Every 14 to 21 days, depending on water temperature, special, larger, brood stock goldfish are seined from an outdoor brood pond. Goldfish can begin to spawn at between two and three years old. During their time in the brood ponds, eggs have been growing inside the females — between 5,000 and 10,000 pencil-lead-sized eggs per fish.
The brood stock are placed in concrete spawning tanks, with the water carefully regulated to 72 degrees; the optimal temperature for them to spawn. After dark, the water level in the tanks is lowered to around two and a half inches for spawning (they have to do it after dark, Pool said, because goldfish will sunburn in shallow water in the daytime).
On the floor of the spawning tanks are "spawning mats" — thick three-foot-square pads, made from the same wiry material used in home air-conditioning filters, to mimic grass. The mats are black so the eggs on them will be easier to see, and are sandwiched between pieces of heavy wire grid.
Using their "whiskers" — rough, cat-tongue-like patches on their cheeks (this is how you can tell a male from a female, along with the female's rounder belly) — several male goldfish gang up to push a female onto the spawning mat, where she releases her eggs. The males then release their sperm to fertilize the eggs. The eggs adhere to the mat. During the peak of spawning season in the spring, each mat can eventually hold 50,000 to 100,000 eggs.
Once the eggs have been laid and fertilized, the brood stock go back to their brood pond, while the egg-covered spawning mats go to oxygenated, temperature-controlled tubs, each about the size of a washing machine, in an indoor hatchery. Fingerling goldfish will hatch within two to three days, with 750,000 to a million fish per tub. All baby goldfish are black when they first hatch as natural protection against predators. Until they are around two weeks old, even touching the fingerlings with a net will kill them. When they're large enough, the fish are removed from the tubs via a standpipe system, which drains each tub down to five gallons of water, and then moves the fish and water at the same time through a hose.
From there, the fish are transferred to outdoor ponds to grow up. Around 80 percent of the hatched fish won't survive to be shipped. "Generally about 50 percent survive from the hatch. You lose half," Pool said. "The rest of them are lost either to disease or depredation from birds, snakes, turtles, frogs, crawfish. They're a feeder fish. The reason they're a great feeder fish is that everything in the world preys on them and eats them. They're not very smart. They'll literally swim into a snake's mouth."
While being held in the outdoor ponds, the number of fish in each pond is carefully regulated to the point where the uninitiated might consider them overcrowded. That's because, Pool said, when a goldfish is in a crowded environment, hormones in the fish's brain make his body stop growing. Amazingly, while a one-inch goldfish can stay a one-inch goldfish for years or even decades in a small bowl, if you take him out of that tiny bowl and put him in a huge aquarium, the hormones kick in, and he can grow up to 18 inches long within a few years (before you get the idea of pan-seared Goldie, Pool said he doesn't recommend eating goldfish no matter what size they are, as they're much too bony). In order to hold the fish at the one-to-two inch and two-to-three inch sizes preferred by wholesalers, Pool Fisheries carefully controls fish density in their ponds.
When they have reached maturity, the goldfish are seined out of the pond and transferred to an indoor warehouse in preparation for being shipped. Just before shipping, salt is introduced to the water to cause the fish to purge all their waste. While some of the goldfish are shipped via air-freight in insulated boxes (most of the fish headed to stores and suppliers on the West Coast travel this way), more than one million at a time are loaded onto tractor-trailer rigs with dozens of individual tanks on the back and an onboard oxygenation system. For all fish that are shipped out, whether by truck or air, the temperature of the water in each box or tank is carefully regulated by way of ice or cold packs to closely resemble temperature at the ZIP code where the fish are going, to keep their systems from going into shock when they're unloaded. Fish going to Arizona, for example, might get two ice packs, while those going to Wisconsin might just get chilled water.
Like I said: They've got it down to a science.