Manila Clam (Tapes philippinarum Adams & Reeve, 1852) in the Lagoon of Marano and Grado (Northern Adriatic Sea, Italy): Socio-Economic and Environmental Pathway of a Shell Farm - Aquaculture and the Environment: A Shared Destiny - page 72

Fig. 9. Hydraulic clam dredge “idrorasca”
In 2008 the use of idrorasca was authorized and tested in the Lagoon of Grado too, but the
experiment failed because of the high mortality of Manila clam juveniles in that area. Thus
the fishermen of Grado had to give up the first attempt of cultivation in their lagoon. Vice
versa the area entrusted to maranese fishermen seems to be very suitable to the growth of
clams. In winter 2011 the cooperative has granted to fishermen the use of 30 idrorasca to
treat the bottom before the seeding, whereas a plot was already seeded in 2010. Before
starting the new gear, a monitoring program was established with the regional agency for
the protection of the environment (ARPA FVG), in order to evaluate the sustainability of this
new method of harvesting in the Lagoon of Marano during a whole production cycle. In this
way seven monitoring stations were selected (Fig. 8) to check the status of
macrozoobenthos, sediment texture, chemical pollutants in clam tissues, both inside and
around farm areas. Of course in this initial phase the fishermen are strictly watched to
prevent any accident or illegal harvesting out of areas. They have to use the gear strictly
following the procedures established by the regional authority: max speed of tow 1 km/h,
pressure of water flux must not exceed 3.5 atm, no more than two hauls in each pathway
and over all they must operate during the high slack tide, to prevent as much as possible the
loss of fine sediments.
The environmental and socio economic vicissitudes of the Manila clam in the Lagoon of
Marano and Grado could represent a case study: after more than 20 years of fights, farmers,
fishermen and environmental policy seem to have found the pathway toward a sustainable
shell farm. T. philippinarum arrived in the northern Adriatic lagoons as an alien species in
'80 th , leading to a total derangement of socio economic and environmental conditions. Now
after almost 30 years, thanks to the model of shell farming in the Lagoon of Marano, this
acclimated species could constitute strength for the fisheries economy of the lagoons and the
northern Adriatic too.