Aquaculture: Improving Farm Efficiency

Although catfish prices have risen to $0.72 - 0.75 per pound, producer profits are squeezed by ever-increasing costs. For economic survival, producers must operate as efficiently as possible. This article examines some avenues for savings and provides tips for improving farm efficiency.

Rising Fuel Costs and Equipment Maintenance

Fish producers pay close attention to the price of farm diesel. The current price is roughly $1.95 per gallon for a transport load, 7,500 gallons, and this price excludes delivery costs. Diesel is used to supply power to nearly all tractors, and many wells, hauling trucks, and emergency generators on Arkansas fish farms. The rising cost of diesel must be tempered to some degree by proper maintenance and operation of equipment.

Dirty injectors cause inefficient combustion of fuel and a loss of power. If black smoke is seen in the exhaust, clean the injectors. Sometimes a fuel additive can be used to do this. Make sure to use a product intended for cleaning diesel injectors. If in doubt, contact the machinery dealer to identify acceptable types of fuel additives. If your engine continues to release black smoke even after using a cleaning additive then have a qualified technician clean and service the injectors. Contact your machinery dealer for recommendations on cleaning and service intervals.

Dirty air filters restrict the flow of air needed for the combustion process. Insufficient air flow results in an excessive fuel-air mixture so fuel consumption increases. The result is higher fuel cost. Excessive fuel burning also results in black exhaust smoke. Check the air flow indicator found on the air cleaner. Service the air cleaner and replace the filter if needed.

Use the proper viscosity of oil in the engine to maximize engine efficiency. Oils that are too thick decrease power and lubrication and increase fuel consumption. Change the oil on a regular schedule to remove contaminants, improve lubrication, and reduce friction between moving parts.

Contaminants change the viscosity of the oil and cause corrosion of engine parts if left in the engine too long. Running an irrigation engine for 24 hours is equivalent to 1,000–1,200 miles on an automobile. Engine use hours add up fast. Oil and filter changes must never exceed one year and many service manuals call for oil and filter changes at 250 hours.

Fish producers will improve efficiency with proper training of tractor operators. Operating a tractor in a low gear at high engine speed increases fuel consumption and wear on the drive train components. If the task allows, operate the tractor in a higher gear and at a lower throttle setting. This conserves fuel and reduces drive-train wear. Reducing engine speed by 300 rpm reduces fuel consumption by about 10%.

Another way to improve efficiency is to match tractor size to the load. A large horsepower tractor isn’t needed to operate a small “bushhog” rotary cutter. Most emergency aerators in use today are “sidewinders” and designed to be powered by a 50 or 60 hp tractor. Using larger tractors for that purpose is a waste of energy.

Reduce fuel and maintenance costs by shutting off engines rather than letting them idle for hours. Recent studies show significant savings by not letting a diesel engine idle for more than ten minutes.

Train operators to perform daily service on-site. Notice and correct small maintenance tasks at the pond bank to avoid hauling the machinery back to the shop for repairs.

Improving Feeding Practices

Enterprise budgets show feed cost to be the major expense associated with a catfish operation, accounting for approximately 45% of the total costs. Feed is a major expense. It is often possible to make significant gains in overall farm profitability through small improvements in feeding.

The practice of multiple batch stocking of catfish makes it difficult to accurately determine the feed conversion ratio (FCR). However, FCR is a critical factor for anyone working to improve farm management and budgeting. Small improvements in FCR sometimes indicate substantial increases in overall farm profits.

Most producers estimate FCR at 2.3 or higher for budgetary purposes. A hypothetical 200 acre catfish farm uses six tons of feed per acre per year. The whole farm uses 1,200 tons or 2.4 million pounds of feed, and produces 1.043 million pounds of fish. An improvement in the FCR from 2.3 to 2.2 would yield an increase of 48,000 pounds of fish. At $0.75 per pound each 0.1-unit improvement in FCR yields $36,000 more in gross farm revenue.

Much attention is focused on ways to improve FCR. Producers, researchers, and Extension specialists have debated this for years. Many factors influence FCR. The following suggestions are offered. Feed a high quality diet. Most feed manufacturers offer this. Use floating feed. Use good feeding techniques. “Work” the fish. That is, feed a small area of the pond and wait for the fish to consume everything. Drive down the levee and blow out more feed. Be observant and focus on the task. Feed the fish to satiation but avoid overfeeding. Avoid the tendency to work too fast even if you are responsible for feeding 400 to 500 acres in a day.

As we know, over-feeding wastes money and affects water quality and fish health. Using the hypothetical situation mentioned above, 1,200 tons of feed was used across the farm. If the farm is overfed by 5% for the season, 60 tons or 120,000 pounds of feed will be wasted. At a cost of $250 per ton, that corresponds to $15,000 worth of feed wasted. As you can see, it is vitally important to feed as efficiently as possible.

Aeration Practices

Farmers like to argue about the benefits of permanently wired aeration versus PTO-powered emergency aeration. This debate ranges from the number of horse power per acre to the minimum level of oxygen to initiate aeration. Other factors include the effect of orientation of the aerators on current. Many producers have two or more aerators per pond. When oxygen levels drop to 4 ppm, the first aerator is turned on. If oxygen drops to 3 ppm the second aerator is started. Some producers prefer to aerate for a set time period each day, from 8 or 10 o’clock in the evening to 8 o’clock the next morning, regardless of oxygen levels. Other producers have decided to aerate only in extreme emergencies to cut fuel and electricity costs.

According to results of our catfish yield verification program, electricity accounted for 1 cent per pound of fish harvested if one paddle-wheel was turned on when oxygen dropped to 4 ppm and kept on until oxygen recovered to that level. Other ponds in the verification program which were aerated with two paddlewheels from 8:00 pm to 8:00 am nightly resulted in electricity costs of over 5 cents per pound of fish harvested. Aeration is most efficient if used only when oxygen levels are well below saturation. The trade-off is, of course, higher labor costs to monitor night oxygen levels.

Another important aspect of pond aeration concerns the amperage drawn by an electric motor. Aerators must draw no more than 90% of the ampere load rating. This amperage usually coincides with a paddle depth of 4 inches. Pay attention to paddle depth. Floatation devices sometimes corrode and develop leaks, particularly in the high salt areas of Chicot County. This causes aerators to run deeper and thus draw excess amperes, causing circuit breakers to trip off and result in oxygen depletion and many dead fish.

Balance your need for sleep with the number of hours you run your aerators. Maintain your equipment. Feed the fish well but don’t overfeed. Flexible, committed management is the key to economic success.

By Larry Dorman, Extension Fisheries Specialist
University of Arkansas Cooperative Extension Program
Arkansas Aquafarming newsletter (Vol. 23 No. 1, 2006)