Shrimp—A Delicacy From a Farm?
BY AWAKE! CORRESPONDENT IN ECUADOR
YES, this seafood delicacy enjoyed by millions often comes from a farm. Yet, the consumer may never know this because farm-grown shrimp differ little, if at all, from the ocean-grown variety. Indeed, many shrimp ponds in Ecuador are stocked with young shrimp taken directly from the ocean.
These juvenile shrimp, not more than a half inch [one and a half centimeters] long, are netted in the mangrove-lined estuaries along the coast or in ocean breakers, by fishermen called larveros. Then they are taken to the ponds to grow. However, not enough shrimp can be provided in this manner. Thus, many shrimp farms depend on hatcheries with modern aquaculture methods to provide young shrimp for their ponds. Let’s take a closer look at how shrimp farms operate.
A Visit to a Hatchery
The hatchery we visited was located on a beautiful beach on the Pacific Coast. A shrimp hatchery must be situated near a large body of saltwater in order to meet the needs of its complex water-distribution system. Water from the ocean is pumped in, filtered, heated as necessary, and sent to various tanks inside.
We were met by a friendly group of casually dressed marine biologists, technicians, and other workers. Our first stop was the maturation room. Here, fully grown wild shrimp are kept in 4,500-gallon [17,000 L] maturation tanks. “These shrimp are not for eating,” our guide explained. “They were caught full-grown and brought in for brood stock.”
A strict lighting schedule is followed in the maturation room. Between 3:00 p.m. and midnight—the mating period—the low-intensity lights are turned off, and workers search with flashlights for females that are ready to spawn. Females of the Penaeus vannemei species are easy to detect, since the male attaches a sperm pack externally to their abdominal area. Once workers spot a pregnant female, she is removed and taken to a smaller, 70-gallon [260 L] spawning tank.
There the pregnant female is placed on a platform near the top of a conical tank—one female per tank—until she spawns her 180,000 or more eggs. As the eggs are expelled, they are fertilized upon contact with the gelatinous sperm pack. Afterward, the eggs and the water are drained through the funnellike base of the spawning tank. Technicians record the number of eggs from each spawning.
Hours after hatching, the larvae are transferred in controlled quantities to what are known as culture tanks. These look like giant bathtubs, and they hold about 3,000 gallons [11,000 L] of water. For the next 20 to 25 days, these tanks serve as home for the developing larvae, which feed on algae and dried seafood.
Where the Shrimp Mature
The shrimp, now called postlarvae, are transferred to the farms. Once there, both the hatchery-produced shrimp and their ocean-bred relatives receive similar care. They are put in small pools to control their adjustment to the new temperature and salinity levels of the water. After a few days, they are ready for the large ponds. These man-made ponds are adjacent to a reservoir canal. Water is regularly pumped from the ocean or estuary into this canal. The adjoining ponds range from about 12 to 25 acres [5 to 10 ha] in size. For three to five months, the juvenile shrimp are allowed to grow in these ponds.
During the growth period, the oxygen level in the water of the ponds is monitored daily. Also, the growth rate of the shrimp is checked weekly in order to adjust the feeding program. An effort is made to maintain a weight gain of 1 to 2 grams per week.
Harvesttime
At harvesttime, while the pond is being drained, the shrimp are netted or pumped out as they near the gate. Then, the freshly harvested shrimp are rinsed and covered with ice for immediate transport to a packing plant. There, unless the purchaser specifies otherwise, the heads of the shrimp are removed, but their tails are left unshelled. The shrimp are washed and sorted according to size, after which they are packed and frozen for shipment, usually in five-pound boxes.
So the next time you enjoy shrimp, you might remember that this seafood delicacy may well have been pond-raised in a place such as Latin America or Asia.
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Size of shrimp at harvest
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Fishermen netting juvenile shrimp
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Culture tanks inside the hatchery
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Cleaning shrimp at the packing plant
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Packing shrimp according to size