Each year, wild fish are caught by the thousands and turned into fishmeal to feed farmed fish. But wild fish populations are already stressed as the culinary demand for fish is on the rise, so researchers are looking for a fishmeal substitute. Host Jeff Young talks with Dr. Rick Barrows, a USDA fish physiologist about a promising alternative.
YOUNG: So the search is on for something better to feed farmed fish. Dr. Rick Barrows thinks he might have a candidate. He’s a fish physiologist with the USDA’s Agriculture Research Service. Dr. Barrows, welcome to Living on Earth.
YOUNG: So, you’re looking for a new, effective fish feed? What have you come up with?
BARROWS: Well, one of the promising areas is barley protein concentrate. It’s similar to soy protein concentrate, which is used in human foods all the time, but it’s produced using a different method that results in the co-product production of bio-fuels. And we take the carbohydrate portion of the barley, we take that off to make ethanol and then what’s left over is this high quality, good amino acid profile protein that we can then feed to fish.
YOUNG: And why would this be a good choice to feed to farmed fish?
BARROWS: Part of it is availability; there is a lot of barley around right now with not a lot of demand. Barley also has very low anti-nutrient levels and a good nutrient profile. Anti-nutrients are substances in plants that basically evolved to keep other animals from eating them. And that can be a problem with some alternative sources, where barley doesn’t have that.
YOUNG: Now, most of the fish species that we are looking to here are carnivores – they eat other fish – so could a fish that normally eats other fish get by eating barley?
BARROWS: Yes because fish and other animals require nutrients, not ingredients. It’s really the nutrition out of the meal that they need. We have found over the last six years that there are several substances that are found in high levels of fish meal that aren’t found in plants, but when you feed a fish meal-free, all plant diet to carnivorous fish you need to supplement those nutrients, as well.
YOUNG: And would this produce a fish that would have the nutritional benefits that consumers are looking for?
BARROWS: Well, those benefits include high protein, which of course it will have, but the fatty acid profile, the heart healthy characteristics of fish that really comes from the oil source. So we still need to provide the fish with an energy source, which has been fish oil in the past, to get those same heart healthy benefits.
YOUNG: So if you have to supplement their feed here in order to get the high omega three, where do you get the fish oil, and is that carry risk of contaminating the fish?
BARROWS: Very good question. Right now the primary source of omega three fatty acids for fish is from fish oil, which is wild harvested – it will carry the PCBs – but the majority of fish oil that is fed to fish now is carbon-filtered to remove those PCBs.
YOUNG: And if this were to become a major part of how we feed farmed fish, would this improve the environmental impact of fish farming?
BARROWS: Yes, it can improve sustainability because we’re growing the food for the fish, rather than harvesting it from the sea. But it’s also – plants have a very low levels of phosphorous. Fish meal carries high levels of phosphorous with it, more than the fish require and so then you have lots of phosphorous going downstream from a fish farm; feeding plant-based diets you have much lower levels of phosphorous.
YOUNG: And would we have farmland sufficient to meet the demand if we go this route?
BARROWS: No, there isn’t going to be enough barley around to make barley protein concentrate for all farmed fish, but it could become another important tool in the tool box.
YOUNG: You’ve been in this business for quite a while, have you noticed an uptick in general interest here?
BARROWS: Yes, definitely. There’s a lot of concern over environmental pollution from fish farms, there’s a lot of concern over the sustainability of the fishmeal, there’s a lot of concern over PCB levels in farmed fish. Every system can be improved by critical evaluation, and that’s really what has been happening the last couple years and the industry’s responding and producing fish in a more sustainable fashion.
YOUNG: Fish physiologist Rick Barrows, thanks very much.
BARROWS: You’re welcome, nice talking with you.
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