Small-Scale Catfish Production: Holding Fish for Sale

University of Arkansas, United States Department of Agriculture and County Governments Cooperating

Robert Rode
Research Specialist

Nathan Stone
Extension Fisheries Specialist

Holding fish for sale allows small scale catfish producers to take advantage of higher fish prices obtainable through direct sales to the public.  Adequate holding facilities and proper handling practices can make a big difference in a producer's profits.  customers who have to be turned away because fish are not readily available or because fish have died in tanks are problems that can be minimized through planning.

The type of holding facility and equipment needed depends upon the market to be serviced and the mount of capital available.  If fish are to be sold at irregular intervals they can be held caged in ponds.  This allows ready access to the fish while maintaining fish in good condition.

Holding fish in tanks would be the best option for supplying customers with fish on a regular basis.  Fish are harvested ahead of time and can be readily netted from the tanks as needed.

A third option is to truck fish to market.   Fish straight form the pond, cages or holding tanks can be loaded into a hauler and taken to the customer.  Farmers' markets, certain street corners or parking lots can sometimes serve as sales locations.  With care, unsold fish can be safely returned to the pond or holding facility.

This fact sheet describes the different methods for holding fish and their advantages and disadvantages.  Losses from holding fish can be considerable if proper care is not taken, and such losses directly reduce producer profits.  Success as a small-scale fish producer requires careful consideration and selection of holding facilities best suited to the chosen market(s).

Holding in Ponds

Holding fish in ponds is the easiest and cheapest method of direct sales.  Fish can be held in cages or net pens placed in a pond and taken out whenever needed.  Food-sized fish can be held in densities from 7.5 to 15 lb/cubic foot of cage, depending on water temperature and circulation.  At higher temperatures, it is advisable to stock fewer fish.

One of the advantages of this method is that, with proper care, fish can be held for long periods.  By feeding a maintenance diet, fish not immediately sold can be held without severe weight loss or deterioration of health.   A maintenance diet (1 percent of the weight of the fish in the cage) should be fed daily to prevent weight loss, although fish should not be fed the day before harvest.

With feeding, water quality concerns become more important.  Supplemental aeration may be needed if the pond is fed heavily.   Fish crowded in cages will die at oxygen levels that are not lethal to fish loose in a pond.  Fish density can be increased towards the upper end of the recommended range where there is good water circulation around the cage.  Good circulation of pond water through cages helps remove metabolic wastes.

There are several disadvantages to holding fish in cages.  Locating cages away from shore allows for better water circulation but necessitates the use of a boat or a pier out to the cages.  Dipping fish out of a cage from a boat or pier can be difficult, particularly if large or heavy cages are used.   Any off-flavor problems in the pond will affect caged fish as well, postponing sales indefinitely.  Caged fish are also more susceptible to disease problems.

Direct sales of live fish is possible only if the fish stay alive.  Transferring fish from production ponds to holding facilities or hauling tanks is stressful to the fish.  Care must be taken to avoid abrupt changes in water temperature or water quality.  If the difference in water temperature is greater than 5 degrees Fahrenheit, water should be changed gradually to allow the fish time to adjust.

Equipment needed for this option includes cages or net pens (preferably attached to a pier out into the holding pond), dipnets, legal-for-trade scales, waders and plastic baskets.  Where a producer has an existing pond and pier, the additional investment required to hold 1,000 lb of fish at a time in cages would be approximately $1,000.

Holding in Tanks

Fish can be held in tanks if they are to be sold over a two to three day period.  Tanks vary greatly in size, material and cost.   The three most common types are holding vats, tanks and aquaria.

Concrete vats may vary in size but are generally rectangular in shape, with a water inlet at one end and a drain at the other end.   Dimensions range from 10 to 40 feet long, 3 to 6 feet wide and 2 to 3 feet deep.   Tanks are constructed on top of a concrete slab, with side walls of concrete block or poured concrete.  Generally built outside, most are covered by a roof.  A typical facility is shown in Figure 1.  Fish in tanks are particularly susceptible to theft, so an enclosed facility may be necessary.

Fish can be held in fiberglass, plastic or metal tanks.  These also vary in shape and size.  All materials should be FDA approved for food grade use.  Although they do not have the longevity of concrete facilities, tanks give more flexibility in installation and can always be moved at a later date.   Fish can also be held in large aquaria ranging from 250 to 1,000 gallons.   Aquaria cannot hold large quantities of fish due to their small size, but are useful for display purposes.

Fish in any of these systems should not be held more than 2 to 3 days at a stocking rate of 0.6 lb/gallon of tank capacity.  Crowding fish in tanks causes stress and leads to losses of fish.  Fish in tanks are not fed since fish wastes would foul the water.  Channel catfish held at 71 degrees Fahrenheit lose 4.5 of their body weight in just two days as a result of stress and lack of food.

To remove ammonia and other waste products, tanks should receive a constant flow of water (10 percent of tank volume/hour) or be flushed completely at least twice a day with fresh water.  The quantity and quality of water supplied to fish in holding tanks is a critical factor in successfully holding fish.   Use of public water supplies is not feasible as the water is chlorinated, and the chlorine will kill fish.  chemical removal of chlorine permits the use of small volumes of water, as practiced by some bait shops, but this is not practical for holding larger numbers of fish.  Good quality well water is preferred for holding fish, although pond water may be used.  As in the case of caged fish, pond water may bring in problems such as off-flavor and disease.

Holding tanks should be supplied with aeration.   For a single small tank, a hanging agitator works well.  For aerating larger or multiple tanks, a low pressure - high volume air blower is ideal.  To reduce noise, the blower should be located in a sheltered location away from the sales area.   Air is fed to tanks through air-stones, connected by plastic tubing to a plastic PVC pipeline from the blower.  One airstone for every 2 to 3 feet of tank is adequate.

Fish tanks should be covered with netting, particularly at night, to prevent fish from jumping out.  Pieces of old seines can be used as covers.  An emergency generator and a spare air blower are essential to preventing losses during power outages or in case the primary blower fails.

Investment requirements for holding tanks vary considerably.  Construction costs for the concrete vat facility shown in Figure 1 are approximately $1,500 per vat.  This estimate includes the 1,300 gallon capacity vat (17' long by 4' wide by 3' deep), roof, aeration and electrical wiring.  Additional equipment such as dipnets, scales and plastic baskets is also required.

Holding Fish in Haulers

One potential market outlet for small-scale catfish producers is to take fish to the customer, whether it is a farmers' market or a busy street corner.  With proper stocking rates and handling, fish can be sold live from a hauling tank and unsold fish returned to the farm unharmed.

A variety of hauling tanks can be purchased or constructed.  Most are rectangular in shape for ease of mounting on a truck or trailer.  Most haulers are a box with a hinged lid, drain opening, and openings for agitators or air hoses.  Commercially manufactured tanks usually are made of aluminum or fiberglass.  Tanks can also be constructed of marine plywood or made by modifying an existing tank (milk bulk storage, galvanized watering trough) for holding fish.   Internal dividers or baffles are used in larger tanks to reduce sloshing of the water.  Insulated tanks are useful for reducing temperature changes in the hauling water when fish are held for several hours, and will help keep fish in better condition.

In constructing a hauling rig, the opening needs to be made large enough so that it is convenient to dip fish from the tank and that all areas of the tank can be reached with a dipnet.  This reduces time spent chasing fish around the tank.

When purchasing or building a hauling tank, an important consideration is the vehicle or trailer that will be used to haul the tank.   Water is very heavy (8.3 lb/gallon), and a tank full of water and fish along with other assorted equipment can weigh quite a bit.  The vehicle used should have a carrying capacity that allows for a full hauling  tank as well as other equipment.

Food-sized catfish can be held in hauling tanks at a rate of 5 lb/gallon of water for 16 hours with proper care.  Note, however, that for hauling tanks the "gallons of water" refers to the quantity of water in the tank after the fish are added, not the tank capacity.  A tank with a capacity of 200 gallons loaded at a rate of 5 lb/gallon can haul only 600 lb of fish, since with the fish in the tank there is room for only 120 gallons of water.  Catfish weigh almost as much as water (8 lb of fish/gallon), so an easy way to calculate capacity is: tank capacity in gallons x 3 = lb catfish that can be hauled.

Fish to be placed in the hauler should be starved for several days prior to sale to purge any feed from their digestive tract.  Water used for hauling should be of good quality, preferably well water.  Since fish are destined for sale, hauling aids such as salt are not recommended.  Ice may be added to cool the water, reducing fishes' metabolic rate and making them easier to handle.   A producer may have to make his or her own ice to insure that it is not made with chlorinated water.  Most commercially available ice is made from municipal water that contains chlorine.

Air (oxygen) must be added to the hauling tank water during transport and sale.  Several options are available.  Small 12 volt agitators that run off the vehicle battery can be used on small loads.  Larger quantities of fish may need air or oxygen diffuser systems.  An air blower powered by a small gasoline engine, compressed (bottled) oxygen, or liquid oxygen systems can be used to provide oxygen to fish.

A 300 gallon fiberglass hauling tank (for a full size pickup) costs $1,200 - $1,500.  Additional equipment such as a 12 volt compressor and diffuser tubing or agitators, dipnets, scales, baskets and sandwich board signs would increase the total investment to around $2,000.

With any of these methods of holding fish, it is advisable to start at recommended stocking rates and plan on selling the bulk of the fish quickly.  By reducing the quantity of fish within the first few hours, the remaining fish have a better chance of survival.

Off-Flavor and Quality Control

Off-flavor is a major problem in the catfish business and affects large and small operations alike.  Fish that taste bad will ruin a business.  Typical off-flavors include muddy, musty and weedy.  Frequency of off-flavor increases during the summer months, but fish can be off-flavor at any time of the year.  Several fish from every pond to be sold should be flavor-checked before selling the fish.  Some off-flavors can be purged  relatively quickly, so that holding fish in tanks or in another pond may bring them back on flavor.  Learning the different off-flavors and flavor-checking insures that fish sold are acceptable to clientele.

It is normal to have a few fish die in holding tanks.  If large numbers die, the density of fish may be too high or they may have been stressed in harvesting and hauling.  It is better to remove distressed fish before they die than to wait until they show up dead.  Fish that have been dead for any length of time should not be sold. Fish quickly spoil at water temperatures used to hold catfish, and sale of an inferior product will quickly ruin a producer's reputation and business.  Fish that are  freshly dead, with clear eyes, can be dressed and iced for home consumption.  Selling dressed fish requires facilities that meet Health Department regulations.

Sales and Service

Fixed dates and times of sales allow for operating as a part-time business.  Customers can count on the store being open and plan their visits accordingly.  Customers will call asking for fish at other times of the week when the store is not regularly open.  A uniform policy for customers (e.g. a minimum quantity for off-hour sales) is recommended.  There will be fluctuations in demand on a seasonal basis, with spring and fall peaks in sales and little demand around Thanksgiving and Christmas.  A number of live fish markets operate seasonally to avoid these slow periods.

A certified scale should be used for weighting fish, and this should be done in front of the customer.  People may want to select their own fish or they may desire particular sizes of fish.  One method to cope with this situation is to post signs indicating that customers will be charged more per pound for this service.

Most people have no idea how many pounds of catfish are needed to feed a given number of people.  A bulging sack of live catfish slims down to a small stack of fillets.  Customer disappointment is reduced when he or she buys enough fish to satisfy the family and friends.  Catering services plan meals based on one-half pound of fillet per person.  For every 10 pounds of live catfish, only about 6 to 6.5 pounds of headed and gutted fish or 3.5 to 4 pounds of fillets result.   Feed sacks can be saved for use in bagging live fish for sale.

Direct sales of fish is away to get more value per pound or fish raised.  The profitability of an operation depends on sales and profit margin, not on how many pounds are raised.  Fact sheets on marketing and advertising   provide useful information on selling fish, and there are several agencies that offer free business advice and information.  A fish farmers permit from the Arkansas Game & Fish Commission ($25) is required, as well as any appropriate business licenses form county and/or city revenue offices.

ROBERT RODE, research specialist, and NATHAN STONE,
Extension fisheries specialist, are located at the Arkansas
Agricultural Experiment Station, University of Arkansas at Pine
Bluff.

Issued in furtherance of Extension work, Act of September 29, 1977, in cooperation with the U.S.D.A., Dr. Mazo Price, Director, Cooperative Extension Program, University of Arkansas at Pine Bluff.  The Arkansas Cooperative Extension Program offers its programs to all eligible persons regardless of race, color, national origin, sex, age or disability, and is an Equal Opportunity Employer.