Collecting and importing oyster spat

The first step in oyster aquaculture is finding a good source of spat (oyster larvae). The successive steps of growing and maturing depend on the quantity and quality of the spat.

Importing spat

Queensland oyster farmers have, for some time, relied on importing spat from New South Wales for on-growing into Queensland waters. Some spat is still collected, but the amount is small compared to the spat sourced from New South Wales.

Because an oyster is considered spat up to the age of 12 months, size can vary considerably. Many growers ask to see a sample of the stock before they buy.

Selection of spat has become an important issue for Queensland growers, as they need to source supplies of stock that are both economical and contaminant-free. Restrictions are in place to prevent importing the Pacific oyster (Crassostrea gigas) into Queensland. This introduced species competes with rock oysters for food and space.

Collecting spat

Crucial considerations for spat collection include:

  • deciding on an area in which to collect (this must be an area where spat are known to be present in the water)
  • developing a suitable substrate for the spat to settle on.

The influences of tide, wind and currents must be considered before placing spat collection devices. The artificial substrate must be attractive to the larvae to encourage them to settle and attach.

Stick placement is one of a variety of proven methods used for collecting spat. In this method, 6–8 sticks are nailed to cross-beams to form frames that are then grouped to form batches. The batches are placed in the mid to lower part of the tidal range, where the spat settle on the sticks.

Known spat-catching areas in southern Queensland are the Great Sandy Strait, Pumicestone Passage and the leeward sides of Moreton, North Stradbroke and South Stradbroke Islands. Spatfall occurs throughout the year, but peaks in Moreton Bay between November and March.

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