Members of Dr. Jim Morley’s Fisheries Ecology Lab have been hard at work this summer spending much of their time in the field at oyster leases in the Pamlico Sound. While one ECU student was busy listening to the soundscapes of oyster leases, another conducted research to learn more about a species of fish known as Sheepshead. Keep reading for fascinating updates below!
Underwater Soundscapes on an Oyster Farm
Louder and more complex soundscapes in marine habitats have been associated with healthy and diverse species communities. Two classic examples of this are coral reefs and natural oyster reefs- habitats where fish and invertebrates make an assortment of different noises associated with feeding and communication. Oyster farms are also a complex, human-created, habitat in estuaries. But the question remains: how do their soundscapes compare to the natural habitats that they displace? This summer, Ray Delvillar, an undergraduate biology major at ECU and participant in the Undergraduate Semester Experience at the Coast, sought to answer this question by conducting an independent research project with Dr. Jim Morley’s Fisheries Ecology Lab at CSI. Delvillar was uniquely qualified to conduct this research because he is an oyster farmer himself and oversees the demonstration oyster farm at the North Carolina Coastal Federation’s Northeast Office in Wanchese, NC.
At five different oyster farms in Pamlico Sound, Delvillar deployed a hydrophone to record the soundscape. Hydrophones were also placed at nearby control sites for comparison. He found that oyster farms were “louder” across the full range of the acoustic spectrum (from low to high-frequency noises) which suggests that the animal community becomes more diverse when an oyster farm is added to a habitat. Also, sounds made by fish were much more common on oyster farms. For example, on a farm near Engelhard, NC, sounds that are associated with courtship and spawning by silver perch and oyster toadfish were continuously heard, while the control site just a few hundred meters away was relatively quiet.
This image is an acoustic spectrogram, showing noise levels (cool to warm colors) across the acoustic spectrum (vertical axis) over time (horizontal axis). Note the distinct characters of the two types of fish calls.
Hatch Date, Diet, and Habitat Use of Juvenile Sheepshead in Pamlico Sound
Within structured habitats of marine ecosystems, both natural and human-made, sheepshead is a common species of fish. Sheepshead occupy a unique niche among fishes, feeding on a huge diversity of invertebrates and plant matter like seagrass and algae. Little is known about sheepshead reproduction or about the ecology of early life stages. To fill some of these knowledge gaps regarding the life history of this species, Madeline Johnson is collecting juvenile sheepshead in multiple types of habitats within several regions of Pamlico Sound. Johnson is conducting this research for her graduate thesis in conjunction with the Fisheries Ecology Lab at CSI and Dr. Jim Morley from the ECU Department of Biology.
Forty open mesh traps containing a layer of oyster shell have been set out in the sound and are checked monthly. When the traps are lifted from the bottom, sheepshead tend to shelter inside them, allowing for their collection while minimizing impacts to other species. Based on these collections, the distribution of juvenile sheepshead can be examined along with their habitat preferences. Johnson will also be dissecting each fish and removing their otoliths, or “ear bones,” which can determine birth dates. Diets of juvenile sheepshead will also be examined by measuring stomach contents. Results from this research will inform fisheries management of this poorly understood species and further efforts towards valuing different estuarine habitats.
An image of an “oyster shell trap” deployed near Cape Hatteras, showing a sheepshead (middle) and gray snapper (right).
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ECU's Integrated Coastal Programs (ECU ICP) is a leader in coastal and marine research, education, and engagement. ECU ICP includes the Coastal Studies Institute, ECU's Department of Coastal Studies, and ECU Diving and Water Safety.
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