Sustainable shellfish aquaculture in Saldanha Bay,South Africa |
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| Authors: | A Santa Marta JG Ferreira GC Pitcher J Lencart e Silva |
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| Institution: | 1. Longline Environment Ltd, London, United Kingdom antonio.marta@longline.co.uk https://orcid.org/0000-0001-9239-7110;3. Longline Environment Ltd, London, United Kingdom;4. Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisbon, Portugal;5. Department of Environment, Forestry and Fisheries (DEFF), Cape Town, South Africa;6. Department of Biological Sciences, University of Cape Town, Cape Town, South Africa https://orcid.org/0000-0001-8536-9314;7. Longline Environment Ltd, London, United Kingdom https://orcid.org/0000-0001-8237-6981 |
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| Abstract: | The carrying capacity for bivalve shellfish culture in Saldanha Bay, South Africa, was analysed through the application of the well-tested EcoWin ecological model, in order to simulate key ecosystem variables. The model was set up using: (i) oceanographic and water-quality data collected from Saldanha Bay, and (ii) culture-practice information provided by local shellfish farmers. EcoWin successfully reproduced key ecological processes, simulating an annual mean phytoplankton biomass of 7.5 µg Chl a l–1 and an annual harvested shellfish biomass of about 3 000 tonnes (t) y–1, in good agreement with reported yield. The maximum annual carrying capacity of Small Bay was estimated as 20 000 t live weight (LW) of oysters Crassostrea gigas, or alternatively 5 100 t LW of mussels Mytilus galloprovincialis, and for Big Bay as 100 000 t LW of oysters. Two production scenarios were investigated for Small Bay: a production of 4 000 t LW y–1 of mussels, and the most profitable scenario for oysters of 19 700 t LW y–1. The main conclusions of this work are: (i) in 2015–2016, both Small Bay and Big Bay were below their maximum production capacity; (ii) the current production of shellfish potentially removes 85% of the human nitrogen inputs; (iii) a maximum-production scenario in both Big Bay and Small Bay would result in phytoplankton depletion in the farmed area; (iv) increasing the production intensity in Big Bay would probably impact the existing cultures in Small Bay; and (v) the production in Small Bay could be increased, resulting in higher income for farmers. |
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| Keywords: | blue mussel carrying capacity ecological model EcoWin Pacific oyster phytoplankton biomass production scenario water quality |
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https://orcid.org/0000-0001-9239-7110;3. Longline Environment Ltd, London, United Kingdom;4. Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisbon, Portugal;5. Department of Environment, Forestry and Fisheries (DEFF), Cape Town, South Africa;6. Department of Biological Sciences, University of Cape Town, Cape Town, South Africa