The aim of this project was to develop a water-stable and palatable diet for the supplementary feeding of wrasse deployed in salmon sea-pens using a gelling agent mixed with a manufactured dry-feed component. Three binders (gelatine from cold water fish skin, beef gelatin and agar-agar) were compared for water-gel strength over a range of concentrations. Gel formed using agar was found to be significantly stronger than the other binders tested. An experimental aqua-feed made using a grinded, dry ingredient mix binded with 20g/L agar solution at 1/1.6 (w/v) ratio and offered as blocks within individual feeders was water-stable for 7 days when deployed fresh or following a week of preservation at -20°C. Farmed ballan wrasse in tanks fed on the agar-based diet within 2 days of deployment. Wild wrasse stocked in salmon sea-pens at low density (1.2-2.1%), up to 4 weeks prior the start of the trial and not previously fed a manufactured diet first ingested the agar feed within 2 weeks and total feed intake significantly increased afterwards. Feed intake was significantly higher from feeders placed within a small feeding shelter made of artificial kelp than within the large wrasse shelter. No nutrient leaching after water immersion and no alterations in the fatty acid profile after preparation of the experimental feed was found. A manufactured grinded ingredient mix binded with 20g/L agar solution at a 1/1.6 (w/v) ratio and offered within static feeders is proposed as the basis of a novel supplementary feeding methodology for cleaner fish wrasse deployed in salmon sea-pens. This methodology has the potential to facilitate wrasse feeding and to allow the monitoring of feed intake to safeguard the health, welfare and delousing activity of the biological stock over the salmon rearing cycle

Microplastics debris (<5 mm) are increasingly abundant in the marine environment, therefore, potentially becoming a growing threat for different marine organisms. Through aquatic animals, these can enter in the human food chain, and can be perceived as a risk for consumers' health. Different studies report the presence of particles in marketable shellfish including the world wide commercially grown Pacific oyster Magallana gigas (Thunberg, 1793). The aim of this study is to examine the potential risk of microplastics entering in the human food chain through this shellfish species, investigating the dynamics of the uptake, egestion (faeces) and rejection (pseudofaeces) of microplastics in Pacific oysters under controlled conditions. M. gigas collected from a farm in the San Teodoro lagoon (Italy), were exposed to 60 fluorescent orange polystyrene particles L-1 of known sizes (100, 250 and 500 µm). The uptake of each particle size was 19.4 ± 1.1%, 19.4 ± 2 % and 12.9 ± 2 % respectively. After exposure M. gigas were left to depurate for 72 hrs, during which 84.6 ± 2 % of the particles taken up were released whilst 15.4 ± 2 % were retained inside the shell cavity. No microplastic particles were found in the animals' soft tissues. The results of this study, suggest that depuration is an effective method to reduce presence of large microplastic particles, in the size range 100 to 500 µm, in M. gigas. Importantly, the data suggests that the burden that could theoretically be up taken by consumers from these shellfish is negligible when compared to other routes. Capsule Microplastic of tested sizes were not retained in the tissues but can be retained in the shell cavity; Depuration is an effective method to reduce microplastics in farmed Pacific oysters

Bivalve farming is a major European aquaculture activity, representing 48.5% of total biomass produced. Italy is one of the largest consumers of oysters but local production does not meet the market demand. Italy has approximately 384 000 ha of shallow lagoons in its coastal area, already devoted to extensive aquaculture activities which could also represent potential locations for Pacific oyster (Crassostrea gigas, Thunberg, 1793) farming. The aim of this study is to enhance Pacific oyster farming in shallow coastal lagoons by testing novel farming technologies and validating an existing bioenergetic growth model (ShellSIM). Commercial performance of Pacific oysters and associated environmental parameters were monitored in two Sardinian coastal lagoons (San Teodoro and Santa Gilla, Italy). Oyster growth and survival were compared during a production cycle for two rearing systems: traditional systems (floating bags or lanterns) and Ortac units. The latter has not been previously tested in coastal lagoons. Measured performances were compared with ShellSIM predictions to evaluate the model's ability to predict growth and the potential production in other coastal lagoons. Results showed that at the end of a six months cycle the oysters mean weight and Condition Index were significantly higher (p value < 0.05) in floating bags than in Ortac, (55.8 ± 0.9 g and 50.1 ± 1.3 g; 4.6 ± 0.1 and 3.9 ± 0.1 respectively). Also, the minimum commercial size (40 g) was reached by 98 % and 68 % of the oyster farmed in floating bags and Ortac units respectively. On the other hand, oysters reared in the Ortac showed a higher survival than in the floating bags (95.8 ± 0.9 % and 82.1 ± 3.4 %, respectively). ShellSIM growth predictions were highly correlated with the observed data in both lagoons. However, high values for RMSD indicated that ShellSIM predictions were significantly validated for San Teodoro lagoon but not for Santa Gilla suggesting further tailoring to some environmental conditions to produce more realistic growth predictions. Results of this study indicate that both floating bags and Ortac system should be employed during the production cycle to maximise oysters' survival and growth performances. Furthermore, this study provides a new validated tool to farmers and stakeholders to monitor oysters performances and estimate productivity in local waters.

Shell characteristics and consequent marketability of the oyster Crassostrea gigas are influenced by several factors, and most important of which are the rearing methods and gears. In this study, we investigated the effects of two different gears on the quality aspect (shell shape, weight meat percentage, backward shell shape, epibionts and blisters) and growth rate (weight and length) of C. gigas by adopting the innovative Ortac Oyster Farming System, during the field grow‐out phase of production. Aspect and growth of oysters farmed in Ortac and floating bags were compared. After 14 weeks, the aspect of the animals was influenced by the gear, resulting in a lower quality in the Ortac (i.e. worse shell shape, lower weight meat percentage, higher percentage of backwards and blisters) than in the floating bag, while the incidence of epibionts was less in the Ortac. Regarding the growth performance, total wet weight gained in the Ortac was lower (~28.3 g) than in the floating bag (~32.4 g; p < .05). These results highlight the efficiency of the floating bag as oyster rearing system in the Mediterranean basin and suggest the need to alter the Ortac gear to these environmental conditions.