New research on aquaculture feed will test alternative ingredients to minimize water pollution

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Researchers at UC Santa Cruz’s Organic Aquaculture Laboratory received a three-year grant of $ 1 million from the USDA National Institute of Food and Agriculture’s Agriculture and Food Research Initiative. This funding will support joint research to develop, test and evaluate new low-pollutant fish feed recipes for farmed rainbow trout.

Associate Research Professor of Environmental Studies Pallab Sarker will lead this work along with Environmental Studies Professor Anne Kapuscinski and Luke Gardner, a California Sea Grant Renewal Specialist at UC San Diego. The team will use a marine microalgae as an ingredient in their fish feed, and the resulting experimental formulas will be field tested on trout farms in California.

The aim is to create an environmentally sustainable and economically viable new feed option that will maximize fish growth while limiting the potential for water pollution during fish farming.

Water pollution is a challenge for aquaculture as fish waste contains nitrogen and phosphorus. These are nutrients that have the potential to fuel algal blooms in nearby waterways if wastewater from large-scale fish production is not properly treated. But low-pollutant fish feeds have been specially developed to meet this challenge.

Low-pollutant fish feeds contain as little nitrogen and phosphorus as possible and provide these nutrients in a form that is easily digestible and absorbable for fish in order to minimize the subsequent excretion of the fish in their excretions. These feeds are a great example of how scientific innovation has helped make aquaculture more sustainable.

“Redesigning the composition of aquaculture feed has been an important lever in combating nutrient pollution“Sarker explained. “Low-pollutant aquaculture feed helps to preserve natural ecosystems and provide clean water.”

The UC Santa Cruz team hopes their work will help increase the variety and quality of low-pollutant feed options for fish farmers.

Sarker and Kapuscinski have worked for years developing new sustainable fish feed formulas by recycling leftover biomass from commercial production of marine microalgae used to make omega-3 nutritional supplements for humans. Most of the team previous work was designed to combine various marine microalgae to replace traditional wild-caught fish meal and fish oil ingredients. But the team also wants their feed formulas to help reduce water pollution. So the new grant will help them test this aspect.

Sampling fish waste for digestibility analysis. Photo: Carolyn Lagattuta

First, the researchers are experimenting with various methods of processing microalgae ingredients to make them as digestible as possible for rainbow trout. Next, they determine the ideal amount of microalgae that fish-based ingredients can replace. They then develop a low-pollutant diet and determine both its impact on trout growth and its potential to minimize water pollution from the resulting trout waste.

These first steps will take place in the aquaculture research laboratory at UCSC Farm, but thanks to the partnership with California Sea Grant, the team also has the ability to evaluate the feed’s performance in the real world through trials on fish farms. Anne Kapuscinski and Luke Gardner will jointly lead this collaboration with a small group of trout farms in California. You will also be recruiting other executives from across the aquaculture industry to learn more about a low-pollutant diet and generate commercial interest.

“We are very pleased that with this grant we can test our new diets on commercial trout farms,” ​​said Kapuscinski. “The proof is in the pudding – or in this case, fish farming – so I think this will go a long way in convincing more farmers and aquafeed makers to adopt a low-pollutant diet.”

The project’s research staff will also scale the economic feasibility of the new feed. A life cycle assessment compares the overall environmental impact of the new formula with that of conventional feed – from the initial production of the feed ingredients to the finished fish fillet – in a variety of impact categories, including greenhouse gas and eutrophication emissions, water consumption and biotic resource use.

Sarker and Kapuscinski are experimenting with recycled marine microalgae biomass as an alternative feed ingredient, also because they believe that it has the potential to be more sustainable than conventional feed ingredients such as fish meal and fish oil or agricultural crops such as corn, wheat or soy. The life cycle assessment of your feed will provide valuable new insights into this question.

Ultimately, the team hopes aquaculture will grow to meet global protein needs, and hopes that continued research will ensure the sustainability of the industry grows in parallel.

“Aquaculture has a bad reputation with American consumers and this is slowing the progress of aquaculture, especially for species such as farmed salmon and farmed trout, where the required feeding has a greater environmental impact,” said Sarker. “But that impact is likely to continue to be mitigated by research and innovation that find better ways to feed fish and help promote best and most responsible aquaculture practices.”

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