Soybean meal can serve as the primary protein source in all-plant protein diets for freshwater omnivores, sparing more expensive fish meals and animal meals for more specialized feeds.

Soy protein concentrate has been shown to be effective in replacing fishmeal in the fingerling diets in freshwater omnivore diets, allowing production of all-plant protein diets for all life stages of the majority of the cultured freshwater fish species.

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Freshwater Cage Technology

Some freshwater fish species are adaptable to culture in cages in freshwater lakes, reservoirs, rivers, and canals. The three species of freshwater fish most typically cultured in cages are common carp, tilapia and channel catfish. A variety of cage sizes and styles are used to culture freshwater fish.

LVHD cages
Tilapia cultured with soy feeds in LVHD cages in China yield quality fish with a low FCR.

USSEC’s International Soy in Aquaculture Program uses low-volume high-density (LVHD) cage technology to demonstrate the production of fish in cages with soy-based feeds. LVHD cage fish culture is defined as the raising of fish at densities of 400 – 500 fish per cubic meter (m3) in cages of size 1-m3 to 4-m3, with optimum yields of 150 -250 kg/m3. USSEC uses LVHD cage technology because it is inexpensive to demonstrate production techniques and feeds and provides significantly higher productivity per unit of cage volume than larger cages. The high productivity rate in LVHD cages is due to the rate of water exchange that allows for a well-oxygenated culture environment. In comparison, larger traditional cages generally yield only 20-25 kg/m3.

Freshwater Pond Technology

USSEC defines 80:20 pond fish culture as the raising of fish crops in ponds where a single feed-taking species of a single size group composes approximately 80% of a total fish harvest weight and one or more other “service” or non-feed-taking species compose the other 20%. The “service” species could be filter feeders that feed on waste or predators that control population in a pond with both genders that could reproduce. This technology, which is a modification of standard intensive pond monoculture, was developed in China and is mainly used in freshwater pond production.

Grass carp
Grass carp produced as the fed species in an 80:20 pond system grew from 84g to 1,053 g in 138 days with a FCR of 1.19:1.

Silver carp, a filter-feeding freshwater fish native to China, is typically used as the service species in an 80:20 system, as it does not compete for feed and has reasonable economic value in the marketplace.

A predatory species can also be used as a service species in 80:20 systems, such as to control tilapia reproduction where there is less than 100% all-male progeny.

In-Pond Raceway System

Developed at Auburn University with investment from the U.S. soybean checkoff program, the In-Pond Raceway System (IPRS) creates a healthier environment with a riverine flow for fish and shrimp in pond raceways while greatly reducing the environmental impact. The system protects water quality by removing waste and recycling it for other uses such as biodiesel and fertilizer, enabling reuse of the pond water and significant conservation of limited water resources.

carp stocked in raceways
A small scale IPRS operation with carp stocked in raceways. Water flows through the raceways and around the larger pond area, allowing fish waste removal from the raceways and conserving water quality for reuse.

The IPRS technology was first brought to China by USSEC’s International Soy in Aquaculture Program in 2013 through a demonstration project in Pingwang, Jiangsu Province. Together with the use of high protein soy-based feed, the IPRS demonstration achieved notable success in tripling yields, better fish performance, health and quality, lower feed conversion ratio, labor savings and higher profitability.

The technology is being rapidly adopted in China and throughout Southeast Asia and is currently being introduced by USSEC to other regions. To support the expansion of IPRS technology, USSEC’s International Soy in Aquaculture Program provides on-site technical services and training seminars and organizes visiting teams to well-operated IPRS units.

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