THA/75/012/WP 15 COMPARISON OF THE EFFECTS OF TRASH FISH AND PELLETED DIETS IN CLARIAS GROW-OUT OPERATIONS CONTENTS

by

Vijai Srisuwantach, Rangsarn Soungchomphan
and
Prasert Sitasit

Programme for the Development of Pond Management Techniques
and Disease Control (DoF - UNDP/FAO THA/75/012)
Thailand

National Inland Fisheries Institute
Bangkok, Thailand
1981

PREFACE

The “Programme for the Development of Pond Management Techniques and Disease Control (THA/75/012)” was implemented in Thailand during 1979–82 as a joint project by the Department of Fisheries (DoF) and UNDP/FAO. The purpose of the project was to improve DoF support services for Clarias farming through strengthening:

1. the skills of Fisheries staff in aquaculture disciplines such as disease diagnosis and treatment, pond management and extension,

2. the research on solutions for problematical aspects of Clraias culture,

3. the system of relaying problems from the farms to DoF and of transferring improved technologies, and

4. the equipment and facility base of DoF for working on aquaculture problems.

Although the UNDP/FAO participation was structured terminate in August 1981, DoF committed continuation of the project to at least August 1982.

This report is one of several Working Papers prepared on various aspects of the project. A list of titles of reports completed in the series is annexed.

Inquiries concerning the subject matter of any particular report should be directed to the author,

Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibility for the opinions, ideas, data or products presented at these locations, or guarantee the validity of the information provided. The sole purpose of links to non-FAO sites is to indicate further information available on related topics.

This electronic document has been scanned using optical character recognition (OCR) software. FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.

CONTENTS

ABSTRACT

1. INTRODUCTION

2. METHODS

3. RESULTS

3.1 Environmental Conditions

3.2 Fish Production

4. DISCUSSION

4.1 Water Conditions

4.2 Fish Growth

4.3 Feed Convention

4.4 Disease Outbreaks

5. REFERENCES

List of Figures

1. General plan of the Suchart Farm

2. Daily fluctuation of air temperature (morning and afternoon) at the site of study ponds, November 1980 to March 1981

3. Water temperature (morning and afternoon) in four study ponds, November 1980 to March 1981

4. Secchi disc transparency in four study ponds, November 1980 to March 1981

5. pH values (morning and afternoon) in four study ponds, November 1980 to March 1981

6. Carbon dioxide (morning and afternoon) in four study ponds, November 1980 to March 1981

7. Dissolved oxygen (morning and afternoon) in four study ponds, November 1980 to March 1981

8. Morning nitrite nitrogen in four study ponds, November 1980 to March 1981

9. Afternoon ammonia nitrogen and un-ionized ammonia in four study ponds, November 1980 to March 1981

10. Daily values of primary production and biological oxygen demand in four study ponds, November 1980 to March 1981

11. Daily mortality for Clarias reared on trash fish (pond 1 and 4) and commercial pellets (pond 5 and 6) in four study ponds, November 1980 to March 1981

List of Tables

1. Mean values of water characteristics in four study ponds during the grow-out period (November 1980 to March 1981)

2. Production parameters of Clarias reared on trash fish and commercial pellets in four study ponds, November 1980 to March 1981

3. Seed fish and feed costs compared with revenue in grow-out operations of Clarias reared on trash fish and commercial pellets, November 1980 to March 1981

COMPARISON OF THE EFFECTS OF TRASH FISH AND PELLETED DIETS IN CLARIAS GROW-OUT OPERATIONS¹

Vijai Srisuwantach², Rangsarn Soungchomphan²
and
Prasert Sitasit³

ABSTRACT

The environmental characteristics of four ponds and the production performance of Clarias in the ponds was investigated in response to the application of two feeds from November 1980 to March 1981. Each of the 800 m² ponds was stocked with 20,000 fry, averaging 6.8 g; trash fish was applied in two ponds and a pelleted diet in the other two. After 5 months 26% of the Clarias fed on trash fish survived; they had attained an average weight of 94.2 g at the rate of 0.61 g/day. The survival rate of Clarias fed a pelleted diet was 22%; the fish reached an average weight of 86.2 g in 5 months at the rate of 0.55 g/day. Corresponding net yields for the period were 0.434 and 0.279 kg/m².

Water quality conditions were comparable in each pond throughout the grow-out period with the exception that BOD values in ponds fed on trash fish averaged 8.4 g O₂/m³/day is opposed to 6.9 g O₂/m³/day in ponds where pelleted food was used.

Chemical adversities were not as pronounced as recorded in similar culture operations. The difference was attributed to relative low stocking densities and to frequent water exchanges in the study ponds.

The high mortality, slow growth and outbreaks of disease was related to the relatively low water temperatures and the amplitude of change which occurred through the culture period.

¹ Completed as a component study under the DOF-UNDP/FAO “Programme for the Development of Pond Management Techniques and Disease Control (THA/75/012)”.

² Fisheries biologists, Ecology Unit, National Inland Fisheries Institute, Kasetsart University Campus, Bangkhen, Bangkok 9, Thailand.

³ Chief, Fish Nutrition Unit, National Inland Fisheries Institute, Kasetsart University Campus, Bangkhen, Bangkok 9, Thailand.

1. INTRODUCTION

One of the most problematical aspects of Clarias grow-out operations in Thailand is the incidence of relatively high mortality. The deaths are usually attributable to adverse water conditions and infectious disease. Srisuwantach et al., (1980) indicated the occurence of deleterious concentrations of un-ionized ammonia (NH₃) and the prolonged deficiency of dissolved oxygen (DO) in typical Clarias grow-out ponds. The authors, postulated a stressing effect of these water conditions which rendered the fish vulnerable to Aeromonas spp., disease. The high NH₃ and the low DO were related to the decomposition of uneaten food (chiefly trash fish) and of Clarias excretory products.

Amongst the general advancements in aquaculture is the practice of using pelleted food which allows close control on amounts being delivered and which results in reduced water degradation when uneaten pellets decompose. A few Clarias farmers in Thailand have recently tried pelleted food and some report very satisfactory results. Interest is growing, commercial feed companies are now marketing pelleted fish food and increased applications are expected. No systematic information, however, has yet been assembled to demonstrate the growth and production response of Clarias to pelleted food or to show the effects on water conditions. This study was thereby undertaken to help establish the required reference information by comparing the relative effects of a traditional trash fish diet and a pelleted diet on water quality and fish yield in Clarias grow-out operations.

2. METHODS

The field component of the study was conducted at the Suchart Farm, a Clarias fingerling production farm, in Chacheongsao Province, Thailand, during the 5-month period, November 1980 to March 1981. A general plan of the farm is shown in Figure 1.

Clarias in the study were cultured in 4 of 6 earthen ponds (Nos. 1, 4, 5 and 6) having the same dimensions, 16.7 x 48 m (800 m²). Water levels were maintained at a maximum depth of 42 cm. Each pond was stocked at the rate of 25/m² with fish having an average weight of 6.8 g.

The fish in ponds No. 1 and No. 4 were fed the traditional diet of trash fish and rice bran (9:1 by weight) but fortified with a vitamin and mineral premix. A commercially prepared floating pelleted food was applied in ponds No. 5 and No. 6. The amount of feed initially delivered to each pond was determined on the basis of 10% of the body weight of the fish/day in the case of the trash fish diet and 5%/day in the case of the pelleted diet. Ration size was then adjusted every week in correspondence with observations on the extent that the fish consumed the food given to them in the previous week. If accumulations of uneaten food were apparent in a week then smaller amounts were given in the following week and vice versa.

Figure 1: General plan of the Suchart Farm.

Water was exchanged in the ponds once per month in the first two months and twice per month during the last three months of the growout period. Additional exchanges were made when fish were evidently in distress. During an exchange, half of the pond water was removed, formalin was added to a concentration of 30 mg/1, then after a few hours the pond was filled to maximum level with khlong water.

Physical and chemical conditions of the ponds were measured twice a day (7.00 a.m. and 3.00 p.m.) on a biweekly basis through the 5-month period. Water samples were drawn from the center of ponds with a Van Dorn sampler. Parameters and the methods of measurement were the same as reported in Srisuwantach et. al., (1980) with the exception of NO₂-N. It was determined on filtered samples assayed by a spectrophotometer (Spectronic 88, Baush and Lamb) using the method described by Stainer et. al., (1977).

3. RESULTS

3.1 Environmental Conditions

Most of water quality parameters were similar in all four ponds as summarized in Table 1.

Air temperature (Fig. 2) of the culture site varied from 18.5 – 26.0°C (morning) and 27.0 – 36.0°C (afternoon).

The temperature of the pond water (Fig. 3) ranged from 22.0 – 29.5°C (morning) and 26.5 – 37.0°C (afternoon) in all ponds.

Secchi disc transparency (Fig. 4) was relatively low throughout the growing period. It ranged from 2 – 20 cm in all ponds. Averaged Secchi disc of the two ponds receiving the same diet were 9.0 cm (trash fish) and 9.1 cm (pellet).

Daily fluctuation of pH was similar in all ponds (Fig.5). The morning pH was low (6.4 – 7.5) while afternoon values were high (6.8 – 9.6). The average pH during the grow-out period of two diets was the same (7.05).

Concentration of CO₂ (Fig. 6) was low in all ponds both in the morning (1 – 4 mg/1) and afternoon (0 – 2 mg/1).

Table 1: Mean values of water characteristics in four study ponds during the grow-out period (November 1980 to March 1981)

Figure 2: Daily fluctuation of air temperature (morning and afternoon) at the site of study ponds, November 1980 to March 1981.

Figure 3: Water temperature (morning         and afternoon -----) in four study ponds, November 1980 to March 1981.

Figure 4: Secchi disc transparency in four study ponds, November 1980 to March 1981.

Figure 5: pH values (morning         and afternoon -----) in four study ponds, November 1980 to March 1981.

Figure 6: Carbon dioxide (morning         and afternoon -----) in four study ponds, November 1980 to March 1981.

Do levels (Fig. 7) were low (0 – 3.2 mg/l) in the morning and high (0.9 – 17.8 mg/l) in the afternoon throughout the growing period. The average values were 0.7 mg/l (morning) and 9.7 mg/l (afternoon) in ponds fed on trash fish and 0.6 mg/l (morning) and 8.6 mg/l (afternoon) in ponds fed on pelleted food.

NO₂ was low in all ponds (Fig. 8) with the average values of 0.029 mg/l (trash fish) and 0.013 mg/l (pellets).

Ammonia concentrations (Fig. 9) were low; the averaged concentrations in trash fish and pelleted food ponds were 0.3 mg/l and 0.14 mg/l, respectively. Un-ionized ammonia was also low (Fig. 9). The averaged values were 0.09 mg/l (trash fish) and 0.02 mg/l (pellet).

Primary production (Fig. 10) was high throughout the growing period. The averaged gross production were 4.41 g O₂/m³/d (trash fish) and 5.12 g O₂/m³/d (pellet). BOD was also hi gh (Fig. 10) with averaged values of 8.42 g O₂/m³/d (trash fish) and 6.91 g O₂/m³/d (pellet).

3.2 Fish Production

Stocking survival, harvesting and growth data of fish in the four study ponds are presented in Table 2. An economic evaluation of the production is summarized in Table 3 where revenue is compared only with the cost of input materials (seed fish plus feed).

At the end of the 5 months Clarias fed on trash fish attained an average weight of 94.2 g while those fed on pelleted diet averaged 86.2 g. The average daily increments by treatment were 0.61 and 0.55 g fed on trash fish and pellets, respectively.

Feeding rates were computed by assuming a straight-line-mortality based on biomass at stocking and biomass at harvest then using the slope of the line to estimate biomass at any time in between. The averaged feeding rate of the grow-out period worked out to be 11.5 and 7.8% for trash fish and pelleted food, respectively. The same procedure was applied to Clarias fed on trash fish at Jalernphorn Farm (Srisuwantach et. al., 1980) and the averaged feeding rate turned out to 6.5%.

An average net yield of 0.587 kg/m² (trash fish) and 0.432 kg/m² (pellet) was obtained. Food conversion ratios were quite high with an average of 14.5 (trash fish) and 9.7 (pellet). The survival rate was low in both diets with an average of 26% (trash fish) and 22% (pellet).

Disease outbreaks were observed twice in all ponds (Fig. 11). Each outbreak occurred at the same period from day 15 to 30 and day 105 to 125.

Figure 7: Dissolved oxygen (morning         and afternoon -----) in four study ponds, November 1980 to March 1981.

Figure 8: Morning nitrite nitrogen in four study ponds, November 1980 to March 1981.

Figure 9: Afternoon ammonia nitrogen (         ) and un-ionized ammonia (-----) in four study ponds, November 1980 to March 1981.

Figure 10: Daily values of primary production (         ) and biological oxygen demand (-----) in four study ponds, November 1980 to March 1981.

Table 2: Production parameters of Clarias reared on trash fish and commercial pellets in four study ponds at Bang Pakong, November 1980 to March 1981.

Table 3: Seed fish and feed costs compared with revenue in grow-out operations of Clarias reared on trash fish and commercial pellets, November 1980 to March 1981.

Figure 11: Daily mortality for Clarias reared on trash fish (pond 1 and 4) and commercial pellets (pond 5 and 6) in four study ponds, November 1980 to March 1981.

4. DISCUSSION

4.1 Water Conditions

High levels of DO (Fig. 7) observed in the afternoon throughout the growing period were caused mainly by the high rate of photosynthesis (Fig. 10) which inturn result in low NH₃ (Fig. 9) due to algal assimilation. The average BOD of the ponds fed on trash fish (8.42 g O₂/m³/d) was higher than that fed on pellet (6.91 g O₂/m³/d) probably caused by the higher rate decomposition of trash fish than pellet. Better water quality in study ponds (ie. high DO and low NH₃) than that of ponds reported by Srisuwantach et. al., 1980. was probably due to a combination of more flushing and lower fish densities.

4.2 Fish Growth

The average daily increment in weight per fish in this study (0.61 g fed on trash fish and 0.55 g fed on pellet) were lower than that at Jalernphorn Farm (0.76 and 0.94 g.) which reported by Srisuwantach et. al., (1980). The lower growth rate may have been due to low water temperatures (26.2°C at 7.00 a.m. and 31.9°C at 3.00 p.m.) which prevailed through the grow-out period (November 1980 to March 1981) and influenced the rate of metabolism and therefore the growth rate (Bennett 1970). This period corresponds to the winter in Thailand. There is little information to show the exact effect of temperature on growth of warm water fish and no data are available to serve as a quantitative reference for this effect on Clarias. However, the better growth rate of Clarias reported by Srisuwantach et. al., (1980) where the average water temperature during the grow-out period (March to July) was 29.4°C (6.00 a.m.) and 32.7°C (4.00 p.m.) showed that summer grow-out period had more favourable thermal conditions than winter grow-out period.

4.3 Feed Conversion

The high feed conversion ratios (14.5 fed on trash fish and 9.7 fed on pellet) were probably the result more feed being applied than the fish could consume under the temperature circumstances. The rate of food consumption increase with increased temperature (Brett, 1979). At lower temperature, food consumption decreased (Shell, 1966).

4.4 Disease Outbreaks

Disease is not a simple result of contact between host and pathogen; it is a complex interaction between host, pathogen, and environment (Snieszko, 1974). Environment is the most important and unstable of these three factors and its importance is intensified by the presence of potential pathogens that commonly coexist in the water (Walters and Plumb, 1980) Change in water quality may be directly lethal to fish and sublethal changes may stress fish sufficiently to predispose them to infectious diseases. In attempting to discuss the role of environmental stress on outbreaks of infectious diseases of fishes one has to consider the relationship between the noxious stimulus and outbreaks of disease (Snieszko, 1974).

Adverse water quality, resulting in lethal and sublethal conditions, often involves low dissolved oxygen, elevated carbon dioxide and elevated ammonia levels. The addition of 1.1 mg/1 NH₃-N significantly increased mortality in channel catfish as did the addition of 6.0 mg/l CO₂ and DO being maintained at 1.5 mg/l (Walters and Plumb, 1980). The role of these three factors (0.1 – 0.4 mg/1 afternoon average NH₃-N; 1.7 – 1.9 mg/l morning average CO₂; 7.9 – 10.1 mg/l afternoon average DO) as stressors relating to disease was less pronounced in our study.

Temperature - induced stress might have been significant in the study ponds. Temperature has a particular significant influence on diseases of fishes in areas where there is a wide amplitude in daily and seasonal temperature changes (Meyer, 1970). Average daily amplitude of water temperature in study ponds before disease outbreaks was 7.2°C (26.9°C at 7.00 a.m. and 34.1°C at 3.00 p.m.) for the first outbreak and 4.2°C (25.4°C at 7.00 a.m. and 29.6°C at 3.00 p.m.) for the second outbreak. High daily amplitude of water temperature in the study ponds may have been related to the shallowness of the ponds (0.42 cm) as well as to the winter season.

5. REFERENCES

Bennett, G.W., 1970.
Management of lakes and ponds. Van Nostrand Reinhold Comp. 375 p.

Brett, J.R., 1979.
Environmental factors and growth. In Fish Physiology, (W. S. Hoar, D. J. Randall and J. R. Brett, eds) Vol. VIII, p. 599–675. London Academic Press.

Meyer, F.P., 1970.
Seasonal fluctuations in the incidence of disease on fish farms. In a symposium on diseases of fishes and shellfishes, (S.F. Snieszko, ed.) p. 21–29. Special Publication No. 5 Washington, D.C. American Fisheries Society.

Shell, E. W., 1966.
Relationship between rate of feeding, rate of growth and rate of conversion in feeding trials with two species of tilapia Tilapia mossambica Reters and Tilapia nilotica Linnaeus. FAO Fisheries Reports No. 44, Vol. 3, III/E-9 p. 411–415.

Snieszko, S.F., 1974.
The effects of environmental stress on outbreaks of infectious diseases of fishes. J. Fish. Biol. 6: 197–208.

Srisuwantach, V., R. Soungchomphan and P. Sae-Eng, 1980.
Water quality condition as disease related stressors in Clarias ponds. Ecol. Tech. Pap. No. 3 National Inland Fisheries Institute, Bangkok, Thailand 33p.

Stainton, M. P., M. J. Capel and F. A. J. Armstrong, 1977.
The chemical analysis of freshwater. Fish. Res. Board Can. Misc. Spec. Publ. 25. 125p.

Walters, G. R. and J. A. Plumb, 1980.
Environmental stress and bacterial infection in channel catfish, Ictalurus punctatus R.J. Fish. Biol. 17: 177–185.

The Programme for the Development of Pond Management
Techniques and Disease Control
(DoF-UNDP/FAO THA/75/012)

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