Dedicated To Tribal Aquaculture Programs December 1998 ~ Volume 26 Coordinator: Frank G. Stone  (715-682-6185) Ext. 12 U.S. Fish and Wildlife Service Email: Frank_Stone@fws.gov

Topics of Interest:

Index to Previous Issues of the MTAN

Previous MTAN Volumes and Topics Of Interest

Fish Health Management Review

Basic Types of Pond Fertilizers

Walleye Fingerling Culture In Undrainable Natural Ponds

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Index to Previous Issues of the MTAN

The first issue of the MTAN appeared in June 1992. The concept of the newsletter was conceived by Tom Busiahn (Project Leader of the Ashland Fishery Resources Office) as a means of sharing both fish culture and Tribal fish hatchery information. Over the six years that the MTAN has been providing information for Tribal fish hatchery programs, numerous topic areas have been discussed. The MTAN felt it was time to print an index of previous issues as an aid to help our readers locate specific articles of interest. We are also proud to announce that ALL the previous issues of the MTAN are now linked to the MTAN Internet web site: http://www.fws.gov/midwest/ashland/mtanhome.html

Topic Area/MTAN Volume Numbers:

 

 

Previous MTAN Volumes and Topics Of Interest

Volume 1: The First Midwest Tribal Aquaculture Newsletter Goes to Print, Egg Incubation Systems and Rearing Tanks Find a New Home, Hatchery Tips, Manufacturers of Fish Hatchery Related Supplies.

Volume 2: Walleye Fingerling Fertilization in Earthen Ponds, FmHA Aquaculture Loans, Zebra Mussel, Toxic Bait For Carp Control, Stress and Fish Culture, Walleye - A Light and Temperature Experiment, Radon Gas.

Volume 3: The Twilight Zone Comes To Your Fish Hatchery, Walleye Spawn Collection and Big Redd, Operating Procedures, Brown Trout Spawning Protocol, Fish Hatchery Supplies, Hatchery Tips.

Volume 4: MTAN's New Administrative Coordinator, Fish Culture and Resource Agencies, Equipment Disinfection, Miscellaneous Stuff, Hatchery Tips.

Volume 5: Great Lakes Spotted Muskie Production - 1990, Aquaculture Publications, Use and Application of Salt in Aquaculture, Financial Sources For Funding Aquaculture Programs, Hatchery Tips, Product Manufacturers.

Volume 6: Intensive Culture Techniques For Lake Whitefish, Alternative Methods For Anesthetizing Fish, Eggs/Apples and Fish, Applications For Synthetic Liners In Fish Hatchery Rearing Ponds, Plastic Pond Liners At Lac du Flambeau, Wisconsin Aquaculture Advisory Council.

Volume 7: Swim Bladder Inflation in Walleyes, Surface Water Spray, Diet and Phase Feeding, Protecting Genetic Resources, Therapeutic Salt Treatments for Preventing Transport of Zebra Mussels, Trap and Gill Nets, Larval Diet Studies for Lake Sturgeon, Diet Preferences for Lake Sturgeon, Pond Liners for Hatchery Rearing Facilities (two reports).

Volume 8: Application Process for an Environmental Protection Agency Permit To Use MS-222, Proper Storage and Handling of Fish Feeds, Great Lakes Fish Disease Control Policy, An on Site Mini Hatchery System for Walleye, Common-Sense Rules for Research Recordkeeping, Influence of Stocking Densities on Walleye Fry Viability in Experimental and Production Tanks, Detecting Swim Bladder Inflation in Fingerling Walleyes, Hydrogen Peroxide Controls Fungal Infections On Trout Eggs, Product Manufacturers.

Volume 9: Sucker Propagation and Rearing, Fee Fishing Operations, Oxygen Supplementation, Warts On A Walleye, Floating Raceway System, Automatic Phone Dialer.

Volume 10: Lake Sturgeon Egg Take Procedures, Lake Sturgeon Management, Twelve Uses Of Salt, Salt Fungicidal On Trout Eggs, Pump Alarm System, Hatchery Fomites, Hatching Eggs Out Of Water.

Volume 11: Aquaculture On Line And On Screen, Oxygen Injection Backup System, Maximize Your Hatchery Budget, Intensive Walleye Culture, Tank Culture Techniques For Walleye, Fingerling Walleye Production At Garrison Dam, BGD In Hatchery's, Hatchery Tip.

Volume 12: Hatchery Operations, Hatchery Security System, Brookstock Isolation Facility, Cotton Wool Disease On Fish Eggs, Early Mortality Syndrome, Old Generator Finds New Home, Hatchery Tip, The Last Word.

Volume 13: MTAN Needs Your Help, Chemical Treatments, Work Those Gills, Education>Awareness=Support, Baitfish Production, Disease Problems In Baitfish Culture, Flow Rates Control Fungal Infections, Hatchery Tip.

Volume 14: Baitfish Production (part 2), Using Light To Harvest and Feed Fish, Fish Health Management For Intensive Fish Farming, A Fish Health Note, Walleye Production Using Pond Liners, Hatchery Tip.

Volume 15: Meeting Announcement, Bacterial Diseases, Treatment Of Fish Diseases, Pond Culture Of Walleye Fingerlings, Water Quality Test Methods, Effluents From Coolwater Ponds, Hatchery Tip.

Volume 16: Pond Aeration, Pond Aeration-Matching Equipment To Needs, Tribal Hatchery Updates, 2 Hatchery Tips.

Volume 17: Dome Technology In Aquaculture, Control Growth Rate Of Trout, Effects Of Density On Fish Growth, Walleye Spawning In Michigan, External Signs Of Disease Problems, Tribal Hatchery Updates, Hatchery Tip.

Volume 18: Tribal Resource Programs May Be Required To Pay For NETC Courses, Walleye Culture Manual, Managing Around Cool Water Disease Problems, Clinical Signs Of Toxicosis, Product Manufacturers, 2 Hatchery Tips, Last Word.

Volume 19: Leech Lake's Winnibigoshish Fish and Wildlife Pond Complex; Stripping, Fertilizing and Incubating Walleye Eggs with Big Redd Incubators; Status of Aquaculture Drugs; Fish Marketing Concepts; Hatchery Tips.

Volume 20: Tribal Fish Hatchery Programs Find A New Home On The WWW, Fish Transportation Methods Used on the Leech Lake Reservation, Coaster Brook Trout Eggs, Aeration May Consume More Than 50% Of Your Total Electrical Energy, Air Lift Systems Used To Recirculate Water, It Takes A Lot More Than A Few Bubbles To Do It Right, Pure Oxygen or Aeration, How to Clean Diffusers, Incubation Of Walleye Eggs At Garrison Dam National Fish Hatchery, Arctic Char Culture in Wisconsin, The Right Equipment and Technology To Raise Fish for the Future, Hatchery Tip.

Volume 21: Keweenaw Bay Tribal Hatchery Helps USFWS Trout Program, Liming Of Ponds, Reducing Fish Production Cost, Using Bentonite Clay To Seal Leaking Ponds, Guidelines For The Use Of Rotenone, Sand Filters, Silicones Show Promise As Net Antifoulants, The Use Of Ozone In Hatcheries, Hatchery Tip.

Volume 22: 3 MTAN Updates, Big Redd Incubator Problems, Anesthetizing Hatchery Brook Trout with Sodium Bicarbonate, Fry Culture Technique Successful, Cold Water Feeding of Trout, Hatchery Tip, Feed Sizes For Trout.

Volume 23: Pond Fertilization Methods and Walleye Rearing Techniques, Growth Performance of Juvenile Lake Sturgeon, BGD, Aquaculture Web Sites on the Internet.

Volume 24: New Aquaculture Alliance Proposed for the Red Lake Reservation, Hatchery Tips From Across the Nation.

Volume 25: Matters of Fish Health, Zebra Mussels, Muskrat Control, Bird Damage Control, Maximize Your Hatchery's Budget To Train Your Staff.

Volume 26: Index to Previous Issues of the MTAN, Previous MTAN Volumes and Topics Of Interest, Fish Health Management Review, Basic Types of Pond Fertilizers, Walleye Fingerling Culture In Undrainable Natural Ponds.

 

Fish Health Management Review

Starting October 1, 1998, the La Crosse Fish Health Center (LFHC) will offer a fish health management review to any Tribal Fish Hatcheries in Region 3 (MN, IA, MO, WI, MI, IL, IN & OH) at no cost. This would include an on-site review of their staff/facility, discussion of ways to improve and/or minimize the threat of fish diseases and a written report of recommendations. There would be no charge for this service but do to travel costs, only one review per facility. All requests would be scheduled as first come, first served and time permits.

LFHC continues to be a strong supporter of Tribal Fisheries programs. We feel a fish health management review may help smaller or newly established fishery operations to get off on the right foot! Well established facilities may also have recurring problems that an outside review might pick up?

Contact Rick Nelson, Director, La Crosse Fish Health Center, 555 Lester Ave. Suite 100, Onalaska, WI., 54650-8552, Ph.608/783-8441, Fax 608/783-8450, Email: Rick_Nelson@fws.gov

 

Basic Types of Pond Fertilizers 

Organic Fertilizers:

Mortimer and Hickling (1954) classified organic fertilizers as follows: (1) those containing little or no carbohydrates - such as dried blood, urine, guano, offal, and liquid manure, (2) those containing considerable carbohydrates with nitrogenous matter - such as manure, brewery refuse, and sewage, and (3) those containing mainly carbohydrates - such as plant material, cellulose waste, and wood shavings.

Advantages:

(1) Organic fertilizers have a shorter production cycle than inorganic fertilizers. Zooplankton, such as Daphnia spp. and other microorganisms, may feed directly on organic matter, thus shortening the food chain. In this case, the phytoplankton link in the food chain is temporarily bypassed. Some aquatic plants, such as duckweed, can directly assimilate the complex dissolved organic matter contained in manure. Thus, yields of duckweed in manured ponds are much higher than yields in ponds receiving inorganic fertilization alone.

(2) They decompose to liberate free carbon dioxide. Free carbon dioxide may be used directly during photosynthesis or it may combine to form bicarbonates and carbonates, both storehouses for carbon.

(3) They help to clear muddy water. Positively charged cations produced from decomposition of organic matter combine with negatively charged clay particles; flocculation occurs and muddy water settles out. Clear water is sometimes an advantage.

(4) They also serve as supplemental feed. In some cases organic manures may be eaten directly by aquatic species . In the IndoPacific Region it is common to see hog pens, poultry pens, and even latrines built next to or over fish ponds. Tilapia, various carps, and other species may feed directly on the droppings. It is therefore sometimes difficult to distinguish between the use of organic manure as food or fertilizer.

(5) They may help to condition pond muds. In newly constructed ponds, adding organic fertilizers helps to form the desirable pond muds. This is beneficial for the growth of benthos (bottom organisms). Further, the formation of bottom muds helps to prevent seepage by sealing the pond bottom.

Disadvantages:

(1) The Food and Drug Administration in the United States has classified farmyard manures as filth. However, the FDA has allowed individual states to set their own standards. It is uncertain whether aquatic species grown in ponds with farmyard manure would be accepted by the U.S. consumer as human food. In China and certain other countries, however, manure is an integral part of pond culture.

(2) Organic fertilizers are generally more expensive than inorganic fertilizers.

(3) More labor is required to apply organic than inorganic fertilizers. Only a few sacks of inorganic fertilizer will provide the same amount of chemical nutrients as will many kilograms of organic fertilizer. Organic fertilizer may be high in moisture and carbon content, and this adds to the weight that must be handled.

(4) Organic manures are prone to promote growth of undesirable filamentous algae. This is partly because waters fertilized with organic materials tend to be clear.

(5) They may "smother" the pond bottom. The use of green manure with hard plants, such as mangrove leaves as used in Indonesia, may cause the formation of cellulose-mud that smothers the pond bottom. The harder parts of plants, put in as green manure, should be removed once the softer parts have decomposed.

(6) Manures may cause oxygen depletion. Organic fertilizers use oxygen as they decompose.

(7) They may increase the potential for disease. Where Salmonella is a problem, poultry manure should not be used. Gill rot also has been associated with organic manures.

Inorganic Fertilizers:

Inorganic or chemical fertilizer is usually preferred over organic fertilizer when it is available. It has none of the disadvantages of organic fertilizer. It is usually less costly and easier to apply because of less bulk to handle. Inorganic fertilizer is termed complete when it contains the three basic nutrients of nitrogen, phosphorous, and potassium and incomplete when one or more of these nutrients are missing.

Chemical compounds used to fertilize pond waters are the same as those used for agricultural crops. Swingle and Smith (1939) found that in freshwater phytoplankton efficiently used inorganic fertilizers in vitro with N-P ratios (nitrogen to phosphate) of 2: 1. Since in natural waters soluble phosphate is rapidly bound by adsorption or precipitation, the amount of phosphate was doubled for use in pond water, giving a 4:4.6 N-P ratio. Eight pounds (3.6 kg) of N or P2O5 are enough to supply 1 ppm in about 3 ac ft (3,700m3) of water; similarly 2 lb (0.9 kg) of K2 0 would supply about 0.25 ppm.

 

Walleye Fingerling Culture In Undrainable Natural Ponds

Because natural ponds are highly variable in size, depth, water quality, and fertility cultural practices are not standard and experienced growers encounter substantial variation in survival, yield (lbs/acre) and size at harvest. What follows is a description of the general practices used to produce walleye fingerlings in Minnesota.

1992 Survey:

A 1992 survey (Minnesota Aquaculture Report, 1993) of commercial aquaculture producers in Minnesota indicated that 53 of 79 (69%) producers used natural waters for some of their production. About 1,206 natural ponds, totaling 39,291 acres (mean was 33 acres) were used to raise bait fish, such as suckers and fathead minnows, and to produce walleye fingerlings for stocking. The survey reported that over 600,000 walleye fingerlings, valued at $328,000 ($0.54/fingerling), were sold by private growers in 1992. Data were not obtained from all producers in 1992, so actual production was probably higher. Minnesota producers are able to produce more fingerling walleyes than the existing market can bear in most years. Expanded markets in Minnesota and other states could significantly benefit producers.

Natural Pond Selection

Ponds vary considerably in size, depth, fertility, and many other features. Finding an available pond that is appropriate for fish culture can be difficult. Typically in Minnesota, commercial producers lease ponds from a farmer or farmers with riparian lands. The most productive ponds for aquaculture purposes are in west-central Minnesota. Competition for water in this area of the state can be high.

As a rule, ponds used to raise walleye fingerlings must not have other fish present or at least nothing other than minnows. Other fish in the pond may be predators or competitors, and they may greatly reduce walleye production.

A carryover of walleye will severely limit the following year's production because the older fish will prey on newly stocked fry. Thus, the best fingerling culture ponds winterkill every year. The process which eliminates oxygen from the water and causes winterkill can vary from one year to the next, so a pond that has a complete kill one year may only have a partial kill another. Checking dissolved oxygen levels in late winter will help predict the extent of winterkill in a pond.

The size of the winterkill ponds that are used for walleye culture can range from 1-100 acres, but the typical pond ranges from 5-30 acres. Although ponds approaching 100 acre can be productive, it is often very difficult to harvest a high percentage of the fish from large ponds. Higher percentages of available walleyes can be harvested from small ponds.

Physical and chemical characteristics of ponds also vary. Bottom type may be sand, clay or muck, but harder bottoms are preferred because harvest is easier. Brush, logs, heavy vegetation and rocks make harvest more difficult. Total alkalinities of around 150-200 ppm are typical, but alkalinities may range from 50-300 ppm. The typical pH of the waters used ranges from 6.5-9.0; however, pH varies in a daily cycle, with highest values at mid-afternoon and lowest values before sunrise. Presunrise dissolved oxygen levels should not drop below 5 ppm. It is the opinion of producers that ponds in good farm country are often more productive than ponds in wooded areas, and ponds with embayments are usually more productive than circular ponds.

Fingerling Culture and Pond Management:

Controlling Insects

Ponds should be checked before fry are stocked to assess the numbers of predatory invertebrates such as beetle larvae and backswimmers. One practice is to kill predatory air breathing aquatic insects by covering the pond with a thin film of oil. According to Dobie (1956) kerosene, fish oil, No.2 fuel oil, and cod liver oil can be used for this purpose. Recommendations include using 3-5 gallons of fuel oil/acre, 10-12 gallons of kerosene per acre, or 4-5 gallons of fish oil per acre. The oil is applied along the windward side of the pond when it is windy enough to spread the oil over the pond surface, but not so windy that it all blows to one shore. One producer used soybean oil mixed with kerosene, but he has since stopped the practice of oiling his ponds. Although the producer thinks an oil treatment improves survival, he has halted the practice because of costs for the oil and labor and to maintain landowner relations which could be strained by perceived negative environmental impacts. Another producer uses vegetable oil without kerosene mixed in.

Monitoring Zooplankton Densities

Many producers check zooplankton densities with a plankton net before walleye fry are stocked and one experienced grower stated that a plankton net is essential for walleye pond management. Zooplankton are sampled with a plankton net towed 50-100 ft. through the pond early in the morning or in the evening when zooplankton are higher in the water column. Experience is generally used to determine if fry should be stocked rather than specific zooplankton counts. If sufficient numbers of rotifers, daphnia, and copepods are not found, fry should not be stocked because survival will be low.

Zooplankton populations must be surveyed far enough in advance of stocking to allow zooplankton time to respond to fertilization. Most producers do not fertilize large ponds. Many ponds in the row-crop area of west-central Minnesota receive sufficient fertilizers from runoff of adjacent farming operations. Fertilization may also be warranted after stocking if zooplankton numbers start to decline. The use of water clarity (Secchi disk-transparency) to determine when and how to fertilize (as recommended for southern U.S.) is not recommended by experienced growers in Minnesota. Better results are achieved by examining zooplankton numbers and composition than by looking at water clarity. Zooplankton can also be trapped from enriched ponds and stocked before fry are stocked or when zooplankton numbers decline (at least until the walleye reach 1.5-2 in when they become piscivorous).

Sources and Stocking of Fry:

In Minnesota, walleye fry are purchased from the Department of Natural Resources or from private producers. Although the number of commercial sources are limited, the number of fish farmers building facilities for holding brood fish is increasing. Producers pay around $7 to $9 per thousand for walleye fry. Prices vary from place to place and by the size of the order.

When the fry reach the pond it is important that they be acclimated to both the temperature and chemistry of the water. The plastic bags are typically floated in the pond until the transport water temperature equilibrates to the pond water temperature, then the bags are opened and pond water allowed to slowly enter the bag. Once the pond and transport water have mixed, the fry are slowly released into the pond. If pH of the pond water differs substantially from the transport water, additional acclimation procedures may be warranted. Some producers allow fry to escape slowly into the pond on their own from an acclimation chamber; others spread the fry throughout the middle of the pond to reduce predation by any minnows and aquatic invertebrates that may be present.

Stocking Density:

Most producers stock 2,500-10,000 walleye fry per surface acre. Stocking rates of 20,000-30,000/acre or higher are used if the pond is known to be very productive, artificial aeration is used, and it is more intensively managed. Usually, when higher stocking densities are used, fingerlings are harvested or thinned in early July.

Pond Aeration:

It is a general practice to aerate small fertile ponds if there is access to electrical power. The risk of catastrophic loss is greatly reduced, and some producers think that aeration increases production. Because many of the ponds are large, they are not fully aerated to the manufacturer's recommendations because the expense would be too great. The most common type of aeration is an air compressor with a bottom diffuser.

Feeding:

For production of advanced fingerlings, that is, fish larger than 2 in, many producers feed fathead minnows to their walleyes once they reach 2-3 in. Appropriate sized fathead minnows are less then 1.5 in and they pass through a 16 to 17 grader. Fatheads are added to the pond on a regular basis to maintain an adequate food resource. Without minnows, walleye can become quite cannibalistic. An indicator of cannibalism is a wide range of fingerling sizes; cannibalistic walleye grow faster than other walleyes. Some producers stock fathead minnow broodstock into ponds after stocking walleye fry. Fathead reproduction through the season is then a food source for the walleyes.

Bird Predation

Bird predation is regarded by the fish farmer as a significant cause of mortality in natural ponds. Fish farmers have said that cormorants and pelicans can wipe out an entire pond very quickly. Flocks of 100-200 have been seen on some production ponds. The stomach of one cormorant contained 42 four-inch walleye. Retail value of that one meal was about $42. While larger ponds seem to be at greater risk to bird predation, even smaller ponds are not safe. One experienced fish farmer claimed that if he had known how much of a problem birds can be, he never would have gotten into the walleye fingerling business. For more information about bird predation problems and solutions, the Southern Regional Aquaculture Center publications, numbers 400, 401, and 402 are useful. They can be obtained from your state aquaculture extension specialist or from the state USDA, APHIS, Animal Damage Control office, or the Regional Office of APHIS in Nashville, TN.

Harvest:

Some walleye fingerlings may be harvested in early July when they are 2-3 in, but most are harvested during September and October when water temperatures cool to below 60 F. Fingerlings harvested from warmer water can be stressed and are difficult to hold and transport. High and even total mortality can occur when fingerlings are captured in trap nets when the water temperature exceeds 70 F. If catches are small, walleye have been successfully trapped in warmer waters, but risk of loss is still high. The disadvantage of waiting for cooler water temperature is that there is less time to harvest the fingerlings before ice-up, resulting in reduced harvest rates. Walleye fingerlings can range in size from 3-10 inches in September, although they are generally 4-8 inches long and 15-25/lb.

Walleye fingerlings are usually captured in trap nets, but may be seined if pond conditions permit. Traps are set along the shoreline at intervals of 150-200 yards. Catch rates vary daily. It can be very frustrating to realize that the fish are in the pond but are simply not moving enough to encounter the nets. It is speculated that when food is abundant, fish move less. Therefore, feeding is usually discontinued prior to harvest. Various methods to induce fish movement have been tried with variable success. Development of more effective harvest methods would be very beneficial.

The yield of stocked fry varies considerably among ponds and years, but it generally ranges from 10-15%. In any given year there are ponds in which harvest may be zero, while other ponds may produce up to a 30-40% or greater return. Prices for walleye fingerlings vary, but a general rule of thumb is that walleye fingerlings less than 8 inches sell for around $0. 10/in wholesale and about $0.15-$0.30/in retail. The wholesale price for fingerlings greater than 8 inches is about $0.12-$0.15/in and the retail price is about $0.18-$0.40/in. Walleye longer than 12 inches are generally sold for around $3-$4.50/lb round weight.

Summary:

Successful producers of walleye fingerlings in undrainable, natural ponds are experienced. Their advice is "get to know your ponds" and do not stock walleye fry in ponds if fish have survived the winter or if zooplankton populations are not sufficient in density and composition. Another recommendation from experienced fish farmers is to clean boats and equipment thoroughly before moving to another pond. This will help prevent introducing unwanted aquatic vegetation (e.g. Eurasian water milfoil) from one pond to another.

Experienced producers are moving towards exerting more management control over the production of walleyes in undrainable, natural ponds, but it remains an extensive type of aquaculture with inherent risks. Bird predation and weather are important factors that are difficult to manage. Manuals and case studies like this one provide insights and guidelines on culture techniques for the beginning fish farmer, however, experience is required to appropriately apply the information to each specific set of environmental conditions.

 

Return to MTAN selection page Return to Ashland NFWCO home page Return to Region 3 U.S. Fish and Wildlife Service

Product and company names mentioned in this publication are for informational purposes only. It does not imply endorsement by the MTAN or the U.S. Government.

 

 

 

Last updated: November 20, 2008

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