Institute of Aquaculture
Mixed
models Boosting oyster production in coastal lagoons of the Mediterranean THE demand for shellfish products is constantly expanding in Europe, and the Mediterranean Sea could offer potential locations for growth. After France, Italy is one of the largest consumers of oysters but the local production (50 tonnes per year) of Pacific oyster (Crassostres gigas, Thunberg, 1793) is not enough to meet the market demand, resulting in 6,500 tonnes of Pacific oysters being imported every year. The Italian region of Sardinia contributes to 60% of the national oyster production; however, a single company - Compagnia Ostricola Mediterranea in San Teodoro Lagoon - is responsible for most of this contribution. The company has therefore been selected to be a partner of the OstrInnova local government funded project, which aims to further develop sustainable oyster production in the region. Sardinia has many shallow coastal lagoons already employed for extensive farming, and it also has potentially productive sites for more intensive Pacific oyster culture, allowing this region to significantly contribute to national production. The overarching aim and practical impact of the OstrInnova project is to improve and increase Pacific oyster farming in Sardinia, providing information to stakeholders on how to best evaluate productivity in the available environments (shallow coastal lagoons); which technologies and farming methods could be used to maximise production; and how sustainable this commercial activity is. To answer some of these questions, two farming systems were compared: poches, the conventional farming system used in San Teodoro lagoon, versus Ortac units. These are a new farming tool already applied in the UK, which promise to boost flat oysters’ production by increasing survival and growth rate. The results indicate that oysters’ survival was sig- Above: Philip Graham nificantly higher (over 20% increase) in the Ortac units when compared to the survival achieved in the more traditional farming system. Nonetheless, growth and meat yield were higher
“
The results provide valuable information to improve the robustness of growth prediction tools
”
88
Stefano - Oysters.indd 88
in the poches system and of a full production cycle, 98% of the Pacific oysters farmed in the traditional system reached the smallest commercial size of 40g while only 68% of the oysters reached this size in the Ortac units. From these result, we are able to suggest a mixed use of the two different tools, the Ortac in the earlier production stages to boost spat survival in the face of challenging environmental conditions, and the poches thereafter to maximise growth potential offered by warm and rich waters characteristic of the lagoons’ environment. Finally, in order to inform sustainable development policies, oysters’ growth measured in the field and a large suite of environmental and biological parameters have been collected during two different growing seasons. These were used to validate outputs of the bioenergetics model ShellSIM (http://www.shellsim.com/) to establish the suitability of this tool to predict Pacific oyster growth in the local context. Our results indicate that simulated growth fitted well with field observations, although seasonality and farming system used still influence the ability of this software to perform realistic prediction, providing scope for further tailoring of the model under the local conditions. These results provide valuable information to improve the pacific oyster farming and robustness of growth prediction tools in Mediterranean shallow coastal lagoons. For further information on this project, contact Philip Graham (philip.graham@stir.ac.uk) or Dr Stefano Carboni (stefano.carboni@stir.ac.uk). Institute of Aquaculture
08/05/2018 12:04:05