ON NO~T.uthN POND
Largemouth Bass
:Angling and Catchability
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By Dr. Dave Willis and Bill Cody
H
ave you ever caught a bass in your pond
you swear has been caught before?
There's that telltale hook mark in the lip, and
some special marking you have seen in the not
too distant past.
Are largemouth bass "smart?" Well, that
probably depends on who you talk to and what
they are doing. So, we won't try to unload
that loadedquestion.However,we do believe
that largemouth bass can learn from past
expenences.
In this article, we discuss two inter-related
topics. First, we discuss how angler catches can
be used to monitor largemouth bass populations
in ponds. Then, we'll get into effects angling has
on largemouth bass catchability. High angling
effort can throw a wrench into using your ability
to use angling catches to track density or the
relative sizes of your largemouth bass.
bass density was moderate (900-1300/acre), we
caught 6-8 bass per hour. When bass abundance
was the highest (2100/acre),we caught an
amazing 19 bass/hour.
Biologists and pondmeisters often want to
know numbers and sizes of largemouth bass in a
pond or lake. In our 9-pond study, we compared
sizes of bass caught by angling to sizes we
caught in our electro fishing samples (Figure 2).
Once again, we were pleased with the results.
When electrofishing indicated very few bass in
the pond were greater than 12 inches, anglers
caught a low percentage of bass over 12 inches.
The four ponds that contained lots of smaller
bass were classic examples of "stunted" (high
density, slow growing) bass populations.
numbers of largemouth bass were 12 inches or
longer, then anglers caught more medium sized
bass. In the one pond with primarily larger bass,
90% of the bass caught by electrofishing were
12 inches or longer. At that pond, 94% of the
bass caught by anglers were also 12 inches
or more. [Which pond do you want to fish?]
Results of this study showed that sampling
of bass by angling can provide a pretty good
estimate of the numbers and relative sizes of
bass present in a pond.
The key to our success in this study was that
ponds were either unfished or lightly fished.
Several fisheries studies have shown largemouth
bass exposed to high levels of fishing pressure
do become more difficult to catch. Conditioning
When electrofishing indicated moderate (or learning) of bass to avoid fishing lures
Angling to Monitor Bass Populations
We designed a study to assess angler-catch
information for largemouth bass in nine South
Dakota ponds. The ponds ranged from less than
I to almost 20 acres. All ponds were "sampled"
by angling and also with our electrofishing
boat. The boat has a generator that produces
electricity, and a control unit that allows us
to regulate how much electricity is used to
temporarily stun fish. Electrofishing is most
effective at night and is accepted and widely
used by fishery biologists as a standard method
for monitoring largemouth bass populations.
Earlier in our study, we used what is known as
a "mark and recapture" technique to actually
estimate the number per acre for largemouth
bass in each pond.
Not surprisingly, as numbers of largemouth
bass increased, anglers also caught more
largemouth bass per hour of angling (Figure I).
When bass density was low (50-250/acre), we
caught only 2-5 bass per hour of angling. When
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Figure 1. As the density of largemouth bass increased in 9 South Dakota ponds, so did
the number per hour caught by anglers.
POND BOSS j MarchjApril2006
throws a wrench into the concept that angling
can be a good sampling method for largemouth
bass. Next, let's explore some evidence that
"experienced" bass become harder to catch.
Largemouth Bass Catchability
Researchers at the Illinois Natural History
Survey completed an interesting study on this
topic. First, let's look at their study design. They
used three ponds, all about 0.2 acres in size. All
ponds were stocked with the same number
(420/acre)and the same sizes (9-13 inches)
of largemouth bass. After bass were stocked,
anxious samplers waited 2 weeks before fishing
began. They varied amounts of fishing pressure
at each pond (low, moderate, and high). All
fishing was catch and release. At the end of the
3-month study, only two bass had died. One
was lost in the low-pressure pond, and one in
the high-pressure pond.
In the low-pressure pond, fishing amounted to
170 hours/acre, and anglers caught 3.0 bass per
hour. In the moderate-pressure pond, anglers
fished 340 hours/acre, and caught 1.2 bass per
hour. In the high-pressure pond, angling was
680 hours/acre of water, and they only caught
0.4 bass per hour. The more experienced bass in
the higher pressure ponds certainly learned, and
were less likely to bite.
In the second part of the same study,
researchers stocked each of three small ponds
with 75 bass per acre. During the next 49 days,
each pond received 23 sessions of catch and
release fishing. Each session, Pond A was fished
for 0.8 hour, Pond B for 1.6 hours, and Pond C
for 3.3 hours. Figure 3 shows what happened.
As fishing pressure increased, fish became
harder to catch. Near the end of the study, no
bass could be caught in Pond B or Pond C. The
best bass fishing occurred and catch rates of
bass persisted throughout the study period in
Pond A, which had the shortest fishing sessions
(0.8hr/ac). Bass seemed to learn more from
the length of fishing sessions rather than the
number of times the pond was fished. Again the
more experienced the bass became, the harder
they were to catch.
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40
60
80
100
Percent >12 inches (electrofishing)
Figure 2. Comparison between the percent of largemouth bass> J2 inches caught by
angling and caught by electro fishing in 9 South Dakota ponds.
hooks or using larger hooks can greatly reduce
hooking mortality by reducing the chance of a
bass swallowing the offering.
A second "solution" is when you go, fish
each outing for shorter periods of time. This is
especially true if you have a smaller pond. The
longer bass are exposed each time to fishing
pressure the wiser they become. Spend some
of your extra time fishing for other types of fish
in the pond - maybe panfish or catfish. Spend
Potential Solutions?
So, what the heck can a pondowner do to
combat this learned behavior of largemouth
bass? We have a few suggestions.
The first "solution" for pondowners is to vary
fishing technique. While this certainly does not
solve the problem, it can help. New techniques
with different types of lures are more likely
to catch bass than methods previously used.
Live bait often will help catch older and more
elusive, experienced fish, but remember circle
March/April 2006 / POND BOSS
How many times will this bass be caught?
27
more time managing fish by keeping track of
their numbers, checking weights or measuring
lengths and focus on removing selected fish to
improve the balance of the overall fishery.
Our third "solution" borders on sacrilege!
Perhaps we should consider eating some of
the bass! While harvest may seem strange
after years of kissing and releasing your bass,
some turnover in the population will probably
help angling catch rates. New or younger bass
will not be as "experienced" or as cautious
as old timers. A pondmeister with a typical
Midwestern pond might have 50 pounds/acre
of largemouth bass in a 3-acre pond, for a total
of 150 pounds. What if 30 or 40 pounds of bass
were filleted and eaten per year? That harvest
would allow for turnover in the population
because with harvest of some older and wiser
bass there would be room for new, younger bass
4.5
to grow into the adult population. Plus, that
level of harvest would not affect predator-prey'
relations in a pond that contained 150 pounds
of bass.
Always remember the concept of selective
harvest. Which bass are the most experienced
or the most abundant and thus best suited for
harvest in your pond? 00 you need to primarily
harvest bass less than 14 inches long? Maybe
only bass between 12 and 16 inches long should
be harvested? The appropriate harvest will
vary by I) what is in your pond and 2) your
management goal. If you are most interested in
producing larger bass, then you probably should
concentrate your harvest on the smaller bass
(although the big ones may become tough to
catch). If you are managing for a high-quality
bluegill population by purposely crowding
your largemouth bass, then perhaps you should
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4
3.5
Harvest is important. This 'double' is
unusual, but happens in overcrowded bass
populations.
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have less total harvest of bass, and be sure that
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all 8-12 inch bass are protected. Harvest the
occasional big and smart bass to keep bass catch
rates at a higher level.
ell
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Sacrilege indeed! Good fishing to all.
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1.5
1
0.5
0
0
50
100
150
Hoursfished per acre
Figure 3. Largemouth bass caught per hour of angling related to total hours fished in
three small Illinois ponds. Each pond contained 75 bass per acre and each was fished
23 times over 49 days.
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References
Isaak OJ., T.O. Hill, and O.w. Willis.
1992. Comparison of size structure and catch
rate for largemouth bass samples collected
by electrofishing and angling. The Prairie
Naturalist 24(2): 89-96.
Mankin, P.c., O.P. Burkett, P.R. Beaty, W.E
Childers, and O.P. Philipp. 1984. Effects of
population density and fishing pressure on
hook-and-line vulnerability of largemouth bass.
Transactions of the Illinois Academy of Science
77(3-4): 229-240.
Dr. David W. Willisis a professor in the Department
of Wildlife and Fisheries Sciences, South Dakota
State University in Brookings. Bill Cody is an
expert aquatic microbiologist, based in Ohio.
Both can be reached on the PB forum.
c<~
POND BOSS / March/April 2006