Oysters return to the Tagus estuary through an ecological model

Dissertation submitted to the Faculty of Sciences and Technology of New University of Lisbon for obtaining the degree of Master in Environmental Management Systems

Aquaculture is an activity that has been increasing along the last years. Until the 1970’s Portugal and more specifically the Tagus estuary, was the major exporter of oysters in Europe. Factors like TBT and oysters gill disease had made that the shellfish aquaculture has never been again practised in Tagus estuary. According to that, this work intends to concept and to implement an ecological model that develops the oysters growth in order to them return to the estuary. To begin with, the model was calibrated with data from Database of 1980 and then validated with Database of 1982. The model results have shown a good correlation with measured data, so it was supposed as a good model. After that, it was simulated two different scenarios. The first one it was increased 30C in water temperature and in the second one it was changed the seeding day to the 90 day instead the 120 day. The results illustrate that in scenario I, the production of oysters decrease as well as the oyster individual weight and length, and in scenario II, however the oyster individual growth as decrease a little the oyster total harvest as increase. With these approaches, it will be possible to define the better conditions in order to achieve a good model that can be able to optimise the production of oyster in the Tagus estuary.