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5 - Management Actions

Predator/Prey Manipulation

The need to improve crappiei 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).
Overwinter 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 Reservoiri, 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.
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-
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. 19
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). Angleri 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 20
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.
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. 21
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 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 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 22
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).
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
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 23
to positively influence water control policy and operations on Federal water project lakes
to benefit crappie fisheries.
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 Coveri 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 24
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.

Information Provided by Arkansas Game and Fish Commission

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