SUSTAINABLE CHANNEL CATFISH FARMING

 

Low management production through modified stocking and feeding practices

World Aquaculture, 26(3): 54-59.

 

(view also as PDF)

 

William A. Wurts and Forrest Wynne

Kentucky State University Cooperative Extension Program

www.ca.uky.edu/wkrec/Wurtspage.htm

 

Sustainability has become the recent “buzz-word” in aquaculture and agriculture.  As Claude Boyde indicated in San Diego (Aquaculture ‘95), aquaculture is not truly sustainable because it relies on external feed, chemical and energy inputs.  The United States Farm Bill of 1990 more narrowly defined the key components of sustainability as: maintaining profitability, supplying food and fiber needs, using non-renewable resources efficiently, enhancing renewable resources and improving the quality of life in rural areas.

 

Intensive aquaculture practices have pushed production as high as 7,000 to 10,000 lb/acre.  The objective has been to increase profitability by maximizing harvest weight (biomass) per unit volume or area of production system.  However, these practices almost always exceed the biological carrying capacity of the production unit.  As with feedlot livestock production, overcrowding usually leads to problems with environmental degradation, disease, off-flavor (in aquatic animals), and a reduction in individual performance of the cultured species.  In several instances (e.g. shrimp farming in Bangladesh, China, Taiwan, and Thailand), the long term results of intensive production practices appear to have been economically and (potentially) environmentally devastating.

 

While the U.S. catfish farming industry has not experienced the catastrophies observed in the shrimp farming industry, it has manifested several of the warning signs which indicate production is at the upper limits of carrying capacity.  Widespread disease, antibiotic resistant bacteria, off-flavor problems and routine aeration have become common for intensive channel catfish culture.

 

In recent years, Enteric Septicemia of Catfish (ESC) has flourished in the crowded production ponds of Mississippi.  Off-flavor results from dense phytoplankton (algae) blooms and micro-organisms which accompany the heavy nutrient and organic loads produced by fish wastes (ammonia and manure) and uneaten feed.  On any given day during the catfish production season, as many as 40-60% of the ponds sampled can contain off-flavor fish.  Nighttime aeration, throughout the summer, has become the standard not the exception – because oxygen demand exceeds the natural regenerative processes of the pond environment.

 

Sustainable or Low Management Catfish Production

 

For the purposes of this discussion, sustainable aquaculture will be viewed as commercial channel catfish production which:

•    respects the biological or ecological limits of the production pond

•    requires minimal external inputs; and

•    can be conducted with limited technical skills.

 

Basically, this is fish farming that can be “done with a 5-gallon bucket and a pick-up truck (or horse-drawn cart)” and without quitting the day job.  The underlying concepts are:

•    maximize biological efficiency in the production pond environment without exceeding natural carrying capacity;

•    reduce the cost of production; and

•    establish profitable, low management production techniques.

 

Several field demonstrations have been conducted in Kentucky to examine the feasibility of improving production efficiency and pond yields using low stocking density and modified feeding practices with no aeration.  Altering the time of year for stocking channel catfish fingerlings was also explored.  The primary objectives were to: take advantage of cool-weather growth; closely match feeding with actual catfish growth; and keep pond biomass at or below natural, pond carrying capacity (approx. 1500 lb/acre) during critical periods – the hot weather experienced from July through mid-September.  A second objective was to avoid heavy nutrient loads from fish waste products and uneaten feed.

 

Autumn Fingerling Stocking

 

This project demonstrated that autumn stocking increased channel catfish fingerling weight by 70 to 90% between the beginning of October 1991 and mid-April 1992.  Fish were stocked in 0.5- and 1.0-acre ponds.  Fingerlings (0.1 lb each) were stocked at 2000 fish/acre.  Feeding, at 1-3% of biomass, was adjusted in accordance with standard temperature-based recommendations.  Surface water temperatures reported for a large, local reservoir (Lake Barkley) were used to adjust feeding.

 

Channel catfish fingerlings (0.1-lb) are in their rapid growth (exponential) phase.  By stocking fingerlings in early autumn rather than the following spring, they benefit from cool-weather feeding (when water temperatures are greater than 50EF).  Fingerling growth is reduced but still good during cool weather.  Because temperature and biomass are low, pond carrying capacity is not taxed.  In west Kentucky, water temperatures are usually below 50EF from mid-December to early March.

 

Low density, autumn stocking in combination with temperature-based feeding substantially increased channel catfish fingerling weight by the subesequent spring.  The advanced spring fingerling size (0.19-lb) allowed production of a 1.45-lb food-fish (1343 fish/acre) in 180 days.  These findings exceeded expectations for single-season, catfish growth in northern latitudes of the Southeastern United States.  This was accomplished by a “first-time” fish farmer, a teen-age boy still in high school.

 

Low Stocking Density and Modified Feeding

 

These two practices were demonstrated through the use of mathematically generated feeding tables (Table 1) and low stocking density (1500 fingerlings/acre).  Growth was assumed to be exponential for fish weighing from 0.1 to 0.53 lb each and linear for catfish larger than 0.53 lb (Figure 1).

 

 

Table 1.  Channel Catfish feeding table predicting catfish weights and daily feeding rates at 7-day intervals, assuming exponential growth for 0.1- to 0.53-lb fish and linear growth for fish greater than 0.53 lb (1.0 lb = 454g).  Daily feeding is capped at 30 lb feed/acre.
			1500 Fish
Fish Size		Time	Wt.	Feed Fed
(lb)	(g)	(days)	(lb)	(lb)
0.10 0.12 0.15 0.19 0.23 0.29 0.35 0.43 0.53 0.59 0.66 0.73 0.79 0.86 0.92 0.99 1.05 1.12 1.18 1.25 1.31 1.38 1.45 1.51	45 54 68 86 104 132 159 195 240 270 299 329 359 389 418 448 478 507 537 567 596 626 656 685	0 7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 112 119 126 133 140 147 154 161	149 179 225 284 344 437 526 645 794 892 990 1088 1187 1285 1383 1481 1579 1678 1776 1874 1972 2070 2169 2265	4.5 5.4 6.7 8.5 10.3 13.1 15.8 19.3 23.8 24.2 24.6 25.0 25.5 25.9 26.3 26.7 27.1 27.5 27.9 28.3 28.8 29.2 29.6 30.0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Channel catfish with an average, individual weight of 1.3 lb (1.0 lb = 454 g) were produced within 175 days using low stocking densities and tables to adjust feeding.  These studies were done in 2.25 and 2.5 acre ponds.  Catfish fingerlings were 0.1 lb each at the beginning of the study, 21 April 1993.  Ponds were sampled and partially harvested on 14 October 1993.

 

Fish were fed a 32% protein, floating commercial catfish diet.  Daily feeding was capped at 30 lb feed/acre but could go as high as 35 lb/acre.  Fish were fed once each day.  Feed was offered when dissolved oxygen would be highest, late afternon or early evening.  Feeding rates were adjusted every seven days (Table 1).

 

After 175 days, survival was estimated to be greater than 95% and biomass to be 2,000 lb/acre.  Food conversion ratios were 1.68 and 2.0.  Fish weights as well as projected pond yields and food conversion ratios were 25-30% better than traditional expectations for channel catfish production in Kentucky.  Projections and estimates were based on mean, individual weights and daily feed consumption, measured at the end of the study.  This was accomplished by a “first-time” fish farmer who had no university training.

 

It is likely that channel catfish growth is truly a sigmoidal pattern (S-shaped curve, Figure 2).  However, an S-shaped growth curve is approximated reasonably well by an exponential curve followed by a straight line (Figures 1 and 2).  The math for linear and exponential equations is much easier to handle than the math for a sigmoidal function.  Retrospectively, it seems that channel catfish growth is exponential (rapid) a little longer (up to a 0.7 lb fish) and more rapid than was originally assumed (Figure 2 and Table 2).

 

 

Table 2.  Channel catfish feeding table predicting catfish weights and daily feeding rates at 7-day intervals, assuming growth is exponential for fish between 0.1-0.7 lb each and linear for fish greater than 0.7 lb (1.0 lb = 454 g).  Daily feeding would increase by 0.47 lb every 7 days for fish greater than 0.7 lb each and would be capped at 35 lb feed/acre.
			1500 Fish
Fish Size		Time	Wt.	Feed Fed
(lb)	(g)	(days)	(lb)	(lb)
0.10 0.13 0.16 0.21 0.27 0.34 0.43 0.56 0.71	45 58 74 95 121 154 197 252 322	0 7 14 21 28 35 42 49 56	150 195 240 315 405 510 645 840 1065	4.5 5.9 7.2 9.5 12.2 15.3 19.4 25.2 26.6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Combining Low Density and Autumn Fingerling Stocking with Modified Feeding

 

 

 

 

The results of these demonstrations suggest individual channel catfish growth is rapid from 0.1 to 0.7 lb (50-60 days) and then slows for larger fish (Figures 2, 3 & 4).  Therefore, the most critical time to feed accurately is during the first 2 months of the spring-summer production season.  Mathematically generated, feed tables improve production efficiency by allowing the farmer to closely match feeding with natural growth rates.  Nitrogenous and organic wastes as well as uneaten feed would be minimized because the amount of feed offered is not in excess of that needed for good growth.

 

Stocking fingerlings in autumn produced larger fingerlings and food-fish by the subsequent spring and autumn harvest, respectively.  Catfish fingerlings stocked at the beginning of October (1500 fingerlings/acre) could easily attain a weight of 1.50 lb each and a total biomass of 2250 lb/acre by October of the following year.  Continued feeding until December (up to 35 lb of feed/acre daily) in conjunction with periodic, size selective harvest (fish greater than 1.25 lb each) through mid-spring of the next year could further increase pond yields.  Second season fingerlings  would be

autumn stocked “under” harvest-size catfish.  These fingerlings could consume uneaten feed and natural foods left by the larger, first season

catfish – improving net feed utilization.

 

Because low fish biomass and the use of feeding tables limits waste production, the nutrients released would stimulate (fertilize) pond productivity rather than pollute it.  It is generally accepted that fertile ponds will support 300 to 600 lb of fish/acre without additional feed or energy inputs.  Low stocking density allows fish to take advantage of naturally available food organisms in addition to commercial feed.  In theory, the fish manure and uneaten  feed  associated  with 1500 fish could  support  sufficient aquatic  life (insects, crustaceans, worms, etc.) to support 500 lb/acre of bonus fish growth.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

A general estimate for channel catfish production is to assume that 1.0 lb of food-fish will be harvested for each fingerling stocked.  Using this projection, 1500 fingerlings could be expected to yield 1500 lb/acre.  The estimated biomass of the low stocking density demonstration was 2,000 lb/acre – 500 lb/acre more than generally accepted.  It seems plausible that this bonus growth is related to an increase in pond fertility (natural foods) promoted by fish wastes, and efficient (table) feeding.  Low biomass (fish density), efficient feeding (good growth and limited wastes), and nutrient (fish wastes) stimulated fertility take full advantage (improved efficiency) of the pond ecosystem without exceeding biological and environmental limits.

 

Sustainable Low management Practices

 

It seems feasible that a combination of low density, autumn stocking (1500 fish/acre), table feeding, and continuous size selective harvest from autumn through spring could produce catfish yields as high as 2,250 to 3,000 lb/acre.  Ponds are not aerated because biomass and oxygen demand do not become critical during hot weather.  Also, the larger fish are removed with selective harvesting.  However, feeding is stopped during periods of low oxygen and resumed when fish begin feeding aggressively again.  Disease is not treated except in the case of a serious outbreak – low fish density minimizes stress as well as disease occurrence and spread.  Low biomass and limited waste production promote pond fertility and natural foods while maintaining acceptable water quality.  Heavy nutrient and organic loads are absent, and the likelihood of off-flavor problems is reduced.  All of this can be done with 5-gallon buckets, a team of horses, and without quitting the “day job.”

 

 

 

 

 

Intensive Channel Catfish Production

 

Intensive catfish production techniques leave little room for error and can be unforgiving for the novice.  Withholding antibiotics during a disease outbreak or eliminating summer aeration is likely to cause a 50 to 100% fish-kill in intensive production systems.  With the low management approach, not treating a disease or no aeration might result in a 5 to 10% fish loss, possibly as high as 25% under unusual circumstances.

 

As the number of pounds of catfish produced per acre increases, the cost to produce a pound of fish increases.  A catfish yield of 4500 lb/acre requires significant external inputs: energy (e.g. aeration), chemicals, antibiotics, feed, time, labor, etc.  These additional inputs cost money and cut into potential profits.  There is a point at which additional inputs do not increase yields and profits sufficiently to offset the extra costs and “risk” involved. Somehow, intensive aquaculture seems to have avoided the close scrutiny of “the economics of diminishing returns.”

 

The basic costs for low management catfish production, feed ($630; $0.14/lb) and fingerlings ($225; $0.15/fish), would be $855/acre.  Similar costs for intensive production, feed ($1260; $0.14/lb) and fingerlings ($675; $0.15/fish), would be $1935/acre.  Using the basic costs above and a wholesale catfish value (live-weight) of $0.80/lb, low management production would yield 2,250 lb fish/acre worth $1,800 and intensive production would generate 4,500 lb/acre worth $3,600.  Net profit (harvest value minus “basic costs”) would be $945/acre and $1,665/acre for low management and intensive farming, respectively.

 

A few hundred dollars profit per acre is significant when considering a 1,000 acre channel catfish operation.  However, deducting the costs associated with aeration, antibiotics, algicides and a 15% fish loss would substantially reduce the profit/acre for intensive practices.  The additional costs and risk of intensive catfish farming might not be acceptable for the 1.0- to 5.0-acre producer.

 

Marketing more than a few thousand pounds of fish requires wholesale pricing, bulk sales and large-scale processing.  The opportunities for local retail sales ($1.25/lb, live-weight) are more realistic when working with the smaller harvest of a low management, channel catfish business.  Similarly, retail sales can provide greater net profits, as high as $1950/acre, for 1.0- to 3.0-acre farms.

 

Towards the Future

Ninety thousand individuals, each farming a “low management,” 2.5-acre channel catfish pond, could surpass the total annual, channel catfish production for the Southeastern United States in 1993 (440 million pounds).  Future producers may improve pond efficiency further by incorporating filter feeding fish and mollusks into sustainable low management systems, taking advantage of the plankton populations present, yet largely unused, in catfish production ponds.  Furthermore, new technology may radically redefine the production unit as we know it.

 

Undoubtedly, competition for aquatic resources will continue to escalate in the 21^st century.  Moderate increases in the cost of electricity or petroleum based fuels could significantly affect the profitability of intensive fish production practices.  Whether channel catfish production is done in high-tech raceways and recirculation units, intensively managed ponds or sustainable low management systems; the practice used must be energy efficient and environmentally sound.  Ultimately, in order to benefit the most people, production technology must be user friendly and practicable with limited resources.  Bottom line, “keep it simple.”

 

Acknowledgements

The demonstrations reported were funded, in part, by the Tennessee Valley Authority.  We gratefully acknowledge assistance with demonstrations by Kenneth Perry and William Green, Cooperative Extension Agents for Agriculture with the University of Kentucky Cooperative Extension Service