Last year, the world produced more seafood than beef in the world and aquaculture is growing as a food production system to meet that demand. With that growth, however, we need sustainability, says Dr. Allen Place, professor at the Institute of Marine and Environmental Technology.
Fish raised in aquaculture were mostly being fed a protein diet that included other fish, predominantly menhaden and alewife. While humans don’t typically harvest those fish to eat themselves, those fish are common prey for the larger fish humans do like, and efforts to meet demands in aquaculture were paving the way to overfishing our oceans. The solution seemed simple—create a plant-based diet that would turn farmed fish into vegetarians. Dr. Place talks about how he approached his research and what he ultimately found.
What research are you working on at IMET?
We’ve been developing a way to raise a protein source—fish—in a sustainable manner. For so long, fish, such as menhaden and alewife, have been harvested as a food source for other fish.
My first student who got involved in this project, Aaron Watson (now at South Carolina Department of Natural Resources) and I wondered, “Is there a way to develop a plant protein-based diet to replace fishmeal?” You would have thought this should be possible, but nobody had succeeded. Nobody had been able to completely replace fishmeal in these diets.
What steps did you take to do this research?
We looked at a fish called cobia, a very fast-growing fish that’s very popular in sport fishing. When looking at a new protein source for diets, the first study you do is determine its digestibility. You mix fishmeal and plant protein 50-50, put a ma rker in, feed them, collect the poop, and you basically look at the percentage that’s digested. We did this for 6 or 7 plant protein sources—soy, corn, wheat, so forth—and determined several were well digested. Barley, for example, was poorly digested.
Then we made a protein mixture with the same percent protein as in a commercial diet with fishmeal and fed it to young cobia. And they wouldn’t eat it. So we discovered, basically, what everybody else discovered—you can’t completely replace fishmeal.
What happened next?
We looked back at our formulation and realized we had inadvertently left out a small molecule called taurine. If you look at your 5-hour Energy or Monster energy drink, the number one component is taurine. It’s a really important molecule: it enhances fat digestion, it is in our eye and brain, and it’s a really good antioxidant. What we did next was make a solution of taurine and sprayed it on the pellets. Now when the fish swallowed the pellets, they ate it. So we remade the diet with taurine from the beginning.
What did you learn from this research?
The take-home is everybody who failed in the past was missing this key ingredient in fishmeal. It turns out many of these species that we want to raise like cobia, like tuna, like European sea bass, have a taurine requirement because it’s naturally in their diet in high amounts. Aaron and I published this formulation in International Aquafeed for others to replicate. As long a diet contains around 1.5% taurine, fishmeal can be replaced completely.
