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B. Central America

B. Central America



Characterization of Shrimp Farm Effluents in Honduras and Chemical Budget of Selected Nutrients

Work Plan 7, Honduras Study 2

David Teichert-Coddington
Department of Fisheries and Allied Aquacultures
Alabama Agriculture Experiment Station
Auburn University, Alabama, USA

Delia Martinez and Eneida Ramírez
Laboratorio de Calidad de Agua, La Lujosa,
Choluteca, Honduras

Abstract

Intake and discharge from six shrimp farms located on riverine or embayment estuaries of the Gulf of Fonseca were sampled during rainy and dry seasons of 1993 to 1994. There was a mean net consumption of inorganic nitrogen and phosphorus, and a mean net discharge of organic matter. Discharged material was greater in embayment estuaries. Use of inorganic fertilizers promoted discharge of phosphorus and nitrogen. Total settleable solids and most nutrients were greater at the end than at the beginning of pond draining. An exception was BOD, which did not change during the course of pond draining. The majority of nitrogen entered and left ponds by water exchange. Most phosphorus entered ponds with feed, but left ponds by water exchange. Mean conversion ratios of feed nitrogen to shrimp flesh ranged from 1.4 to 4.1. Mean phosphorus conversion ratio was 6.3. Pond discharge of both nitrogen and phosphorus increased linearly with the feed conversion ratio. Nitrogen conversion ratios were not different for embayment or riverine estuaries. However, the conversion of feed and nitrogen to shrimp flesh was greater during the wet than the dry season.


Relationships among Stocking Density, Survival and Yield in Ponds Affected by the Taura Syndrome During Wet and Dry Seasons in Honduras

Work Plan 7, Honduras Study 3C

David Teichert-Coddington
Department of Fisheries and Allied Aquacultures
Alabama Agriculture Experiment Station
Auburn University, Alabama, USA

Wayne Toyofuku, John Harvin, and
Rigoberto Rodriguez
Grupo Granjas Marina
Choluteca, Honduras

Abstract

Relationships among stocking density, survival, and yield were evaluated in ponds affected by the Taura Syndrome during wet and dry seasons in Honduras. Ponds were stocked with juvenile Penaeus vannamei at 6, 8, 10, or 12/m 2. The design was tested on two farms during the wet season and on three farms during the dry season. There was no significant correlation between shrimp stocking density and survival during either season. Season did not affect survival. Production increased with density during both seasons. Net income increased with density during the wet season, but decreased or remained neutral with an increase in density during the dry season. Net income was related to both production and individual shrimp weight. Mean shrimp weight did not decrease predictively with stocking density. Management strategies for ponds affected by Taura are discussed.


Nitrogen Fertilization in the Presence of Adequate Phosphorus

Work Plan 7, Honduras Study 4D

David Teichert-Coddington
Department of Fisheries and Allied Aquacultures
Alabama Agriculture Experiment Station
Auburn University, Alabama, USA

Nelson Claros
El Carao National Center for Fish Culture Research
Comayagua, Honduras

Abstract

Effects of nitrogen fertilization on water quality and tilapia yields in earthen fish ponds supplied with adequate levels of phosphorus was tested. Ponds were stocked with tilapia at a density of 2/m 2. Nitrogen was supplied as urea at 0, 7, 14, or 28 kg/ha-wk. Primary productivity responded positively to nitrogen fertilization. Chlorophyll a increased linearly (P <0.01), and Secchi disk visibility decreased curvilinearly (P <0.05) with increasing rate of fertilization. However, fish yields were not significantly correlated with nitrogen input, despite higher phytoplankton biomass. Cool dry season water temperatures apparently inhibited fish growth. Fish were unable to take advantage of higher available nutrient supply.


Effect of Diet Protein on Food Conversion and Nitrogen Discharge during Semi-Intensive Production of Penaeus vannamei

Interim Work Plan, Honduras Study 1

David R. Teichert-Coddington and Bartholomew W. Green
International Center for Aquaculture and Aquatic Environments
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA

John Harvin and Rigoberto Rodriguez
Grupo Granjas Marinas
Choluteca, Honduras

Abstract

Previous studies demonstrated that shrimp production is similar at protein levels between 20% and 40%, when shrimp are stocked at densities between 5 and 11/m2. Feeding rates in these studies were such that feed efficiency was relatively low. Another trial conducted in Choluteca with shrimp stocked at 7.5/m2 demonstrated that production during the dry season was not significantly affected by a 50% reduction in feeding rate. Wet season production was impacted significantly by the 50% reduction in feeding, but feed efficiency was improved. These results indicated that too much feed was applied during the dry season, and that wet season feeding rates might be reduced, but not by half. It is possible that a comparatively high protein diet might improve shrimp growth and feed conversion, if used at a feeding rate that is low compared with that employed with lower protein diets while reducing nitrogen levels in pond effluents. Pond chemical budget studies indicate that nitrogen discharge increases with both feeding rate and diet protein level. Primary productivity in estuaries appears to be limited by nitrogen. It is therefore economically and ecologically important to feed at appropriate rates with an appropriate protein level.

The objective of this research is to test the effect of diet protein level on food conversion and nitrogen effluents during the production of Penaeus vannamei at semi-intensive stocking levels during the warm (wet) season and cool (dry) season. The null hypotheses to be tested are: 1) Shrimp growth, yield, and feed conversion during each season will be independent of feeding rate and dietary protein level, and 2) Nitrogen discharge from shrimp ponds during each season will be independent of shrimp feeding rate and dietary protein level.

A completely randomized design in 2x2 factorial arrangement was used to test two feeding rates (50% and 75% of feeding curve) each at two levels of protein (20% and 30% protein); each treatment was replicated three times. Penaeus vannamei post-larvae (PL 8-10) were stocked at 25/m (250,000/ha) in earthen ponds (0.7-1.0 ha) on 10 August 1995. A survival rate of 30% was assumed because of Taura Syndrome-induced mortality. Inlet and outlet water samples were collected for analyses of water quality variables. The experiment is scheduled to be harvested in December 1995.