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Special Topics Research


G. Special Topics Research

Economic Analysis of Different Tilapia Pond Culture Systems in Egypt

Work Plan 7, Egypt Study 1A

Hussein A. Hebicha and Abdel R. El Gamal
Central Laboratory for Aquaculture Research
Agricultural Research Center
Abbassa, Egypt

Bartholomew W. Green
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA

Abstract

Five different tilapia pond management strategies were evaluated for economic potential in 0.1-ha earthen ponds at the Central Laboratory for Aquaculture Research, Abbassa, Egypt. Pond management strategies were based on use of chemical fertilizer only, feed only, combination of organic fertilizer and feed, and combination of organic and chemical fertilizers and feed. Ponds were stocked with either mixed-sex or all-male populations of Nile tilapia. Yield and input data from 145-day pond trials were used to develop full-cost budgets for each management system. Net returns, values for production for major inputs, break-even prices and yields, and average rates of return to capital were estimated for each system based on a 2.1-ha production pond.

Net returns ranged from Egyptian pounds (L.E.) 19,102/2.1 ha for ponds stocked with all-male tilapia and receiving organic fertilizer and feed to L.E. 985/2.1 ha for ponds stocked with all-male tilapia and receiving chemical fertilizer only. The rates of return to capital for these two systems were 29.97% and 2.42%, respectively. Net returns to land and management for management systems that combined fertilization and feeding were, on average, 16.1 times the net returns for the extensive system. Management systems that combined fertilization and feeding also had the highest margins between average prices and break-even prices to cover total costs, which indicated reduced risks to farmers in the event of a decline in market prices. Sensitivity analyses indicated that combined fertilization-feeding systems maintained positive net returns if fish yield decreased by two standard errors and price decreased by 20%.

Effect of Stocking Rate on Growth and Yield of Nile Tilapia

Bartholomew W. Green
Department of Fisheries and Allied Aquaculture
Auburn University, Alabama, USA

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

Zeinab El Nagdy and Abdel R. El Gamal
Central Laboratory for Aquaculture Research
Agricultural Research Center
Abbassa, Egypt

Abstract

Nile tilapia are generally stocked at 20,000 fish/ha in semi-intensively managed production ponds. Nutrient inputs into these ponds include fertilizers and supplemental feeds; both natural pond productivity and supplemental feed contribute to fish growth. Often, pond carrying capacity and critical standing crop are not attained during the 5-month grow-out period, which indicates under-utilization of available pond nutrient resources. Knowledge of pond carrying capacity and density-dependent fish growth for a particular management system provides the ability to manipulate production management to improve efficiency and economic returns. The objective of this experiment was to quantify the growth and yield of Nile tilapia stocked at 30,000 and 40,000 fish/ha in production ponds.

This study was conducted at the Central Laboratory for Aquaculture Research (CLAR), Abbassa, Egypt. Three replications of each treatment (stocking rates of 30,000 or 40,000 Nile tilapia/ha) were randomly assigned to 0.1-ha earthen ponds. Sex reversed Nile (Oreochromis niloticus) tilapia fry (mean weight: 0.5 g/fish) were stocked into ponds on 20 and 24 July 1994. Chicken litter was applied weekly at 1,000 kg dry matter/ha for the first eight weeks of the production cycle followed by feed (25% protein commercial fish feed) only. Average mean individual fish weights based on seine samples were 69.9 and 79.4 g/fish for the 30,000 and 40,000 fish/ha stocking rates, respectively. Estimated respective mean fish biomasses, assuming 100% survival at the effective stocking rates, were 2,098 and 3,178 kg/ha. Ponds are scheduled to be harvested after 150 days of grow-out.

Mass Production of Nile (Oreochromis niloticus) and Blue (O. aureus) Tilapia Fry

Bartholomew W. Green
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA

Esam H. Rizkalla and Abdel R. El Gamal
Central Laboratory for Aquaculture Research
Agricultural Research Center
Abbassa, Egypt

Abstract

A consistent, reliable supply of fingerlings of the desired species, sex, and size is critical to the success of any aquacultural enterprise. Of the four tilapia species endemic to Egypt, Nile and blue tilapia are considered better species for pond culture than Sarotherodon galilae and Tilapia zilli. Hormonal sex reversal is the most efficient means of mass production of monosex tilapia fingerlings at present. Newly hatched fry of 9- to 11-mm total length are given an androgen-treated feed during a 28-day period. Fry for sex reversal can be mass produced in earthen ponds, but water temperature can affect productivity. The objective of this research is to quantify production of Nile and blue tilapia fry in relation to water temperature in Egypt.

A total of 68 reproduction pond harvests have been completed since trials were initiated on 17 April 94. To date, 858,300 fry have been harvested; of these 659,000, or 79%, were suitable for sex reversal. The contributions of Nile and blue tilapia to these totals was approximately equal. The reproductive performance of Nile and blue tilapia appeared similar. Grading fry through a 3.2-mm square plastic mesh consistently yielded fry of uniform size and weight; fry passing the grader were within the size range (9- to 11-mm TL) desired for sex reversal.

Forty-nine sex reversal trials have been completed and 16 were in progress at the time of this report. The mean stocking rate of fry in 2-m2 treatment hapas was 4,200 fry/m2. Two hundred sixty-nine thousand Nile tilapia fry and 275,600 blue tilapia fry have been stocked into treatment hapas to date. After the 28-day androgen treatment period, fry averaged 23.8 mm total length. Overall mean survival has been 51% to date. Water quality deterioration, primarily due to high concentrations of ammonia caused by high feeding rates, was probably responsible for much of the fry mortality. Tank management was modified and survival improved. However, limited availability of water, because of equipment malfunction, continued to restrict the ability to manage water quality in tanks, even at moderate feed loading rates.

Growth of Control and Androgen-Treated Nile Tilapia, Oreochromis niloticus (L.), during Treatment, Nursery and Grow-Out Phases in Tropical Fish Ponds

B.W. Green and D.R. Teichert-Coddington
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA

Abstract

(Printed as submitted)

Masculinization of sexually undifferentiated tilapia fry is achieved by oral administration of the androgen 17a methyltestosterone (MT). An anabolic response to androgen treatment of tilapia has been reported. Growth of control and MT-treated tilapia was evaluated during consecutive treatment, nursery and grow-out phases under conditions approximating commercial, semi-intensive tilapia farms in Central America. Oreochromis niloticus (L.) fry were fed a 0 or 60 mg/kg MT diet for 28 days. Growth curves for control and MT-treated fish did not have significantly different slopes. Mean harvest fry weights were similar, averaging 0.1 g/fry for both treatments. Fry were subsequently stocked into 0.2-ha nursery ponds for 94 days of growth. Slopes of control and MT-treated fish growth curves were significantly different. Mean final individual weights did not differ significantly between treatments. Control fish did not deviate from the 1.1 male:female ratio, but MT-treated fish were 97% males. Control-male and MT-treated male fingerlings were stocked for grow-out into 0.1-ha organically fertilized earthen ponds. No significant difference in growth was observed between control and MT-treated fish. Mean gross yields after 150 days and mean final individual weights were similar for both treatments.

Published in Aquaculture and Fisheries Management 25:613-621.

Production of Oreochromis niloticus Fry for Hormonal Sex Reversal in Relation to Water Temperature

B.W. Green and D.R. Teichert-Coddington
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA

Abstract

(Printed as submitted)

Recently hatched tilapia 9 to 11 mm total length (TL) are preferred for hormonal sex reversal because they are most likely to be sexually undifferentiated. Thirty-three trials were conducted in Honduras between September 1998 (sic) and March 1990 to quantify the effect of water temperature on Oreochromis niloticus fry production in earthen ponds for hormonal sex reversal. Two 0.1-ha ponds were simultaneously stocked with brood fish in each trial; generally, one pond was harvested after 17 days, the other after 20 days (range 16 to 21 days). Fry production was evaluated in relation to degree-days from the threshold temperature of 15deg.C. Harvests averaged 86,000 fry/0.05 ha. A total of 4,897,000 fry were produced, of which 4,363,000 fry were of appropriate size for hormone treatment. No fry production occurred at less than 140 degree-days; fry production increased significantly with increased degree-days above this level. Above 195 degree-days percent of the population retained by a 3.2-mm vexar-mesh grader (too large for androgen treatment) increased significantly with increased degree-days. Fry retained by the grader averaged 14.2 mm TL, while fry not retained by the grader averaged 9.5 mm TL. No significant linear relationship between degree-days and number of fry not retained by the grader was observed between 140 and 280 degree-days. However, production appeared to peak at about 210 degree-days.

Published in Journal of Applied Ichthyology 9:230-236.

Phosphorus Fertilization Strategy in Fish Pond Based on Sediment Phosphorus Saturation Level

Madhav K. Shrestha and C. Kwei Lin
Agricultural and Food Engineering Program
Asian Institute of Technology
Bangkok, Thailand

Abstract

(Printed as submitted)

Two experiments were conducted to determine effective phosphorus (P) fertilization strategy in fish ponds in relation to sediment P saturation level. Experiment 1 was conducted in cement tanks with five levels of P saturated sediments (5%, 24%, 44%, 60% and 79%) and with three P-fertilization rates (0.2, 0.1 and 0.05 g/m3/day, N:P ratio of 2:1, 4:1 and 8:1, respectively. Nile tilapia (Oreochromis niloticus) were cultured in those cement tanks for 57 days. Results showed that the mean concentration of soluble reactive phosphorus (SRP) in water column increased with increasing sediment P saturation and P fertilization rate. The maximum net fish yield (NFY), 4.2+/-0.3 g/m3/day, was obtained at SRP concentration of 0.3 mg/L and higher concentrations did not increase fish yield. This level of SRP and NFY were attainable with P fertilization rate of 0.2, 0.1 and 0.05 g/m3/day and N:P ratio of 2:1, 4:1 and 8:1 in ponds were the level of sediment P saturation was below 10%, above 45% and above 60%, respectively. Experiment 2 was conducted in earthen ponds to test and verify the P fertilization rate based on cement tank experimental results. Three new and three old ponds with 8+/-1.7% and 88+/-7.3% sediment P saturated in top 5-cm mud were fertilized at a rate of 0.2 and 0.05 g/m2/day and N:P ratio of 2:1 and 8:1, respectively. Nile tilapia were cultured at 2/m2 for 85 days. The mean NFY obtained in new and old ponds were 1.73+/-0.08 and 2.24+/-0.32 g/m2/day, respectively, which were not significantly different (P > 0.05). Results conclude that P fertilization rate should be based on P saturation level in mud to overcome the problem of under supply or over supply of P in fish pond.

Accepted for publication by Aquaculture.

Determination of Phosphorus Saturation Level in Relation to Clay Content in Pond Mud

Madhav K. Shrestha and C. Kwei Lin
Agricultural and Food Engineering Program
Asian Institute of Technology
Bangkok, Thailand

Abstract

(Printed as submitted)

An experiment was conducted to determine the amount of phosphorus (P) needed to saturate simulated fish pond sediments which were made up to contain six levels of clay at 0%, 30%, 41%, 64%, 73% and 81% by weight. A series of cylindrical cement tanks were filled to 20 cm depth with six sediment types and triple superphosphate (TSP) solution was added to reach P saturation in sediment. Results showed that all sediment types reached constant inorganic-P concentration in upper 5-cm after 12 weeks of TSP application, and P adsorption capacity of sediment increased with increasing clay content. Sediment P adsorption was slower and not significant (P > 0.05) below the 5-cm depth except that contained 0% clay. Regression analysis showed that rate and adsorption capacity of P in sediment are primarily governed by clay content and its dominant minerals. While organic-P and loosely bound-P are commonly deposited in sediment most inorganic P is absorbed by cations to form cation-P complex. The linear relationship between cation-P saturation level and percent clay in sediment is highly significant (r2 0.34, P < 0.001) and therefore, the maximum adsorption capacity of cation-P in pond sediment can be calculated by Y = 0.019 X (Y = 100% saturation level mg-P/g soil: X = % clay in sediment). In practice the level of P saturation (%) in sediment can be calculated by the initial cation-P and clay content (%) in top 5-cm of pond mud using the equation: P saturation (%) = initial cation-P (mg/g soil) X 100/P adsorption capacity (mg/g soil).

Accepted for publication by Journal of Aquaculture Engineering.