0:00:01.5 John Sheehan: We've discussed a few times on this podcast that there's a real opportunity for the growth of US aquaculture or farmed seafood, particularly in light of current US demand for seafood.

0:00:12.9 Dr. Michael Aquafredda: We Americans import about two thirds of the seafood we eat, and half of that's from aquaculture from other countries. So much so that imported farm shrimp and salmon are now the most consumed seafoods in the US.

0:00:24.5 JS: And along with growth, there is an opportunity for another great American propensity innovation. This is dive in with NOAA Fisheries. I'm John Sheehan. And today we'll hear about a system of aquaculture that's more complex than simply growing a single species of fish or kelp or shellfish at a time and that has the potential for greater returns.

0:00:47.3 DA: With every unit of food you're feeding your fish, you're getting more out of it, you're getting more bang for your buck.

0:00:52.2 JS: This is Dr. Michael Aquafredda.

0:00:53.6 DA: Aquaculture specialist at the Rutgers University Haskin Shellfish Research Lab.

0:00:57.4 JS: Mike is interested in a specific kind of aquaculture called Integrated multi-trophic aquaculture, or IMTA.

0:01:06.6 DA: Integrated multi-trophic aquaculture is a specific form of aquatic polyculture, which simply put is growing more than one species in the same place at the same time. And what's unique about IMTA is that the wastes from one of those species gets transformed into the resources for another.

0:01:24.9 JS: As a postdoctoral researcher with the National Research Council, Mike spent two years at NOAA's James J. Howard Marine Sciences Lab in Sandy Hook, New Jersey, and part of the Northeast Fisheries Science Center. And there he ran an experiment farming striped bass using IMTA.

0:01:40.1 DA: IMTA reduces the environmental impact of food production by reducing pollution that arises from the excretions of a fed species like finfish or crustaceans and it's paired with what we call lower trophic level species like bivalves, worms that can be co-cultured with the fish and eat the excretions from the fish or the crustaceans. And then oftentimes there's also an autotroph or a species like algae or plants that photosynthesize and they'll soak up the liquid excretions from all of the species in the mix.

0:02:15.0 JS: Yeah, and I think you can kind of imagine this on the ground version, right? So the manure of cow is being used to feed plants. It's the same kind of concept for aquaculture.

0:02:29.7 DA: Absolutely. It's taking kind of an ecosystem approach to aquaculture the same way as you mentioned, that the manure from a cow eventually is used to grow the grass that the cow will later eat. We're doing something very similar but in an aquatic system.

0:02:44.9 JS: And so what can these systems sort of look like? Can you give us some examples of how big, how complex they can get?

0:02:50.0 DA: Yeah, so IMTA can be conducted in many different ways. It could be conducted in an open water setting, so think farms that are in bays or estuaries or off a coast, and those systems can include things like steelhead, trout or salmon. And then downstream of that species you might have something like a mussel or an oyster, something that's going to extract the particles that are excreted by the fish and also the uneaten food from the fish. And then downstream of that, you might have something like kelp that's going to soak up all the dissolved nutrients. So kinda like the liquid fertilizer of the system. But IMTA could also be conducted on land in recirculating aquaculture systems or something called RAS. And these land-based systems, sometimes IMTA is referred to as aquaponics. That terminology came up in like the freshwater world, whereas IMTA is often used in the marine or estuary world, but effectively it's the same principle of just having species at different trophic levels or trophic level is a fancy name for like different steps in the food chain or different links in the food chain. And having those different links, those different species using shared space and shared resources.

0:04:06.2 JS: Yeah, and saying it out loud, it just sort of makes all the sense in the world, like that's how ecosystems work. It makes complete sense that you would try and replicate that for a farming environment. Why doesn't more aquaculture sort of take that approach?

0:04:23.5 DA: I often think about that as well, It makes a lot of sense to me. But the one I think kind of drawback that's kind of inherent to IMTA is that it's you're building a complex system, and the complexity is what causes limitations. So sometimes the different organisms in the IMTA mix will need slightly different conditions or at very least different husbandry techniques, right? So to grow fish, you need to have a pen or you need to have a tank to grow mussels or to grow oysters, you need to have them in a cage or growing on a rope. On the business side of things, there's also different markets. So you might be selling your kelp to a very different market than you would be selling your steelhead. And I think kind of the biggest issue with complexity is also labor costs. The labor takes to care for these different species probably varies significantly. And most aquaculture is conducted as monoculture. Monoculture benefits from efficiency and simplicity. IMTA is efficient when it comes to resource utilization, but not necessarily efficient when it comes to labor.

0:05:34.4 JS: Yeah, and I'm glad you brought up the economic aspect of it because at the end of the day, it does become this question of, how do you make these systems generate profit, which is not quite as simple as does it work?

0:05:47.1 DA: Exactly. And I'm a biologist, so a lot of my work has been focused on like, is it feasible biologically speaking? But I'm really cognizant of the fact that what's holding this back is economics, so I've been trying to incorporate more of that thinking in my own research.

0:06:04.6 JS: So let's talk about your research. The project you conducted a couple of years ago now at this point at the Howard Lab, and NOAA's Northeast Fishery Science Center. What was going on?

0:06:16.0 DA: Yeah, so I was working at the James J. Howard lab and I had the pleasure of working with two of their recirculating aquaculture systems. So these are systems that can recycle close to 100% of the water in the systems. They're really powerful tools that allow us to conduct experiments, and they're also used commercially to grow fish. So in my experiment, I was hoping to investigate whether IMTA would be a feasible and environmentally sustainable system for producing striped bass. Striped bass are native fish that live along the east coast. Their husbandry techniques are pretty well worked out. They're also delicious and recognizable. People like to eat them and people are already farming them on commercial scales. So in my experiment, the idea was to compare striped bass growth in a regular recirculating aquaculture system that was just monoculture. So just bass in those tanks and compare that to a system where the bass were in tanks and the water that they were grown in was shared with water that was being used to grow worms and also used to grow something called sea beans, which is an edible marsh plant sometimes called pickleweed or sea beans.

0:07:30.5 JS: And what did it look like? Do you have like a big tank of fish, and then below that there's the sea beans, and then below that there's like the worms crawling around in the bottom? Like is it like a, like a big tank you can sort of like see the striations of?

0:07:45.2 DA: Not quite. I think if you were to try to grow the bass and the worms in the same tank, the bass would eat all the worms. So these were in separate tanks, but they were all plumbed together. So we had these big circular tanks that held about a thousand liters of water each. The water would flow from those tanks into a smaller tank that contained the worms. And then downstream of that worm tank, there was another tank that held the sea beans. And the sea beans were held on these styrofoam rafts that you see commonly in hydroponics or aquaponic systems. And we had grow lights that would provide the light that the plants would need to grow. And then downstream of the plants, the water would then flow into a filtration system and then back into the fish. So it was a closed system, and we would do water changes approximately every 10 days to two weeks.

0:08:40.0 JS: Okay. And that gives an idea, paints a picture anyway, of sort of the complexity you mentioned. This isn't as simple as just a really impressive tank of fish.

0:08:50.2 DA: Right. And when we were designing the experiment, we wanted to make sure that it would be a good comparison to what would be conducted in a commercial atmosphere. We wanted these results to be really be applicable to the commercial sector. So we were really thoughtful about the structure and design of the study so that it could be scaled up.

0:09:08.9 JS: And so how did it go? What happened?

0:09:10.6 DA: Yeah. So we saw some really interesting results. I think the first result was that, there was no difference in striped bass growth between the two systems. And when you first hear that, you might say, oh, well they didn't do better in the experimental group, so the experiment must have been a failure. But the way I look at it is that the bass didn't grow any worse in this kind of new system, right? And because the bass are kind of the principle organism in the mix, the people who would be adopting IMTA would most likely be striped bass farmers and we would be encouraging them to modify their practices. So to go to them and say, Hey, your bass aren't going to suffer if you grow them in this new system. That's a result that I was really excited about.

0:09:52.4 DA: We also found that the worm biomass increased by about 114%, and they were able to utilize almost 45% of the waste produced by the fish. So if we had more worms, more of the fish waste probably could have been mitigated. We also produced over 50 pounds of sea beans. We had two different crops. And this wasn't a big area, by the way. It was only about two feet by eight feet, so 16 square feet. So that was pretty good yield and yield that was better than we would expect in kind of a commercial sea bean farm. And overall, the IMTA did reduce the amount of nutrients in the water. So the water was cleaner for the fish. Water changes didn't have to occur as frequently. And I think the most exciting result overall was that the food conversion ratio, which is a little bit technical, but simply put, it's the amount of food you put into the system divided by the amount of biomass you get out of the system, that was decreased in the IMTA system. So you got more bang for your buck. You had more biomass coming outta the system for each unit you put into the system. And that's really important in this resource scarce world that we live in, it's important that all the resources that we're putting in to grow our food are being used as efficiently as possible.

0:11:08.0 JS: Yeah, absolutely. So you're saying that the amount of resources that you had to use to grow fish and food from the IMTA system, you got more bang for your buck, you got more out of it than the conventional recirculating system?

0:11:23.1 DA: Absolutely, yeah. And to be clear, the food in that system include things like the fish and the sea beans. The sea beans are edible, the fish are edible, the worms, not so edible, but the worms have other purposes, right? They could be sold to other markets, they could be used as bait and those worms could also be processed into fish food, so they could be kind of recycled and eventually used back in the system.

0:11:45.5 JS: You mentioned the product of sea beans, which I feel like if you watch Top Chef, you might've seen these used a few times. They're sort of like a niche ingredient, but are they good?

0:11:58.4 DA: Yeah, they're delicious. Salty, right? Sea beans are these marsh plants that can tolerate really high concentrations of salt. They basically are plants that could grow in full strength sea water. They're Latin name sala cornea means salt horn because when you see them in a marsh, they actually look like little horns cropping up and they're full of salt. They are succulent and so they have a nice snap to them and we eat them in a lot of different ways. One of my colleagues made pickled pickleweed, so we pickled them and they were really good that way. I made them in a shrimp scampi. We blanched them to get some of the salt out of them. They also could be dried and used as like a salt alternative. I think they actually taste a little bit like crab, believe it or not. I was eating them and pulling the tissue from the sea beans like off of the main stem and I felt like I was eating crab legs. So even my my vegan wife tried some and I think she was convinced that they could be like vegan crab.

0:12:56.6 JS: That's really interesting. It feels like is there something there, is there a market?

0:13:00.0 DA: Maybe. There are folks who are growing sea beans commercially, both in the US and across the world. So sea beans are used in a lot of different applications. They have oil rich seeds, so they could be used as biofuel. They also can be used to grow fodder for livestock. So because they could grow in really salty environments, they could be grown in what's called marginal land. So I think like really arid or salty environments, places where it would be really costly to grow things like corn or soy or wheat. So in those environments you could grow sea beans that kind of like the harsh environments, and then also kind of that niche ingredient that's eaten and has been eaten for generations in places like Northern Europe, in Korea, southern Europe. So I think it's still, like you said, a very niche market, but my hope is that it kind of goes mainstream.

0:13:49.2 JS: Yeah. And just to sort of reiterate, so this system that you created, you had high value fish, you had product that could be eaten or consumed as food, but also could be used as biofuels and plant fertilizer. So many uses.

0:14:06.0 DA: Yeah. And that's one of the benefits of IMTA. One of the problems that it solves is crop homogeneity in our food system. A lot of aquaculture is conducted as monoculture. So those are simple and efficient, but it leaves farmers at risk of crop failures, whether it's from disease or a drop in prices like we saw over covid. So that's one of the real benefits of IMTA is diversification.

0:14:34.7 JS: So Mike, how did you get the idea for this? What was the inspiration?

0:14:39.4 DA: So. I always have had an interest in figuring out ways that our food system could be diversified. My PhD was focused on improving diversification in the northeast aquaculture sector. I think it kind of stems from my love of aquaculture and food. So I always was interested in marine biology as a kid and come from a big Italian family where food was really important. And my favorite holiday was Feast of the Seven Fishes, which if your audience doesn't know is a way that Italian Americans and Italians celebrate Christmas Eve. It's just a big feast of fish. And I think my love of like diverse cuisine and diverse seafood kind of permeated my interest in marine biology. And I thought, oh, well wouldn't it be cool to try to grow things, grow an array of different species like the array of different seafood on my Christmas table. This specific project also kind of has a funny story.

0:15:31.1 DA: I was at a brewery one time waiting for some colleagues to meet me there, and while I was waiting, I decided to read a scientific paper about IMTA and it was about growing shrimp and growing these a different species, but a type of sea bean over in Portugal. And I was like, wow, that's a really cool idea for a study. I wonder if something like that can take place here in the United States and if we could modify the species slightly, if it would still work. And lo and behold, a couple of years later I was doing it myself.

0:16:03.5 JS: Thanks to your late friends. Yeah.

0:16:05.5 DA: Yeah. That's right. [laughter]

0:16:06.1 JS: So Mike, what are you working on now? You're no longer at the Howard Lab, but you're still with Rutgers?

0:16:14.4 JS: That's right. Yeah. I'm no longer at the Howard Lab, but I still have a really soft spot in my heart for everyone at the Howard Lab and they're doing some amazing work over there. Now I'm back at Rutgers University where I conducted my PhD and I've shifted my focus now towards shellfish and I'm primarily working on a species called the Atlantic Surf Clam. The Atlantic Surf clam is a native species and it supports a really lucrative fishery. Actually, if anyone has ever had canned clams or clam chowder, they've eaten a surf clam. And my work is focused on how we can grow surf clams in aquaculture, so farm them, and specifically I'm looking at whether or not we could hybridize surf clams. So I am breeding them in our laboratory and figuring out which group of these surf clams would perform best on farms.

0:17:06.5 JS: Wow. Does your previous IMTA research factor into this at all? Can shellfish be part of IMTA systems?

0:17:15.5 DA: Absolutely. Shellfish definitely can be part of IMTA systems. They're normally part of that middle ring or that middle rung of the ladder. Shellfish have to eat, but on shellfish farms, they're getting their food from the environment, any kind of phytoplankton that naturally exists in the water. But they also could consume particles of waste that are produced by a fed species like fish. I'm actually working with some colleagues right now on hopefully acquiring a grant to look at whether or not sea beans can be co-cultured with shellfish. So I'll let you know in a couple of months if that works out. But I still have an interest in IMTA and trying to start up some projects that'll allow me to continue scratching that itch.

0:18:00.4 JS: Yeah, I have a new interest in sea beans. I've gotta try these things.

0:18:05.1 DA: Yeah. If they aren't appearing in your supermarket, you could find a marsh near your house and go foraging. You wanna be thoughtful, don't pick too many, but they are pretty common across the northeast and even the southeast as well and they're pretty recognizable. There's not many other things that look like them, so there's not much of a risk of finding the wrong thing and eating something that's not good for you. But yeah, as long as the marsh is supplied by clean water, you're probably good to go. Frage some yourself.

0:18:31.8 JS: Amazing. Dr. Michael Aquafredda, thanks so much.

0:18:34.8 DA: Thank. You so much. It was a pleasure.

0:18:36.1 JS: Dr. Michael Aquafredda is an aquaculture specialist at the Rutgers University Haskin Shellfish Research Lab, and spent several years at NOAA's Howard Lab, part of the Northeast Fisheries Science Center. You can learn more about all kinds of aquaculture at our website, fisheries.noaa.gov, or sign up for one of our newsletters, like the newly launched Taste of the Times for quarterly Seafood Insights and News. I'm John Sheehan and this has been Dive In with NOAA Fisheries.