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Production of Walleye As Potential Food Fish by R.C

Production of Walleye As Potential Food Fish by R.C

North Central Regional Aquaculture Center

Production of as Potential Food by R.C. Summerfelt, R.D. Clayton, J.A. Johnson, and R.E. Kinnunen

alleye is a prized sport Because of their popularity and distribution, brokerage fees, or and food fish and is limited supply, walleye are a markup required by other retail Woften on the menu high value species, with retail markets. of white tablecloth restaurants prices in the range from $6 to throughout the / 12/lb ($13 to 26/kg) for skin-on The well-developed commercial North Central Region (NCR) of markets for walleye and its high the U.S. Commercial fisheries for walleye in the Canadian por- tion of , inland lakes in , and a few tribal fisher- ies in U.S. These sources pro- vide fish that are distributed by brokers for retail food chains and restaurants. The Marketing Corporation (FFMC) of Win- nipeg, Canada, purchases 7 to 11 million lbs (3.2 to 5 million kg) of walleye each year, and then processes, packages, and Figure 1. Supermarket price of skin-on walleye fillets in central Iowa, compared markets them to the U.S. The with that of other species. FFMC purchases most fish from Aboriginal fishers. fillets, equivalent to the priciest market value suggest an oppor- in Midwest supermar- tunity for fish farms to culture kets (Figure 1). walleye for food-fish markets. The small producer must under- How valuable are stand that the quantities of fish cultured walleye? needed for a full-time processing As a point of reference, in July facility will exceed their produc- 2008, tribal fishers received tion, and that they will rarely North Central Regional $2.00/lb ($4.40/kg) for whole have the opportunity to market Aquaculture Center wild caught walleye from a to chain supermarkets or fran- Fact Sheet # 116 processing facility; chise restaurants. USDA Grant #2003-38500-12995 the processor retailed the fillets July 2010 for $6.00/lb ($13.20/kg). There were no additional costs for

1 Inevitably, the small producer How are walleye currently used for production of other must master direct marketing to cultured? species (e.g., hybrid striped , consumers and to farmer's mar- The majority of walleye cul- yellow ). kets, in addition to periodic sales tured by both public and pri- Private producers of walleye to local, owner-operated food vate producers are raised to fingerlings have the opportunity markets, and to small but upscale fingerling size to stock lakes for to utilize information on cul- "white tablecloth" restaurants. recreational . There are tural technology for on-growing many commercial producers of After adjustment using the aver- fingerling walleye for a size walleye fingerlings in the NCR, age Consumer Price Index (CPI), suitable for food-fish markets. especially in , and the retail price of walleye fillets Research-based information on Wisconsin, but there are also fin- at supermarkets and specialty production of food-size walleye gerling producers in Iowa, Ohio, fish markets from 1987 to 2010 and hybrid walleye has been and Michigan. Little, if any ranged from $7.63 to $16.95/lb described several times (Sei- food-sized walleye are currently for May 2010 (Figure 2). The gwarth and Summerfelt 1993; cultured in the . slope of the line in that interval Summerfelt and Summerfelt showed an upward trend in the Pond-raised fingerlings can be 1996; Stevens 1996; Coyle et al. price, which is a positive indica- habituated (trained) to manufac- 1997). The economics and mar- tor for potential culture. tured (pelleted) feed in indoor keting of walleye food fish have facilities, then raised to food size been reported by Edon (1994), An effective business plan must Makowiecki (1995), O’Rourke focus as much or more effort in either cages in ponds, indoor or outdoor raceways, circular (1996), Riepe (1998, 1999), on strategies for niche market- and Mahoney (2003). ing as for fish culture. This fact tanks, or recirculating systems sheet describes a cultural process for producing walleye to a size suitable for marketing as a food fish. The reader should examine other North Central Regional Aquaculture Center (NCRAC) publications for economic and marketing information: Hushak 1993; Swann and Riepe 1994; Riepe 1998 and 1999. This fact sheet builds on the foundation of cultural technol- ogy for walleye that has been described in the Walleye Culture Manual (WCM), which is an extensively illustrated reference for walleye culture that was prepared with support from the NCRAC. The WCM is available on the web, www.ncrac.org/Topics/ walleyemanual.htm, and can be Figure 2. Retail price of walleye fillets in central Iowa, 1987-2010. Prices were downloaded, chapter by chapter. adjusted with Consumer Price Index (CPI) to reflect 2010 values.

2 Surveys conducted by Ma- What is the minimum 151 g) yields two 1.1-oz (32-g) honey (2003) in 2000 and 2003 food size for walleye? fillets at a 45% dress out (Hart showed that walleye were the A food fish is defined as the size et al. 2006). Therefore, perhaps clearly preferred fish in con- that is acceptable for the market. markets for would sumer perceptions, scoring the Thus, market size is of major im- also accept walleye fillets of highest in comparison to or- portance for fish culture because similar size. ange roughy, cod, and sunfish the less time it takes to raise in each category of appearance, fish to the required market size Our experience indicates that flavor, mouth feel, and overall. means reduced costs for feed and yield of skinless fillets of differ- operation, and faster turnover of ent cohorts is related to the skill What size walleye is stock. of the technician, the speed at most desired? which fillets are processed, and Frozen skin-on fillets is the Similar considerations have been the relative robustness of the type of walleye purchased by given for striped bass and its hy- fish. the majority of restaurants and brids in South Carolina. Smith wholesalers (Riepe 1998). An and Jenkins (1985) proposed a What system is best for 8- to 10-oz (227-284 g) production model for pan-sized culturing walleye? is the most common/desired (0.66 to 1 lb, 300 to 450 g) fish Walleye are adaptable to both size for both restaurants and that can be produced within a pond and tank culture systems, wholesalers. A skin-on fillet of year in temperate climates; basi- but overwhelmingly, ponds are that size would require a live cally, a model plan for walleye. the cultural system for rearing weight of 1.7 to 2.2 lbs (0.75 to As previously noted the mini- fry to fingerling size for stock- 1.0 kg), assuming a 45% dress- mum size for the current walleye ing. In the NCR, however, it is out yield. market is ca. 4-oz (113-g) fillet. unlikely that producers north of A fish that will yield two 4-oz the borders of Michigan-Ohio, The smallest product in the sur- (113-g) skin-on fillets would Wisconsin-Illinois, Minnesota- vey of Midwest restaurants and require a live weight of 1.25 lb Iowa, or Nebraska-South Dako- wholesalers was a 4-oz (113 (570 g) with 40% yield. Pub- ta, will be able to raise walleye -g) fillet (Riepe 1998). Fillets lished studies have noted higher in ponds to a 0.33-lb (151-g) of this size comprised only 5% yields of skin-on fillets from 43- market size in one growing of the fresh fillets but 20% of 45% (Summerfelt et al. 1996a) season. the frozen fillets purchased by up to 50-55% (G. Fischer, If young of the year fingerlings restaurants, and 12% and 9%, UWSP-Northern Aquaculture are transferred from ponds to an respectively by wholesalers. Demonstration, Wisconsin, per- indoor facility for habituation, sonal communication). Riepe (1998) pointed out that and then maintained over-winter opportunities exist for selling However, to achieve a produc- at a temperature suitable for different sizes of products, but tion model where fish can be growth (≥ 68°F, 20°C) they can walleye producers of food fish marketed in one season (i.e., be grown to a food size in 16 need to shop around to find from spawning to harvest in to 18 months. Summerfelt and buyers willing to accommodate October), a smaller size will Summerfelt (1996) produced in their (i.e., the seller’s) prefer- be required. A 10-in (25-cm) intensive culture a 1.25-lb (567- ences regarding product forms walleye will weigh about 4.8 g) walleye in 16 to 18 months, and sizes. oz (136 g) and a 14-in (35-cm) and Malison et al. (2003) grew walleye will weigh 14 oz (400 walleye in indoor tanks to 0.5 lb g). The standard market size of (227 g), 12 in (30 cm) in 477 d cultured yellow perch (0.33 lb, (~16 months) at 70°F (21°C).

3 What are the desired Phase II. Habituation (train- 3) use a dark room with no tank carcass qualities? ing) pond-reared fingerlings to covers, but with low inten- Besides palatability, dress-out formulated feed in tanks. sity, in-tank lighting situated or carcass yield is an important under the feeder (Rathbun The habituation process has been characteristic for production of Fish Hatchery[RFH] proce- described by Kuipers and Sum- fish for the food market. Skin- dure). merfelt (1994), Flowers (1996), less fillets from tank-cultured Malison and Held (1996), and Fish size and condition: The walleye had protein content of Nagel (1996). RFH in southern Iowa starts with 20.5%, and a fat content of 0.1 to pond-reared walleye that are 0.4%, values which place them Keys to feed training: about 1.8 in (45 mm) total length in the low fat and high protein and weigh 0.02 to 0.03 oz (0.57 category of food (Yager • Culture system with covered to 0.75 g). Survival at RFH and Summerfelt 1996). tanks or a dark room with tanks equipped with sub- during the habituation interval Walleye fillets are generally sold merged lights on a production scale has been as with skin-on (scaled). Relative high as 92%. Whatever the size, to live weight, the yield of skin- • Larger fingerlings to start the fish should be graded to obtain on fillets was 44% for males and habituation process uniform size in each tank. 39 to 41% for two cohorts of • Grading of fingerlings to Water temperature and growth: female walleye from Spirit Lake, uniform size to reduce can- Water temperature during the Iowa (Summerfelt et al. 1996b). nibalism habituation interval will have a Rock Lake, Wisconsin walleye major impact on growth, and that and hybrid walleye (saugeye) • Otohime™ feed (Reid Mari- will ultimately impact the size at had slightly lower yields. Dif- culture, Campbell, Califor- harvest (Table 1). For example, ferences in head weight account nia) for initial habituation at RFH, the temperature during for gender differences in yield of 2007 habituation interval was skin-on fillets—the head weight Tank size: The dimensions of the 6.1°F (3.4°C) warmer than in of males were less than the head culture tank is a matter of econ- 2008, which resulted in 21 g and weight of female fish from Spirit omy of scale, but circular tanks 27 mm (~1 in) difference in size Lake, Iowa. from 5 to 20 ft (1.5 to 6.1 m) diameter have been used. Rect- on October 1, 2008, when the What are the three phases angular tanks are also suitable, fish were harvested. In addition, of walleye production? but circular tanks are self-clean- whereas 91% of the fish at har- Phase I. Fry to fingerling in ponds. ing and are more favorable to the vest in 2007 were greater than condition and health of the fish. 9 in (23 cm), only 63% reached Detailed procedures for pond that size in 2008 (Table 1). culture are described in the Light: Light is a critical issue as Walleye Culture Manual for both walleye are sensitive to light in- Feed and Feeding: Note since drainable (Summerfelt 1996) and tensity. There are three options the publication of the Walleye undrainable ponds (Kinnunen for dealing with light: Culture Manual, BioKyowa Fry 1996). A key to success dur- 1) use uncovered tanks with Feed is no longer available in the ing Phase II is to reduce stock- low intensity (~ 10 lux) over- United States. ing during pond culture (Phase head lighting (Kuipers and I) to produce a fingerling with Summerfelt 1994), During the first 10 d fingerlings good condition. Fingerlings 600 are fed 100% of a specialty diet, to 800/lb (0.76 to 0.57 g) were 2) cover tanks with low inten- preferably the Otohime feed, or obtained with a fry stocking den- sity in-tank lighting (Nagel EPAC (INVE Aquaculture, Inc.). sity of 50,000/acre (20,234/ha). 1996), or Feed size is about 1 mm to start.

4 Although one may be tempted to (Nelson and Sons, Inc., Mur- of feed acceptance, and canni- use a less expensive starter diet, ray, Utah), and availability has balism. Although cannibalism is survival will decrease, cost- been seasonal; however, highly a frequent concern, it generally ing the culturist the price of the specialized diet formulations accounts for much less mortal- fish that did not survive, which (e.g., WG) are not required for ity than disease. Columnaris would likely be more expensive juvenile walleye (Summerfelt disease (Flavobacterium colum- than the higher cost of the spe- and Clayton 2007). The price of nare) is a major cause of disease cialty feed. the WG feed is higher than other in the first week of feed training feeds from the same source, but and is more prevalent at temper- The specialty diet (Otohime C2) not all commercial feeds produce atures above 68°F (20°C). is systematically reduced un- similar growth rates (Stettner et til day 17 when the fish are on al. 1992). A substitution of soy When columnaris occurs, treat- 100% of a growout diet. They oil for fish oil lowered the price ment is required. The most can be maintained in the same of the WG diet by 10 cents per effective treatment has been site for another week or moved pound without a significant dif- with diquat dibromide but it is to the growout site. Feeding rate ference among diet treatments in not a FDA/CMA approved drug. and frequency are important to relative growth, specific growth, Diquat, however, may be used survival. During the habituation or survival (Clayton et al. 2008). with an approved INAD (Inves- interval, the initial feeding rate is The feed, however should not tigational New Drug). 6 to 8% body weight per d, with have less than 45 to 50% protein. A quick reference guide to the feeding frequency of 5 minutes, FDA/CVM web site should be 18 to 22 hours/d. Initial density Disease: Most mortality occurs consulted for approved drugs of 0.19 lb/ft3 (3 kg/m3) is suit- in the first 8 d of feed training (Available: www.fda.gov/Ani- able. and results from a combination malVeterinary/DevelopmentAp- of handling stress, disease, lack provalProcess/Aquaculture/de- The traditional growout feed is the walleye grower formulation Table 1. Mean water temperature during the culture interval and fish size at the (WG). end of Phase II and III; and size distribution of walleye cultured at Rathbun Fish Hatchery in 2007 and 2008. • Day 1-10:100% C2, 0.900 to 1,400 µm (0.9 to 1.4 mm) 2007 2008 Temperature °F (°C) • Day 11-12: 75% C2, 25% 1 Phase II (June - July) mm WG Mean 75.6 (24.2) 69.5 (20.8) Range 70-82 (21.1-27.8) 63-74.2 (17.2-24.2) • Day 13-15: 50% C2, 50% 1 Phase III (July - October 1) mm WG Mean 75.6 (24.2) 74.6 (23.7) Range 68-81 (20.0-27.2) 69-81 (20.6-27.2) • Day 16-17: 25% C2, 75% 1 mm WG Fish data end of Phase III • Day 18-24: 100%, 1 mm WG Length, in (mm) 9.9 (251) 9.1 (230) Weight, oz (g) 4.8 (137) 3.9 (110) • Day 25-28: 100%, 2 mm WG Length Distribution at Harvest % % The WG feed is an open formula 7-7.9 in (178-200 mm) 1.0 4.0 described in the Walleye Culture 8-8.9 in (203-226 mm) 7.8 33.4 Manual (Barrows and Lellis 9-9.9 in (229-251 mm) 44.4 57.9 1996). It has 47% crude protein 10-10.9 in (254-277 mm) 44.1 4.7 and 17% crude fat. Only one 11-11.9 in (279-302 mm) 2.7 0.0 mill has manufactured this feed Total 100.0 100.0

5 fault.htm June 2010). Treatment culture, but research has not ally reduce to 4%, 3%, and 2% is usually 15 to 18 mg/L for 1 to been done to define the relation- depending on water temperature. 2 h for 3 to 4 consecutive d. ship between photoperiod and At RFH walleye grow to 9 to 10 growth, or the likely interaction in (230 to 254 mm), 3.9 to 4.8 Hydrogen peroxide is an ap- between photothermal conditions oz (110 to 137 g) in about 155 proved drug (35% PEROX-AID, and reproductive development. d from stocking ponds with 2-d NADA 141-255) for use with Onset of sexual maturity will not old fry to October 1 with 80% freshwater-reared coolwater be a problem in the first summer, survival (Johnson and Rudacille finfish to control external colum- but will slow growth rate by the 2008, 2009). Their experience naris disease. Although hydro- end of the second summer. Wa- demonstrates that with optimum gen peroxide at 50 mg/L (ppm) ter quality must be monitored for temperature walleye can reach for 60 min significantly reduced dissolved oxygen, pH, nitrites a market size in one summer mortality in walleye infected and ammonia. (Tables 1 and 2). with external columnaris (Rach et al. 2003), it is toxic to wall- Feed, Feeding, and Growth: Af- Processing: In the Great Lakes eye at concentrations that do not ter habituation, fish may be fed region there are some small- harm other species. Clayton and WG or a high quality salmonid scale aquaculture producers who Summerfelt (1996) reported a feed. Feeding rates after ha- manage the hurdle of processing lethal concentration (LC50) of bituation should start at 6 to 8% their own fish using an estab- 145 mg/L from a 1 h exposure. body weight per d, then gradu- lished Hazard Analysis and To provide a safety margin, they Table 2. Size and fillet characteristics of 181 d posthatch juvenile walleye (hatched recommended that fingerling May 2 and processed October 30, 2009) that were cultured in indoor tanks at Rath- walleye not be exposed to more bun Fish Research Facility. than 50 mg/L. Diquat has a much larger safety margin. English Metric Whole fish Phase III. Growth of feed-trained Length inches/mm 9.7 245.8 fingerlings to market size. Weight lb/g 0.315 143.1 Number of fish per lb or kg 3.2 7.0 Fish should be graded before stocking for Phase III culture to reduce cannibalism. Grow-out Individual Fillets 2 may be done in tanks, raceways, Fillets, skin-on oz/g 1.23 35.0 or cages. It would be best to Fillets, skin-off oz/g 1.01 28.7 shade the fish from bright light. Although RFH does not shade Yield (both fillets as % wet weight)3 their tanks, the water supply has Fillets, skin-on 48.7 48.7 a natural turbidity due to sus- Fillets, skin-off 39.9 39.9 pended solids in the lake water. A water temperature of 75 to Summerfelt et al. 1996 Table 2 values ° ° 77 F (24 to 25 C) provides for Fillets, skin-on (%) 42.1 optimum growth but fish should Fillets, skin-off (%) 33.6 not be handled or stressed at that temperature or risk outbreak of columnaris disease. There is no 1Wr = (w /w )100, where w = observed weight and w = standard weight of each growth at temperatures less than o s o s specimen of the measured length (Murphy et al. 1990). 59°F (15°C). A 16L:8D photo- 2 period is appropriate for indoor Scales were not removed. 3Skin-on fillets in that study were scaled and both skin-on.

6 Critical Control Points (HACCP) large production operation. The Ichthyoptherius multifilis, which program. Or they can have their variable costs were about $1.10 made chemical costs a substan- product processed by a commer- for a 10 in (254 mm) fish. Most tial part of total costs (Figure 3). cial processor. of the expenses were in Phase III (73%) when all inputs (i.e., feed Advice that favors Variable Production costs: Pro- costs) are substantially greater. success duction costs at a commercial fa- Although costs per pound of Start with robust (good condi- cility will vary with economy of feed were higher in Phase II tion), pond-reared fish that have scale and the local infrastructure for specialty feeds, the Phase II no signs of disease. for aquaculture. For propriety interval is short. Note that fixed • Transport fingerlings from reasons, it is difficult to obtain costs, e.g., building construction pond site to growout facil- economic information from can be substantial. private producers, therefore, ity in 0.5 to 1% salt, NaCl (8 data presented from the 2008 At Rathbun, the use of a raw lbs/100gal for a 1% solu- operation at the Rathbun Hatch- water supply contributed to a tion). ery serves as an example of a constant problem treating ich, • Maintain the temperature of transport water at or below 68°F (20°C) to reduce prob- Labor lem with columnaris disease. 26% • Conscientiously follow light Phase I 10% and feeding protocols during Transport Phase II culture. Phase III Chemical 28% 12% 73% Phase II • Do not substitute lower cost 17% Other starter diets for the specialty 5% Feed diets in Phase II. 29% • Develop niche markets that will accept a petite fillet, about 1.1 to 1.4 oz (31 to 40 Figure 3. Production costs for the 5-month, three phase production process (left): g) size. Phase I is pond culture of fry to June fingerling, Phase II is the habituation of pond-reared fish to formulated feed (indoors); and Phase III is the growout to fall (outdoor tanks). Total variable costs (right) for the 2008 culture season at Rathbun Fish Hatchery to produce a 9-10 inch (228-254 mm) walleye with 80% survival from fry was $1.10 per fish.

Suggested Readings/Citations Barrows, F. T. and W. A. Lel- ling . Journal of Ap- Coyle, S. D., J. H. Tidwell, and lis. 1996. Diet and nutrition. plied Aquaculture 6(3):39-49. F. T. Barrows. 1997. Prelimi- Pages 315-321 in R.C. Sum- Clayton, C., J. E. Morris, and R. nary studies on walleye feed merfelt, editor. Walleye cul- C. Summerfelt. 2008. Com- training in cages and second- ture manual. NCRAC Culture parison of soy and fish oils in year growth in ponds. The Series #101, NCRAC Pub- practical diets for fingerling Progressive Fish-Culturist 59: lications Office, Iowa State walleyes. North Ameri- 249-252. University, Ames. can Journal of Aquaculture Edon, A. M. T. 1994. Eco- Clayton, R. D. and R. C. Sum- 70:171-174. nomic analysis of an intensive merfelt. 1996. Toxicity of recirculating system for the hydrogen peroxide to finger- production of advanced wall-

7 eye fingerlings in the north Publications Office, Iowa J.A. Malison, editors. Pro- central region. Master thesis, State University, Ames. ceedings of Percis III: The Illinois State University, Nor- Kuipers, K. L. and R. C. Sum- Third International Percid mal Illinois. merfelt. 1994. Converting Fish Symposium, Madison, Flowers, D.D. 1996. Intensive pond-reared walleye finger- Wisconsin, July 20-24, 2003. walleye culture in : lings to formulated feeds: Ef- University of Wisconsin Sea Advanced fingerling produc- fects of diet, temperature, and Grant Institute, Madison, WI. tion methods. Pages 213-214 stocking density. Journal of Murphy, B. R., M. L. Brown, in R.C. Summerfelt, edi- Applied Aquaculture 4:31-57. and T. A. Springer. 1990. tor. Walleye culture manual. Mahoney, E. M. 2003. Sub- Evaluation of the relative

NCRAC Culture Series #101, objective 3-Assess consumer weight (Wr) index with ap- NCRAC Publications Office, (supermarket/consumers plication to walleye. North Iowa State University, Ames. and restaurant/consumers) American Journal of Fisheries Hart, S. D., D. L. Garling, and perceptions and likelihood Management 10:85-97. J. A. Malison, Editors. 2006. of purchasing hybrid sunfish Nagel, T. 1996. Intensive cul- Yellow perch (Perca flave- and walleye fillets relative to ture of fingerling walleye on scens) culture guide. NCRAC substitute fish. Pages 2-3in formulated feeds. Pages 205- Culture Series #103, NCRAC, R.E. Kinnunen, E.M. Ma- 207 in R.C. Summerfelt, edi- Publications Office, Iowa honey, W.C. Nelson, and P.D. tor. Walleye culture manual. State University, Ames. O’Rourke, Project Termina- NCRAC Culture Series #101, Hushak, L. J. 1993. North tion Report, Economics and NCRAC Publications Office, Central Regional aquaculture Marketing. NCRAC Pub- Iowa State University, Ames. industry situation and outlook lications Office, Iowa State O’Rourke, P. D. 1996. Econom- report. Volume 1. NCRAC, University, Ames. ic analysis for walleye aqua- Publication Office, Iowa State Makowiecki, E. M. M. 1995. culture enterprises. Pages University, Ames. Economic analysis of an 371-384 in R. C. Summerfelt, Johnson, J. A. and J. B. Ru- intensive recirculating system editor. Walleye culture man- dacille. 2008. Fish Culture for the production of walleye ual. NCRAC Culture Series Research. Iowa Department from fingerling to food size. #101, NCRAC Publications of Natural Resources. Federal Master thesis, Illinois State Office, Iowa State University, Aid in Sport Fish Restora- University, Normal Illinois. Ames. tion, Project F-160-R, Annual Malison, J.A., and J.A. Held. Rach, J. J., S. M. Schleis, M. Performance Report, Des 1996. Habituating pond- Gaikowski, and A. Johnson. Moines. reared walleye to formulated 2003. Efficacy of hydrogen Johnson, J. A. and J. B. Ru- feed. Pages 199-204 in R.C. peroxide in controlling mor- dacille. 2009. Fish Culture Summerfelt, editor. Walleye tality associated with external Research. Iowa Department culture manual. NCRAC columnaris on walleye and of Natural Resources. Federal Culture Series #101, NCRAC channel fingerlings. Aid in Sport Fish Restoration, Publications Office, Iowa North American Journal of Project F-160-R, Annual Per- State University, Ames. Aquaculture 65:300-305. formance Report, Des Moines. Malison, J. A., A. B. Head, J. A. Riepe, J. R. 1998. Walleye Kinnunen, R. E. 1996. Walleye Held, and T. P. Barry. 2003. markets in the North Central fingerling culture in undrain- Onset of sex-related dimor- Region: Results of a 1996-97 able ponds. Pages 135-145 in phic growth in juvenile hybrid survey. NCRAC, Technical R.C. Summerfelt, editor. Wall- walleye ( vitreus Bulletin #113, Iowa State eye culture manual. NCRAC female x S. canadensis male). University, Ames. Culture Series #101, NCRAC Pages 41-42 in T.P. Barry and

8 Riepe, J. R. 1999. Marketing eye culture manual. NCRAC Summerfelt, R. C. and R. D. seafood to restaurants in the Culture Series #101, NCRAC Clayton. 2007. Evaluation North Central Region. NC- Publications Office, Iowa of open-formula grower diets RAC, Fact Sheet Series #110, State University, Ames. for juvenile walleye. North Iowa State University, Ames. Summerfelt, R. C., editor. 1996. American Journal of Aquacul- Siegwarth, G. L. and R. C. Sum- Walleye culture manual. ture 69:53-58. merfelt. 1993. Performance NCRAC Culture Series #101, Summerfelt, S. T. and R. C. comparison and growth mod- NCRAC Publications Office, Summerfelt. 1996. Aqua- els for walleyes and walleye Iowa State University, Ames. culture of walleye as a food × hybrids reared for Summerfelt, R. C., R. D. Clay- fish. Pages 215-230 in R.C. two years in intensive culture. ton, T. K. Yager, S. T. Sum- Summerfelt, editor. Walleye The Progressive Fish-Cultur- merfelt, and K. L. Kuipers. culture manual. NCRAC ist 55: 229-235. 1996a. Live weight-dressed Culture Series #101, NCRAC Smith, T. I. J. and W. E. Jen- weight relationships of wall- Publications Office, Iowa kins. 1985. Aquaculture eye and hybrid walleye. Pages State University, Ames. research with striped bass and 241-250 in R. C. Summerfelt, Swann, L. and J. R. Riepe. its hybrids in South Carolina. editor. Walleye culture man- 1994. Niche marketing your Proceedings of the Annual ual. NCRAC Culture Series aquaculture products. NC- Southeastern Association of #101, NCRAC Publications RAC, Technical Bulletin Fish and Wildlife Agencies Office, Iowa State University, #107, Iowa State University, 39(1985):217-227. Ames. Ames. Stettner, C. R, R. C. Summer- Summerfelt, R. C., C. P. Clouse, Yager, T., and R.C. Summerfelt. felt, and K. L. Kuipers. 1992. L. M. Harding, and J. M. 1996. Sensory evaluation of Evaluation of commercial Luzier. 1996b. Walleye fillets from intensively cul- feeds for rearing advanced fingerling culture in drainable tured walleye. Pages 237-240 fingerling walleye. Proceed- ponds. Pages 89-108 in R. C. in R.C. Summerfelt, edi- ings of the Annual Conference Summerfelt, editor. Walleye tor. Walleye culture manual. Southeastern Association of culture manual. NCRAC NCRAC Culture Series #101, Fish and Wildlife Agencies Culture Series #101, NCRAC NCRAC Publications Office, 46: 402-412. Publications Office, Iowa Iowa State University, Ames. Stevens, C. 1996. Cage culture State University, Ames. of walleye and its hybrids to food size. Pages 273-274 in R. C. Summerfelt, editor. Wall- Series Editor: Joseph E. Morris, Associate Director, North Central Regional Aquaculture Center Layout/Design by Sue Ryan Weiss Originally published by Iowa State University, Ames, Iowa

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