Composizione biochimica di quattro specie fitoplanctoniche impiegate in acquicoltura

The protein, lipid, carbohydrate, and amino acid content of four algae of the genus Chlorella, Dunaliella, Nannochloris and Tetraselmis was determined: each species was grown on Walne's media containig two different levels of nitrogen. The results show how tbe media influenced the biochemical composition of the algae

Variations of biofouling communities in an off-shore fish cage farm from North-Western Sardinia = Variazioni del biofouling in un allevamento ittico in gabbie off-shore della Sardegna nord-occidentale

Biofouling variations were studied in a fish farming facility near Alghero (Italy) between November 2007 and November 2008. Net panels suitable for the settlement of encrusting organisms were immersed in cages in which large and small gilthead seabream specimens were reared. Significant differences in biofouling biomass and coverage were observed between cages containing fish and controls. The results obtained revealed that gilthead seabream can exert a crucial role in controlling biofouling growth, independently from its size

A Meramod^® model approach for the Environmental Impact Assessment (EIA) of the off-shore aquaculture improvement in the Alghero Bay (North western Sardinia, Italy)

Marine fish farming generates particulate wastes which are dispersed in the sea environment. To deal with this problem, particulate waste dispersion models have been developed to predict the effects of fish cage culture. In this study, we evaluated the seabed deposition of a fish farming facility located in the central western Mediterranean by using the Meramod® model. The objectives where first to assess the actual scenario, and second to forecast the possible impact due to the forthcoming enlargement of the farming area with the addition of new fish cages. By computing the hydrodynamic measurements and the daily amount of feed recorded between July and December 2006, the impact seabed surfaces forecasted by the model increased from 5.6ha in the actual scenario, up to 7.3ha in the future. The model estimated a maximum level of total solid flux deposition of 3,800g/m2bed/year and a maximum level of total carbon flux deposition of 1,350g/m2bed/year for both scenarios. Furthermore, the model predicted that the installation of 4 new fish cages (with an hypothetical mean daily amount of feed of 50kg/cage) will produce a total solid and carbon flux deposition levels ranging 0-400 and 0-150g/m2bed/year respectively, under the new fish cages location

A Meramod® model approach for the Environmental Impact Assessment (EIA) of the off–shore aquaculture improvement in the Alghero Bay (North western Sardinia, Italy)

Marine fish farming generates particulate wastes which are dispersed in the sea environment. To deal with this problem, particulate waste dispersion models have been developed to predict the effects of fish cage culture. In this study, we evaluated the seabed deposition of a fish farming facility located in the central western Mediterranean by using the Meramod® model. The objectives where first to assess the actual scenario, and second to forecast the possible impact due to the forthcoming enlargement of the farming area with the addition of new fish cages. By computing the hydrodynamic measurements and the daily amount of feed recorded between July and December 2006, the impact seabed surfaces forecasted by the model increased from 5.6ha in the actual scenario, up to 7.3ha in the future. The model estimated a maximum level of total solid flux deposition of 3,800g/m2bed/year and a maximum level of total carbon flux deposition of 1,350g/m2bed/year for both scenarios. Furthermore, the model predicted that the installation of 4 new fish cages (with an hypothetical mean daily amount of feed of 50kg/cage) will produce a total solid and carbon flux deposition levels ranging 0-400 and 0-150g/m2bed/year respectively, under the new fish cages location

Suspended culture of Ostrea edulis in the Calich lagoon (North western Sardinia, Italy): preliminary results

Suspended culture is a widespread farming method used for many bivalve species such as mussels, oysters and scallops. In the Mediterranean, this technique is mainly practised in lagoons or in sheltered coastal areas using floating lines from which molluscs are suspended in several ways. In this study, the European flat oyster (Ostrea edulis Linné, 1758) was grown in suspended lantern nets in the Calich lagoon (Sardinia, Mediterranean Sea) from March 2004 to March 2005. Two distinct groups of 6 lanterns each were hung to longline ropes near the mouth (station 1) and in the central portion of the lagoon (station 2). In each lantern (diameter=50cm; height=30cm), 90 O. edulis specimens were grown and, in order to ensure good water circulation inside the lantern net, fouling organisms were removed every month. Overall mortality, shell length (anterior-posterior axis), shell width (maximum distance on the lateral axis, between both valves of the closed shell) and total wet weight of a 180 specimen oyster sample (30 from each lantern) were recorded every 2 months at each site. In addition, water temperature, salinity, dissolved oxygen, and pH were monitored monthly by means of a multi-parametric probe at both sites (between 10a.m. and 12p.m.). One-way ANOVA was used to test for differences in oyster final mean morphometric characters recorded at the 2 growing stations. Chi-square test (with Yates correction for continuity) was performed to compare survival rates at the end of the trial. From an initial mean shell length of 49.5±4.6mm, O. edulis growth rate showed a similar trend at both the stations. Nevertheless, ANOVA detected significant differences (F=7.10; p<0.01) in final mean oyster length values (83.7±6.5mm at station 1 vs 81.7±7.6mm at station 2). Significant differences (F=9.74; p<0.01) were also found in final mean oyster width (28.4±3.1mm at station 1 vs 27.5±2.8mm at station 2) and weight (F=4.00; p<0.05) values (91.4±16.7g at station 1 vs 87.7±18.3g at station 2). Moreover, chi-square test revealed a significantly different survival rate (χ2=10.04; p<0.01) between the 2 groups (57.4% at station 1 vs 47.6% at station 2).Water temperature, salinity, dissolved oxygen, and pH monthly values recorded at the 2 growing stations were almost identical. Thus, the observed differences in oyster growth and survival seemed not to be due to the hydrological variables considered. Instead, they could probably be related to mechanical and chemical effects of water renewal by coastal waters, which may have led to different seasonal seston food supplies at the 2 sites. The suspended culture of the European flat oyster described in this paper can increase the mollusc production of the Calich lagoon by growing a valuable bivalve species which is naturally scarce in this biotope. In fact, our preliminary results showed good survival and growth rates of O. edulis especially near the mouth of the lagoon. Furthermore, this farming technique could be a possible source of economic benefits for local fishermen and, above all, a low impact aquacultural activity compatible with the environment

Suspended culture of <i>Ostrea edulis</i> in the Calich lagoon (North western Sardinia, Italy): preliminary results

Suspended culture is a widespread farming method used for many bivalve species such as mussels, oysters and scallops. In the Mediterranean, this technique is mainly practised in lagoons or in sheltered coastal areas using floating lines from which molluscs are suspended in several ways. In this study, the European flat oyster (Ostrea edulis Linné, 1758) was grown in suspended lantern nets in the Calich lagoon (Sardinia, Mediterranean Sea) from March 2004 to March 2005. Two distinct groups of 6 lanterns each were hung to longline ropes near the mouth (station 1) and in the central portion of the lagoon (station 2). In each lantern (diameter=50cm; height=30cm), 90 O. edulis specimens were grown and, in order to ensure good water circulation inside the lantern net, fouling organisms were removed every month. Overall mortality, shell length (anterior-posterior axis), shell width (maximum distance on the lateral axis, between both valves of the closed shell) and total wet weight of a 180 specimen oyster sample (30 from each lantern) were recorded every 2 months at each site. In addition, water temperature, salinity, dissolved oxygen, and pH were monitored monthly by means of a multi-parametric probe at both sites (between 10a.m. and 12p.m.). One-way ANOVA was used to test for differences in oyster final mean morphometric characters recorded at the 2 growing stations. Chi-square test (with Yates correction for continuity) was performed to compare survival rates at the end of the trial. From an initial mean shell length of 49.5±4.6mm, O. edulis growth rate showed a similar trend at both the stations. Nevertheless, ANOVA detected significant differences (F=7.10; p&lt;0.01) in final mean oyster length values (83.7±6.5mm at station 1 vs 81.7±7.6mm at station 2). Significant differences (F=9.74; p&lt;0.01) were also found in final mean oyster width (28.4±3.1mm at station 1 vs 27.5±2.8mm at station 2) and weight (F=4.00; p&lt;0.05) values (91.4±16.7g at station 1 vs 87.7±18.3g at station 2). Moreover, chi-square test revealed a significantly different survival rate (χ2=10.04; p&lt;0.01) between the 2 groups (57.4% at station 1 vs 47.6% at station 2).Water temperature, salinity, dissolved oxygen, and pH monthly values recorded at the 2 growing stations were almost identical. Thus, the observed differences in oyster growth and survival seemed not to be due to the hydrological variables considered. Instead, they could probably be related to mechanical and chemical effects of water renewal by coastal waters, which may have led to different seasonal seston food supplies at the 2 sites. The suspended culture of the European flat oyster described in this paper can increase the mollusc production of the Calich lagoon by growing a valuable bivalve species which is naturally scarce in this biotope. In fact, our preliminary results showed good survival and growth rates of O. edulis especially near the mouth of the lagoon. Furthermore, this farming technique could be a possible source of economic benefits for local fishermen and, above all, a low impact aquacultural activity compatible with the environment

Response of captive seabass and seabream as behavioural indicator in aquaculture

Welfare of cultivate fish at high-density represents an important concern for modern aquaculture. The behaviour of European seabass (Dicentrarchus labrax) and seabream (Sparus aurata) reared in cages was studied in a fish farm of northern Sardinia (Italy) in autumn 2006 to test whether captive condition had an effect on the movement patterns of these two species.Video images recorded before, during and after the manual feeding distribution allowed us to collect data on different behaviours of captive fish. Thus, behaviours indicating the position of fish in the water column, swimming direction and possible aggressive behaviours (aggression, direction change and collision) showed juveniles and adults of seabass and seabream were overall affected by feeding rhythms and captive overcrowding. Seabream had a major tendency to swim towards the bottom and higher frequency of horizontal swimming and collisions than seabass. The overall behavioural difference between two species was explained in terms of their differences in ecological features in the wild

Small-scale perturbation on soft bottom macrozoobenthos after mechanical cleaning operations in a Central-Western Mediterranean lagoon

1 - Sardinia Island (Italy), even if relatively small, has over 100 lagoons totalling some 12,000 ha. Yet their potential yield remain often unexpressed because they are subjected to environmental stress and degradation. As far as benthic communities are concerned, one of the main disturbances is certainly the accumulation of shell detritus, which progressively modifies the way benthic organisms interact with the sediment. 2 - An experimental dredging study was therefore performed in the Calich lagoon (NW Sardinia), due to its particular interest for fishing activities and potential semi-intensive mollusc culture. Changes in benthic community structure were examined in two areas of the lagoon by analysing both the demographic profile of several abundant species and the features of sedimentary matrix immediately after the cleaning operations and seven months later. Data obtained were compared with those collected in undisturbed areas of the lagoon. This allowed us to evaluate the effects of dredging operations on the benthic assemblages unaffected by natural temporal shifts of the system. 3 - Univariate and multivariate analyses indicated a strong relationship between macrofaunal community structure and intensity of the cleaning activities. At the dredged sites benthic fauna was not depleted but did exhibit higher diversity and evenness indexes than at the undisturbed sites. This seemed to be a consequence of decrease in the density of some abundant species at the dredged sites. Furthermore, a general reduction of total organic content was observed in the upper sediment layer. Lastly, the cleaning method employed is discussed in relation to its potential for impacting the benthos

Preferenze alimentari della magnosa, <i>Scyllarldes latus</i> (Latreille, 1803), in cattività = Feeding preferences of slipper lobster, <i>Scyllarides latus</i> (Latreille, 1803), in captivity

Four different types of Molluscs (Patella, Bolinus, Tapes and Mytilus) were tested to assess feeding preferences of Scyllarides latus (Latreille, 1803) in captivity. The results of the trials indicated that Patella was the preferred food-item followed by Mytilus, while the other 2 species of Molluscs were only occasionally consumed

Contribution to the knowledge of 'banquettes' of <i>Posidonia oceanica</i> (l.) Delile in Sardinia Island

In the framework of the Sardinia and Corsica Interreg II Project, a study on the dead leaves of Posidonia oceanica, washed up along the beaches and forming banquettes, was carried out in different sites of the 2 islands. As far as Sardinia is concerned, biomass, biochemical composition (including heavy metals), detrital fractions and sand contents of the banquettes were investigated