If you’re eating a good steak, you don’t need sauce to enhance the flavor, and the same thing is true for good shrimp. That’s the kind of shrimp Ashtyn Chen is working to produce in his central Ohio aquaculture facilities. He is cultivating whiteleg shrimp in indoor saltwater tanks with a biofloc system that mimics the ocean ecosystem. His production practices and quick delivery after harvest result in sweeter, more flavorful shrimp than the imported shrimp often found in restaurants and supermarkets, he explains. High-quality fresh shrimp tastes good no matter how it’s prepared, and it doesn’t rely on added ingredients to provide flavor, he says. “You should never need a sauce.”
Chen started his shrimp farming business, The Ocean’s Friend Aquaculture, in 2015, shortly after he graduated from the University of Southern California with a degree in biochemical engineering. He works full time as an engineer and spends his spare time working on the aquaculture business. It started with tanks in a remodeled warehouse facility near Zanesville, Ohio, and has expanded to additional locations in Etna and Pataskala. In all, he’s currently harvesting about 2,100 pounds of shrimp a month, with about 70% sold wholesale and the rest sold retail through his Pataskala facility. The location of the aquaculture facilities near Interstate 70 gives Chen convenient access to buyers who haul wholesale shipments to New York City and Toronto. He also sells to several restaurants in central Ohio.
The production process starts with tiny baby shrimp he gets from a hatchery in Texas. “About six or eight of them will make an eyelash,” Chen points out. The baby shrimp start in a 210-gallon nursery tank for 24 days. Next, they spend 14 days in a secondary tank before being moved to a 3,300-gallon tank, where they remain until harvest at about 4.5 months. The usual harvest size is between 25 and 35 shrimp per pound; he sells some smaller shrimp to Japanese chefs, however, who like the smaller shrimp to make sashimi.
Water in the tanks is constantly circulated using a regenerative blower that moves air through PVC pipelines connected to each tank. The system draws water from the bottom of each tank and expels it at the surface, creating a circulating current. The shrimp swim against the current, eating as they go. They can move toward the center of the tank where the current is not as strong to nap, but the current tends to push them toward the outside of the tanks so they’ll keep moving and eating, Chen explains.
The young shrimp start out in water with salinity of 35 to 40 parts per thousand; as they grow, the salinity is reduced to 6 to 15 parts per thousand. This change mimics the migration of shrimp in nature, from the ocean where they hatch to brackish estuaries, where they mature, Chen says. He uses a boiler system that circulates warm water through hoses submerged in the tanks to keep the tanks at 78 to 80 degrees F. Shrimp will grow faster at higher temperatures, but mortality tends to increase, he notes. Death losses not only hurt harvestable numbers, but they also throw off the stability of the tank environment, he adds. “Whenever something dies in these tanks, it affects the ecosystem.”
The biofloc waste removal system Chen uses forms an ecosystem within each tank that manages waste from the shrimp, without filtration. “We’re managing each of these tanks as its own ocean,” Chen explains. Each milliliter of water contains about 8 million microbes, which consume the waste from the shrimp. He got his first bacteria starter from aquaculture researchers at Purdue University for his first tank, and has propagated additional microbe populations as he has added tanks. The microbes keep levels of ammonia and nitrites from building up in the water and also provide a food source for the shrimp. The microbial activity can be adjusted as needed by adding brown sugar or sodium bicarbonate (baking soda) to the water, Chen explains. The sugar provides a carbon source to balance the nitrogen in the system. Baking soda adjusts the water’s alkalinity, which decreases when the shrimp molt. To remove excess solids from the tanks, Chen pumps water into settling tanks, and he then reuses the water after the solids drop to the bottom.
Microbes in the biofloc provide about a third of the shrimp’s diet. They are also fed a ration of mealworms and fish meal. Babies eat six times a day, and older shrimp are fed three times a day. To keep the tanks’ ecosystems in balance, the water in each tank is tested before each feeding for dissolved oxygen, nitrate, nitrite, pH and alkalinity. However, Chen notes, once a tank is balanced, it ordinarily doesn’t need much adjustment.
Chen’s mother, Carol, handles most of the daily management of the three shrimp facilities since Chen works full time. For her, it’s a retirement career after many years spent in the restaurant business, Chen explains. His dad, Chao, will also be retiring from the restaurant business in a few years, and he plans to help with the aquaculture business as well.
As he has expanded the business, Chen has fine-tuned his production system and facilities. He designed and built the Pataskala facility specifically for shrimp production, doing most of the work himself. The insulated, 6,000 square-foot building is equipped with LED lighting and a 240-volt blower system to circulate water in the shrimp tanks. It is significantly more energy-efficient than his other facilities, he notes.
Chen has also saved money by putting together his own tank systems rather than buying commercially available aquaculture kits. He estimates he spent about $600 to set up each tank, compared to a price tag of $4,200 for a kit system. The plastics used for aquaculture do need to be FDA-approved for food production, but that information is available from manufacturers, he points out. Buying from an aquaculture supplier may be convenient, but prices may be lower elsewhere, he adds. For instance, instead of buying hose from an aquaculture supplier, he found similar, FDA-approved hose available from an agricultural spray equipment company at a lower price.
In addition to the shrimp, Chen is raising crawfish, which are currently going into the pet market. He is working to develop a production system for pompano (a saltwater fish species) as well. He is also experimenting with growing salt-tolerant vegetables, such as sea asparagus and kale, to make use of the nutrients in the solids removed from the tanks. An aquaponics system with shrimp and vegetables in the same tank won’t work, though. Shrimp can jump out of the water and would end up on the vegetables, he explains. “They can jump 4 feet up — and out.”
Chen owns seven sets of shrimp for breeding, but he contracts with a hatchery to handle breeding and hatching. Having his own breeding stock cuts his cost for baby shrimp, he explains, but he doesn’t want to hatch them himself. The process is complicated and requires expensive specialized equipment, including a spherical tank and green mood lighting. Shrimp breed simply by colliding with one another and then instantly bouncing apart, he adds. “It gives a new meaning to the term ‘quickie.’”
One female shrimp can produce 300,000 eggs at a time, six times a year. Shrimp mature at about 6 months old and can live to be about 4 years old, but they are typically used for breeding for only about a year, Chen explains. Like other farmed species, shrimp have been selectively bred to improve growth rates. And, as with other species, growth rates must be balanced with other desirable characteristics. “You don’t want to sacrifice the disease resistance they’re known for,” Chen points out.
Keck writes from Raymond, Ohio.