Bluff oysters & blue cod: something special in the deep south

Science Centres: Fisheries

A unique partnership in Southland is working to increase the sustainable population of Bluff oysters and blue cod, restoring the seabed habitat in Foveaux Strait at the same time.

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To do this, NIWA is working with a broad community stakeholder group, involving the Bluff Oyster Management Company, Foveaux Strait blue cod fishers, iwi, recreational fishers, divers, other recreational users, Environment Southland, and DOC, as well as the Ministry of Fisheries. The ultimate aim is to develop a practical and effective ecosystem approach to the management of fisheries in this area.

NIWA scientist Keith Michael says at first there were many conflicting views. ‘It’s a tremendous achievement that such a diverse group has come together and is now actively involved in the research,’ he says.

NIWA’s challenge is to marry fisheries science and ecology into a tool to evaluate different strategies for managing the fisheries and their ecosystem relationships. This will take the form of a sophisticated mathematical model. But first, says Keith Michael, ‘we need to understand how the ecosystem functions, its relationship to oyster and blue cod production, and its response to fishing.’

So far, we have:

  • developed an oyster population model, which is now used to make projections of future harvests
  • started on a model of how bonamia and the oyster populations interact
  • produced high resolution maps of Foveaux Strait, which are used to identify areas with different habitats and relate these habitats to their oyster production
  • begun to monitor these habitats to determine how they respond to fishing and how they change over time

NIWA and the Bluff Oyster Management Company have just begun trials to evaluate a strategy for the regeneration of the habitat (and thereby boost oyster and blue cod numbers) by returning shells to the seabed and using underwater camera systems to monitor progress. Part of this trial is looking at what happens to small oysters on the shells returned to the sea. Short-term survival is over 90%.