Prehistoric Fish Discovered in the Depths of Bluff LakeWednesday, July 27, 2016
By: Sarah Buckleitner, MSU Forest and Wildlife Research Center
Gilliland, a wildlife, fisheries and aquaculture graduate student
in Mississippi State's College of Forest Resources, holds a
paddlefish caught from Bluff Lake at the Sam D. Hamilton Noxubee
National Wildlife Refuge. (Photo submitted)
STARKVILLE, Miss. - Alligators aren't the only prehistoric
creatures lurking in the depths of the Sam D. Hamilton Noxubee
National Wildlife Refuge's waterways.
Mississippi State researchers recently recorded unexpectedly
high numbers of paddlefish near the refuge's spillway-a shocking
discovery given the size of the waterway and what is currently
known about paddlefish biology.
Paddlefish are a large fish whose lineage dates back to the late
Cretaceous Period (roughly 70 million years ago). American
paddlefish are native to the Mississippi River Basin, and
traditionally have been thought of as a species that prefers large
However, after initial exploration revealed that there were
paddlefish in the spillway for Noxubee's Bluff Lake, researchers
launched a full scale investigation to garner estimates of
population size and to determine what factors drew them to the
"It was pretty astounding," said Michael Colvin, assistant
wildlife, fisheries and aquaculture professor in MSU's Forest and
Wildlife Research Center. "We pulled up all these paddlefish using
gill nets. They can grow to over five feet long, so it was fairly
dramatic to see these giant, prehistoric fish come out of that
Given the number of paddlefish they caught, researchers estimate
there are up to 200 individuals in the spillway area. This
population of paddlefish is unique because of the high densities of
fish in such a small system and the fact that they appear to be
year-round residents. Because of these aspects, the study has the
opportunity to contribute information on an unexplored aspect of
"Initially, we thought that we were catching them during
migration, and they were coming up from the Tennessee Tombigbee
waterway. However, as we get later into the year and they're still
present, we're beginning to wonder if it's a resident population,"
In order to help answer this question, 30 fish have been tagged
with acoustic tags, which will trigger sensors set up along the
Noxubee River with their unique IDs, enabling the researchers to
track where each individual fish goes. If the paddlefish are
migrating, they will be recorded in different geographic areas, and
the researchers will have a better idea of where they are coming
from, and their usual migration pattern.
Paddlefish are highly migratory; the distance from the Tombigbee
waterway to Noxubee is tiny compared to some of the epic treks
paddlefish take. Some tagged in the Delta have even been recaptured
in the Missouri River.
Collaboration with the Alabama Game and Fish Division has
allowed the researchers to track the fish even as they move into
the Tennessee-Tombigbee River. They have set up sensors within
Alabama that share data with those in Mississippi, allowing the
researchers to gauge just how far these fish are traveling.
Because paddlefish have never been seen in such high densities
in a small system like this one, Colvin and colleagues are not sure
what to expect from this population. However, they suspect that the
spillway's management creates conditions that attract the fish, so
they may veer off course from their traditional migratory route and
end up staying through the year.
This could create problems for the species, which already is
endangered and even extirpated in parts of the United States due to
over-fishing for caviar.
To look for correlations between water conditions and paddlefish
presence, graduate student Chelsea Gilliland set up sensors to help
monitor the temperature, water levels, and flow within the
spillway. They hope to find a link between spillway conditions and
paddlefish behavior which may explain why they're drawn to the
"If the paddlefish are being drawn to this area due to the
spillway conditions and then aren't spawning-or aren't spawning
successfully-it could be an issue for the species," Gilliland
"Mostly paddlefish are studied in really big systems-like the
Mississippi River, one of the biggest systems. No one has
documented them in a small system like Noxubee, so this is really
unique. Even just comparing our results so far, I can tell that
they're different. And it's important to know if the fish are
spawning in this system because if they aren't, that's potentially
a huge loss of genetic diversity for the species," explained
To try to determine whether they're spawning, Gilliland has been
sampling the area on a regular basis in search of young paddlefish.
So far they haven't found any, and it's getting late in the
"We've found gravid (pregnant) females, and at this point in the
year, you would expect them to have already spawned," Gilliland
The next step for this project depends on what they
If it appears as though the paddlefish are successfully spawning
near the spillway, the refuge managers may undertake habitat
restoration efforts to help ensure the population's success.
However, if the paddlefish aren't spawning, or the young are being
eaten by predators, they will look for ways to change the spillway,
so the prehistoric fish aren't drawn to it.
"I think the most important takeaway from this project is that
you should never underestimate a habitat. I never in a million
years would have looked at that spillway and guessed prehistoric
fish swam right below the surface," said Gilliland.
The U.S. Fish and Wildlife Service's Inventory and Monitoring
and the U.S. Geological Survey's Quick Response Program are funding