How are fish impacted by pollution?

What happens in a marsh at night? Researchers at the University of North Carolina are observing “what goes bump in the night” to determine how fish populations are impacted by pollution, development and erosion.

TRANSCRIPT

Take a look at our next segment.

We can get it off the boat.

Yeah, we can.

Okay.

So, Rich, the last one's, like, out of the water.

The last minnow trap.

That one's good.

Wait.

That's fine.

Let's do this salinity at least.

To shed light onto what's really happening in a marsh...

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...you have to wade through the dark waters in the dead of night.

So, we are trying to understand how different marshes can actually affect fish populations.

So we're looking at the types of fish that we're seeing on the marsh.

We're looking at how good the habitat is.

The marsh comes alive at night, as creatures move into and out of the wetlands.

So, researchers from the University of North Carolina Institute of Marine Sciences are setting three different types of nets in the marsh.

The idea is to catch as many fish and crustaceans as possible.

What's captured will be identified, counted, measured, and weighed.

So, we have minnow traps, which are smaller traps that we're using on the marsh surface to try to catch smaller animals that might be using the marsh when it's flooded.

We then have a gill net, and that's trying to catch larger predatory fish.

And then we have our fyke nets, which are really good at capturing what is using the marsh surface when it's flooded.

Yeah, the sunrises definitely make the night sampling worth it.

Tiny shrimp.

The one pinfish is the lowest we've gotten in any of the gill nets today.

Sunrise brings discovery.

Yeah, absolutely.

Every time, it's a new mystery.

You never know what's gonna come up.

Every season, all the species are changing.

I mean, you have new predators, new juveniles.

Researchers return to the nets that were set overnight to record what was caught.

Speckled trout -- pretty small size, juvenile.

And then we have some pinfish, silver perch, silversides, some brown shrimp, and blue crabs, and then quite a bit of algae.

18 marsh sites are being studied -- 3 large mainland marshes, 3 thin, fringe marshes, and 12 marsh islands.

That's because not all marshes are the same.

Part of our project is looking at how different-sized marshes are affecting fish diversity or how those are tied together.

We have to make sure that we are protecting species that we need recreationally.

What are we consuming?

What are we fishing for fun?

So we need to make sure that the species stay around.

In order to do that, they have to have their habitat.

And salt marshes are valuable nursery habitats for fish and crustaceans.

Without this habitat, we probably wouldn't have a lot of these species and probably wouldn't have them to grow up to become food for us or food for other animals.

The problem is that coastal habitats are being degraded.

We see lots of commercially and recreationally important fish using these habitats as juveniles, and so they're growing up here.

But we also see larger, legal-sized commercial and recreational fish that are foraging at the edge of these marshes.

And so if we're losing that edge, they're losing the ability to prey upon the smaller organisms.

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And then a menhaden.

130.

Researchers hope this unique project will help them understand how different marsh configurations act as nursery habitat, whether the size and shape of a marsh is important for habitat, and which marsh nursery habitats are the most valuable for fish and crustaceans.

Yeah, that's a stone crab.

And the rest are brown shrimp.

We're looking at the types of fish that we're seeing on the marsh.

We're looking at how good the habitat is, so how fatty the fish are.

So, the fatter the fish, the healthier they are, the better habitat quality.

We're doing that because marshes have been lost over the past few hundred years, and as the marshes become lost, they become more fragmented and they become these smaller islands of marsh, compared to a larger, continuous habitat.

Silverside. 68.

Silverside. 50.

The findings should also help guide plans for marsh conservation and restoration.

And, so, this research is really trying to understand, 'How is that going to affect our fish?

And how is that going to affect the fish that we like for seafood in particular?'