Identifying sustainable aquaculture management areas
“[C]urrent approaches to the management of marine and coastal resources have not always proved capable of achieving sustainable development, and coastal resources and the coastal environment are being rapidly degraded and eroded in many parts of the world….Systematic collection of data on marine environmental parameters will be needed to apply integrated management approaches.”
Extracts from Articles 17.4 and 17.96, Agenda 21, United Nations Earth Summit, 1992.
The growth of New Zealand’s aquaculture industry - which has seen greenshell mussel export volumes double in the decade to 2005 - is now putting pressure on regional councils to identify Aquaculture Management Areas (AMAs) in open coast locations.
Inferior site location is one of the most common reasons for aquaculture project failure and for adverse environmental effects, while good sites in sheltered bays and harbours are close to saturation.
Pioneering methodologies developed by University of Waikato researchers mean Environment Bay of Plenty is now one of the first regional councils to be able to identify sustainable coastal marine locations for AMAs via a computerised mapping system.
Over the past three years Dr Peter Longdill and Professor Terry Healy have modelled the seasonal hydrodynamic patterns of the Bay of Plenty coastal marine area by combining satellite data revealing phytoplankton concentrations with continuous recordings of wave and current patterns, imaging of the sea floor, acoustic doppler profiling of the water column, and hundreds of samples of sediments, nutrients and water temperature measurements taken on regular excursions using the University’s research vessel, Tai Rangahau. These hydrodynamic models have been linked with Geographic Information Systems commonly used by councils for data storage applications for planning purposes.
With specific reference to suspended mussel (Perna canaliculus) aquaculture, the results show maximum aquaculture sustainability may be achieved in about 420 sq km (18%) of the coastal marine area from Maketu to the Motu River. The most sustainable sites are characterised by silty sediment with low natural organic content, depths of between 40 and 100 metres, in areas well-flushed with nutrients, but protected from both ocean swells and freshwater river flooding, and where there are no conflicts with a range of other factors from visual amenity to other recreational and commercial uses.
External funding gratefully acknowledged: Technology for Industry Fellowship, Bright Futures Scholarship, ASR Ltd, Environment Bay of Plenty.
COASTAL MARINE GROUP
DEPARTMENT OF EARTH AND OCEAN SCIENCES
FACULTY OF SCIENCE AND ENGINEERING
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