by Jolly Ghanawi, Editorial Contributor, International Aquafeed and Fish Farming Technology, UK
Aquaculture has become one of the fastest-growing ways of producing food, but traditional methods are showing their limits. In China, a common approach has been to raise shrimp and shellfish together in the same pond, known as polyculture. While this can work in the short term, the system often runs into problems when stocking densities are high. Water quality declines, algae can bloom, diseases spread, and farmers face economic losses. To find a better way forward, researchers at Ningbo University tested a new approach called tandem aquaculture, where shrimp and razor clams are farmed in separate but connected ponds.
Tandem aquaculture concept
The researchers chose to work with Pacific Whiteleg Shrimp and Razor Clams. Pacific Whiteleg Shrimp are among the most widely farmed shrimp in the world because they grow quickly, tolerate different conditions and generate strong economic returns. Razor Clams, by contrast, are filter-feeding shellfish that play a very different role in the ecosystem.
They consume algae and organic matter suspended in the water, and in doing so, they help keep the environment clean. The idea behind tandem aquaculture is that the waste from shrimp farming, which normally pollutes the water, becomes food for the clams. This not only benefits the clams but also improves water quality for the shrimp, creating a healthier and more efficient system overall.
Pond design & experimental setup
To test the concept, the researchers set up two large ponds: an 8000-square-meter pond for shrimp and a 4000-square-meter pond for razor clams. The ponds were connected by pumps that circulated water between them, carrying nutrients and waste from the shrimp pond into the clam pond. The clams filtered the water and removed excess material before it flowed back into the shrimp pond. For comparison, the team also stocked a smaller pond with both shrimp and clams living together, representing the traditional polyculture method. Shrimp were stocked at 40 per square meter and clams at nearly 500 per square meter across both systems.
Growth performance & water quality
Over the course of 317 days, the researchers monitored growth, water quality and overall carrying capacity essentially, how many animals the ponds could support without collapsing. The findings showed a clear advantage for the tandem system. The clam pond could support much higher densities than the polyculture pond, with between 364 and 427 clams per square meter compared to fewer than 110 in the mixed pond. The shrimp pond also performed better, sustaining 64 to 73 shrimp per square meter compared with only 31 to 42 in polyculture.
Water quality improved as well. The tandem system kept nitrogen and phosphorus levels under control, preventing excessive algae growth that could have led to oxygen depletion. The clams acted as natural filters, ensuring that the water returned to the shrimp pond was cleaner and more stable. In the polyculture pond, on the other hand, nutrient levels rose more quickly, creating greater risks for the animals and the system as a whole.
Improved yields & profitability
These improvements in carrying capacity and water quality translated directly into higher yields. In the tandem setup, razor clams produced an average of 6.81 kilograms per square meter, compared to just 0.77 kilograms in polyculture. Shrimp also grew better, reaching 1.24 kilograms per square meter against 0.47 kilograms in the traditional method. When the researchers calculated profitability, the tandem system generated nearly three times the income, averaging 105.68 CN¥ per square meter compared to just 37.16 CN¥ in polyculture.
To make sure these results were not a fluke, the team repeated the trial the following year using the same stocking densities predicted by their models. The second round confirmed the findings: the tandem ponds once again outperformed polyculture in growth, water quality and profitability. This consistency suggests that tandem aquaculture could be a reliable alternative for real-world farming operations.
Environmental & operational benefits
The study demonstrates that separating shrimp and clams into their own connected spaces makes both species thrive. Shrimp benefit from cleaner water, clams benefit from the steady supply of food in shrimp waste and farmers benefit from stronger yields and higher profits. It is a model that balances productivity with environmental responsibility, pointing toward a more sustainable future for aquaculture.
In a field under pressure to feed a growing population without damaging fragile ecosystems, tandem aquaculture offers a fresh solution. By making simple design changes dividing species into complementary roles rather than mixing them together the system shows that farmers can raise more seafood, make more money and reduce environmental harm all at the same time.
