| Has the Large Mouth Bass Virus Stricken The Lake Of The Ozarks? | |
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by Phil Williams
Mid-America Bass
Starting
in late summer and continuing into the fall, bass anglers have been reporting
slower- than-normal fishing for black bass on Lake of the Ozarks. The
uncharacteristically low tournament weights throughout the fall have supported
these reports. Anglers have commonly mentioned listless behavior of those bass
caught and numerous sores and lesions on the fishes skin.
MDC biologists attended the day 1 weigh-in at last week’s BASS tournament to
collect fish for analysis. Of the approximately 250 bass examined at the
weigh-in, only 14 fish (6%) appeared to either have difficulty remaining upright
in the water, exhibited significant amounts of sores or lesions on their skin,
or were excessively thin. All of these fish were examined. The remaining 94% of
the fish appeared to be in good health.
Lately, rumors at the local boat ramps and tackle shops have attributed the poor
fishing to Largemouth Bass Virus (LMBV) which has been blamed for fish kills in
high-profile fisheries such as Lake Fork in Texas and has hit as close to home
as Table Rock Lake here in Missouri. LMBV was detected in Lake of the Ozarks
during routine spring sampling in 2001, but fish kills attributed to LMBV are
typically summer events where significant numbers of dead bass fish are readily
observed. Other than isolated fish, MDC officials have not received reports of
dead bass at Lake of the Ozarks this year. Although several bass collected at
the BASS tournament will be tested for and will likely contain the LMBV virus,
completed analysis has already identified the most likely source of the problem.
The fish collected at the BASS tournament were suffering from an infestation of
several parasites, which occur naturally in Lake of the Ozarks and most, if not
all other lakes and rivers in Missouri. Among the most prevalent of these
parasites were Epistyles, a protozoan that can trigger an allergic-type response
in some fish resulting in sores on the skin. Another, the bacteria Acrimonies
can often cause the loss of skin and scales in heavily infested fish. Fish
infected with significant amounts of these parasites often act lethargic and
feed poorly.
There are hundreds of different viruses, bacteria, protozoan and fungi that
exist in all of our lakes and streams all of the time. Many of these can cause
illness or death in fish. But only in certain situations do they cause problems
with the fishery. So why this year?
In this part of Missouri, 1999 and 2000 were extremely dry in terms of rainfall.
During dry years, nutrients from many sources build up on fields and in small
feeder creeks in the watershed. Then comes along 2001 with a more normal
rainfall, including a few extremely heavy rains, which impacted a large
proportion of the Osage River basin. As a result, a large quantity (2+ years
worth) of nutrients gets washed into Lake of the Ozarks. This shot of nutrients
is partially responsible for the numerous shad we are seeing this year, an
unusually successful crappie spawn, and unfortunately, a population explosion of
parasites that can negatively affect fish and fishing. A situation nearly
identical to what we are experiencing occurred several years ago on Clearwater
Lake.
Unfortunately, when a virus or other parasite impacts a fishery in a body of
water the size of Lake of the Ozarks, all that can be done is let it run its
course. Presently, it is not possible to treat sick fish in large bodies of
water. The good news is that these outbreaks are typically temporary in nature,
only a small percentage of the population is affected, and the fisheries quickly
rebound.
The spring 2001 electrofishing sample indicated that the number of legal bass in
both the Glaize and Niangua arms of the lake was higher in 2001 than in 2000.
Unless we experience a visible fish kill, we will not know if a kill has occurred
until we can compare the 2001 sample results with the upcoming 2002 sample.
I hope this has answered your questions. Please feel free to call me if you have
further questions.
Sincerely,
Greg Stoner
Fisheries Management Biologist
Mr. Stoner’s answers show
a ray of light for the bass at one of the nation’s finest fisheries. We will
just have to wait until next years reports are out to find out how much damage
has been done to the population. Though the Large Mouth Bass Virus has reared
its ugly head at the lake, it doesn’t appear to be a significant problem at
this time. Hopefully the virus and the other parasitical problems the fish are
experiencing will run their course and return this fishery to the way she was.
Until then keep your fingers crossed.
Next page > Part 1 - LMBV In Lake of the Ozarks? > Page 1, 2
