6 / OutdoorIllinois June 2006
under a specified length from harvest.
This regulation is most effective for
species exhibiting average or above
average growth rates combined with low
natural recruitment. They are most com-monly
used to protect fish until they
reach sexual maturity, or to allow fish to
attain a quality or trophy size.
By increasing predator densities, min-imum
length limits also can function as a
tool to reduce the density of prey
species. For example: A minimum length
limit can be used to increase the number
of bass which will, in most cases,
increase predation on the sunfish popu-lation.
This increased predation can in
turn reduce sunfish numbers, resulting in
improved growth rates and an increase
in average size. Minimum length limits
typically increase angler catch rates,
reduce harvest and increase the size
structure of the population.
Slot length limits protect a specific
size of fish while allowing anglers to har-vest
fish larger and smaller than the pro-tected
size. This type of regulation is
most effective for species exhibiting high
rates of natural reproduction and recruit-ment
combined with slow growth rates.
Successful slot limits reduce the den-sity
of the smaller fish, improve growth
rates and increase the size structure of
the population. Harvesting fish below
They are used to reduce angler-induced
mortality and, in conjunction with length
limits, protect a species or certain size
of fish from over-harvest. They are
especially useful for less abundant
predator species such as bass, walleye,
sauger, northern pike and muskie, but
also can be useful in some instances for
more prolific species such as crappie,
white bass and bluegill. These limits typ-ically
range from one to 10 fish per day
depending upon the circumstances and
the specific management objective.
Creel limits also can be used to dis-tribute
the catch more equitably, provid-ing
the opportunity for more anglers to
participate in the harvest. This technique
is generally used for more prolific
species—crappie, sunfish or white
bass—and for species whose popula-tions
have been enhanced by DNR’s
stocking program, a practice sometimes
referred to as put-grow-and-take. Daily
creel limits for the latter are typically
conservative, ranging from one to six
fish per day, while those designed to
distribute the harvest of more prolific
species are more liberal, ranging from
15 to 25 per day.
Length or slot (size) limits protect a
specific size of fish from harvest. In Illi-nois,
the most common types of size
limits are minimum length limits and slot
Minimum length limits protect fish
information necessary for developing
management plans tailored to enhance
the fishing potential of Illinois’ waters.
A multitude of factors are taken into
account when developing a manage-ment
plan—fish growth rates, species
composition, body condition, reproduc-tive
success and recruitment (the num-ber
of fish surviving to reach one year of
age), natural mortality, density, popula-tion
size structure, food availability, fish-ing
pressure, and the species composi-tion
and abundance of aquatic plants.
The physical and chemical characteris-tics
of each body of water—size, fertility
and maximum and average depth—also
Careful analysis of these data allows
biologists to design an integrated, multi-faceted,
management plan and maxi-mize
fishing opportunities for each spe-cific
body of water. Plans typically
include a combination of site-specific
recommendations for fish stocking or
Story By Mike Hooe
Photos By Joe McFarland
Understanding the role of length and creel limits—and
angler compliance—in fisheries management.
removal, vegetation control and habitat
But, arguably, the most important
management tools are species-specific
length and creel limits, the foundation of
most fisheries management plans.
These limits are designed to manipulate
angler harvest in a manner that will
enhance the density and size of the
sportfish population. To understand why
length and creel limits are such impor-tant
management tools, one must
understand how they function and what
they are designed to accomplish.
Creel limits—sometimes referred to
as daily bag limits—restrict the number
of fish an angler can harvest per day.
Sometimes, micromanagement is a
good thing. When it comes to the
management of Illinois’ individually
unique fisheries, it’s absolutely
Example: There is no statewide length
limit for largemouth bass. Ever wonder
why? It’s because some lakes or rivers
benefit from specific size or catch limits—
a 14-inch minimum length with a 6-per-day
limit, for example—while others need
something entirely different.
Providing anglers with diverse, high-quality
fishing opportunities requires an
intimate understanding of the fish and
aquatic communities in Illinois’ lakes,
ponds, rivers and streams. Department of
Natural Resources (DNR) fisheries biolo-gists
routinely conduct surveys to collect
June 2006 OutdoorIllinois / 7
Electrofishing sampling provides
fisheries biologists a harmless way
to examine fish populations.
Illinois anglers enjoy quality fishing
opportunities thanks to scientifically
A healthy Illinois lake should have
quality bass and bluegill populations.
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