BIL GILBERT
Audubon:March 1981
Sport fishermen, riparian ecologists, and authors
of guidebooks invariably refer to the "prehistoric paddlefish," as if this were
a common name like Dolly Varden trout or smallmouth bass. Technically it is not
inaccurate, since all living creatures, ourselves included, are, in a sense,
prehistoric. But it is inadequate for the same reason it would be inadequate to
describe Tutankhamen as "the late art collector."
The paddlefish is
exceptional in that it has not changed much in three or four hundred million
years. In fact, paddlefish may be the oldest big animals surviving in North
America. Polyodon spathula (as the species is formally known) was swimming in
the warm continental waters when today's coal deposits were still forests of
tree ferns. Paddlefish evolved way before the perch and pike, gar and grayling,
and our other true fishes. They were here fifty million years or so before the
first dinosaurs. Compared with P. spathula, the natural history of mastodons,
mockingbirds, men, and other recent experimental models is as today is to last
year. Prehistoric indeed.
By what we call "historic" times, i.e., after
tile advent of European-style observers and record-keepers, paddlefish inhabited
only the rivers and sloughs of the Mississippi Basin-from the larger tributaries
of the western Appalachians to those of the eastern Rockies. There is only one
similar species, in the Yangtze River of China. Why these two closely related
creatures should live so far from one another is a mystery. In our major midland
waterways the paddlefish did well. There are old records of two-hundred-pound,
six-foot-long .fish and rumors of much larger ones. These days a
one-hundred-pound, five-foot paddlefish is considered large. A century ago, and
for many hundreds of years before that, the paddlefish apparently was one of the
most abundant species, and because of its size and numbers made up a
considerable portion of the riparian biomass.
In comparison with other
fish Polyodon are primitive in appearance and behavior, but given their
longevity and success it is unseemly to be patronizing about the adaptations
they have made. The most visible of these adaptations is the snout which has
given the creature its common names (spoonbill and spoonbill cat, among others).
This snout is up to two feet long, a rigid protuberance that looks something
like a narrow beaver's tail or a fat cake spatula. In times past it was believed
the bill was used to scoop out deep, secure resting holes in the bottoms of
muddy rivers. Current biological thinking is that the paddle is a kind of
antenna in which there are sensory organs that enable the fish to detect and
react to water currents, underwater obstacles, and the topography of riverbeds.
How this apparatus functions is not clearly understood. However, the advantage
of having some sort of nonvisual direction-finding device is obvious, since
paddlefish operate for the most part in the deep waters of big, muddy rivers.
Not surprisingly, their eyes are tiny, pea-sized organs.
Underneath the
frontal paddle there is an impressive mouth which when opened encompasses an
area equivalent to that of a gallon bucket. Generally it is open, since the
paddlefish feeds by cruising along, sucking in water containing microscopic
animals:daphnia, diatoms, rotifers, and others collectively known as
zooplankton. The water, silt, vegetable matter, and other debris (occasionally
including a minnow or fishhook) are filtered through an intricate, sieve-like
arrangement of gill rakers which serves the paddlefish as baleen does the great
whales. The zooplankton is retained and ingested.
For the first few
months of life paddle-fish have a full set of tiny teeth; however, by midsummer
of their first year they have shed these baby teeth in favor of gill rakers.
During the summer, young paddle-fish-which in April are approximately the size
of newly hatched tadpoles-grow rapidly and have been known to attain lengths of
twenty-eight inches by October. This impressive rate of development is not
maintained, but no one is certain what the limits of growth for a paddlefish may
be. Tagged individuals are known to have lived for at least thirty years, and
the assumption is they can live much longer. Apparently they continue to grow as
long as they live, and they feed almost constantly. Therefore biologists believe
that the nineteenth-century stories about three- and four-hundred-pound
individuals cannot be dismissed out of hand.
In addition to being
toothless, mature paddlefish are scaleless, with a smooth, green hide as tough
as heavy-duty vinyl. Underneath the skin is a thick layer of meat that is red
because it is finely laced with blood vessels. This layer has a lung-like
function and helps the animal to absorb oxygen in the deep, turgid waters it
prefers. Also, in part because of this characteristic, paddlefish are strong and
durable swimmers. They may travel five hundred miles or so to spawn and can move
along at three miles per hour against a current running at the same rate. For
short bursts they may sprint along at ten miles per hour.
Underneath the
red vasculated layer, the flesh of the paddlefish is white, firm, and, like that
of sharks, boneless; the paddlefish is, stiffened entirely by cartilage. The
lack of bone, plus the fact that the paddlefish has a tail remarkably like that
of a shark, led to speculation that it might be a primitive or degenerate
freshwater shark. Now, however, it is believed that sharks and paddlefish simply
made similar environmental adaptations but are not connected in any direct
evolutionary way.
During their first year or so, paddlefish are
vulnerable to predation by other carnivorous fish, birds, and occasionally
mammals, but thereafter their size makes them inconvenient food for anything but
parasites. Additionally, because of what they feed upon and how they feed,
competition between them and other large river species is minimal. Paddlefish
apparently slurped along through the big rivers, not bothering or being bothered
by anybody from the late Devonian period until the nineteenth century. Then they
met us, and the hard times began.
As was the case with the grizzly bear,
rattlesnake, and Yellowstone geysers, the first Europeans who met paddlefish
told a lot of frightful stretchers about them. Early frontier accounts of
paddlefish had them overturning rowboats, swallowing small livestock and
children, ramming and jamming the works of paddlewheel steamers. However,
river-men began taking a more clinical and exploitative look at the fish and
discovered that in spring a big female might hold as much as twenty-five pounds
of eggs similar enough to those of the scarce sturgeon to bring caviar prices.
In consequence, by the 1890s two million pounds of paddlefish were being netted
annually in the Mississippi, Ohio, and Missouri rivers. They were taken
principally for the roe. The flesh, if marketed, was usually dried or smoked
since fresh paddlefish meat was then generally considered coarse and rank. The
paddlefish trade was unregulated, and by 1907, when the first formal study of
the species was published, the catch had declined drastically. Since then there
never have been enough big paddlefish to be of much commercial
importance.
In addition to overfishing, certain environmental alterations
contributed to the paddlefish's decline. Among the most critical were the
massive flood control, hydroelectric, and channelizaton projects that have
changed the characters and courses of nearly all our big midland rivers. The
rivers have been "improved" for people by straightening them, removing
obstacles, squeezing them into narrower channels, and increasing the rates of
runoff and flow. By way of illustration, the Missouri River, a notably unruly
one, now, occupies about half the surface area it did before the Army Corps of
Engineers began "improving" it, and it flows almost twice as fast. Much of the
riverbed that was eliminated was' prime paddlefish habitat. Paddlefish thrive in
deep, slow, meandering backwaters where the zooplankton is rich and where the
lack of current enables them to feed efficiently-the type of habitat the Corps
and other public agencies found most untidy. For example, islands create the
kinds of pools in which paddlefish prosper. However, all but eighteen of the 161
major islands in the Missouri have been eliminated. The situation is similar
elsewhere.
Until recently no one knew the species was being affected.
Commercial fishermen had lost interest, and sportsmen never had much interest in
a fish that did not take a bait or hook. Therefore there was no public clamor
about the status of the paddlefish and no pressure on wildlife managers or
researchers to look into the matter.
The situation changed abruptly in
the 1930s when Bagnell Dam, a 150-foot-tall hydroelectric facility, was built
across the Osage River, a major tributary of the lower Missouri. Bagnell Dam
produced much of the electricity used in the St. Louis area, and it created the
Lake of the Ozarks, a 60,000 acre impoundment which has since become one of the
notable recreation areas and tourist traps of the Midwest. The project also had
a profound and unanticipated effect on paddlefish. The creation of Lake of the
Ozarks set in motion a chain of ecological events which resulted in:
+
What appeared to be a paddlefish population explosion;
+ The emergence of the
paddlefish as a popular game species and the consequent creation of a
pro-paddlefish constituency;
+ Considerable investigation into the natural
history of the fish;
+ The present probability that the paddlefish, which has
survived for a third of a billion years, may not make it into the twenty-first
century.
It is now believed that the Osage River just prior to the
construction of Bagnell Dam, may have supported the largest, most vigorous
population of paddlefish remaining in the Mississippi Basin. When Lake of tile
Ozarks was filled, many of these fish were permanently trapped behind the dam.
The lake provided tile fish with the kind of habitat they liked best, and they
multiplied rapidly. They became very visible, especially in spring. Schools of
paddlefish, larger than anybody had ever seen, congregated in the narrow upper
reaches of Lake of the Ozarks. This same increase in paddlefish populations
immediately following the creation of impoundments had been observed on other
rivers, but generally it was a short-lived phenomenon. In most cases the fish
would begin to decline after a few years and then disappear. However, in
Missouri they remained and continued to do well.
Lake of the Ozarks was a
boon to fishermen as well as paddlefish. In the mid-1930s it was discovered that
paddle fish-which cannot be taken by conventional means-could be snagged by
dragging big triple hooks through the channels and holes where large numbers of
them gather in spring. Once hooked, a paddle fish provides a considerable amount
of excitement. The fish's immediate reaction, according to veterans of the
sport, is to make a strong run of fifty yards or .so during which a big
individual can pivot a johnboat and sometimes tow it. Thereafter the snagger,
using ll0-pound-test or strong line, may play the fish for half an hour or so
until both parties are exhausted and the fish is boated.
Besides being a
sport fish, the paddle fish is good eating. Formerly the fish had been held in
low esteem because nobody bad learned to clean them properly. The trick, Ozark
fishermen found, was to remove the outer layer of red, vasculated meat and eat
only the boneless white meat underneath. This meat resembles that of swordfish
and is excellent by almost any standard.
Ever since 1960, between fifteen
and twenty thousand snaggers have come to Lake of the Ozarks each spring, taking
four thousand or so paddlefish a season. There is some snagging as far west as
Montana, but Missouri remains the center of the sport because the Osage drainage
system is the only place where there is a sizable paddlefish population. The
paddlefish rapidly acquired a consumer lobby, and public agencies-specificallly
the Missouri Department of Conservation-are giving it more
attention.
Twenty years ago, little was known about the reproductive
cycle of the paddlefish. It was assumed that the springtime schooling in Lake of
the Ozarks was associated with spawning, but there was no biological information
about when, where, and how this took place. Even more puzzling, nobody had seen
paddlefish fry or fingerlings. Back in the 1920s the mystery of where the baby
paddlefish were had so intrigued Edward Phelps Allis of Allis-Chalmers that he
offered a $1,000 reward to anyone who could find a paddlefish as small as two
inches. The money was never claimed, and the reward was withdrawn. It was not
until the spring of 1960 that Charles Purkett, a Missouri fisheries biologist
who had been investigating tributary streams above Lake of the Ozarks, located
the first spawning paddlefish. Purkett described his discovery in the May 1961
issue of the Missouri Conservationist:
"On April 20, the seventh day
after a nine-foot rise, and for several afternoons and nights following, fish
were observed in what we later proved to be spawning activity over the gravel
bars near the mouth of Weaubleau Creek. The only evidence of spawning was the
appearance of a single fish at the surface where it would agitate its tail
rapidly, then disappear after a few seconds. It appeared this was a female that
had started near the bottom over a large gravel bar and made a spawning "rush"
during which eggs were released. Presumably; accompanying males then released
milt which fertilized the eggs. This happened every few minutes during the
afternoons and evenings while the water level remained high.
"By the
afternoon of April 24 the water level had fallen seven feet very rapidly,
exposing the gravel bar where spawning had been observed. That afternoon I
walked to the area where most of the activity had been and picked up a
paddlefish egg almost immediately-and dropped it into the flowing water!
Fortunately there were many more just downstream, and as I searched I also found
hatching eggs and some which had hatched only a couple of hours
before.
"Gravel bars which are kept clean by flowing water and are deep
enough for the thirty- to seventy-pound fish are preferred for spawning. Much of
the gravel and rocks in these bars is small and is not silted over as it would
be in the lake. This is the reason these paddlefish make the long trip up the
lake and river.
"The eggs, when released from the female, flow freely and
do not stick to anything. Immediately after fertilization a very adhesive
coating forms which causes the egg to stick to the first object it touches. Most
eggs adhere singly to a pebble or rock so strongly that some eggs were broken in
trying to remove them. Some were coated with silt before they became attached,
and some attached to floating sticks and were washed downstream. We dredged up
quite a number of these in places where they probably wouldn't have hatched and
survived. The most favorable location for hatching obviously was the clean-swept
gravel bar. Here they were not covered with silt and aeration was
good."
Subsequent studies indicated that paddlefish need a very specific
combination of conditions for spawning:clean gravel bars that are briefly
inundated by spring floods, floods that provide at least a five-foot rise in the
stream level, and a water temperature of about 60 degrees. This combination
occurs for only a few days in the spring, but not every spring. In years when
conditions are not suitable, female paddlefish resorb their eggs, retreat
downstream, and do not spawn.
This information made it rather obvious why
paddlefish had done very well in Lake of the Ozarks but badly in most other
areas of the Mississippi Basin. The waters backed up behind Bagnell Dam did not
extend far enough upstream to silt over the gravel spawning bars. But in the
other rivers these breeding grounds, as well as feeding areas, had been
eliminated or degraded by impoundments and channelization. Paddlefish
populations, sharply reduced at the turn of the century by overfishing, could
not recover and were growing steadily smaller. The lack of early records makes
accurate comparisons impossible, but Missouri biologists speculate that the
Mississippi drainage system may now support only 10-20 percent as many
paddlefish as it once did. In many rivers, particularly in the eastern half of
the basin, the fish is now extinct.
Unfortunately, the paddlefish
sanctuary in Lake of the Ozarks proved temporary. In 1954 the Corps of Engineers
proposed the Harry S. Truman Dam, to be built on the Osage River some fifty
miles above Bagnell Dam. The resulting impoundment would effectively double the
size of the Lake of the Ozarks complex and flood out the gravel bars on
Weaubleau Creek and those on all the other tributaries where paddlefish were
known to spawn. After Purkett and other researchers documented this, the fate of
the paddlefish became a considerable issue in the controversy about whether the
dam should be built. However, in 1973 a federal court gave final approval for
the project, and in late 1977 Truman Dam was finished and Lake Truman
filled.
During the past three springs paddlefish have congregated below
the new Truman Dam, vainly seeking to reach their traditional spawning beds
above it. A snagging season has been permitted both below and above the dam on
the grounds that these fish are effectively sterile, since they now have no
place to reproduce.
The environmental changes caused by Truman Dam
scarcely came as a surprise since the project had been under argument and
construction for nearly a quarter of a century. In the 1960s the Missouri
Department of Conservation began considering what it would do after the
impoundment destroyed the paddlefish spawning beds, and opted for trying to rear
the fish artificially. After considerable experimentation, this is now being
done at the Blind Pony Hatchery near Sweet Springs in the western part of the
state. The hatchery biologist, Jerry Hamilton, is regarded as something of a
genius for having found out how to hatch and raise paddlefish, something nobody
else had done previously and which thus far has not been done elsewhere with
much success.
In spring, as paddlefish begin their spawning run in Lake
of the Ozarks, Hamilton and his associates net thirty or so gravid females and a
dozen mature males. The females weigh between thirty-five and sixty pounds, and
each may contain half a million eggs. At the same time, Hamilton and his crew
make arrangements to take a quantity of pituitary glands from fish caught by
snaggers. These glands are immediately frozen and stored.
The captured
fish are held in small ponds at Blind Pony Hatchery and observed closely until
Hamilton judges the females are ready to lay their eggs. Then each female is
moved into a laboratory holding tank and injected with pituitary material
extracted from the frozen glands. Without this injection of hormone material the
sows will not release eggs.
Paddlefish eggs, unlike those of nearly all
other freshwater species, are not contained in a single sac and deposited at one
time. Rather, the roe is held within the ovaries in a series of flat "leaves,"
which are released individually over a period of twenty-four hours or longer. In
the hatchery, females that have been induced to begin laying are tended
constantly, and as a leaf is released, the eggs are immediately fertilized with
milt extracted from one of the captive males. Eggs are then held, under constant
temperature, in large test tubes. They hatch in about seven days. The fry are
transferred to outdoor rearing ponds, rich in zooplankton, and kept there until
early fall.
Despite the great quantity of eggs produced by each female,
the survival rate of fry, at least with captive fish, is not high. Thus far,
only about 150-200,000 fingerlings are being raised at the hatchery each season.
However, Hamilton believes this figure could be increased to half a million. A
small number of paddlefish have been hatched in South Dakota, but the Blind Pony
laboratory is the only place where they are produced regularly in quantities.
Fry and fingerlings have been shipped from there to other states and also to the
Soviet Union, where it is hoped dwindling sturgeon populations can be
augmented-and the caviar industry supported-by the introduction of North
American paddlefish.
In 1972 the Missouri Department of Conservation
began stocking paddlefish in Table Rock Reservoir, a large impoundment along the
Missouri-Arkansas state line that was selected as a controlled testing site
because it previously had no paddlefish. The habitat there proved suitable, and
Table Rock now has an established though presumably nonbreeding population. In
1978 the first ten- to thirteen-inch fingerlings were released in Lake Truman,
and during the next several years Lake of the Ozarks will be stocked.
Kim
Graham and Tom Russell work full-time as paddlefish field biologists in
Missouri. Graham is reasonably confident that a respectable number of the fish,
enough to support a sport fishing season, can be maintained in the Osage River
impoundments, Table Rock, and perhaps other new areas. However, he feels that
there is little chance these can be anything other than stocked fish, hatched at
Blind Pony. "There may be a few small gravel beds in Missouri where there is
natural reproduction," says Graham, who has searched persistently for such
areas, "but we don't know where they are and haven't seen any that looked very
promising. As far as we know, this is the situation throughout the Mississippi
Basin. Spawning beds are scarce, and prospects are that there are going to be
fewer rather than more of them in the future."
The sterile, brightly lit
laboratory building at Blind Pony Hatchery is perhaps the best paddlefish
spawning ground left in this country. In it, in a steel tank, lies a gravid,
fifty-pound sow that has been captured, transported, manipulated, probed, and
stimulated by attending biologists and technicians. If their techniques continue
to be effective; if the thermostats, water filters, circulators, and
air-conditioners are properly maintained; if secondary support systems,
telephones, combustion engines, highways, petroleum refineries, and electrical
generating plants continue to function as planned; if legislative appropriations
committees, bureau supervisors, taxpayers, and voters remain supportive; if
inflation or depression, and political, social, or international crises do not
disrupt everything, this paddlefish will give up her eggs, and some of her
daughters will do the same in the same way. The eggs will hatch, and the line of
the species, which has survived the settling of continents, the lifting of
mountains, the ages of ice, coal, and reptiles, may continue in the late
Engineering Age.
That we have figured out how to do these things to and
for such an ancient creature is a credit to our intelligence. That we want to do
them speaks well for our compassion-or at least says something about how well we
regard sport. That we need to do these things-that the paddlefish, her
attendants, and the rest of us have met for these purposes at Blind Pony-is
unspeakably sad.
