in tanks at 20–22 °C, supplied with cultured algae and with salinities of 25–32 ppt. These individuals can be induced to spawn by thermal shock treatment. Yet, the eggs from a small sample of females (about six) are more commonly stripped from the gonads using Pasteur pipettes and fertilized by sperm from a similar number of males. Larval and postlarval culture Pacific oysters have a pelagic veliger larval stage which lasts from 14–18 days. In the hatcheries, they are kept at temperatures of 25–28 °C with an optimum salinity between 20 and 25%. Early-stage veligers (<120 nm shell length) are fed daily with flagellated algal species (Isochrysis galbana or Pavlova lutherii) along with diatom species (either Chaetoceros calcitrans or Thalassiosira pseudonana). The larvae are close to a settlement stage when dark eye spots and a foot develop. During this time, settlement materials (cultch), such as roughed PVC sheets, fluted PVC pipes, or shells, are placed into the tanks to encourage the larvae to attach and settle. However, particularly on the US West Coast, mature larvae are commonly packed and shipped to oyster farms, where the farmers set the oysters themselves. Nursery Pacific oyster spat can be grown in nurseries by sea-based or land-based upwelling systems. Nursery culture reduces mortality in small spat, thus increasing the farm's efficiency. Sea-based nursery systems are often located in estuarine areas where the spat are mounted on barges or rafts. Land-based nursery systems have spat mounted on barges in large saltwater tanks, which either have a natural algae supply or are enriched with nutrients from fertilizers. Ongrowing techniques This stage of oyster culture is almost completely sea-based. A range of bottom, off-bottom, suspended, and floating cultures are used. The technique used depends on site-specific conditions, such as tidal range, shelter, water depth, current flow, and nature of substrate. Pacific oysters take 18–30 months to develop to the market size of 70–100 g live weight (shell on). Growth from spat to adults in this species is very rapid at temperatures of 15–25 °C and at salinities of 25 to 32 ppt. General production In 2000, the Pacific oysters accounted for 98% of the world's cultured oyster production, and are produced in countries all over the world. Production statistics Global production has increased from about 150 thousand tonnes in 1950 to 1.2 million tonnes in 1990. By 2003, global production had increased to 4.38 million tonnes. The