla specie sull’isola. La quantità
delle nuove segnalazioni puntuali riportate nel presente contributo (corredate di coordinate
UTM 10x10Km) consente di rilevare che il granchio di fiume presenta attualmente una buona
distribuzione in Sicilia orientale e nord-orientale.
Tuttavia sono state rilevate nell’area d’indagine le principali cause di minaccia per i crostacei
d’acqua dolce, quali la riduzione del regime idrico di piccoli corsi d’acqua ed il degrado
ambientale degli habitat dovuto all’inquinamento ed alla loro modificazione fisica causata
dalle attività antropiche.
In conclusione i risultati ottenuti ampliano considerevolmente le conoscenze disponibili sulla
distribuzione delle popolazioni siciliane di P. fluviatile e consentono di riconfermare con
nuovi dati di presenza quelli storici riportati nella letteratura scientifica.
Summary
Population levels of Potamon fluviatile have declined dramatically in recent years throughout
its range. In Sicily, data on the status and the general distribution of this species are very few
and most of them refer to records dating back more than 90 years ago. Therefore an
investigation was initiated to determine the current distribution of this crab in the
watercourses of Sicily. The large number of new reports presented in this contribution, allows
us to observe that at present the river crab shows a good distribution in the island. But many
freshwater habitats where P. fluviatile occurs are increasingly subjected to pollution, habitat
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alterations and anthropogenic disturbance. The protection of river crabs needs to be regulated
by regional laws to preserve this species from decline. The conservation of this crustacean
depends heavily on habitat protection and the preservation of sicilian freshwater ecosystems.
New data reported significantly expand the available knowledge on the distribution of Sicilian
populations of P. fluviatile, contributing to improve the monitoring and the protection of this
species.
Introduction
The river crab Potamon fluviatile (Herbst, 1785), belonging to the family Potamidae, is the
only brachyuran crab inhabiting the Italian freshwater.
It is a crustacean of medium-large dimension, brownish-gray or gray-purple coloured with
large and robust claws. P. fluviatile has a generalist diet and consume a wide variety of food
items, that is either dead or alive, plant of animal. River crabs have few, not specialized
predators, including rats, foxes, weasels, birds of prey and crows. They are found in rivers,
streams and vegetation-rich lakes, in areas with slow moving water, where crabs shelter under
stones or among vegetation, or occupy their burrows dug into the banks; burrows are up to 50
cm deep and have water at the bottom (Gherardi et al., 1987).
The distribution range of P. fluviatile is highly fragmented, and covers parts of many
countries with a Mediterranean coastline: this species is found in Italy, Maltese Islands,
Balkan Peninsula and Greece (Jesse et al., 2009). Recently, in North Africa, P. algeriense has
been described as a new species, where before it was considered a subspecies of P. fluviatile
(Fancelli et al., 2005). In Italy, the river crab is distributed in Sicily, from Calabria to Eastern
Liguria and Tuscan-Emilian Apennines and, with sporadic and most historical records, to the
north of the Apennines (Vannini, 2003).
Population levels of P. fluviatile have declined dramatically in recent years throughout its
range. The river crab used to be present as far north as Lago di Garda in Italy. Nowadays, the
river Po marks its approximate northern distribution limit (Jesse et al., 2009). This trend
towards a decline in population levels is often explained as the result of factors such as
pollution, overharvesting and habitat damage. This species is therefore assessed as Near
Threatened (NT) by IUCN, because it is possible that populations of P. fluviatile in parts of its
range might be in danger of extirpation in the future, especially those on islands or near
centers of human population on the mainland. Due to the population reduction, this species
may already be close to qualify as Vulnerable (VU), but data are lacking (Cumberildge,
2008).
In Sicily, no accurated and updated data are available on the status and the general
distribution of this species (Restivo & Giacobbe, 2009): the data are very few and most of
them refer to records dating back more than 90 years ago (Misuri, 1914; Matteotti, 1919;
Magrì, 1926; Pretzmann, 1983).
Therefore an investigation was initiated to determine the current distribution of this crab in
the watercourses of Sicily, to compare it with historical and bibliographical data when
available and to gather informations about the populations found.
Materials and Methods
First of all has been consulted CKmap database (Stoch, 2000-2006 - version 5.4) and was
carried out a literature research of records and UTM 10x10 Km coordinates recently reported
for P. fluviatile, in order to obtain an accurate and up to date distribution of this species in the
investigation area (Ferrito, 1994; Pasta et al., 2008; Jesse et al., 2009; Duchi, 2010).
New data were collected through field visits undertaken from 2006 to 2010 along several
rivers and streams in Sicily, mainly in the eastern part of the region. The presence of river
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crabs in the sites investigated was detected by direct sighting, the presence of burrows,
exuviae, remains of individuals killed by predators or by vehicles.
The testimonies of other persons about the presence of river crabs have been included in the
study only when supported by appropriate documentation.
Altitude, geographical coordinates, biological and ecological data were recorded in every
presence site found. Individuals were collected, sexed, measured by using a Vernier caliper
(reading error 1/20 mm = 0.05 mm) and released soon after. In some cases, tissue samples
taken from one leg were collected to study the genetic structure of population. The
information collected in the field were stored in a computer database.
Results
The name of the sicilian watercourse and the related UTM 10x10Km squares coordinates
where P. fluviatile has been identified are given (Fig. 1) (Note: “Fiumara” is a local name
used to describe seasonally flowing streams of Calabria and Sicily in Southern Italy):
Modione River UB06; Belice River UB38, UB39; Sosio River UB57; Frattina River UB59;
Nocilla Walloon UB69; Ponte Walloon UB74; Fichera River VB08; Northern Imera River
VB09; Vicaretto Torrent VB29; Simeto River VB85, VB87, VB88; Sarracena Torrent VB89;
Flascio River VB89; Spring of Paradiso VB91; S. Maria di Licodìa VB96; Pollina River
VC20; Canneto Walloon VC40; Mascarino Walloon VC60; San Basilio Torrent VC80;
Fiumara Sinagra VC81; Zappardino Walloon VC92; Cassibile River WA19; Ciane River
WA29, WB20; Anapo River WB00; Cava dei Molini WB01; Leucatìa WB05; Roccella
Torrent WB09; S. Paolo River WB09, WB19; Fiumefreddo River WB18, WB28; Alcantara
River VB99, WB19, WB28; Petrolo Torrent WB29; Munofu Walloon WB29; Fiumara
Elicona WC01; Tripi Torrent WC01; Fiumara Fantina WC10; Fiumara Santa Venera WC11;
Barcellona P.G. WC12; Fiumara of Agrò WC20; Mela Torrent WC21; San Nicola Walloon
WC21; Fiumara Santa Lucia WC21; Gualtieri Torrent WC21, WC22; Fiumara Floripotema
WC21, WC22; Fiumedinisi River WC30; Briga Torrent WC31; Fiumara Niceto WC32;
Spring of Camaro WC42; Fiumara Corsari WC43; Fiumara Marmora WC43; Fiumara Rodia
WC43; Fiumara Tarantonio WC43; Fiumara Tono WC43.
Fig. 1. Geographical distribution of P. fluviatile in Sicily (Map with UTM 10x10Km squares)
Discussion
Comparing the results of the study with data derived from the distribution of literature, new
data greatly increase the distribution area occupied by P. fluviatile on the island. The large
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number of new reports presented in this contribution, allows us to observe that at present the
river crab shows a good distribution in Sicily.
It is not possible to know the trends of the populations because of the lack of historical data.
During the surveys it was noted, that some stream beds have been concreted and probably this
has adversely affected crab populations by preventing them from digging burrows for shelter
and breeding. In many streams surveyed were found several pipes for water extraction to
supply agriculture and an elevated volume of water extracted from streams and rivers can lead
drying and a subsequent loss of aquatic habitat. In large part, harvesting of river crabs is no
longer practiced in Sicily, but many freshwater habitats where P. fluviatile occurs are
increasingly subjected to pollution, habitat alterations and anthropogenic disturbance.
However, in some cases, crab has also been found in altered aquatic habitats in which the
resilience of this crab and its opportunistic habit, probably, allow its survival.
In Sicily, P. fluviatile is not protected by local regulations or regional laws.
In this island where many rivers naturally flow only for a part of the year, rivers and streams
should be protected against further drying causes and their beds should not be concreted.
New data, reported in this study, significantly expand the available knowledge on the
distribution of Sicilian populations of P. fluviatile, contributing to improve the monitoring and
the protection of this species.
Acknowledgements
We wish to thank Ignazio Sparacio, Salvatore Pasta and Fabio Liberti for the informations
provided and Gabriella Grippa who kindly revised the English language.
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