A new US project will develop a more ocean-friendly feed formula for farm-raised rainbow trout. Two faculty members from UC Santa Cruz’s Environmental Studies Department, Pallab Sarker and Anne Kapuscinski, won a $496,000 grant from the U.S. Department of Agriculture and will test proteins and oils derived from a combination of marine microalgae to replace traditional fishmeal and fish oil ingredients sourced from wild-caught forage fish.  Sarker and Kapuscinski published a major breakthrough on this front in 2020, the first fully fish-free feed formula for farmed tilapia to demonstrate across-the-board gains in sustainability, fish growth, economic viability and nutritional value for human consumers. Now, the researchers are hoping to replicate their success with rainbow trout. That goal is especially important since trout and their relatives, salmon, are some of aquaculture’s largest consumers of fishmeal and fish oil. But getting these particular species onto a fish-free diet will be challenging.

Unlike tilapia, trout and salmon are natural predators that evolved to eat other fish. Marine microalgae are much lower down in the ocean food chain, however, they’re still part of the same systems of nutrient and energy transfer. That gives researchers hope that the right combination of microalgae species could potentially match the nutritional value of fish-based ingredients. Their experiments will be aimed at finding the right fit for the needs of rainbow trout.

Researchers expect to start experimenting soon with various processing methods for manufacturing feed using these and other ingredients. They’ll also test the digestibility of their formulas. Juvenile rainbow trout will be stocked into the team’s newly-constructed recirculating aquaculture facility at the UCSC Farm. With a new facility up and running and new grant funding in hand, the research team members said they are feeling optimistic about the road ahead.