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PD/A CRSP Research Reports 92-46 to 93-50

PD/A CRSP Research Reports 92-46 to 93-50

Substitution of organic manure for pelleted feed in tilapia production

Bartholomew W. Green, Department of Fisheries and Allied Aquacultures, and Alabama Agricultural Experiment Station, Auburn University, AL 36849-5419, USA

29 May 1992, Research Reports 92-46

Abstract The partial substitution of organic manure for pelleted feed in monosex Oreochromis niloticus (20,000/ha) production ponds was studied in Honduras. Treatments were: (1) pelleted feed only (23% protein; 3% fish biomass/day), (2) organic manure (1000 kg total solids (TS)/ha per week chicken litter) only during the first 60 days, followed by pelleted feed only, and (3) organic manure (500 kg TS/ha per week chicken litter) and pelleted feed (1.5% fish biomass/day) offered simultaneously. Mean gross yields after 151 days were 5305, 4794, and 4351 kg/ha for treatments 1 through 3, respectively. At harvest, fish averaged 262, 284, and 251 g/fish, respectively. No significant differences were detected among treatments for gross yield or average individual weight. Feed conversion ratio for treatment 1 (1.83) was significantly greater than for treatment 3 (0.95). Layer chicken litter can replace 27 to 58% of pelleted supplemental feed without significantly affecting tilapia yield. Total production costs from enterprise budgets were $5336/ha (feed only), $4645/ha (manure followed by feed), and $3471/ha (manure and feed simultaneously). Net returns to land, labor, and management were $2469/ha, $2956/ha, and $3330/ha, respectively.

This abstract was reprinted from the original which was published in Aquaculture, 101:312-222, 1992.


Comparison of two samplers used with an automated data acquisition system in whole-pond, community metabolism studies

Bartholomew W. Green and David R. Teichert-Coddington, Department of Fisheries and Allied Aquacultures, and Alabama Agricultural Experiment Station, Auburn University, Alabama 36849-5419, USA

29 May 1992, CRSP Research Reports 92-47

Abstract Automated data-logging equipment permits frequent in situ measurements of water quality variables and allows for better estimates of primary production and community metabolism in aquaculture ponds. A system to sample four contiguous 0.1-hectare earthen ponds is described. Two samplers for obtaining water samples for analysis were designed and compared. The first sampled at discrete depths throughout the water column, whereas the second obtained a composite water column sample. Samplers were constructed from readily available stocks of iron accessories or polyvinyl chloride fittings. Mean dissolved oxygen concentration, pH, and temperature did not differ significantly between water samples taken by the two samplers.

This abstract was reprinted from the original which was published in The Progressive Fish-Culturist 53:236-242, 1991.


Bioenergetic modelling of effects of fertilization, stocking density, and spawning on growth of the Nile tilapia, Oreochromis niloticus (L.)

Kwang Ming Liu, School of Natural Resources, University of Michigan, Ann Arbor, Michigan, USA

William Y.B. Chang, Division of International Programs, National Science Foundation, Washington DC, USA and Center for Great Lakes and Aquatic Sciences, University of Michigan, Ann Arbor, Michigan, USA

29 September 1992, CRSP Research Reports 92-48

Abstract A bioenergetic growth model was developed to examine the integrated effects of fertilization, stocking density, and spawning on the growth of tilapia, Oreochromis niloticus (L.), in pond aquaculture. The analyses showed that growth rates increase with higher levels of organic fertilization up to 500kg/ha/week. Growth rates increased with added food rations in ponds, reaching a maximum growth of 2.07g/day at about 44-48 days after stocking. Fish growth rates decreased with increased levels of stocking density. The stocking density for optimal growth is 1 fish/m2; the optimal density for total harvesting weight and fish size is 2 fish/m2. Model sensitivity analysis indicated that tilapia growth is most sensitive to catabolism (metabolism) and anabolism (synthesis) coefficients, both of which are geometrically related to the fish body weight. Food assimilation efficiency (b) and the food consumption coeffcient (h) have a modest effect on fish growth. Spawning in grow-out ponds can have a major effect on fish growth.

This abstract was reprinted from the original, which was published in Aquaculture and Fisheries Management, 23: 291-301, 1992.


Influence of site and season on water quality and tilapia production in Panama and Honduras.

D.R. Teichert-Coddington, B.W. Green, and R.P. Phelps, Department of Fisheries and Allied Aquacultures and Alabama Agricultural Experiment Station, Auburn University, Alabama.

30 April 1993, CRSP Research Report 93-49

Abstract Data from two years of standardized experimental protocols in Panama and Honduras were analyzed to ascertain the influence of site and season on production of Oreochromis niloticus in earthen ponds. In Experiment 1, ponds were fertilized every two weeks with triple superphosphate at 4 kg P2O2/ha, and were monitored to establish baseline of edaphic, climatic and fish production data. In Experiment 2, ponds were fertilized weekly with chicken litter at 125, 250, 500, or 1000 kg total solids/ha. Both experiments were repeated during wet and dry seasons at each site.

Honduras ponds were more alkaline and higher in phosphorus than Panama ponds that were excavated in acidic soils. However, Honduras ponds were turbid with clay. The net result of acidic, nutrient-poor soils in Panama and clay turbidity in Honduras was low biological productivity at both sites for inorganically fertilized ponds.

Primary productivity and net daily fish yield significantly increased with increasing chicken litter application (P<0.05). Primary productivity, chlorophyll a, and net daily fish yield were similar at both sites in ponds fertilized weekly with chicken litter at 125-500 kg/ha; however, at the highest fertilization rate, primary productivity, chlorophyll a, and net daily fish yield were 57, 29, and 37% greater in Panama than in Honduras. Higher fish yield was significantly correlated with higher chlorophyll a and primary productivity. Lower primary production and net daily fish yield in Honduras were attributed to light limitation by clay turbidity.

This abstract was excerpted from the original paper, which was published in Aquaculture, 105 (1992) 297-314.


Tilapia culture in saline waters: a review

Arul V. Suresh and C. Kwei Lin, Asian Institute of Technology, Bangkok, Thailand

30 April 1993, CRSP Research Report 93-50

Abstract This review attempts to evaluate the potential of tilapia culture in saline waters and in the process employs biological, economic and environmental considerations in the analytical framework. Biological potential of many commercially important tilapiine species is promising. They tolerate, grow and even reproduce in saline waters, although this capacity is somewhat offset under high salinity conditions. Particularly, they are sensitive to handling and succumb to secondary infections in seawater salinities. However, it is technically feasible to produce seed by clutch-removal management technique in salinities less than 18 ppt and to grow the fish in 35 ppt. A range of 10-20 ppt is optimal for growth. Optimal dietary protein content is 20-25% and feeding rates close to satiation levels lead to the highest growth. Various production systems ranging from earthen ponds to intensively stocked tanks, raceways and cages have been tested for grow-out; choice of a particular system would largely depend on the economics of water use. Production technology needs to be verified in several locations and, in light of the fact that tilapia get easily established as feral populations in natural ecosystems, extreme caution should be exercised in the introduction of fish into those culture systems connected to estuaries and mangroves.

This abstract was excerpted from the original paper, which was published in Aquaculture, 106 (1992) 201-226.


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