Note: Schedule has been revised. See First Addendum to the Eighth Work Plan and Second Addendum to the Eighth Work Plan

Objective
Significance
Anticipated Benefits
Identification of Beneficiaries
Collaborative Arrangements
Experimental Design
Identification of Deliverables
Schedule/Timeline
References

Objective

To determine the effect of increased stocking rate on pond nutrient budgets, tilapia growth and yield, and production economics.

Significance

PD/A CRSP research areas addressed by this experiment are production optimization and environmental effects. Specifically, increased understanding of pond dynamics and feed utilization in intensively managed ponds and potential pollutional impacts of effluents from such ponds will be studied. In order to increase profitability of tilapia culture, intensification of pond management systems is necessary to produce larger fish for urban markets (450-500 g) and export markets (500-700 g). Tilapia were stocked at 20,000 fish/ha in semi-intensive production with fertilizers and/or supplemental feed. Intensification involves increased stocking rates and use of high quality formulated diets. Tilapia yields of 11,000-15,000 kg/ha in 5-8 months were reported in Thailand in fertilized and fed ponds stocked with 3 fish/m² (Diana et al., 1994; Diana et al., 1995a). Stocking rates of 3, 4.5 and 6 tilapia/m² were tested in Thailand, however low survival complicated data analysis (Diana et al., 1995b). Past Honduras PD/A CRSP tilapia research has concentrated on semi-intensive production practices and response of water quality in fertilized and fed ponds stocked with 2 fish/m² (Teichert-Coddington et al., 1991; Green, 1992; Teichert-Coddington et al., 1992; Teichert-Coddington et al., 1993). These results will serve as a point of reference for the study proposed herein. High feeding rates required for intensive fish production lead to deterioration of pond water quality, which can depress fish growth or result in fish kills (Boyd, 1990; Teichert-Coddington and Green, 1993). However, there is little information available in the literature on the effects of intensive tilapia production strategies on pond nutrient budgets and pond effluents.

Commercial production of tilapia is expanding rapidly in Central America; however, hyper-intensive production systems often are being promoted to potential fish farmers. There are few or no sustainable technological packages for profitable tilapia production available to tilapia farmers in Central America. Only 12 of 41 production systems developed during the mid- to late-1980's by the PD/A CRSP were profitable and none yielded the larger-sized fish required by urban and export markets (Green et al., 1994). Commercial tilapia farms in Honduras routinely stock 5 to 7 fish/m². The goal of the proposed research is to develop sustainable pond management practices for small- to medium-scale commercial tilapia farmers in Honduras.

Anticipated Benefits

Results of this research will provide information on disposition of nutrients added as feed to intensively managed ponds, on quality of pond effluents and their pollutional potential, on growth, survival and yield of tilapia at different stocking rates, and on production economics of intensified pond management strategies.

Identification of Beneficiaries

Small- to medium-scale commercial tilapia producers in Honduras will benefit from systematically derived recommendations on stocking rates for intensive tilapia production. Information generated from this research also should be adaptable by tilapia farmers throughout Central America. Aquacultural scientists and students will benefit from this research through an improved understanding of the effect of intensification of tilapia production systems on pond dynamics, pollutional strength of pond effluents as well as the yields and production economics of these management strategies.

Collaborative Arrangements

This research will be implemented by Auburn University in collaboration with the General Directorate of Fisheries and Aquaculture, Ministry of Agriculture, Honduras.

Experimental Design

Site(s): El Carao National Fish Culture Research Center, Comayagua, Honduras.

Pond Facilities: Nine 0.2-ha earthen ponds.

Culture Period: 240-day grow-out period.

Stocking Rate(s): Ponds will be stocked with a fish at 2, 5, or 8 tilapia/m². Desired initial stocking size range is 50-100 g/fish.

Water Management: Water will be added to ponds as needed to replace losses to evaporation and seepage. Water exchange will not be used.

Other Inputs: Fish will be offered a 25-30% protein extruded formulated feed; actual protein level will depend on feed availability in Honduras. Fish will be fed to satiation once daily. Satiation will be determined weekly in all ponds, and the treatment average will be used for all ponds within a treatment until the rate is adjusted the following week. Aeration (vertical spray-type aerators, 2.5 HP/ha) will be used to maintain pond dissolved oxygen levels above 20% saturation.

Test Species: Male Nile tilapia (Oreochromis niloticus) will be stocked into ponds.

Sampling Plan: Fish will be sampled by seine net at monthly intervals to measure growth; approximately 10% of the initial stock will be seined up, counted and weighed en-masse. Early morning dissolved oxygen will be measured in ponds daily. Total nitrogen, total ammonia nitrogen, nitrate-nitrite nitrogen, total phosphorus, soluble reactive phosphorus, Secchi disk visibility, chlorophyll-a, and total alkalinity will be determined biweekly and primary productivity will be determined weekly according to "standard protocol" detailed in the PD/A CRSP Materials and Methods Handbook. Weather data will be collected daily. Ponds will be harvested by draining upon completion of the trial. Nutrient budgets will be determined for each stocking rate; nutrients as inputs and outputs will be measured. Pond soils (top 2.5-cm core) will be sampled after ponds have been flooded and immediately before ponds are drained.

Enterprise Budgets: Full-cost enterprise budgets will be developed for each stocking rate.

Statistical Methods and Hypotheses: A completely randomized design with three replicates per treatment will be used. The null hypotheses are: 1) pond nutrient budgets are not affected by intensification of management system; 2) tilapia growth and yield are not affected by increased stocking rate; and, 3) production economics are not affected by intensification of management system. Data analysis will be by regression analysis and ANOVA with treatment differences determined by orthogonal contrasts.

Identification of Deliverables

Tilapia growth, yield and production economics at each stocking rate will be determined by this study. Nutrient budgets will describe the effect of feeding at different stocking rates. Research results will be communicated at national, regional and/or international technical/scientific meeting.

Schedule/Timeline

Ponds trial from March to November 1997; data analysis and report preparation from November 1997 to March 1998. Actual schedule depends on date the PD/A CRSP is fully funded and resident researchers are authorized to travel to post.

Final Report Submittal: Final report submitted in March 1998.

References

Boyd, C. E. 1990. Water quality in ponds for aquaculture. Ala. Agr. Exp. Sta., Auburn University, Ala. 482 pp.

Diana, J. S., C. K. Lin, and K. Jaiyen. 1994. Pond dynamics under semi-intensive and intensive culture practices. Pages 94-99 in H. S. Egna, J. Bowman, B. Goetze, and N. Weidner, editors, Eleventh Annual Administrative Report Pond Dynamics/Aquaculture Collaborative Research Support Program 1993. Oregon State University, Corvallis, OR.

Diana, J. S., C. K. Lin, and Y. Yi. 1995a. Timing of supplemental feeding for tilapia production. Pages 147-152 in H. S. Egna, J. Bowman, B. Goetze, and N. Weidner, editors, Twelfth Annual Administrative Report Pond Dynamics/Aquaculture Collaborative Research Support Program 1994. Oregon State University, Corvallis, OR.

Diana, J. S., C. K. Lin, and Y. Yi. 1995b. Stocking density and supplemental feeding in tropical fish ponds. In: H. S. Egna, J. Bowman, B. Goetze, and N. Weidner, (Editors), Twelfth Annual Administrative Report Pond Dynamics/Aquaculture Collaborative Research Support Program 1994. Oregon State University, Corvallis, OR:153-155.

Green, B. W. 1992. Substitution of organic manure for pelleted feed in tilapia production. Aquaculture, 101: 213-222.

Green, B. W., D. R. Teichert-Coddington, and T. R. Hanson. 1994. Development of semi-intensive aquaculture technologies in Honduras. International Center for Aquaculture and Aquatic Environments, Research and Development Series Number 39, Auburn University, AL.

Teichert-Coddington, D. R., and B. W. Green. 1993. Tilapia yield improvement through maintenance of minimal oxygen concentrations in experimental grow-out ponds in Honduras. Aquaculture, 118: 63-71.

Teichert-Coddington, D. R., B. W. Green, N. Claros, and M. I. Rodriguez. 1991. Optimization of feeding in combination with organic fertilization. Pages 30-32 in H. S. Egna, J. Bowman and M. McNamara, editors, Eighth Annual Administrative Report Pond Dynamics/Aquaculture Collaborative Research Support Program 1990. Oregon State University, Corvallis, OR.

Teichert-Coddington, D. R., B. W. Green, C. E. Boyd, and M. I. Rodriguez. 1992. Supplemental nitrogen fertilization of organically fertilized ponds: variation of C:N ratio. Pages 21-27 in H.S. Egna, M. McNamara and N. Weidner, editors, Ninth Annual Administrative Report Pond Dynamics/Aquaculture Collaborative Research Support Program 1991. Oregon State University, Corvallis, OR.

Teichert-Coddington, D.R., B.W. Green, C.E. Boyd, R. Gomez and N. Claros. 1993. Substitution of inorganic nitrogen and phosphorus for chicken litter in production of tilapia. Pages 19-27 in H.S. Egna, M. McNamara, J. Bowman, and N. Astin, editors, Tenth Annual Administrative Report Pond Dynamics/Aquaculture Collaborative Research Support Program 1992. Oregon State University, Corvallis, OR.