[upbeat music] - A lot of people, they don't really know what a oyster farm is.

You know, sometimes people ask me, do I grow oysters in Durham or do I grow oysters where I live in New Bern?

So people don't know that an oyster farm, it's a lease.

It's a part of the water that you just lease from the state that's out here with all the wild oysters.

- [Narrator] This story is not just about oyster farms.

- Oyster culture industry nationwide has been growing really fast, and it looks like it's gonna continue to grow.

It's a really important source of aquaculture local seafood.

- [Narrator] It's about measuring change.

- Essentially, when you put these oyster farms in, you're transforming the estuarine landscape to some extent.

You're taking a area of the estuary, which is important for natural resources, and you're converting it into a mariculture operation.

- [Narrator] But the effects of oyster farms on fish habitat isn't known.

- [Jim] Do the fish like it?

Does it destroy the habitat?

What are the costs and benefits of it?

- [Narrator] Researchers wanna know how oyster farms are changing North Carolina's estuarine coast.

- You're taking what is probably a semi-featureless bottom.

Most oyster leases are on muddy bottoms, sandy bottom, and you're putting in your oyster bags, right, all these pilings.

You're putting in ropes.

You're putting in buoys, right?

So you're adding huge amount of structure to that area, right?

And so clearly, fish are gonna act differently in a highly structured environment than the way they would act on just empty bottom.

- [Narrator] So this is also a story [oysters clattering] about how scientists got creative [oysters clattering] to answer an important question.

- The initial project that we did was build our own miniature oyster farms [gentle music] and measure them continually over the course of four years and record how many fish are in these areas.

We recorded fish abundance before we put these oyster farms in, and then we continued to monitor them for three more years to see how the the fish abundance has changed over time.

- So this is an ARIS.

And this is an acoustic imaging system.

So basically what it allows us to do is it shoots sound, right, kind of like an array of beam coming out of here sound into the water.

[ARIS whirring] [gentle music] And what we are able to get from that is essentially like a video of what's in the water column.

- We can sample across an oyster farm and look right past all of the oyster gear and not have to worry about entangling nets and things like that.

Additionally, it allows us to watch the movements and the behaviors of the fish without interrupting them with fishing gear.

So we get an idea of the natural behavior of fish on oyster farms using this technology.

And we had one of our technicians basically pretend to be the oyster farmer, flip the bag and shake it, [cage rattling] and we would record with the sonar in real time.

And a lot of times it was just a swarm of fish, because when you disrupt the oysters, a lot of these small crustaceans and particles are showering off of the oysters and the fish are just gobbling it all up.

We find that the abundances of fish are about twice as high on oyster farms as compared to a nearby untampered control habitat.

- [Narrator] North Carolina has strict rules about where oyster farms can be located.

For example, oyster aquaculture can't be located in seagrass meadows, [soft upbeat music] but there's also the question of what the fish are doing on the farm and how the farm is connected to the surrounding habitat.

- To address that question, we did a tagging study.

We used acoustic transmitter tags.

We tagged about 30 fish, and we tracked their movements on a minute-by-minute basis.

- [Narrator] Researchers captured and tagged sheepshead, a fish that lives around structures such as docks or, in this case, oyster farms.

Tiny electronic tags were surgically implanted in the fish.

After recovery, the fish were released back into the estuary.

- So we had nine transmitters just like this kind of surrounding the farm.

And then we had a bunch that were sort of farther placed away.

Each of these transmitters pick up the pings from those acoustic tags, and each fish has a unique tag.

So the actual acoustic signal it sends out is unique for each fish so we can identify the individuals.

And based on the difference in when each receiver picks up that signal, we can actually triangulate the the exact location of each fish each minute.

So we can track the fish on a meter-by-meter scale as it moves through this area.

- [Narrator] And it turns out the oyster reefs and surrounding estuary became one giant habitat for the fish.

The population appears to thrive.

- [Jim] They're not just kind of showing up and leaving quickly, they're staying in the area.

And they're using surrounding habitats and then coming back to the farm.

- [Narrator] And then there was the ah-ha moment.

- As soon as the sun sets, right, they basically stop moving.

They come back to the oyster lease or some associated structure and basically stop pretty much all night long.

And then sunrise, they all start moving again, right, and I mean like all perfectly in sync, right?

They're all sitting completely still.

Sun comes up, and they're all just like all over the place.

- [Narrator] So the fish are sleeping if the fish sleep, I guess?

- Yeah, yeah.

And so that's like an interesting question, but I think you can at least assume that they're resting, right, and that they're resting on the oyster lease because it's a good place of refuge, right.

- [Narrator] Or they're watching TV and streaming something.

- Yeah, or hanging out.

Yeah, watching Netflix.