Held, J. A., and J. A. Malison. 1996. Pond culture of hybrid walleye fingerlings. Pages 31 1-313 in 

R. C. Summerfelt, editor. Walleye culture manual. NCRAC Culture Series 101. North Central 

Regional Aquaculture Center Publications Office, Iowa State University, Ames. 

Pond Culture of Hybrid Walleye Fingerlings 

James A. Held and Jeffrey A. Malison, University o f Wisconsin-Madison Aquaculture Program, Department o f 

Food Science, 123 Babcock Hall, Madison, Wisconsin 53706 

Introduction 

Natural hybridzation between walleye and sauger has 

been documented, and hybrids have been artificially 

propagated (Nelson et al., 1965; Colby et al., 1979). 

Here, we will use the term hybrid walleye (otherwise 

known as "saugeye") to refer to the progeny of the cross 

between walleye female x sauger male, and the term 

reciprocal cross to refer to the cross between sauger 

female x walleye male. Our laboratory has produced 

both hybrids since 1986, and our first report was a 

comparison of survival, growth, and reproductive 

development of walleye, sauger, and their hybrids 

(Malison et al., 1990). In this study, and in subsequent 

work with hybrids, we have used fertilization, incubation, and culture practices similar to those employed for 

purebred walleye production. 

extender (Moore 1987) retains good motility for up to 

14 d when stored in oxygen and under refrigeration 

(3540°F [24"C]). In our storage protocol, a thn layer 

< 0.2 in [OS cm] in depth of extended semen is kept in 

a screw cap NalgeneQ container and oxygenated every 

other day. For both walleye and sauger good sperm 

motility is characterized by an excited response of 

virtually 100% of the cells lasting for at least 15 s after 

activation with water. As the quality of the semen 

degrades, both the number of respondmg cells and the 

duration of their activity diminish. When using undiluted semen obtained from outside sources, we have 

found that motility, and therefore success at fertilization, decreases rapidly with age, even if such samples 

are stored under similar conditions as extended semen. 

In adhtion, traces of blood and other contaminants in 

the semen reduce the length of time that semen can be 

successfully stored. 

Spawning, fertilization, and incubation 

Initially, hybrids were the offspring of ripe walleye 

captured from Rock Lake, Jefferson County, WI, and 

ripe sauger captured from the Mississippi River (from 

northern Iowa and central Minnesota), the latter with 

the help of the Minnesota and Iowa Departments of 

Natural Resources, and the U.S. Fish and Wildlife 

Service. Following capture, the broodfish were transported to our aquaculture facility located at the Lake 

Mills State Fish Hatchery, Lake Mills, WI, and held 

indoors in 200-gal (750-L) circular tanks supplied with 

well water at 52°F (1 1 "C). Ultimately, we produced and 

maintained captive, fertile broodstocks of walleye, 

sauger, and both hybrids, and evaluated various 

performance traits, as well as reproductive development 

and sexual expression. 

To produce hybrid walleye, eggs were stripped from 

female walleye into a slightly dampened plastic bowl. 

Semen was collected from at least three male sauger, 

pooled, and added to the eggs. We have used stored 

semen with good success; semen &luted 1:4 with 

Water (52°F [1 1"Cl) is added to activate both the eggs 

and sperm, and the eggs are gently swirled in the bowl 

for 45 s to allow fertilization to be completed. A 

suspension of bentonite (a slurry made by mixing 

powdered bentonite and water to a creamy consistency) 

is added to prevent clumping, and the swirling is 

continued for an additional 2 min. The eggs are then 

rinsed repeatedly to remove excess semen and bentonite, and are allowed to water harden for 2 h. Waterhardened eggs are transferred into the traditional 

McDonald jars for incubation. On occasion we added 

eggs to jars prior to water-hardening, with no apparent 

reduction in hatching success. We incubate the eggs 

under a gradually increasing temperature regimen (+ 

1 "F [0.5OC] daily, from 52-59°F [ 11-1 5"C]), which 

results in an incubation period of approximately 1 1-1 3 

d. Eggs are treated with formalin (1: 1000 static bath for 

15 min) once daily to inhibit fungal growth. 

One difference noted during the fertilization and 

incubation of purebred and hybrid walleye and sauger is 

that the eggs obtained from sauger females are signifiNCRAC Culture Series 101 - Walleye Culture Manual 31 1 
Chapter 12 - Hybrid Walleye 

cantly smaller than those from walleye. When measured 

by volumetric dsplacement, we calculated sauger eggs 

to be 208,00O/qt (220,OOO/L), and walleye eggs 90,000/ 

qt (95,OOOL). These calculations were based on 

subsamples of a pool of water-hardened eggs taken 

from no less than five females. Many factors affect egg 

size, and variability as high as 30% may be observed 

from batch to batch. 

Sauger eggs are often very adhesive both prior to and 

just after water is added, forming clumps much more 

reahly than walleye eggs. We found that a solution of 

protease (Sigma Chemical Co., St. Louis, MO, Product 

No. P-4630) can be used very successfully to break up 

the clumped eggs. The 0.1 % (1 gL) solution, added to 

the eggs 3 min after fertilization, breaks down the 

clumps within 5 min. The eggs are then rinsed with 

water and are no longer adhesive. 

As one might expect from the comparative sizes of the 

eggs, larvae derived from sauger eggs (sauger and the 

reciprocal cross) are smaller than those of walleye or 

hybrid walleye. In one study, hatching success for the 

reciprocal cross was similar to that for purebred sauger 

(48.0f5.6% and 50.3f5.9%, respectively), both of 

which were lower than that for the purebred and hybrid 

walleye (78.0*6.1% and 79.3*5.9%, respectively). We 

initially attributed this difference to the greater adhesive 

quality of sauger eggs coupled with our relative lack of 

experience in worlung with sauger. However, occasional reductions in hatching success of subsequent 

broods of protease-treated sauger eggs suggest that 

sauger eggs may be more sensitive to collection and 

propagation procedures than walleye eggs. Alternatively, innate differences (e.g. fertility, egg maturity, 

etc.) may be responsible for the differential hatching 

success. 

Pond culture 

shortly after hatch (4-1 6 hr), the fry are stocked into 

fertilized ponds at a rate of 70-1 00,00O/acre (1 75- 

250,000ha). Just prior to stoclung, small volumetric 

subsamples are taken from water-filled buckets containing the fry to be stocked. The number of individual fry 

are counted within each subsample and the resulting fry 

concentration is used to calculate the number of fry in 

each bucket, and ultimately the number of fry stocked 

into each pond. During sampling, water in the stocking 

bucket is agitated to ensure uniform hstribution of the 

fry. 

We attempted to adjust hatchery water temperature to 

within a degree or two of expected pond temperature at 

hatch, however, spring weather fluctuations make exact 

matching of water temperatures an elusive goal. When 

stocking the fry, water in the stocking bucket is finally 

equilibrated to pond temperature by partially submerging the bucket and introducing small amounts of pond 

water into the bucket over the course of approximately 

15 min. Fry are stocked at various points around the 

perimeter of the production pond. 

Fingerling production ponds at the Lake Mills hatchery 

are unlined and range in size from 0.5-1.5 acres (0.2- 

0.6 ha) with an average depth of 4 ft (1.2 m). Two 

weeks prior to hatch, the ponds are filled with water 

from nearby Rock Lake that has been filtered through a 

125 micron rotating drum screen. Ponds are then treated 

with organic and inorganic fertilizers in the following 

manner. Immediately after filling, 250 lb (1 14 kg) 

soybean meal, 10 lb (4.5 kg) phosphoric acid (54% 

P20,), and 5.6 lb (2.5 kg) urea (46% N) are applied to 

each surface acre (0.4 ha). Subsequently, ponds are 

fertilized once per week with 50 lb (22.7 kg) soybean 

meal, 5 lb (2.3 kg) phosphoric acid, and 2 lb (0.9 kg) 

urea per acre (0.4 ha). These quantities are general 

guidelines, and modfications in both the timing and 

level of fertilization are typically made in response to 

the phytoplankton and zooplankton populations of 

specific ponds, which are highly weather-dependent. 

Fingerling size is the primary factor taken into consideration when timing pond harvest. Harvest size is 

usually determined by the disposition of the fingerlings 

after harvest and the requirements of the end users. 

Fingerling growth rates are often influenced by pond 

stocking densities, with lower densities ultimately 

yielding larger fish. We have found that the habituation 

of walleye, hybrid walleye, and sauger fingerlings to 

formulated feed and intensive culture conditions is most 

successful when fingerlings are harvested at 1.2-1.4 in 

(30-35 mm) total length. Additionally, the relative 

condition factor of the fish, together with pond characteristics such as water temperature, dissolved oxygen 

levels, prey abundance, and macrophyte concentrations, 

are important considerations when deciding to harvest a 

31 2 NCRAC Culture Series 101- Walleye Culture Manual 
Hvbrid Walleve - Chanter 12 

pond. Ponds are usually harvested by drawdown, 

however when partial harvests are required, capture 

methods such as fyke nets or light traps can be used 

successfully. 

Pond fingerling production is highly variable for many 

reasons, and we have not conducted a scientific 

comparison (with sufficient replicates) on the pond 

production characteristics between walleye, hybrid 

walleye and sauger. Our observations suggest that 

hybrid walleye fingerlings are generally larger and have 

a hlgher condition factor than purebred walleye cultured 

in similar ponds. 

The improved growth performance and docile nature 

exhibited by the hybrid walleye in our initial studies has 

lead to further studies involving hybridization of 

walleye. Together with Robert Summerfelt at Iowa State 

University we are currently undertakmg growth stuhes 

comparing hybrid walleye produced using broodstock 

from different geographc origins. Initial observations 

from this work indicate that there may be performance 

differences between the various crosses, and that these 

differences may be important considerations to walleye 

aquaculturists. 

References 

Colby, P. J., R. E. McNicol, and R. A. Ryder. 1979. 

Synopsis of biological data conditions. Progressive 

Fis h-Cu It u rist 52: 73-82. 

Moore, A. A. 1987. Short-term storage and 

cryopreservation of walleye semen. Progressive FishCulturist 49:40-43. 

Nelson, W. R., N. H. Hines, and L. G. Bergman. 1965. 

Artificial propagation of saugers and hybridization 

with walleye. Progressive Fish-Culturist 27:216-218. 

NCRAC Culture Series 101 - Walleye Culture Manual 31 3 
Chapter 12 - Hybrid Walleye 

31 4 NCRAC Culture Series 101- Walleye Culture Manual