World Wildlife Fund Sustainability Works

a carp jumps out of the water, above the treeline

How “Carpcake” Can Revolutionize Conservation and Sustainable Nutrition

  • Date: 10 March 2024
  • Author: Ellen Dierenfeld, Lead Specialist, Sustainable Feed Innovation

Many years and another lifetime ago, I headed up the Department of Wildlife Nutrition for the St. Louis Zoo. One day I received a call from the head of a group called “Carpbusters,” who organized bow and fishing tournaments throughout the region to rid the rivers of invasive carp. Sportsmen paid fees to join the festivities, enjoyed their luck with feisty fish, and were awarded prizes for various categories of daily catch.

The lack of a proper outlet for the extracted fish, however, bothered the leaders of this conservation effort as thousands of pounds of high-quality protein rotted on the riverbanks after each weekend. Would the zoo be able to utilize carp for feeding fish-eating species? was the query. They could be delivered fresh and intact, as a free donation.

It was an excellent idea. As with most animal operations, feed costs comprised the largest portion of management, and the annual fish budget was high. If we could make a dent in the budget for feeding endangered species, while at the same time contributing to eradication of invasive species that threatened natives and their habitats, it would be a win-win for conservation.

slices of "carpcake" on a tray

Prototype carpcake recipes

There was literally a “big” problem, however. These are large fish, averaging 20-30 pounds, with some reaching 80 to 100 pounds and over 3 feet long. While they may make great sparring partners for fishers that thrive on a good fight, they don’t make a nutritionally complete meal for anything that can’t eat them whole. Whole prey — fish, rodents, birds, rabbits — can provide complete nutrition for carnivores if the organs, bones, and meat are all consumed. But eaten separately, these portions make up imbalanced diets. The few mouthfuls that a tiny kingfisher might consume from a 20-pound fish would in no way provide an adequate diet. The fish needed to be properly processed to incorporate all the nutrients.

That’s how the potential for turning “bad fish into good food” for animals was hatched. I partnered with food scientists at the University of Missouri-Columbia and the US Geological Survey’s Carp Eradication team members. Together, we developed a process grinding the whole carp into a mince, supplementing it with necessary vitamins to maintain quality, and then adding alginate powder and a catalyst to form it into a firm cold-set loaf: “carpcake.”

One of the important aspects of the gel included mimicking the texture of fish since animals, especially those eating whole prey, can be picky consumers. Plus, it had to hold together when tossed, as was the feeding practice for some species. We tested 19 recipes by playing “carpcake catch” across the diet prep kitchen to evaluate stability before the taste tests, while maintaining quality and safe cold-chain handling throughout the process. But we still hadn’t gotten it into any critter mouths.

The carpcakes were stored either frozen or refrigerated and could be cut into various sizes or shapes for different species. We ran palatability tests of sardine-sized strips on puffins, trout-sized portions on penguins and crocodiles, and herring-modeled fish blend on sea lions. Result: All but the sea lions consumed the reformed carp readily at first exposure.

Cat sniffing strips of carp jerky

Carp can provide high-quality, healthy, sustainable food for humans and animals, including pets.

New possibilities for using invasive carp as a sustainable feed ingredient — tested on some of the most discriminating mouths — had been achieved.

Decades later, I’m part of a team looking to establish an industry group called the Invasive Carp Consortium to take these early explorations to the next level: Fresh, frozen, processed and even dried carp products providing high-quality, healthy, sustainable food and feed for both human and animals of all species.

Carpbusters’ inquiry proved to be tremendously prescient, offering a dual win: eliminating the invasive species and mitigating some of the negative impacts associated with food and feed production. Balancing conservation and sustainable food production doesn’t get better than that carpcake.


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