The Texas Nature Tracker, Spring 2000 Page: 3
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3
THE TEXAS NATURE TRACKER
IN SEARCH OF THE GOLDEN ORB
By Ann MillerWe don't always get instant gratification when we do volunteer
monitoring projects. Sometimes we have to look at the long term and
realize that our data, taken consistently, even when we aren't encoun-
tering the species we are looking for, is important. The absence of
species in areas and at times when they should be present is signifi-
cant and vital to our efforts. But that does not always make for a
memorable field experience.
This year, however, mussel volunteers have hit some interesting pay
dirt. This gold won't make them wealthy, but it is "gold" in terms of
finding something fairly rare. Melba Sexton, science teacher at Luling
Jr. High and 4-H leader involved in snail monitoring at Palmetto State
I.-
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Melba Sexton's students identify musselsfound in the Guadalupe River
Park, sent in a photo of a living freshwater mussel she had collected
from the San Marcos River for the river tank in her classroom.
Dr. Bob Howells, mussel expert at Heart-of-the-Hills Research Station,
identified it as a rare, golden orb. Melba also found a recently-dead
threeridge shell. Despite over 40 collections made by TPW in the San
Marcos and Blanco rivers since 1992, no living, native freshwater
mussels had been found (and none confirmed since 1977). These
specimens indicate that a river recently thought to have lost its entire
mussel fauna does have at least a few remaining. And, golden orb,
known from only 4 remaining populations, now appears to have a fifth
population in the San Marcos River.
Melba wondered how many other golden orbs might be out there, so
she set up a field trip for her students to look for mussels, both in the
Guadalupe River and in the San Marcos. Armed with wading shoes,
data sheets, and some background knowledge about mussels, Melba
and her students first examined a site on the Guadalupe at Lake Wood.Students found, examined, categorized, and identified 5 different
species of mussels, with 2 species of live mussels in the group. All
species found were fairly common and well documented for that
location, but the data is important for long-term monitoring and the
students got some great field experience.
Next stop, the San Marcos River at the Hwy. 90 crossing. Would they be
able to find the golden orb? Alas, after 45 minutes of searching, no
living mussels were found, only some shells of long-dead threeridge
and the exotic Asian clam. Again, the absence of native mussels at this
site is important data.
Next week, Melba returned to the original site where she
had found the golden orb. This time, searching for an
hour with 2 assistants, she found 1 more live golden orb
and more shells of recently dead specimens! All
specimens were found in water less than 6 inches deep,
3- with a muddy substrate, and out of the main current.
Other successes for mussel monitors this year include a
record-setting size for Tampico pearlymussel, collected
by a volunteer on the central Colorado River in August.
That same volunteer also collected very-recently dead
shells of rare Texas pimpleback, which was known only
from 3 surviving populations (now 4), and Texas
fawnsfoot (not confirmed in the Colorado drainage since
a long-dead valve in the mid-1960s was found).
Previously, just over 100 shells of this species had been
found since 1980 (in the Brazos drainage) and only 5 of
these were alive.
Another volunteer found over 35 Texas fawnsfoot
specimens in the Brazos River upstream of College
Station. All were very recently dead and suggested that a
significant population of Texas fawnsfoot is still surviving in the area.
Very few have been documented in this area in recent decades and
never such a large number at one time anywhere. Newly trained
volunteers looked again at the Brazos River after a Texas Mussel Watch
workshop in College Station and found several more Texas fawnsfoot
specimens.
Dr. Howells and another volunteer examined Lake Lewisville and found
living specimens of lilliput for genetic analysis (previously, HOH had
obtained only 4 living specimens in Texas since 1992), a number of
living pimplebacks also needed for genetic analysis, and still other
specimens that may be rare endemic Texas heelsplitter.
Thanks to all those Texas Mussel Watch volunteers who sent in data,
whether or not it has resulted in a significant find. All data is
important since we are just beginning to understand freshwater
mussel populations in Texas.
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Wildlife Diversity Program (Tex.). The Texas Nature Tracker, Spring 2000, periodical, May 2000; Austin, Texas. (https://texashistory.unt.edu/ark:/67531/metapth576122/m1/3/: accessed April 26, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.