Thank you Bill and Dave, I got to read your artical on Catchability. Its excellent. I thought I would copy and post it for everyone.
Largemouth Bass: Angling and Catchability
Dave Willis and Bill Cody
Are largemouth bass �smart?� Well, that probably depends on who you talk to and what
they are doing. So, we won�t try to answer that loaded question. However, we do believe that
largemouth bass can learn from their past experiences.
In this article, we want to discuss two inter-related topics for pondmeisters. First, we will
discuss how angler catches can be used to monitor largemouth bass populations in ponds. Then,
we�ll get into the effects that 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.
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 1 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 stun the
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 the numbers of largemouth bass increased in the ponds, anglers also
caught more largemouth bass per hour of angling (Figure 1). When bass density was low (50-
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250/acre), we caught only 2-5 bass per hour of angling. When 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 the numbers and sizes of largemouth
bass in a pond or lake. In our 9-pond study, we compared the sizes of bass caught by angling to
the sizes we caught in our electrofishing samples (Figure 2). Once again, we were pleased with
the results. When electrofishing indicated that very few bass in the pond were greater than12
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.
When electrofishing indicated that moderate 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 that are present in a pond.
The key to our success in this study was that the ponds were either unfished or lightly
fished. Several fisheries studies have shown that largemouth bass exposed to high levels of
fishing pressure do become more difficult to catch. The conditioning (or learning) of the bass to
avoid fishing lures 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.
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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 the bass were stocked, they waited 2 weeks before fishing began. They
then varied the amount 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 the catch rate of bass persisted throughout the study period in Pond A,
which had the shortest fishing sessions (0.8hr/ac). The 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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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� would be 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 the methods that have previously been used in the pond. Live
bait often will help to catch the older and more experienced fish, but remember that circle hooks
or using larger hooks can greatly reduce the hooking mortality by reducing the chance of a bass
swallowing the hook.
A second �solution� is when you fish, fish each time 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 the panfish or catfish. Spend more time managing the 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 the 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
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room for new bass 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? Do 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 1) 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 have less total harvest of bass, and be sure that all 8-
12 inch bass are protected. Harvest the occasional big and smart bass to keep the bass catch rates
at a higher level.
Sacrilege indeed! Good fishing to all.
References
Isaak D.J., T.D. Hill, and D.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., D.P. Burkett, P.R. Beaty, W.F. Childers, and D.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.
