Rapp. Comm. int. Mer Médit., 36,2001
317
Introduction
The small scale fisheries of the Sicily are suffering a general decline
in the traditional exploited stocks, such as bony fish and crustaceans.
In order to figure out alternative resources, a program was launched
in 1996 by the Regione Siciliana with the aim of evaluating the abun-
dance of natural bivalves stocks inhabiting the soft bottoms along the
coastal strip of the Southern coasts of Sicily (1).
During this research, the presence of Razor shell specimens (Ensis
siliqua minorL., 1758) was observed, with other benthic species.
Moreover the morphometry of the collected E. siliqua minorspeci-
mens is reported.
The distribution area of the Razor shell along the Southern coasts of
Sicily was derived by integrating the specific underwater observations.
These information could be, in fact, useful for any future assessment
by using more specific gear, such the hydraulic dredge.
Materials and methods
The study area, extended from 0 to 10 m of depth from Capo
Granitola to Capo Scalambri (fig.1). Overall 51 stations were carried
on by hauling a “dry” dredge (11 mm mesh side in the bag) regularly
monitored by scuba divers, from September to November 1996 .
Figure 1 : Study area. The dark zone indicates the main occur-
rence area for Ensis siliqua minor.
Sediment samples, collected by divers, were used for granulometric
analysis (2); the mean size values (Mz) were expressed as
F
= - log
2
Ø
mm. The specimens were measured (width, height). The bionomic
significance according to Pérès & Picard (3), was attributed to all the
associated benthic species.
Results
Overall 83 specimens of Ensis siliqua minor were found in 51 sta-
tions, mainly located in the eastern sector (Gulf of Gela) of the sam-
pled area, from 1.6 to 7 m of depth.
The underwater observations and the analysis of the sediment sam-
ples showed E. siliqua minoroccurred on fine and very fine well
classed sand (1.69 < M
z
< 3.35
F
).
Main associated species were the bivalvesTellina tenuis, Tellina
fabula, Donax trunculus, Donax venustus, Mactra stultorum, the echi-
noidEchinocardium cordatum, the polichaetes Owenia fusiformis,
Onuphis eremita, Sigalion mathildaeand decapod crustaceans
Diogenes pugilatorandLiocarcinus vernalis, all characteristic species
of the Biocoenosis of Fine Well Sorted Sand (SFBC) (3).
The morphometry values (width, height) were included between 5.2
and 9.9 cm, 0.6 and 1.5 cm, respectively.
Discussion and conclusion
Considering the obtained results regarding the associated benthic
species, the granulometric and sedimentological features, as well as
underwater observations, it is possible to define the environment in
whichE. siliqua minorwas detected as SFBC biocoenosis. Infact
razor shells are burrowing (till 20 cm in depth) bivalves which occur
on fine and very fine coastal sandy bottoms mainly between 2-4 m of
depth. Moreover this species is exclusive characteristic of SFBC bio-
coenosis (3).
Razor shell (mainly Ensis siliqua minor) represent a very sought
after bivalve in Italy (4; 5) and local beds are exploited even at low
density (6).
In the specific case, it is not possible to evaluate the real abu
n
d
a
n
c
e
of the stock, given the poor effi
c
i
e
n
cy of the dredge employed. Most of
the specimens, in fact, were able to escape from the bottom panel of
meshes by quick movement of the “foot”, indicating that the consistence
of the population is higher than that revealed by the retained catch.
With regard to Italian seas, routine monitoring programs have point-
ed out the wide year-by-year and area-by-area variability in the abu
n-
dance of both target and non target biva
l
ve species, and the periodic
occurrence of catastrophic mortality with the almost total disappearance
of local beds and successive recovery (7; 5). A similar phenomenon wa
s
recently detected in a Tyrrhenian Razor shell population (8).
Given that some period of higher abundance cannot be excluded a
priori, the commercial value of Ensis siliqua minormight justify the
exploitation of beds even at low density (the minimum profitable den-
sity was estimated at 10 g/ m
2
(6).
Present results do suggest a more consistent presence of Razor
shells in the investigated area, also confirmed by underwater observa-
tions as well as by edaphic and bionomic features of the bottom,
although sampling with a specific dredge (for example, longer teeth
and finer mesh) will be necessary to check the usefulness for the
Southern Sicilian small scale fisheries.
References
1. Ragonese S., Riggio S., Chemello R., Rinelli P., Badalamenti F.,1999.
Evaluation of bivalves of the southern Sicily (Mediterranean Sea).
Proceeding of the Medcoast 99-Emecs 99 Joint Conference, 9-12
November,Antalya,Turkey.
2. Buchanan J.B. and Kain J.M., 1971. Measurements of the physical and
chemical environment. pp. 1-334. In : Holme & Mc Intyre (eds.), Methods
for the study of marine benthos. Oxford and Edinbu
rg Press.
3. Pérès J.M. and Picard J.,1964. Nouveau Manuel de Bionomie
Benthique de la Mer Méditerranée. Réc.Trav. Stat. Mar. EndoumeXXXI,
47 : 1-137.
4. Froglia C., 1990. Studio dell'efficienza e degli effetti delle draghe
idrauliche sulle comunità bentoniche. Relazione Finale, MMM, Roma,
Italia, 1-47.
5. Cirspe, 1996. Risorsa Molluschi, 1-86., MRAAF, Roma, Italia.
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Volterra L., 1987. Indagine sui molluschi bivalvi di interesse
commerciale (Telline, Cannolicchi e Vongole) delle coste della Toscana,
del Lazio e della Campania. 1985-1987. Quaderni Ist. Idrobiol.
Acquacultura Brunelli, 7 : 3-58.
7. Froglia C., 1989. Clam fisheries with hydraulic dredges in the Adriatic
Sea.In: J.F. Caddy (ed.), Marine Invertebrates Fishieries : Their
Assessment and Management : Wiley – Interscience Publication (FAO),
752 : 507-24.
8. Mariani A., Maccarone A., Mamo,e R., Dell’Aquila M., Fezzardi D.,
Cerasi A., 1998. Studio sulla biologia e distribuzione del cannolicchio
(Ensis siliqua minor) nei compartimenti marittimi di Roma, Gaeta,
Napoli e Salerno.Biol. Mar. Medit., 5(3) : 457-462.
ON THE PRESENCE OF ENSIS SILIQUA MINOR(BIVALVIA : SOLENOIDEA)
ALONG THE SOUTHERN COASTS OF SICILY (MEDITERRANEAN).
Rinelli P.
1
*, Spaño N.
2
, Ragonese S.
3
1
Istituto Sperimentale Talassografico - CNR, Messina, Italy
2
Dipartimento di Biologia Animale ed Ecologia Marina, Università di Messina, Italy
3
Istituto di Ricerche sulle Risorse Marine e l’Ambiente – CNR, Mazara (TP), Italy
Abstract
During an experimental survey of the Southern coasts of Sicily soft bottoms, carried out by hauling a “dry” dredge regularly monitored
by scuba divers, the presence of Razor shell specimens was observed. The almost totality of the sample was represented by Ensis siliqua
minor specimens caught in 51 stations.
Keywords : Bivalves, Sicilian Channel, Mediterranean
