Entering the World of Dolphins:
Research So Compelling That Andy Read Rarely Takes a Holiday
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Read's laboratory, which has seven doctoral students and
a number of master's students, works with the Florida Keys
National Marine Sanctuary, the Everglades National Park, the
Dolphin Ecology Project and colleagues at the Mote Marine
Laboratory in Sarasota to conduct dolphin research projects
in Florida. As an example, Duke researchers are documenting
how dolphins now use the Florida Bay habitat as a benchmark
for future changes. "As you go east up towards Miami that
environment is hyper-variable in its salinity," he said. He
means that the salt content is much higher in some parts of
the year than in others. "That's a result of the diversion
of a lot of the fresh water that used to flow through the
Everglades for agricultural and other human uses," he explains.
But Florida and the federal government plan a massive decade-long
project designed to restore much of the original circulation
patterns, which should return more fresh water to parts of
Florida Bay. "Right now dolphins don't use the eastern part
very much," Read continues. "Only fish species that can tolerate
great ranges of salinity are found there, and there just isn't
much for dolphins to eat. What we've predicted is that when
it gets re-plumbed and that eastern part of the bay becomes
less variable, the fish populations should move back in and
the dolphins should follow."
In the Neuse River estuary, which empties into the southern
Pamlico Sound west of the Outer Banks barrier island chain,
Read's group is conducting analogous habitat studies in concert
with fish specialists working under Larry Crowder, the Marine
Laboratory's Stephen Toth Professor of Marine Biology. While
hydrological diversion is the issue in South Florida, the
Duke researchers and colleagues at the University of North
Carolina's Institute of Marine Sciences in Morehead City are
trying to discern all the effects of too many nutrient chemicals
finding their way to the Neuse system as a result of upstream
pollution. Among those effects are seasonal algae blooms which
rob oxygen from the water, causing fish to flee and sometimes
die. "We've been trying to understand how dolphins use that
habitat," Read said.
Other work funded by the North Carolina Sea Grant program
seeks to understand why bottlenosed dolphins-despite their
cognitive and echolocative abilities-sometimes get entangled
in gill nets and drown. "It seems counter-intuitive," he said.
To answer that question, Read's group is working with a fisherman
who sets up his gill nets close to shore near Fort Macon while
the researchers track dolphin movements around the nets with
the aid of a surveyor's theodolite, a calibrated optical instrument.
"What has become clear to us is that dolphins use the nets
to their advantage sometimes," he adds. A gill net, so named
because it often entraps fish by its gills, is a long panel
of netting anchored at the bottom and held up by floats. Its
intended targets, fish, try to swim through it and get stuck.
"Some dolphins seem to have specialized in going along the
nets and actually plucking fish out of them," Read notes.
The scientists are pursuing several hypotheses why the nets
can also flummox dolphins: Perhaps the dolphins get entangled
while trying to remove fish. Or perhaps they blunder into
the nets when they're not echo-locating, "the same idea as
somebody not seeing a stop sign and driving through it," he
said. The third possibility is that dolphins get caught while
trying to follow fish through the nets.
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