Pearl Oyster Culture

This chapter covers the culture methods used for pearl oysters during all stages of culture, from hatchery production to the husbandry of oysters "seeded" for pearl production. The major pearl culture industries have traditionally relied on oysters collected from the wild for pearl nucleus insertion. Adult pearl oysters are collected or, alternatively, spat are obtained using various kinds of spat collectors in the field and then on-grown to a size suitable for nucleus insertion. The relatively recent development of hatchery culture methods for pearl oysters has reduced industry reliance on oysters taken from the wild. The methods used in hatchery culture for broodstock conditioning, spawning induction, fertilization, egg incubation, larval culture, and inducing settlement are similar to those typically used in bivalve hatcheries. Larval culture is the most critical phase, with issues of water quality, water exchange, culling, stocking density, nutrition, and food ration. Microalgae differ in their nutritional value for larvae and a mixture of several species is commonly used to provide a better balance of nutrients for larval development. Various culture structures are used in pearl oyster farms: surface rafts and longlines; subsurface longlines; benthic racks, trestles, and fencelines. The oysters are cultured in units suspended from the structure. Growth and survival are substantially influenced by the culture structure and culture units used. Development of hatchery culture methods provides the industry with opportunities to develop selective breeding programs and develop techniques commonly used in other aquaculture industries, such as triploidy and cryopreservation. © 2008 Elsevier B.V. All rights reserved