Rahdiaz Delvillar, most often referred to as Ray, grew up on the North Carolina coast. His time spent fishing, boating, and keeping aquariums as a child connected him to estuarine habitats and the species that utilize them. As an adult, he continued to lean into these interests, gaining experience in aquaculture, field ecology, and acoustic monitoring. It’s likely no surprise that Delvillar’s current research as an ECU biology graduate student is focused on the underwater soundscapes- the collective set of sounds heard underwater- of oyster leases.
For his project, Delvillar is specifically investigating how oyster aquaculture influences estuarine habitats. Oyster farming is becoming more popular in North Carolina, and an ever-growing number of leases have been approved in the last few years. While it seems clear that the leases provide habitat, structure, food, and improved water quality for species living in the estuary, little is known about how the farms compare to natural reefs or how the farms might alter the soundscape of the estuary.
Through his study, Delvillar hopes to answer three main questions:
- Do soundscapes differ between sites with oyster leases and otherwise similar sites without the aquaculture operations?
- Is fish behavior, such as call rates or activity, altered by the presence of oyster farms?
- Does aquaculture gear attract a greater abundance or diversity of fish?
To tackle these questions, Delvillar deploys hydrophones, or underwater sound recording devices, at oyster leases and nearby control sites. The control sites are areas approximately 500- 1000 meters away from the lease that do not have farming operations but are otherwise comparable. The hydrophones are deployed for an extended period and collect sound samples for 10-20 minutes every hour.
Sounds that might be heard on an oyster lease include those made by fish, watercraft, aquaculture gear, and human activity. Red drum and silver perch are examples of soniferous fish, or those that produce sound. Species like these make noise to attract mates, defend territory, and coordinate with schools. By capturing sounds regularly, Delvillar will be able to assess whether fish sounds and activity vary throughout a 24-hour day. He will also be able to determine if certain types of fish behavior are more common than others amongst oyster lease sites. These determinations will be made in the lab with the help of computer programs. Using a program called R, Delvillar can distinguish human noises from fish noises, then count the number of fish calls in each recording. From there, he will estimate the abundance of calling fish and compare the diversity among oyster leases and control sites. Another program, Raven, assists him in visualizing the recordings to provide further details.
Standard Monitoring Units for the Recruitment of Fishes, better known as SMURFs, are also deployed alongside the hydrophones at a subset of the aquaculture and control sites. These passive, larval and juvenile fish collectors made of mesh mimic small reefs. Delvillar will use them to test whether larval fish use the sounds from an oyster farm as a cue to settle among the lease as they would in natural seagrass beds or oyster reefs. By comparing the aquaculture and control sites, Delvillar will assess if the farms can act as nursery habitat, attracting young fish. Upon retrieval of the SMURFs, Delvillar will count and identify the fish, resulting in a dataset that complements the sound recordings captured by the hydrophones.
When asked about the inspiration behind his study, Delvillar explained,
“I’ve always been drawn to aquaculture because it merges food production with habitat creation. Oyster aquaculture in particular is highly sustainable, requiring no feed inputs while providing a wide range of benefits such as water filtration, shoreline protection, and new structural habitat. For me, this project blends personal passion with applied science. I get to use new technologies like hydrophones while tackling practical conservation questions that matter to both fishing communities and coastal managers.”
Though his current study is in its early stages, Delvillar is sure it will yield useful results. Before he began pursuing his masters, he was a participant of ECU’s Undergraduate Semester Experience at the Coast. During that time, he ran a pilot study with identical methods.
“[It] gave me valuable practice and preliminary data. That early experience directly shaped how I designed my current graduate research,” he says.
So, why is this study important? According to Delvillar, it is relevant to future conservation and species management practices and decisions. If oyster farms have similar soundscapes and benefits as natural areas, leases could be a valuable tool for habitat enhancement while also contributing to local seafood industries. On the other hand, if oyster farms produce too much additional sound that overshadows the biological noise produced by soniferous fish, lease siting may need additional consideration.
“Either way, the results will help guide sustainable aquaculture development and fisheries management in North Carolina,” says Delvillar.
To learn more about this project and to hear from Delvillar himself, watch the short video below.
The preceding story first appeared in the Summer/ Fall 2025 edition of CoastLines, published in October.
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