What Happens in a Marsh At Night
STURGEON CITY, N.C. — A marsh at night is normally pretty quiet. The sounds of crickets and others insects mix with the calls of birds, the sounds all seeming to float over the dark water. The almost silent lapping of the water can be heard if you're close to the shore. And in the background you can hear the faint rustle of the cattails and marsh grass. But this night is different.
A boat slowly motors into the marsh—part of Bogue Inlet near Pine Knoll Shores—in what is known as the Southern Outer Banks. There’s the sound of a splash as an anchor is tossed overboard. More splashing, people jump off the board and into the water. Flashlights pierce the darkness. Hammers drive plastic polls into the soft, muddy bottom. Nets are strung between the polls. Small traps, floating on the water, are anchored to the bottom by bricks and ropes.
“We are trying to figure out how different marshes affect fish populations, so we’re looking at the types of fish we are seeing in the marsh and how good the habitat is," explains Shelby Ziegler, a marine ecologist with the University of North Carolina Institute of Marine Sciences. “To do all of that, you have to see what creatures are living and moving around in the marsh and most of the fish and crustaceans move a lot at night.”
Using Nets to Gauge Nightlife
The marsh comes alive at night as creatures move into and out of the wetlands. Researchers set three different types of nets to catch as many fish and crustaceans are possible. What’s captured will be identified, counted, measured and weighed. It’s all part of an effort to study how healthy the marsh is.
The team is using minnow traps, which are smaller traps that float on the marsh surface to try to catch as many smaller animals that might be using the marsh as it's flooded. Gill nets are used to catch larger predatory fish. Finally, fyke nets are deployed to capture larger creatures on the marsh surface, also as it's flooded.
The team is studying 18 different marsh sites. That includes three large mainland marshes, three thin fringe marshes and 12 marsh islands. That’s because not all marshes are the same.
“Our project is looking at how different types of marshes are effecting fish diversity,” says Lauren Clance, a research technician. “We have to make sure we are protecting species that we need recreationally as well as commercially, and that means what are we're eating as well as what we are fishing for fun. But in order to do that we have to save their habitat.”
Morning Data Collection: What's in the Net?
Researchers get about an hour of sleep, after spending most of the night setting nets. But as the sun begins to peak over the horizon, the boat sets out again to see what was caught overnight. Crisp morning air, beautiful sunrises and the surprises that wait when the nets are pulled up make these late nights and early mornings worthwhile.
“The sunrises definitely make the night sampling worth it,” says Ziegler. “It is a mystery every time because you never know what is going to come up,” says Rich Mahoney, a research technician. “Every season, all of the species are changing because you have new predators and new juveniles.”
The nets are emptied into buckets and brought to the boat. The researchers gather along a steel tray at the stern to measure, weigh and record everything. “Speckled trout, which is pretty small so it is a juvenile,” says Danielle Keller, taking account. Keller is a marine ecologist. She moves the fish and crustaceans from a bucket, to a measuring board, to another researcher. That person then clips the tail to a small scale to weigh the fish. At the last station is a person with a clipboard, who records the species and the data.
“We also have some pinfish, silver perch, silverside, brown shrimp, blue crabs and then quite a bit of algae,” Keller concludes. “Pretty amazing for the first stop.”
Marshes are Crucial Fish Habitat, But How Big Do They Need to Be?
It’s a pretty impressive catch considering the net was only in the water for about six hours. Keller says it’s proof of the importance of marshes to the coastal environment and the ocean’s health. “Without this habitat we would now have a lot of these to grow up to be food for us or food for other animals,” explains Keller.
The problem is that coastal habitats are being degraded by development, pollution and erosion. Some marshes have been lost. And as larger marshes are lost, the wetlands either disappear altogether or they become fragmented islands of marsh rather than one large habitat.
Nobody knows how productive those smaller marshes are. “We see lots of commercially and recreationally important fish using these habitats as juveniles so they are growing up here, but we also see a lot of commercial, legal size fish foraging on the edge of these marshes,” says Ziegler. “So not only will there be problems if we lose entire marshes, but if we lose that marsh edge the fish lose the ability to prey upon these organisms."
Researchers are trying to figure out how different marshes effect fish populations. It’s hoped the unique project will help them understand how well different nursery configurations work as a nursery habitat, whether the size and shape of a habitat is important and which nursery habitats are the most valuable for fish and crustaceans.
“By catching fish and crustaceans we are looking not only at the types of fish that use the marsh, we can also see how good the habitat is by how fatty the fish is,” explains Ziegler. “It’s safe to say the fatter the fish the healthier the habitat.” The findings from the research will not only shed light on how productive various types of marsh are. It should also help guide plans for habitat conservation and restoration.