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Oysters - Bluff/Nelson
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Oysters: Quick Facts
Scientific name: Tiostrea chilensis
Other names: tio, tio para, tio repe, tio parupaur (Maori), Dredge oyster, Bluff oyster, Foveaux Strait oyster, Stewart Island Oyster, Nelson oyster, flat oyster.
Ranking: E (Red - Worst Choice)
Best Fish Guide: Oysters - Bluff/Nelson
Ranking: E (Red- Worst Choice)
Description: Wild caught oysters or dredge oysters are endemic to New Zealand and are found in coastal waters, often in dense communities. The fishery is seasonal (open from March to August), with the main commercial fishery operating in Foveaux Strait. A small catch is also taken when harvesting scallops in Tasman and Golden bays and a new fishery has started in Clifford and Cloudy Bays.
Ecological concerns: Wild oysters are collected by dredging – a highly destructive fishing method that digs into the seafloor, destroying seafloor communities in it’s path. The use of heavy box dredgers is especially damaging. Dredging creates considerable sedimentation, which smothers seabed communities in the areas where the fishery operates. In much of the Foveaux Strait, dredging has removed bryozoan reef communities, which has exposed some previously sheltered marine life to storm and tide action. Some oyster beds have not recovered from dredging, even after 50 years.
The oyster fishery also catches a range of non-target species and has impacts on a number of fish populations, especially blue cod stocks. In Tasman Bay and Golden Bay, oysters have declined to low population levels and the fishery has been associated with a decline in fish stocks. The lack of a management plan and inadequate consideration of the impact of dredging in new areas (eg Clifford and Cloudy Bay) is also of concern. The presence of a disease in Foveaux Strait oysters in recent years, which has killed over 60% of the population, has made it difficult to estimate the current status of the population there.
Economic value: Foveaux Strait oysters are sold in New Zealand, while some Nelson/Marlborough oysters are exported (up to a value of $10 million per year).
ASSESSMENT OUTPUT
Biology and risk of overfishing (score D)
Status and sustainability of fish catches (score E)
Impact of fishing method and protected, threatened and endangered species captures (score E and B)
Management and management unit (score C and D)
For a full ecological assessment, click here