Modelling of productivity, water quality effects and profit optimization of Pacific oyster (Crassostrea gigas) farms: application of the FARM model and GIS in the Valdivia estuary of Chile

Gallinato, Cláudio Silva

http://hdl.handle.net/10400.1/521

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Authors

Gallinato, Cláudio Silva

Advisor(s)

Ferreira, J.

Newton, Alice

Valls, Angel Del

Abstract(s)

An integrated approach of the Farm Aquaculture Resource Management (FARM) model and Geographical Information System (GIS) has been applied to Pacific oyster aquaculture in suspended longline systems. The performance of the FARM model, applied to simulate potential production, economical data, and water quality impacts at the farm-scale, was tested in four potential sites (Tornagaleones, Valdivia, bay of Corral and Ensenada San Juan) in the Valdivia estuary of Chile. The FARM model results were integrated in a spatially variable Suitability Index of Sustainable Aquaculture (SISA) through a GIS Multicriteria Evaluation (MCE) technique. To describe the environmental variability of the Valdivia estuary, significant relationships between the environmental variables were estimated applying multivariate statistical analysis, such as Factor Analysis and Principal Component Analysis. Seasonal data were used as drivers for the FARM model. Modelling results show good agreement with reported individual total length at two farm sites during a 395 days culture period: simulated length of 8.1 cm of Pacific oyster in Tornagaleones (7.9 cm, +2.5%) and 6 cm in Valdivia (6.6 cm, -9%). Results of a profit maximization analysis according to seeding densities were determined, as an example, in Tornagaleones with 98 tons of seed was obtained a total production of 1667 tons TFW with a profit of 8237 k€. The eutrophication assessment results for the four potential farm sites show that water quality is at Good status, except in Tornagaleones where is Moderate. The nitrogen mass balance for each farm was also determined. The results show that water quality is either maintained or improved under standard conditions of culture practice. These results highlight the role that extractive organic aquaculture plays in integrated coastal zone and nutrient emissions management. The integration of FARM and MCE GIS approach for aquaculture site selection supports and assists to water coastal managers in the decision making process. The GISbased SISA index integrates different criteria and implies estimates of carrying capacity, eutrophication and optimal profit within a system. The results identify those aquaculture sites most suitable for a sustainable Pacific oyster management within the Valdivia estuary.