Approximately 10 million spat can be expected from the 25 million eyed larvae. Natural mortality and the need to thin out the larvae to proper densities should leave about 25 million eyed larvae ready for setting. Under good conditions 200 million eggs can result in 100 million or more early-stage larvae, which require 2,600 gallons (10,000 L) of treated water. As a rule, ten average females produce about 200 million eggs. Spawning oysters is the first step in the production of spat. Because of the rich array of organisms in Gulf of Mexico waters, mechanical filtration down to 1 ?m with UV treatment can assist in successful spawning and larval production. Mechanical filtration is usually done with a pressurized sand filter, cartridge filters for smaller volumes, or fine-mesh bags. Large-scale operations and “low-tech” or “back yard” facilities may forgo UV treatment but will use some mechanical filtration. Water used for spawning, mixing eggs and sperm, and growing larvae is typically filtered mechanically and treated with ultraviolet radiation. Good water quality is essential to successful hatchery production (see Site Selection) but even high-quality water must be treated to remove unwanted organisms. Another larger space with special lighting, separate from the main hatchery, is needed to grow larger volumes of algae. If algal cultures are to be produced, there must be a clean room with special lighting for starting cultures.

Aeration throughout the hatchery is supplied by an appropriate size blower, overhead PVC piping, vinyl tubing, and good quality air stones. Shallow rectangular tanks with drain pipes provide nursery space for juvenile oysters. 4) that can handle the maximum expected water flow helps keep water off the floor. Drain pipes make it convenient to drain water and sieve larvae. Tanks for larval production are circular, generally 250 gallons (946 L) or larger, and have center drains and sloping or conical bottoms.

Treated sea- water is then suitable for larval and algal production. The plumbing is designed with a water filtration and treatment system consisting of some combination of rapid sand filters, cartridge filters, activated carbon, ultraviolet (UV) sterilization or pasteurization (Fig. Small cartridge and ultraviolet sterilizer filter system for treating seawater.

Seprating single oyster spat