Environmental Engineering Reference
In-Depth Information
salinity and currents. Larval movement mainly depends on wind driven and tidal currents.
Adding pea gravel and small rocks can facilitate species recruitment in natural setting areas.
The larvae settle by attaching a byssus to a pebble or piece of shell. Regarding the
Tapes
longevity, Ponurovski (2008) has reported that the maximum recorded age of
T.
philippinarum
was 7 years, but the maximum longevity of this species that has ever been
reported for Melkovodnaya Bay (Russia) is 25 years.
The reproductive cycle in the northern Adriatic lagoons is quite similar (Da Ros et al., 2005):
the period of sexual rest lasts from October to January, when first specimens start the
gametogenesis. Sexual maturity is observed from April and the first spawning occurs
already in May, the last in September. The theoretical growth curves depend on the period
of larval settlement. When it occurs during the spring, Manila clam can reach about 47 mm
in length after two years (Pellizzato et al., 2005). The maximum length recorded was 78 mm
in Sacca di Goro (Po River Delta), whereas in the Lagoon of Marano the record was 71 mm,
136 g in total weight and about 7 years old.
3. Statistics
3.1 Main producer countries and production statistics
Cultivation of Manila clam, with the world production of 3 million tons/year makes it
economically the most important shell species. In fact, its production represents the 20% of
global world shell market (FAO, 2011).
At the global level, since 1991, global Japanese carpet shell production has shown a huge
expansion, by a factor of nearly six times. China is by far the leading producer (97.4 % in
2002). Disease factors have impacted production in some other countries, notably in the
Republic of Korea. In the decade 1993-2002, production in that country varied between
10,000 and 19,000 tones.
Production in Italy, following its introduction, the development of wild populations, and the
consequential increase in seed supply, is the second highest in the world, followed by United
States of America, Spain and France. Extensive production also occurs in Japan but is not
reported within this specific statistical category, being included within clams (FAO, 2011).
In Europe, 90% (50,000 tons /year) of production derives from Italy, 6-8% from Spain (4,000
tons/year) and 2% from France (1,000 tons/year) (Turolla, 2008).
Italian clam production is mostly concentrated in the lagoons of the North Adriatic.
Northern Adriatic production contributes to overall Italian production by up to 95% (Orel et
al., 2000; Zentilin et al., 2008). This species is one of the most popular and profitable
molluscs of lagoon and coastal sites in the Mediterranean. Production areas in the northern
Adriatic (Lagoon of Venice, Lagoon of Marano and Grado, River Po mouth in the Region
Emilia Romagna, River Po mouth in the Region of Veneto) reached its peak in 1998 and 1999
with over 60,000 tons. In the Lagoon of Marano and Grado the highest production was
registered in 1996 with over 1,500 tons. In 2010 the production in the Lagoon of Marano was
1,042 tons, of which 74% derives from aquaculture in about 130 hectares of lagoon.
Approximately 20 persons are employed in the two main shell farm business operators:
ALMAR Society founded in 1995 and Molluschicoltura Maranese Society (begin of '90
th
),
which took over the shell farm plants of the previous Aquamar Society, founded in 1988.
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