Arkansas Game and Fish Commission Crappie Management Plan
Arkansas Game and
Fish Commission Crappie Management Plan
February 28, 2002
ARKANSAS GAME & FISH COMMISSION
CRAPPIE MANAGEMENT PLAN
MISSION STATEMENT:
Prepared by:
Tim Burnley,
D. Colton Dennis,
Jeff Farwick,
Dean Smith,
Don Turman,
Drew Wilson,
Approved by:
Mike Gibson, Chief of Fisheries
The goal of crappie management is to provide quality
crappie fishing. Management efforts towards improving recreational crappie
fishing will be optimized within the context of a multi-species fishery by
accurately characterizing crappie population density and structure and
enhancing
crappie populations through harvest regulations, stocking, and habitat
improvement.
OBJECTIVES:
1. Develop standardized sampling methodology for evaluating crappie
populations.
2. Develop a set of biological criteria for identifying what a model crappie
population in Arkansas should resemble based on standardized sampling
procedures to manage both black and white crappie populations collectively.
3. Develop a Crappie Stock Assessment to provide a standardized means for
fisheries managers to make objective evaluations of population structure and
population trends over time.
4. Develop a set of biological criteria that would determine when or if
harvest
regulations would be appropriate for improving crappie population structure.
5. Develop guidelines and evaluate effectiveness of crappie supplemental
stockings.
6. Evaluate need for stocking forage species such as threadfin shad when
crappie growth is limited.
7. Evaluate need for stocking predator species such as saugeye when crappie
overpopulation and stunting occurs.
8. Assess crappie habitat needs in Commission-owned and Federal water
project
lakes and implement appropriate habitat improvement projects.
9. Exploit opportunities to influence water management policy and
operational
features on Federal water project lakes to improve crappie habitat.
Crappie collectively are the most sought after sport fish among senior
resident anglers (44%), and second to bass (largemouth and spotted) among
resident (34%) and non-resident (25%) anglers in Arkansas (Duda et al.
2000).
Combined, resident and non-resident anglers spend an estimated $92.6 million
annually fishing for crappie in Arkansas. Because of high angler interest
and the
significant contribution to the State’s economy, the Arkansas Game and Fish
Commission has intensified its efforts towards developing a species plan to
optimize management efforts and enhance the quality of recreational crappie
fishing by characterizing and improving crappie population structure.
A standardized sampling methodology for sampling and evaluating crappie
populations was developed using trap nets. Trap netting will be conducted a
minimum of 30 net-nights per month from September through November in an
effort to collect sufficient numbers of crappie to allow population size and
age
structure analysis.
A set of biological criteria was developed to define a model crappie
population in Arkansas based on standardized sampling results. Objectives
for
the five population parameters of density, growth, age structure, size
structure,
and recruitment were established by examining trap net data from fifteen
Arkansas lakes. Lakes varied from oxbows to large Corps of Engineer
impoundments and from relatively clear and infertile waters to very
productive
lakes with dense algae or plant growth.
A good crappie population has a high density of desirable-size fish
available
for angler harvest. Further, it will have adequate and consistent
recruitment
accompanied with sufficient growth to compensate for harvest.
An optimal crappie population in Arkansas will exhibit a growth rate of 201-
mm to 275-mm (8-11 inches) at Age-2+, have a size structure (percent >
250-mm)
above 30%, and show consistent recruitment. These metrics are minimally
sufficient to describe a good crappie population. Age structure, growth, and
mortality estimates are needed to determine the suitability for enacting
minimum
length limits and/or other harvest regulations.
A crappie stock assessment was developed based on estimates of density,
growth, age structure, size structure, and recruitment. Values for the five
parameters were established by examining trap net data from Arkansas lakes,
and
highest values were assigned to optimum measurements of each parameter.
Values assigned to each population parameter were summed to give an overall
rating for the crappie population condition. The Crappie Population
Assessment
should provide a standardized means for fisheries managers to make objective
evaluations of population structure and population trends over time.
A set of biological criteria was developed to determine when or if harvest
restrictions would be appropriate for improving crappie population
structure.
Management strategies based on growth and mortality rates, and age and size
structure include adjusting crappie creel and length limits, management of
predators, lake fertilization, stocking, and control of aquatic vegetation
and
turbidity.
Angler preference is an important consideration when minimum length limits
are being examined as management strategies. The use of population modeling
programs will be used to predict long-term effects on crappie harvest prior
to
implementation of minimum length limits. Due to the various growth and
natural
mortality rates of crappie populations across the state, statewide length
limits
may be detrimental and result in substantial reductions in yield to some
fisheries.
Therefore, statewide length limits are not a recommended management strategy
for Arkansas crappie populations.
Guidelines for crappie supplemental stocking were developed, in which
stocking rates are determined by lake size. New lakes have the highest
priority for
crappie stockings. Supplemental stockings in other lakes will be based on
technical analysis of cove rotenone population samples and/or trap netting
and
social needs relevant to the fishery. Lakes over 4,050 ha, including Corp of
Engineer impoundments, should be stocked through the nursery pond system.
Crappie should not be stocked in lakes during years of high recruitment,
since
supplemental stocking is not likely to make a significant contribution to
the
naturally produced, strong year-class. Also, crappie should not be stocked
in
lakes where Age-0 to Age-1 mortality is high, because it is likely that
supplemental
stocking will have a similar high mortality rate due to poor conditions such
as lack
of adequate forage, habitat, or high predation. Environmental manipulation
techniques such as lake fertilization, water level manipulation, and habitat
improvement will be used in tandem with regulations and stockings to improve
crappie populations where these techniques are appropriate. Habitat
assessments are to be performed on Commission-owned and Federal water
project lakes to determine crappie habitat needs. Feasibility plans are to
be
drafted and implemented to address these needs as budget and resources allow
in an effort to improve crappie habitat statewide.
No management plan is complete without proper evaluation, and management
strategies suggested in this plan should be appropriately evaluated after
exploitation studies have been initiated, population modeling has been
conducted, harvest restrictions have been imposed, or creel surveys have
been
completed. Evaluation of additional trap netting data using the Crappie
Stock
Assessment will yield further information regarding the effectiveness of the
management plan.
Natural mortality rates of Age-0 to Age-1 crappie should be derived by
fishery
managers to assess where supplemental stockings will be most beneficial.
Fishery managers should also re-evaluate current crappie minimum length
limits
on Arkansas lakes using population modeling programs. Other sampling
techniques such as using larger 8’ x 8’ or 6’ x 6’ trap nets and spring/fall
electrofishing should be explored where standard trap net gear has been
ineffective at sampling the crappie population.
Handling and hauling mortality of crappie must be estimated and reduced by
hatcheries to minimize post-stocking mortality. Acceptable marking
techniques
for identification of stocked crappie also need to be investigated. Once a
desirable marking technique is accepted, future contributions of stocked
fish to
year-classes can be evaluated.
A Crappie Recruitment Model is needed to determine what variables are
having the greatest impact on crappie recruitment in Arkansas waters. The
model
would potentially help fishery managers identify those problems in
reservoirs
where corrective management could be applied, and would also help in
predicting
missing year-classes and thus, supplemental stocking guidelines on an annual
basis.
Finally, the purchase and replacement of boats, motors, trap nets, funding
for
exploitation/tag reward studies, and continued workshops and application of
fish
population modeling is needed for successful implementation of this plan.
Both black crappie Pomoxis nigromaculatus and white crappie P. annularis are
found throughout Arkansas (Robison and Buchanan 1988). Both species prefer
quiet
waters, and are almost always found near cover such as brush piles, tree
tops, standing
timber, and aquatic vegetation. Black crappie prefer cooler, deeper waters
and seem to
dominate in clear, vegetated, acidic waters, while white crappie tend to
dominate in
eutrophic (richer), more turbid, alkaline waters.
Crappie collectively are the most sought after sport fish among senior
resident
anglers* (44%), and second to bass (largemouth and spotted) among resident
(34%)
and non-resident (25%) anglers in Arkansas (Duda et al. 2000). Questionnaire
results
also indicated that a large percentage of anglers (62% of senior residents,
48% of
residents, and 43% of non-residents) choose to consume the different species
of fish
they catch (Duda et al. 2000).
In 1996, resident anglers spent $191.3 million and non-resident anglers
spent
$110.4 million fishing in Arkansas waters (Maharaj and Carpenter 1997).
Combined,
resident and non-resident anglers spend an estimated $92.6 million annually
fishing for
crappie in Arkansas. Because of high angler interest and the significant
contribution to
the State’s economy, the Arkansas Game and Fish Commission has intensified
its
efforts towards developing a species plan to optimize sampling and
management
strategies towards improving the quality of recreational crappie fishing.
For years, biologists believed lakes with large numbers of undersized
crappie were
the result of overpopulation and stunting (Goodson 1966; Ming 1971). As
biologists
began to look more closely at crappie age-and-growth, they often found
over-harvest
instead of over-population (Webb and Ott 1991). Colvin (1991) reported
over-harvest of
crappie in a large Missouri reservoir. However, this is not always the case
as Reed and
Davies (1991) recommended against size restrictions to protect the crappie
fishery from
over-harvest, because high natural mortality would have nullified the
benefits of a
delayed harvest.
Past crappie management in Arkansas was seldom based on well-defined
objectives developed from the three rate functions of recruitment, growth,
and mortality,
which reflect crappie abundance and size structure. Often, crappie received
little or no
direct management. A standardized approach to characterizing the state’s
crappie
populations was needed to provide reliable information. A research team was
formed in
1994 to develop criteria to best characterize crappie population structure
and optimize
management efforts. Fifteen lakes were sampled with trap nets between 1989
and 1993
to gather data to develop this plan (Table 1). Lakes varied from oxbows to
large Corps
of Engineer impoundments and from relatively clear and infertile waters to
very
productive lakes with dense algae or plant growth.
Successfully managing crappie populations requires understanding and
manipulating processes controlling recruitment. Recruitment is the number of
crappie
surviving their first year of life, and is influenced by spawning success,
environmental
conditions (temperature, food availability, water level fluctuation,
turbidity, etc.) and
predation on young-of-the-year (YOY) crappie. Arkansas’ lakes undergo
fluctuations in
water levels, temperature, turbidity and organic inputs. These factors
greatly affect the
success of crappie spawns and produce natural variations in fry production.
Under
proper circumstances these variations are evident later in recruitment and
eventually in
age structure.
Cyclic and highly variable recruitment is a principal management problem in
crappie
fisheries, which generally produce strong year-classes every 3-5 years (Swingle
and
Swingle 1967). Results from Allen and Miranda’s (1997) crappie age-structure
population model suggested that a specific combination of stock abundance
and
environmental conditions produced cyclic recruitment in crappie populations.
These
factors may act in combination resulting in high recruitment when stock
abundance is
low and environmental conditions are favorable, and low recruitment when
stock
abundance is high and environmental conditions are unfavorable. In addition,
modeling
suggested that even with favorable environmental conditions, production of a
strong year
class might lead to reduced or only average recruitment in subsequent (1-5)
years.
The predator population also affects fry/juvenile mortality and subsequent
recruitment. We speculate that a high-density bass population results in low
crappie
recruitment due to intense predation (high natural mortality), in which
surviving crappie
are fast growing and reach large size. Many fishermen would prefer this
situation to
catching numerous smaller crappies (AMRA 1988). An example is Bear Creek
Lake,
which holds a dense population of 250mm-325mm (10-13”) largemouth bass, and
shows
low crappie recruitment and rapid growth with average size of 320-mm (12.5”)
at age 2+.
In contrast, Lake Greenlee has low bass density and shows crappie to be
* anglers who have purchased an Arkansas Senior Citizen (65+) fishing
license
overpopulated, slow growing, and seldom reaching more than 150-mm (6”) in
length as
adults.
Dense predator populations have been shown to be inefficient in controlling
YOY
crappie when turbidity levels are high or thick vegetation is present.
Channel scar lakes
or shallow lowland lakes are perhaps Arkansas’ most fertile lake type and
often have
dense vegetation and/or turbid water used as cover by many YOY fishes. These
lakes
show good to high recruitment values and low mortality of YOY crappie, which
results in
low growth rates. Recruitment must be controlled to properly manage these
lakes.
Added fishing pressure and relaxed limits may not be sufficient to control
overpopulation.
Control of vegetation and turbidity may provide an answer.
In lakes containing moderate densities of largemouth bass and low crappie
density,
natural fluctuations in crappie production show up as inconsistent
recruitment and
missing year classes. Lakes Beaver, Bob Kidd, Nimrod, and Horseshoe show
large
variations in age structure due to inconsistent recruitment. The most
appropriate
management strategy in these situations may be to manage the habitat (water
level,
cover, fertilization) to enhance spawning success and recruitment.
Harvest regulation is one possible way to influence crappie populations when
exploitation (angler harvest) is high. However, only under conditions of
rapid crappie
growth and low natural mortality will minimum length limits improve yield
(average weight
of fish harvested) in crappie populations. Prior to the implementation of
minimum length
limits, population-modeling programs should be used to predict long-term
effects on the
crappie population. Modeling results can be evaluated by subsequent field
data
collections. Knowledge of angler preference when minimum length limits are
being
investigated should also be an important consideration for fishery managers
in the
decision-making process.
Standardized Sampling Procedures
Gear Specifications
Sampling Effort
Site Selection
Net Set Procedures
Limitations
Trap net samples are described as the most efficient and precise means of
sampling crappie. Boxrucker and Ploskey (1988) found trap nets to have a
higher catch
per unit effort (CPUE) and lower within season variability than either
electrofishing or gill
netting, and were the only types to adequately sample YOY crappie. Fall trap
netting
best represented population structure. McInerny (1988) found age and size
structure of
black crappie from fall trap netting similar to that harvested by fishermen
during the
same season. Miranda et al. (1990a) found a significant correlation between
white
crappie abundance from spring trap netting and springtime angler harvest per
hour.
The primary objective of trap netting is to collect sufficient numbers of
crappie to
allow population size and age structure analysis in lakes with significant
crappie
fisheries. Trap netting may also be used to collect fish for mark-recapture
population
and exploitation estimates.
Temporal variations in size and age structure of crappie are evident within
our fall
trap net samples in Arkansas. A higher percentage of YOY are caught in early
fall, while
larger, older fish are caught in late fall. Better estimates of population
parameters can
be obtained by sampling throughout the fall. All fish will be aged by
examining otoliths.
This method results in less error and variability than the scale method (Boxrucker
1986).
GEAR SPECIFICATIONS
Trap nets are constructed with two (2) 3’ x 6’, 5/16” diameter, steel frames
with
center braces and four (4) 2.5’ diameter hoops of 3/8” steel. The 3’ x 6’
frames are 30”
apart, and the first hoop is 32” from the second frame. The hoops are 24”
apart. The
second 3’ x 6’ frame has a slit throat and the first hoop has a 6” throat.
The net material
is 1/2” square NO.105 L knotless nylon, netset treated. The cod end of the
net has a
string closure with a 5’ No. 5 braided nylon string.
The leads are 1/2” square No. 105L knotless nylon hung 14 meshes per foot on
No.
60 nylon twine, netset treated with 2” x 1.5” cork floats spaced at 3’
intervals and 1.5 oz.
weights spaced at 2’ intervals. The leads are 50’ in length and 3.5’ deep
with the
exception that shorter leads can be used near steep drop-offs. Leads are
permanently
attached to the second 3’ x 6’ frame center brace.
Alternatively, Miranda et al. (1996) reported that floating trap nets with
larger
frames, and longer and deeper leads than the standard 3’ x 6’ frame with 50’
lead may
be necessary in larger, deeper reservoirs where catch rates are low. These
large 8’ x 8’
frame floating trap nets with 200’ leads resulted in larger sample sizes
with moderate
sampling effort when fished in habitats that previously were not sampled
effectively by
standard trap net gear.
Although the larger 8’ x 8’ frame net caught more crappies than the standard
net,
fishing the net can sometimes be problematic. The net is bulky, and because
of its size
and weight can be difficult to handle when wet. Wind and wave action can
cause the
nets to be disabled, especially in open-water sets. The large nets are also
at risk
floating in open waters where they are likely to be encountered by boaters.
Isaaks and Miranda (1997) developed a smaller 6’ x 6’ frame floating trap
net with a
150’ lead that is easier to handle than the larger 8’ x 8’ nets. The 6’ x 6’
net resulted in
catch rates that were lower than the 8’ x 8’ net, but significantly greater
than standard
nets. Therefore, the 6’ x 6’ floating nets may be a compromise between the
standard 3’
x 6’ nets and the more cumbersome 8’ x 8’ floating nets.
SAMPLING EFFORT
Trap netting will be conducted during the months of September, October and
November when water temperatures are between 16 - 26 degrees C (61 – 79 °F).
Minimum effort is 30 net nights per month, or 150 crappie greater than Age-0
for lakes
less than 810 hectares (2000 acres), or 250 crappie greater than Age-0 for
lakes 810
hectares or larger.
SITE SELECTION
Nets should be set perpendicular to crappie movement. Suggested areas
include
gradually sloping lake bottoms at the mouths of coves, off points, or areas
adjacent to
old river channels. Net sets in or near standing timber or where the leads
break over a
sharp drop-off should be avoided. To reduce variability over time, the same
locations
should be netted from year to year. Global Positioning Systems (GPS) can
also be used
to record net site locations that are consistently more productive.
NET SET PROCEDURES
Nets should be set at least one hour prior to sunset. If nets are left in
the same
location, then they should be checked at the same time each day if possible.
Also, trap
nets should not be fished at the same set more than two nights in
succession.
All crappie collected are differentiated by species, and total length and
weight for
each fish recorded. When large numbers (>200) of fish <80mm are collected,
subsamples of 25% by number are permitted.
Otoliths will be removed for age determination from a minimum of 10 fish per
25-mm
(1-inch) length group for each species. Otoliths will be read using a
dissecting
microscope or microfiche. A micrometer is optional, but is required for back
calculations.
All trap net sampling data including information obtained from otolith
readings will be
recorded and processed using the Fisheries Division trap net software,
currently being
developed.
LIMITATIONS
There are several problems inherent to this sampling scheme. These problems
should not influence recommendations; however, fish managers should be aware
of
these limitations and make changes in sampling schemes when necessary.
Crappies are growing during the sampling period from September through
November. Differences in lengths during this period may obscure
length-frequency
histograms and length-at-age determinations. Sample variance of
length-at-age will
increase with the width of the sampling window. Growth during the sample
period is
especially critical for younger age groups. This may cause problems when
comparing
population statistics from year to year and make it more difficult to
identify changes.
Young of the year crappie are typically caught in higher proportions earlier
in the
fall, and larger, older crappie are generally caught later in the fall. This
makes it
necessary to sample over the entire 3-month period to obtain a
representative sample.
Should the minimum number of crappie be caught early in the sampling season,
the
older component may not be represented in proportion to their abundance in
the
population.
Additionally, the percentage of crappie of a given age within a size group
can only
be estimated within 10%, if 10 fish per size class are aged. When more
accuracy is
required, more or all fish should be aged. Sampling from September through
November,
calculating length at a standard age (back calculations), and aging all fish
can reduce
these problems.
Developing appropriate objectives for population parameters combined with
standardized sampling procedures are vital to achieving effective fisheries
management
(Anderson, 1975). In the last few years, considerable attention has been
given to the
use of structural indices to describe and classify population structure.
Colvin and Vasey (1986) developed a method of assessing white crappie
populations in Missouri based on fall trap netting. Their system is based on
standard
point values assigned to estimates of density, growth (length-at-age), age
structure, size
structure, and recruitment calculated from fall trap net samples. A 0-10
rating is
assigned to each of the five population parameters. The five scores are then
summed to
give an overall index of population condition. This assessment is currently
used to
evaluate crappie population structures in Missouri (M. Colvin, Missouri
Department of
Conservation, personnel communication).
A primary objective of the Crappie Management Plan was to develop a stock
assessment index to evaluate crappie populations in Arkansas (Table 2).
Missouri’s
Stock Assessment Index was selected as a model from which to begin. The
Missouri
index, however, was developed for large reservoirs and white crappie
populations only.
Arkansas has both species of crappie existing in large impoundments as well
as small
lakes. Therefore, the Missouri Stock Assessment Index was adjusted to
accommodate
for these differences. Trap net data collected between 1989-1993 from
fifteen Arkansas
lakes, which varied from oxbows to large Corps of Engineer impoundments,
were used
to generate the model.
Arkansas’ lakes contain mixed populations of white and black crappie that
must be
managed as a group for regulatory simplification and so are combined for
stock
assessment. Values (1-10) are assigned for ranges of five population
parameters
(density, growth, age structure, size structure and recruitment) calculated
from fall trap
net samples. Highest point values are assigned to optimum measurements of
each
parameter. Because crappie density values varied greatly among the fifteen
lakes
sampled, and recruitment values are sometimes a poor indicator of actual
Age-0
abundance, these two parameters have been weighted disproportionally in the
assessment. Point values assigned to each population parameter are summed to
give
an overall rating for the crappie population condition. However, the values
of the
individual parameters are more useful for management purposes than the final
assessment value.
The Crappie Population Assessment (Table 2) should provide a standardized
means for fisheries managers to make objective evaluations of population
structure and
population trends over time in specific lakes. The assessment can also be
used to
compare indices between similar lake types such as Bull Shoals and Norfork.
CHARACTERISTICS OF A GOOD CRAPPIE POPULATION
A good crappie population has a high density of desirable-size fish
available for
angler harvest. Further, it will have adequate and consistent recruitment
accompanied
with sufficient growth to compensate for harvest.
DENSITY
Density is a function of recruitment and mortality. Catch per trap net-night
of Age-1
and older fish in fall samples is used as an index of density. Age-0
crappies are
excluded because trap nets do not sample Age-0 in proportion to their
abundance and
the presence of a large year-class could bias the sample.
Catch rates of 10 to 39 Age-1 and older crappie per net-night are considered
optimal for our purposes. However, when sufficient forage is available and
growth is
good (mean length @ Age-2+ >250mm) higher densities are acceptable. Lower
scores
are assigned to the same catch per net night if growth is poor (mean length
at Age-2+
<200mm).
Density, fish movement, weather conditions, and other factors influence trap
net
catch rates. Lake morphometry, water levels, presence of cover, etc
influence capture
efficiency. Catch rates may not always represent actual density. For this
reason,
several years of data are desired when analyzing crappie populations.
Population density influences the ratings of 2 other parameters. When
densities of
crappie are good (>20 Age-1+ and older per net-night), broader ranges of
growth rates
and size structure are accepted as desirable.
GROWTH RATE
Growth rate (mean length @ Age-2+) should be a good indicator of the
availability of
forage relative to crappie abundance. Growth influences the size and age
structure of a
population and affects sizes of fish available for harvest by anglers. In a
desirable
population, fish should reach a minimum harvestable size in a reasonable
period of time.
A good crappie population should have a growth rate between 201-mm (8”)
and 275-mm (11”) at Age-2+. Current data shows Arkansas lakes are capable of
growth rates within this range. Crappies above 225mm begin to add weight at
a faster
rate and are valued more highly by fishermen.
High growth rates (> 275-mm @ Age 2+) are associated with lower than optimal
densities and age structure. However, higher growth rates are acceptable
when density
is high since an adequate forage base must be present to produce good
growth. Poor
growth (=200-mm @ Age 2+) may be attributed to other trophic levels other
than forage
fishes, since crappie less than 150-mm (6”) forage primarily on plankton and
aquatic
invertebrates.
Growth influences the value assigned to the density rating. Density is rated
higher
when accompanied by good growth because density is not likely to be the
limiting factor.
Growth indirectly influences age structure by determining at what age
crappie become
vulnerable to angler harvest. Faster growing crappie become vulnerable to
angling
mortality sooner. Growth rate also influences the value of recruitment.
Recruitment is
rated higher when accompanied by good growth since density is not likely to
be a
limiting factor.
AGE STRUCTURE
The age structure of a population is the result of recruitment and mortality
(fishing
and natural). Age structure is most useful as an indicator of mortality and
may be our
best indicator of recruitment, although it takes 1 to 2 years for a year
class to show an
effect. The management objective for age structure is at least 10% of the
population comprised of Age-3 and older crappie. Colvin and Vasey (1986)
used
percentage of Age-4 and older as an indicator of age structure for
Missouri’s crappie
populations. Boxrucker (1989) found the highest mortality of Oklahoma
crappie to occur
before Age-3. Current data indicates Arkansas’ annual mortality is similar,
therefore, the
percentage of Age-3 and older crappie (excluding Age-0 fish) is used to
assess age
structure.
Higher assessment values are assigned to age structure when growth is good.
An
adequate forage base as indicated by good growth will allow for a higher
density of
older, larger fish. High age structure (>25% of adult fish 3+ or older)
indicates strong
recruitment, relatively low angler harvest, and a higher proportion of
larger fish when
growth is good. Low age structure (<10% of adult fish 3+ or older) combined
with good
growth indicates relatively high angler harvest, high natural mortality,
and/or missing
year-classes. Inconsistent recruitment and single year-classes moving
through the
population most likely cause variability in age structure within a lake.
SIZE STRUCTURE
Size structure, the percent of fish greater than 250-mm (10”) excluding YOY,
indicates the percentage of desirable fish available to the angler. Size
structure is
dependent upon recruitment, growth rate, and mortality. It is related to age
structure
since older fish are larger whenever there is sufficient forage.
Size structure is considered optimal if 30-59% of crappie are greater than
250mm (10”). Fewer points are awarded to higher values of size structure
because a
high percentage of large crappie also indicates lowered numbers of younger
fish and
possible missing year-classes. Missing year-classes can cause negative
effects to the
size structure for several years.
High scores for size structure are assigned to a wider range of percentages
when
density is high. In a dense population, high percentages of large fish are
less likely to
indicate missing year-classes.
Size structure assessment is useful in predicting the effectiveness of a
length limit.
For example, a 10” minimum length limit would be less effective when the
size structure
is either very low or very high relative to the age structure. A truncated
size structure
dominated by numerous small fish, relative to age structure, indicates a
lack of forage
and possible stunting. A size structure dominated with a few, large crappies
may
indicate a missing year class.
RECRUITMENT
Recruitment, the number of (YOY) crappie per net-night, is variable between
lakes
and may not accurately describe abundance. Within the same lake, however,
recruitment should be consistent from year to year.
Catch rates of 4 to 29 crappie YOY per net-night is considered optimal.
Recruitment values provide insight into year-class strength. When growth is
good, high
values are given to a wider range of percentages because density is less
likely to be the
limiting factor. Low recruitment (very near 0) probably indicates low
densities of YOY
and potential missing year-classes, while high values are often associated
with lakes
that display higher crappie densities and slower growth. Boxrucker (1989)
suggested
that excessive recruitment may adversely affect growth, but is sometimes
unclear and
usually restricted to the first and second year of growth. Low recruitment
or missing
year-classes also reduces the numbers of fish available to fishermen and the
numbers of
spawning adults.
Recruitment directly affects density, size structure and age structure.
Because
trap nets may not sample Age-0 in proportion to their true abundance, the
contribution of
this metric to the assessment value is reduced. Age structure may be a more
accurate
indicator of recruitment, although, it takes 1 to 2 years for a year class
to show an effect.
In summary, an optimal crappie population in Arkansas will exhibit a growth
rate of
201-mm to 275-mm at Age-2+, have a size structure (percent > 250-mm) above
30%,
and show consistent recruitment. These metrics are minimally sufficient to
describe a
good crappie population. Age structure, growth, and mortality estimates are
needed to
determine the suitability for enacting minimum length limits and/or other
harvest
regulations.
Of the 12 lakes that we have more than 1 year’s data, 4 lakes (Overcup,
Harris
Brake, DeGray, Lake Charles) exhibited metrics described for a good
population. Bear
Creek Lake has a high size structure assessment value, but a high growth
rate may
indicate less than optimal density. Horseshoe and Felsenthal both display
low growth
rates and possible stunting. Lakes Beaver, Bob Kidd, Nimrod, and Horseshoe
all show
large variations in age structure probably due to inconsistent recruitment
and missing
year classes.
Harvest regulations and management strategies are recommended to shift
crappie
populations toward what is considered a good population, as previously
described
(Figure 1). This chart outlines a consistent and objective way of assessing
crappie
populations, which will help fish managers identify problem areas and direct
them
towards needed research and management activities. Harvest regulations
assume
angling exploitation is significantly impacting the size and age structure
of a crappie
population. Crappie 10-inches and larger provide considerably more benefit
to anglers
than do smaller crappie. Ten inches was considered to be the minimum size
that should
be harvested by anglers based on length-weight relationships showing that
white and
black crappie begin adding proportionally more weight per unit length when
they are 8 or
9-inches long. According to Mark Zurbrick, (Missouri Department of
Conservation pers.
comm.), fifteen 10-inch crappie will weigh more than twenty 9-inch crappie.
Durocher
(1990) found that 8-inch crappie would double in weight if allowed to reach
10-inches.
Restrictive size limits can perform an important role in managing crappie
populations.
The success of restrictive size limits meeting certain
managementobjectives for crappie populations has varied among water bodies (Colvin
1991; Larsonet al. 1991; Webb and Ott 1991; Mitzner 1995; Boxrucker 1999).
Length limits
are
probably the most effective tool for controlling crappie harvest, because
creel limits
which are likely to be acceptable to anglers (>15 fish/day) do not
significantly affect
crappie population characteristics (Allen and Miranda 1997). Length limits
can also
increase average weight of fish harvested by anglers without a considerable
decrease in
yield. Allen and Miranda (1995) evaluated published data from crappie
populations
across the southeastern and Midwestern U.S., and indicated that only under
conditions
of rapid growth and low natural mortality would minimum length limits
improve yield in
crappie populations. In addition, crappie populations with slow growth or
high natural
mortality are probably best managed without a length limit.
Crappie populations are dynamic and greatly influenced by annual
recruitment.
Evaluation of a crappie length limit may be misinterpreted when population
or creel
survey data is used, since they are influenced by highly variable
recruitment. Colvin
(1991) reported that poor recruitment prevented an accurate assessment of a
crappie
length limit in a Missouri reservoir. Webb and Ott (1991) discovered that a
10-inch
minimum length limit improved crappie fisheries in three reservoirs,
however, postevaluation
after the limit was established indicated that it was short-lived (3-4
years).
The use of population modeling programs such as MOCPOP or FAST can assume
constant or variable recruitment and predict long-term effects on harvest
prior to the
implementation of minimum length limits. The results of modeling can then be
evaluated
by subsequent collections of field data. Maceina et al. (1998) effectively
used a
Beverton-Holt equilibrium yield model to predict the effects of four
different crappie
length limits in Weiss Lake, Alabama. They found that a 10-inch minimum
length limit
would increase yield of crappie, only if conditional natural mortality rates
were less than
35%. However, anglers would also have to accept a decrease in their creel
limit in
exchange for the increased average weight of crappie.
Recruitment from fry into the adult population and subsequent growth appears
partially dependent on predators, primarily largemouth bass. High predator
densities
may reduce crappie recruitment due to intense predation, in which surviving
crappie are
fast growing and reach large size.
In lakes with dense, slow growing crappie, relaxed creel limits could be
beneficial. If
aquatic vegetation or turbidity is causing inefficient predation, these
conditions should
also be controlled.
Finally, anglers on a particular water body may desire higher numbers of
smaller
fish, and knowledge of angler preference when minimum length limits are
being
investigated should be an important consideration for the fishery manager in
the
decision-making process. Due to the various growth and natural mortality
rates of
crappie populations across the state, statewide length limits may be
detrimental and
result in substantial reductions in yield to some fisheries. Therefore,
statewide length
limits are not a recommended management strategy for Arkansas crappie
populations.
Predator/Prey Manipulation.
The need to improve crappie growth rates in reservoirs has been the focus of
many
management efforts. The strategies used typically involve manipulation of
the
predator/prey balance. This is especially challenging when dealing with
species such as
crappie which are both planktivorous and piscivorous (after reaching
approximately six
inches in length) for significant portions of their lives. A management
strategy that
favorably affects the planktivorous life stage may have no effect or
possibly a negative
effect on the piscivorous life stage.
The introduction of threadfin shad as supplemental forage for a crappie
population
has been met with mixed results. Supplemental stocking of threadfin shad may
adversely impact young crappie in a population. Competition for plankton
between
threadfin shad and young crappie can occur if shad densities are too high.
Kansas
Game and Fish Commission cut their stocking rate of threadfin shad from 25
per hectare
to 12.5 per hectare because of possible problems with competition for
zooplankton on
Osage Lake (Mosher 1984).
Over winter survival and availability of threadfin shad broodstock are viable
concerns
for the fisheries manager. Sustained winter water temperatures below 41
degrees
Fahrenheit are lethal to threadfin shad and will occur in Arkansas lakes
during some
winters.Threadfin shad have also been shown to be valuable prey for crappie (McConnel
and Gerdes 1964; Bartholomew 1966; May et al. 1975; Hepworth and Pettengill
1979).
Some studies have documented growth of larger piscivorous crappie following
supplemental stocking of threadfin shad. These growth gains were most
notable in
systems where forage was deficient before threadfin shad introductions.
Because many
Arkansas lakes and reservoirs already contain adequate shad forage, shad
introductions
may not be beneficial.
Boxrucker (1987) reported the population of crappie in Thunderbird
Reservoir,
Oklahoma improved after the introduction of saugeye. It appeared the
improvement of
crappie population structure was the result of a density dependent growth
response
resulting from predation on crappie by adult saugeye. Horton and Gilliland
(1990) found
that saugeye in Thunderbird Reservoir began feeding on crappie after
reaching 350-mm
(14 inches) and that crappie comprised more than 60% of the diet of saugeye
greater
than 525-mm (21 inches). Saugeye became significant predators of crappie
after
reaching 457-mm (18 inches). This information, along with concerns regarding
overharvest of “needed predators” led to the implementation of an 18-inch
minimum limit
for Thunderbird Reservoir saugeye.
Fisheries managers should consider interactions of adult saugeye and
existing
predator populations. In systems with high shad densities, crappie may not
be readily
utilized as forage by the saugeye. If data from Arkansas lakes indicates
bass
populations are not effective predators due to high turbidity or thick
vegetation, saugeye
might also be poor at controlling crappie density.
CRAPPIE STOCKING GUIDELINES
Supplemental crappie stocking has long been used as a management strategy
when overexploitation, increased fishing pressure, or poor recruitment has
led to a
decline in the crappie population. Currently, the Arkansas Game and Fish
Commission
stocks approximately 0.5 million black and white crappie combined in many of
its lakes
and reservoirs annually to improve crappie fisheries. However, Murphy and
Kelso
(1986) suggest that several factors, including post-stocking survival,
determine the
success of any stocking program.
Post-stocking survival of hatchery-reared fish is related to many variables
including
fish size and condition, pre- and post-stocking environments, genetics, and
handling and
transportation processes (Mazeaud et al. 1977; Parker 1986; Williamson and
Carmichael 1986; Wallin and Van Den Avyle 1995). Estimates of initial
post-stocking
mortality rates of crappie reported from only a few studies in the
literature ranged from 0-
100%.
Sammons et al. (2000) assessed initial post-stocking mortality, year-class
contribution, and predation upon recently stocked crappies in seven
Tennessee
impoundments. Their initial post-stocking mortality rates for crappie ranged
from 0-95%,
averaged 16%, and were most heavily influenced by extreme hauling densities
(144g/L).
Exposure to stresses such as poor water quality and overcrowding during
removal from
hatchery ponds likely influence initial crappie survival and should be
considered to
improve the stocking process.
Year class contribution is commonly used to evaluate the effectiveness of a
stocking
program (Boxrucker 1986; Heidinger and Brooks 1998; Sammons et al. 2000).
Year
class contribution and survival of stocked fish has been shown to vary from
lake to lake
and from year to year within the same waters (Fielder 1992; Elrod et al.
1993; Heidinger
and Brooks 1998; Sammons et al. 2000). Crappie year class contribution from
supplemental stocking ranged from 0-93% in seven Tennessee impoundments, and
indicates that supplemental crappie stocking is not successful in all
Tennessee
reservoirs (Sammons et al. 2000). Angler creel data also indicated that in
one
Tennessee reservoir only 1% of stocked crappies since 1995 had contributed
to the
fishery through 1998, while in another reservoir stocked crappies
contributed
significantly to angler’s creel during the same time. Predation by resident
piscivores on
stocked crappie was a primary factor suspected of limiting stocking success
in some
Tennessee impoundments.
Predation on stocked fishes by resident predator fishes has been commonly
theorized (Fielder 1992; Elrod et al. 1993). The occurrence of stocked
crappies in
predator stomachs containing food ranged from 14 - 41% in five Tennessee
reservoirs
(Sammons et al. 2000). Size of stocked crappie may have increased predation
risk,
because stocked black crappie were on average 30% and 40% smaller than black
and
white crappies found in the wild at the time of stocking. Sammons et al.
(2000)
suggested that high predator densities in some Tennessee impoundments are a
significant factor limiting supplemental crappie stocking success.
Success of stocking contributions have been shown to vary with fluctuations
in
natural year-class strength, in which highest contributions from stocked
fish developed in
years when natural recruitment was low (Heidinger and Brooks 1998). In
Normandy
Reservoir, Tennessee where supplemental crappie stocking was shown to be
successful, natural recruitment was considered below average (Sammons et al.
2000).
Hence, when strong year-classes are present in the fishery, stocking
contributions are
less likely to be effective.
The effectiveness of stocking crappie to supplement missing year classes or
poor
recruitment is currently being evaluated in Arkansas (S. Lochmann,
University of
Arkansas at Pine Bluff, unpublished data). Early results suggest that there
should be
some clear guidelines for stocking crappie in Arkansas’ waters.
1. Crappie should be stocked according to the most successful or dominant
crappie
species in the lake. If the lake is dominated by a particular species, then
the
environmental conditions of the lake are apparently more favorable or
conducive for
that species recruitment and survival.
2. Crappie handling and hauling mortality needs to be minimized to 10-20%.
Handling/hauling mortality estimates in the Lake Chicot Crappie Study ranged
from
1-40%, while the Tennessee study ranged from 0-95% with an average of 16%.
Unless handling/hauling mortality is minimized, time, money, and manpower
are
being misappropriated by supplemental stocking crappie in Arkansas waters.
3. Crappie should not be stocked in lakes where Age-0 to Age-1 mortality is
high. If
the annual mortality rate of Age-0 crappie in the natural population is
high, then it is
likely that stocked crappie will have a similar high mortality rate due to
poor
conditions such as lack of adequate forage, habitat, or high predation.
Fishery
managers can determine mortality rates of Age-0 to Age-1 from cove rotenone
samples conducted over time.
4. Crappie should not be stocked in lakes during years of high natural
recruitment,
because supplemental stocking is not likely to make a significant
contribution to the
year class. For example, if a lake has a natural reproduction of 500
fish/ha, then
stocking 50 fish/ha (10%) would not make a reasonable contribution to the
year
class. This practice would allow for crappie supplemental stockings to be
reallocated to lakes where natural reproduction was unsuccessful.
STOCKING RATE
There is good evidence that supplemental stocking of crappie during years of
unsuccessful reproduction and suitable conditions, such as low initial
post-stocking
mortality and decreased predator densities, can make up a reasonable high
proportion
of missing year-classes (Sammons et al. 2000). Currently, the Arkansas Game
and Fish
Commission stocks approximately 0.5 million black and white crappie combined
in many
of its lakes and reservoirs annually to improve crappie fisheries. The
decision to
supplementally stock a lake will be based on a combination of technical
analysis of
sampling data and social considerations. Lakes with high natural mortality
or high
occurrence of Age 0 crappie will be considered poor candidates for
supplemental
stocking. New lakes and lakes exhibiting poor natural spawns are considered
the best
candidates for stocking. Crappie should be stocked in the fall/winter during
the year in
which natural recruitment was poor in an effort to make a significant
contribution to the
missing year class.
Prioritization of lakes is warranted due to requests for crappie being
greater than the
number produced by the hatchery system. Therefore, new and renovated lakes
have
the highest priority for crappie stockings and should be stocked at a rate
at or near
250/ha (100/acre). Supplemental stocking justification varies on technical
and social
needs as well as hatchery capabilities. Stocking rates are provided as
guidance only to
be considered in the matrix of population needs, social needs, and hatchery
capabilities.
Lakes under 1,215 ha (3,000 acres) will be given next priority and will be
stocked at a
rate of up to 125/ha (50/acre). Finally, lakes ranging in size from 1,215 to
4,050 ha
(10,000 acres) will be stocked at a rate of up to 62/ha (25/acre). Lakes
over 4,050 ha,
including Corp of Engineer impoundments, should only be stocked through the
nursery
pond system to optimize hatchery production space.
NURSERY PONDS
Nursery ponds will be utilized for supplemental crappie stocking when
located on
reservoirs, including Corps of Engineer impoundments, where stocking is
requested.
This will free up hatchery pond space for other species due to the length of
crappie
production (March-October) and also decrease handling/hauling mortality.
However,
crappie may not be needed every year if lakes are capable of producing
adequate
natural spawns, therefore, District Fisheries personnel may choose to
reallocate pond
space to other species, which could benefit from the nursery pond. District
Fisheries
personnel are strongly encouraged to use other means such as lake
fertilization, water
level manipulation (controlled winter drawdowns), and habitat improvement to
enhance
crappie recruitment. Crappie brood stock collection for the nursery ponds
will also be
the responsibility of District Fisheries personnel.
LAKE FERTILIZATION
Lake fertilization is a widely accepted technique used to improve fish
populations.
The fertility or richness of the water determines the productivity of the
lake, and a more
productive lake will support more fish. Fertilizer increases lake
productivity by
stimulating the growth of microscopic plants known as phytoplankton.
Phytoplankton is
the basis of the food chain and is a primary food source for many larval
fishes.
Increases in phytoplankton will increase the production of zooplankton,
which ultimately
increases fish production. This is especially important to crappie, which
are primarily
planktivorous feeders until they reach a length of 150-mm (6-inches) and
then switch to
a more piscivorous diet. Upper and Lower White Oak Lake has been fertilized
since
1978 and 1988 respectively, and has resulted in a 4-5 fold increase in the
number of
crappie YOY/hectare produced since the fertilization program began (D.
Turman, AGFC,
unpublished data).
DRAWDOWNS
Controlled winter drawdowns administered every four to five years is an
effective,
low cost management tool that provides several positive benefits to a
crappie population.
Nutrients tied up in exposed substrate are oxidized and released back into
the system
when the lake is refilled, resulting in a natural lake fertilization.
Reduced lake area
concentrates fish and allows for heavy crappie predation on forage species
and
increases in angler success and harvest. Winter drawdowns are also useful in
controlling, by freezing, undesirable or expanding aquatic vegetation. For
greatest
effectiveness, drawdowns should be conducted from August through January and
expose from 40-50% of the lakebed, which can usually be achieved with a 4-6
foot
drawdown.
HABITAT MANAGEMENT
Fishery biologists have long suspected that reservoir hydrology influences
crappie
reproductive success and contributes to the cyclic nature of these
fisheries. Successful
reproduction and recruitment of fishes has been linked to years when high
water levels
provided more spawning sites and protective cover for larval fish (Bennett
1954, 1970;
Bross 1969). Side channels and backwater areas have been shown to provide
prime
habitat for a variety of fish species (Bade 1980; Pitlo 1992).
Drawdowns or dewatering of backwater areas during spawning can result in
marked
reductions in habitat size and quality, including temporary loss of the
littoral zone and its
associated vegetation. The temporary elimination of the littoral zone can
also result in
the loss of juvenile fish, because they use littoral zone aquatic vegetation
as shelter from
adult piscivores (Werner et al. 1983). Dewatering can also reduce
availability of
spawning substrate, and expose nests with eggs and larval fish to drying
conditions.
Ploskey (1986) found that spawning success for most littoral species was
positively
related to water level increases during the spawning period because
additional spawning
habitat was produced for adults, and increased food and habitat resources
were
available for larval fish.
It is widely recognized that management strategies designed to improve
crappie
populations and harvest is dependent primarily upon water-level management.
Therefore, the Arkansas Game and Fish Commission will actively pursue
opportunities
to positively influence water control policy and operations on Federal water
project lakes
to benefit crappie fisheries.
HABITAT IMPROVEMENT
Lake managers have long recognized the advantages of structure to attract
and
hold fish. The primary purpose of fish shelters or attractors is to
congregate fish to
improve fishing success for anglers. Fish can also be encouraged to spawn
when
provided with good spawning substrate.
Suitable shelters can be constructed from a variety of materials. Brush,
tires, stake
beds, rock piles, standing timber, and shoreline vegetation all make good
fish attractors.
Establishing native aquatic vegetation in the littoral zone is particularly
useful for
impoundments that lack fish cover, and is currently being studied on Greeson
and Bull
Shoals lakes in Arkansas (C. Horton, AGFC, personal communication).
The placing of fish attractors in large impoundments has been shown to
improve
catch rates and harvest of fish. The Bull Shoals/Norfork Fish Cover Project
installed 600
fish attractors containing over 70,000 trees (M. Oliver, AGFC, personal
communication).
The attractors covered 65ha (160ac) of lake bottom and extended 53 km (33mi)
of
shoreline. Scuba inspection and angler reports indicated that the attractors
were
successful in congregating fish and improved fishing and spearfishing over
control
areas. Short-term evaluation of fish attractors in seven Florida lakes
indicated that areas
with attractors produced significantly higher angler catches than control
areas. Both
number and weight of fish increased after the addition of artificial
structures in Wewoka
Lake, Oklahoma (Wright 1979).
Brush shelters have been shown to be more effective than most other
materials
used to construct attractors. Reef construction from tires, brush, and
cement blocks in
Lake Tohoekaliga, Florida revealed that more fish were observed and caught
around
brush than other materials, but all types of attractors congregated more
fish than open
water control areas.
More recently several artificial shelter designs have come on the market
that are
made from plastic or synthetic materials. Fish attractors made from PVC
tubing were
experimented with in Lake Chicot in 1985, and more recently heavy duty snow
fencing
was used to attract and hold fish. Both materials were successful in
congregating fish
and resulted in increased angler success (J. Smith, AGFC, unpublished data).
Habitat assessments are to be performed on Commission-owned and Federal
water
project lakes to determine crappie habitat needs. Habitat assessment
protocols are to
be developed and feasibility plans are to be drafted and implemented to
address the
needs as budget and resources allow. Fisheries Division will actively pursue
opportunities to implement appropriate crappie habitat improvement projects
with the
general goal of improving habitat statewide.
1. No management plan is complete without proper evaluation. Management
strategies suggested in this plan should be appropriately evaluated after
exploitation
studies have been initiated, population modeling has been conducted, harvest
restrictions have been imposed, or creel surveys have been completed.
Evaluation
of additional trap netting data using the Crappie Stock Assessment will
yield further
information regarding the effectiveness of the management plan.
2. Natural mortality rates of Age-0 to Age-1 crappie should be derived by
fishery
managers to assess where supplemental stockings will be most beneficial.
3. Handling and hauling mortality of crappie should be estimated and reduced
by
hatcheries to minimize post-stocking mortality to 10-20%.
4. Crappie marking techniques, such as six-hour oxytetracycline baths,
should be
investigated for supplemental stock identification purposes. Once a
desirable
marking technique is accepted, future contributions of stocked fish to
year-classes
can be evaluated.
5. Fishery managers should re-evaluate current crappie minimum length limits
using
population modeling programs.
6. A Crappie Recruitment Model is needed to determine what variables are
having the
greatest impact on crappie recruitment in Arkansas waters. The model would
potentially help fishery managers identify those problems in reservoirs
where
corrective management could be applied, and would also help in predicting
missing
year-classes and thus, supplemental stocking guidelines on an annual basis.
7. Fishery managers should explore the use of other sampling techniques such
as the
larger 8’ x 8’ or 6’ x 6’ floating trap nets and spring/fall electrofishing
in lakes where
standard trap net gear has been ineffective at sampling the crappie
population.
RESOURCE NEEDS
1. Trap net boats and motors ($6,000) replaced as needed
2. Trap nets ($475/net) replaced as needed
3. Dissecting Microscopes
4. Ocular micrometers
5. Data reduction and analysis software for trap nets (currently being
developed).
6. Exploitation/Tag Reward studies ($2,500/each)
7. Continuing Education workshops on population modeling
8. Develop standardized protocol for assessing habitat needs in Arkansas
lakes.
Upper White Oak
1993 0.68 287 18.03 22.95 30.33 61.25
Lower White Oak
1993 0.06 265 0 16.67 1.92 33.75
Lake Charles
1993 3.2 264 13.75 25.6 0.68 58.75
1994 9.3 260 12.4 26.5 0.65 62.5
==========================================
TABLE 2. ARKANSAS CRAPPIE POPULATION ASSESSMENT
Number per Trap Net-Night (excluding YOY)
0-2 3-4 5-9 10-19 20-29 30-39 >40
Density 1 2 5 8 9 8 5
(good growth) 1 2 5 8 10 10 10
(poor growth) 1 2 3 4 4 3 2
Mean Length (mm) at Age 2+
151-175 176-200 201-225 226-250 251-275 >275
Growth Rate 1 4 8 10 8 6
(w/ good density) 2 6 9 10 10 10
Percent Age 3 and Older (excluding YOY)
<4.9 5-9.9 10-14.9 15-19.9 20-24.9 >25
Age Structure 1 4 8 10 8 6
good growth 2 5 9 10 10 8
Percent Over 250-mm (10”) (excluding YOY)
<10 10-19 20-29 30-39 40-49 50-59 >59
Size Structure 1 3 5 8 10 8 5
good density 1 3 7 10 10 10 8
Number of Age 0 per Trap Net-Night
<1.0 1.0-1.9 2.0-3.9 4.0-9.9 10-18.9 19-29.9 >29.9
Recruitment 1 4 6 8 9 8 4
good growth 1 4 6 10 10 10 6
good growth Mean Length At End of 3rd Growing Season (2+) >250mm.
poor growth Mean Length At End of 3rd Growing Season (2+) <201mm.
good density At Least 20 Age 1 and Older Per Trap Net-Night.
To Calculate Total Assessment Value (Maximum 100) sum:
Value for Number per Trap Net-Night X 1.25 =
Value for Mean Length At Age (2+) X 2.50 =
Value for Percent Age 3 and Older X 2.50 =
Value for Percent Over 250 mm (10”) X 2.50 =
Value for Number of Age 0 per Trap Net-Night X 1.25 =
29
Total Assessment Value =
FIGURE 1. Management strategies for crappie populations under various
population
structure conditions.
START
GROWTH RATE
Mean Length @ Age 2+
<200mm 201-275mm >275mm
Crappie length limits
Crappie stocking
Decrease predator population
Relax predator creel limits
Relax crappie creel limits
Enhance predator populations
Impose predator creel limits
Predator stocking
Control aquatic vegetation
Control turbidity
SIZE STRUCTURE
% Fish > 250 mm
<30% >30%
No change recommended
AGE STRUCTURE
% Fish = 3+
<10% >10%
Habitat improvement
Forage stocking
Fertilization
Drawdowns
Crappie length limit
Crappie stocking
Decrease predator population
Relax predator creel limits
Exploitation studies
Population modeling
Exploitation studies
Population modeling
DENSITY
# of Fish / Net Night > 1+
<20 >20
No change recommended
RECRUITMENT
# of YOY / Net Night
<4 >4
AGE STRUCTURE
% Fish = 3+
<10% >10%
No change recommended
30
REFERENCES
Allen, M. S., and L. E. Miranda. 1995. An evaluation of the value of harvest
restrictions in
managing crappie fisheries. North American Journal of Fisheries Management
15:766-772.
Allen, M. S., and L. E. Miranda. 1997. Management of erratic crappie
fisheries. Pages 178-192
in Evaluation of regulations restrictive of crappie harvest. Completion
Report. Freshwater
Fisheries Report Number 163, F-105. Mississippi Department of Wildlife,
Fisheries, and
Parks, Jackson.
AMRA, 1988. Fishermen attitude study. Arkansas Game and Fish Commission,
Little Rock, AR.
Anderson, R. O., 1975. Optimum sustained yield in inland recreational
fisheries management in
P.M. Roedel, editor. Optimum sustained yield as a concept in fisheries
management.
American Fisheries Society Special Publication 9.
Bade, G., editor. 1980. Side channel work group appendix, Great River
Environmental Action
Team II (Great II). U.S. Fish and Wildlife Service, Rock Island, Illinois.
Bartholomew, J.P., 1966. The effects of threadfin shad on white crappie
growth in Isabella
Reservoir, Kern County, California. California Department of Fish and Game,
Inland
Fisheries Administration Report 66-6.
Bennett, G.W. 1954. The effect of a late summer drawdown on the fish
population of Ridge Lake,
Coles County, Illinois. Transactions of the North American Wildlife
Conference 19:259-270.
Bennett, G.W. 1970. Management of lakes and ponds. Van Nostrand Reinhold,
New York, New
York.
Boxrucker, J., 1986. A comparison of otolith and scale methods for aging
white crappie in
Oklahoma. North American Journal of Fisheries Management 6:122-125.
Boxrucker, J., 1986. Evaluation of supplemental stocking of largemouth bass
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