IV. Abstracts of Technical Reports

D. Southeast Asia

Stocking Density and Supplement Feeding

Work Plan 6, Thailand Study 6

James S. Diana
School of Natural Resources and the Environment
University of Michigan
Ann Arbor, USA

C. Kwei Lin and Yang Yi
Agriculture and Aquatic Systems
Asian Institute of Technology
Bangkok, Thailand

Abstract

The purpose of this experiment was to determine the upper limits of tilapia production utilizing supplemental feeding. Fish were stocked at three, six, and nine fish/m². The fish were supplemen-tally fed to satiation during culture for 194 days. Growth, survival, yield, and water quality were evaluated during the experiment. Growth continued in a linear fashion throughout the experiment. Density-dependent growth occurred with the lowest stocking density, which had a significantly higher growth rate than the intermediate stocking density. The intermediate stocking density had a significantly higher growth rate than the highest stocking density. Survival also differed significantly among treatments, with lowest survival at the highest density. Feeding rate averaged 1.65% BW/d, and was not significantly different among treatments. Feed conversion rate averaged 0.40 and also was not significantly different among treatments. Dissolved oxygen (DO) content differed significantly among treatments, with mean DO at 0600 hr significantly lower in the high density treatment than in the low density treatment. Also, the total number of data-logged hours when DO was less than 1 mg/l was significantly different among treatments, with the low density treatment having significantly fewer hours of low DO than the high density treatment. Alkalinity and dissolved inorganic nitrogen also differed significantly among treatments. The DIN and ammonia levels were significantly higher in high density ponds than in low density ponds. Partial economic analysis indicated that stocking densities of 3 and 6 fish/m² at growout were profitable, while a stocking density of 9 fish/m² was unprofitable. The most profitable system was stocked 6 fish/m² and intensively fed. If the fish had been allowed to grow to 500 g in size and reach a market price of $150 per pond, then this system would have been particularly profitable.

Water Quality in Laboratory Soil-Water Microcosms with Soils from Different Areas of Thailand

Interim Work Plan, Africa Study 5

Claude E. Boyd and Prasert Munsiri
Department of Fisheries and Allied Aquacultures
Auburn University
Auburn, USA

(Printed as Submitted)

Abstract

Forty-five soil samples were collected from aquacul-ture areas in 23 provinces of Thailand to include six soil orders that vary in physical and chemical properties. Soil-water microcosms were prepared containing 5 g of soil and 150 ml of distilled water. Microcosms were held on an oscillating table shaker (150 rpm) for 1 week at 25°C in the dark. Water pH and concentrations of dissolved nutrients, total alkalinity, and total hardness were measured. Differences in properties within soil orders caused wide variation in composition of solutions and differences in concentrations of dissolved substances and pH were not related to soil order. Regression analyses revealed significant correlations between concentrations of soil nutrients extractable in dilute acid (0.05 N HCl plus 0.025 N H₂SO₄) or in neutral, 1 N ammonium acetate and aqueous concen-trations. Correlation coefficients usually were higher for dilute-acid extractable nutrients than for ammonium acetate extractable ones. Correlation coefficients based on dilute-acid extractable nutrients follow: soluble reactive phosphorus (r = 0.816); calcium (r = 0.685); magnesium (r = 0.470); potassium (r = 0.959); sodium (r = 0.977); manganese (r = 0.462); boron (r = 0.399). The correlation between soil and solution iron was not significant and aqueous concen-trations of copper and zinc were below detection limit. Hardness was correlated with soil carbon (r = 0.710) and soil pH was a good predictor of alkalinity (r = 0.877). Soil pH and aqueous pH were also highly correlated (r = 0.939). Findings suggest that soil characteristics can be used to predict pH and concentrations of several dissolved substances in soil-water systems under aerobic conditions.

Finishing System For Large Tilapia

Interim Work Plan, Thailand Study 4

Yang Yi and C. Kwei Lin
Agricultural and Aquatic Systems
Asian Institute of Technology
Bangkok, Thailand

Abstract

An integrated culture system was compared with a mixed-pond culture system in an experiment to achieve the following: 1) determine the effect of different stocking densities of open-pond small tilapia on the growth performance of both caged and open-pond large tilapia, and 2) assess the overall growth performance of both large and small tilapia in each system. Six ponds, each containing two 4 m³-net cages, and six open-water ponds, all without cages, were stocked with 400 sex-reversed, large tilapia (122-125 g) per pond. Sex-reversed small tilapia (15-16 g) were stocked at 1.4 fish/m³ and 2 fish/m³ in both the integrated and the mixed-pond culture systems. Commercial floating pellets containing 30% crude protein were given to cages in the integrated system and to open water in the mixed-pond system twice daily at the feeding rates of 3%, 2.5%, and 2% body weight per day for the first, second, and third month, respectively. Water quality was analyzed biweekly for DO, temper-ature, pH, NH₃, and chlorophyll-a. Growth of large tilapia in cages of the integrated culture system was better than of large tilapia of the mixed-pond culture system. Extrapolated net yields of large tilapia in the integrated culture system (4.3 and 3.3 t/ha/crop for the low and high density treatments, respectively) were signficantly greater than the extrapolated net yields of the mixed-pond culture system (2.8 and 2.7 t/ha/crop for the low and high density treatments, respectively). Feed conversion ratios were also signifi-cantly lower for the integrated culture system (0.92 and 1.04 in the low and high density treatments, respec-tively) than the mixed-pond culture system (1.22 and 1.16 in the low and high density treatments, respectively). This experiment demonstrated the practicality of a tilapia-tilapia cage-cum pond integrated rotation system that is based on the intensive culture of adult Nile tilapia in cages and the semi-intensive culture of small Nile tilapia in the surrounding open-water earthen pond.

Polyculture in Deep Ponds

Interim Work Plan, Thailand Study 3

C. Kwei Lin
Agricultural and Aquatic Systems
Asian Institute of Technology
Bangkok, Thailand

James Diana
School of Natural Resources and Environment
University of Michigan
Ann Arbor, USA

Abstract

The objective of this study was to assess the effects of carp-tilapia polyculture on water quality and fish yield in deep, rain-fed ponds. Four experimental treatments, conducted in twelve 800 m² ponds, at the Department of Fisheries-Udorn Thani Station, Thailand were as follows: (T1) ponds stocked with Nile tilapia (Oreochromis niloticus) at 2 fish/m², (T2) ponds stocked with Nile tilapia (2 fish/m²) and common carp (Cyprinus carpio) at a density of 1000 carp/ha, (T3) ponds stocked with Nile tilapia (2 fish/m²) and common carp at 2000 carp/ha, and (T4) ponds stocked with Nile tilapia (2 fish/m²) and common carp at 3000 carp/ha. Sex-reversed, all male tilapia (4-5 g average weight) and common carp (450-500 g average weight) were used to stock the ponds. Ponds were fertilized weekly with chicken manure and supplemented with urea and TSP; fish were harvested after 186 days of culture. Growth was measured monthly and the chemical and physical conditions of the pond water were monitored. One-way analysis of variance was used to statistically analyze treatment effects. Pond water temperature and DO between surface and bottom water were not significantly different; TAN, TKN, TP and chlorophyll-a concentrations among treatments were also not significantly different. Fish growth performance of Nile tilapia did not significantly differ between monoculture and polyculture treatments. For all polyculture treatments, common carp lost weight during the experimental period. Weight loss of common carp may be attributed to an undesirable feeding environment.

Carp/Tilapia Polyculture on Acid-Sulfate Soils

Work Plan 7, Thailand Study 5

James P. Syzper
Hawaii Institute of Marine Biology
University of Hawaii at Manoa
Kaneohe, USA

Kevin D. Hopkins
College of Agriculture
University of Hawaii at Hilo
Hilo, USA

Abstract

PD/A CRSP research in Thailand has concentrated on the dynamics of Oreochromis niloticus monocultures. Because O. niloticus is primarily a planktivore, the addition of the benthic detritivore Cyprinus carpio was hypothesized to lead to increased system productivity through the conversion of currently unutilized benthic matter into fish flesh. A five-month experiment was conducted in earthen ponds with a 200 m² surface area at the Asian Institute of Technology. Five treatments that included carp stocking densities of 0, 0.1, 0.3, 0.5, and 0.7 fish/m² were conducted in triplicate. Ponds were fertilized weekly with chicken manure, urea, and triple super phosphate (TSP). Preliminary results revealed that tilapia growth was slow and uniform across blocks and treatments. This may have occurred because larger fish (> 25 g/fish) initially intended for the stocking of this experiment were erroneously selected from the batch to stock a different experiment. Carp growth was density dependent and inversely related to stocking density; carp of initial (pond mean) weights ranging from 11 g to 40 g/fish grew to pond means ranging from 41 g to 270 g/fish during a five month period. Through the first half of the experiment, there was little indication of treatment-related differences in water quality except in measures of turbidity. Total suspended solids were markedly lower in ponds without carp.

On-Farm Production Trials with Nile Tilapia in Fertilized Ponds in Highland and Lowland Areas of the Philippines

Interim Work Plan, Philippines Studies 1 and 3

Eduardo Lopez
Freshwater Aquaculture Center
Central Luzon State University
Muñoz, Philippines

James P. Syzper
Hawaii Institute of Marine Biology
University of Hawaii at Manoa
Kaneohe, USA

Kevin D. Hopkins
College of Agriculture
University of Hawaii at Hilo
Hilo, USA

Antonio Circa
Freshwater Aquaculture Center
Central Luzon State University
Muñoz, Philippines

Abstract

Three on-farm yield trials, were conducted during a coherent production period of four to six months on Luzon island in the Philippines. Two of the trials took place in lowland areas of central Luzon, Nueva Ecija province; the third was conducted at elevations of 1000 to 1700 m in Mountain province. The farmers were instructed to use the CRSP fertilization guidelines. Data were collected from 54 ponds ranging in size from 25 m² to 5865 m². Extrapolated yields from fertilized ponds were highly variable ranging from approximately 500 kg/ha/yr to above 3900 kg/ha/yr. The primary factor determining yields was the density of stocked fish which survived to harvest (R² = 0.69). Two of the farmers used feeds and attained yields over 9000 kg/ha/yr.

Global Examination of Relationship between Net Primary Production and Fish Yield

Interim Work Plan, Thailand Study 1

James P. Syzper
Hawaii Institute of Marine Biology
University of Hawaii at Manoa
Kaneohe, USA

Kevin D. Hopkins
College of Agriculture
University of Hawaii at Hilo
Hilo, USA

Abstract

Previous PD/A CRSP research has examined the relationship between primary productivity and net yield of Oreochromis niloticus using data from individual experiments or earlier versions of the Central Database. In an effort to develop a more generalized model, a global analysis of this relationship was conducted using a recent version of the Central Database as the source of raw data. Average daytime net primary productivity (dNPP) and net fish yield (NFY) were computed for 505 ponds. dNPP ranged from < 1 to > 17 mg DO/l/daylight period. NFY were as high as 12 g fish/m²/d although most values were below 2 g fish/m²/d. There was an exponential relationship between dNPP and NFY.