[AUDIO LOGO]
[MUSIC PLAYING]
(VOICEOVER) In this episode, we ask the question,
how do scientists sample populations
of fish and invertebrates along shorelines?
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[WATER BABBLING]
Hey.
Josh Bernstein here.
I'm in Maryland at SERC, the Smithsonian Environmental
Research Center.
I've come here to study coastal ecosystems.
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(VOICEOVER) SERC sits on the Chesapeake Bay, the largest
estuary in the United States, where freshwater from the land
meets saltwater from the ocean.
It is home to a complex food web of plants, fish,
and invertebrates.
I've arranged to meet biologist Stacey Havard,
to learn about nearshore populations of fish
and invertebrates, and how scientists monitor them.
Here at SERC, we study the land, sea interface.
So we measure the fish, and shrimp,
and crab populations in the nearshore or shallow water
zone.
OK.
And one of the ways we do this is by seining.
And anyone who does water ecology--
if you said to them, hey, let's go seining,
they'd know exactly what you meant.
Absolutely.
Shall we go seining?
Absolutely.
Let's do it.
OK.
Great.
(VOICEOVER) Seining involves taking the rectangle-shaped net
into the water.
We will unfurl the net once we reach a standard distance
from the shoreline.
This is considered the nearshore zone.
And you're trained to know exactly how deep to go.
I am, yes.
[LAUGHS] Now what we're going to do
is we're going to unfurl the net.
I'm going to pull it towards me.
Do I unfurl, or do you?
We both unfurl.
So I walk backwards?
You can stay where you are.
I'm staying right here.
I'm going to walk away.
And you're going to unroll it towards you.
But not moving my feet, which are sinking into the mud.
Yes.
Try to-- [LAUGHS]
OK.
Try to stay right where you are.
(VOICEOVER) A seine net has floats
on top, and weights on the bottom,
to help it stay vertical in the water.
Are you ready to seine?
I-- [LAUGHS] Yeah, I'm ready.
Great.
Let's go.
OK.
(VOICEOVER) Stacey and I slowly pull the seine net toward land,
staying parallel to the shore.
As we move, we glide the poles along the sediment
to keep the bottom of the net flush
with the bottom of the river, to prevent animals from escaping.
So just touching the bottom, not dragging, right?
Exactly.
But it is getting heavier, because we're pulling--
It is.
We're pulling all the biomass.
We've definitely got some fish, and probably
a nice chunk of mud in there as well.
(VOICEOVER) Nearshore animals, like the fish, crabs, eels,
and shrimp that we're catching, can
serve as important bio-indicators
or living signals about the health of the water,
and the local food webs.
On land, Stacey's colleagues join
us to empty the nets into bins.
And then identify, measure, and catalog each animal.
So this is a mummichog, one of the most common fish
on the Bay.
Wow.
Can I see?
Yeah.
A baby one?
No, this is actually a full size.
Oh, really?
In fact, I think this is a female who has eggs.
See, she's a little bit fat under her belly right here.
Wasn't going to say anything.
But yeah.
[LAUGHS]
OK.
We would call her gravid, which means she has eggs.
OK.
And yeah, she is one of the staple food
items for a lot of larger fishes in the Bay.
(VOICEOVER) Animals here are small,
and include the larvae of larger animals.
They're here for protection from large predators,
and to find food and shelter.
Can I hold him?
Absolutely.
And it's a her, actually.
How do it's a her?
She has eggs.
Oh, look at that.
All along--
Ooh!
--the bottom there.
[INAUDIBLE]
[LAUGHS]
[LAUGHS] They jump!
And you are discovering that they have a very good escape
mechanism.
That's impressive.
But I got her.
(VOICEOVER) These small animals are an important part
of the food web, serving as food for larger fish and predators.
These shrimp happened to be a favorite food of white perch
and juvenile striped bass, which we also call rockfish locally,
which seek refuge in the nearshore zone.
So without the shrimp, really, the food chain
above wouldn't happened.
It could easily collapse.
(VOICEOVER) By seining the nearshore zones
of the Chesapeake Bay, scientists,
like Stacey and her team, can look for patterns of increases
or decreases in the populations of fish and invertebrates,
which may signal changes in the health of the waters,
and the stability of the Bay's food web.
What I like is that seining is such a simple concept.
Yes.
Dragging a net through the river,
and counting what you catch.
Mm-hmm.
And yet, over time, it becomes a very effective tool
for determining what's happening in the water.
Yes.
Right?
It's a very powerful tool for assessing long-term change.
Sometimes it gets lost that the marsh is
kind of a muddy, smelly place.
And a lot of the animals are very small.
But this is where the action is.
This is, sort of, the engine that's
driving the productivity of the entire Bay.
(VOICEOVER) Nearshore zones are an important part
of estuaries because they're the nursery habitats of fish
and invertebrates, and the refuge of smaller creatures
that are part of the food web.
As for our original question, how
do scientists sample populations of fish and invertebrates
along shorelines?
Seining is one way that scientists monitor these areas,
looking for signals of imbalance in the populations of animals,
and an indication of the health of the Bay.
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