Comparison of three mixing devices in earthen culture ponds of four different surface areas

James P. Szyper, Hawaii Institute of Marine Biology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, P.O. Box 1346 Kaneohe, HI 96744, USA

16 April 1997, CRSP Research Report 97-106

Abstract Mechanical mixing of culture ponds with low-powered devices can conserve photosynthetically-produced dissolved oxygen, and so reduce the need for more expensive aeration. This work aimed to test inexpensive, easily obtained devices and to establish the utility of quantifying stratification and mixing processes in power units to facilitate comparisons and projection of requirements to new situations. Three mixing devices of power consumption less than 0.25 hp (63.5-173.6 W) were compared in tropical earthen ponds of surface areas ranging from 200 to 1400 m². Mixers were operated during the time of maximum stratification in control ponds (13:00-16:00 h), to standardize test conditions. Performance was assessed as reduction in a pond1s stratification energy (SE), contained in the uneven vertical distribution of mass.

Neighboring unmixed ponds showed very similar diel cycles of SE; unmixed ponds also showed similar patterns on successive days, but varied more than neighboring ponds assessed simultaneously. The mixing device of greatest power consumption, a fan-blade aerator-mixer (AM) operated below water surface, reduced stratification energy more quickly than a submersible impeller pump (SP) and an air-lift (AL). The AM and AL were more efficient than the SP, but all were of low efficiency (less than 0.1%). Efficiencies were related to pond size, with perimeter/area ratio being significant but surface/volume not so. Mixing effects propagated rapidly horizontally.

The AM applied sufficient power to exceed the observed daytime rate of increase in stratification energy, i.e. to prevent stratification, in ponds of all sizes except the largest. The AL and SP did not apply power at sufficient rates, and the AM would have been inadequate at other times. It is not necessary, however, to prevent stratification completely for all mixing applications.

This abstract was excerpted from the original paper, which was published in Aquacultural Engineering, 15(5)1996:381-396.

Inclusion of tilapia as a diversification strategy for penaeid shrimp culture

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

28 May 1997, CRSP Research Report 97-107

Abstract The potential for tilapia culture in brackish water shrimp ponds is evaluated. Aquaculturally important tilapia are the Nile tilapia (Oreochromis niloticus), blue tilapia (O. aureus), red tilapia (Oreochromis spp.) and, to a lesser extent, Mozambique tilapia (O. mossambicus). Nile and blue tilapia can tolerate salinities as high as 36‰ to 40‰, but best growth occurs at salinities below 20‰ Red tilapia, either from Florida or Taiwan, survive and grow well in salinities of 36‰. Mozambique tilapia is able to tolerate salinities as high as 120‰, but good growth is reported through salinities of 36‰. While these tilapia can spawn in waters of various salinities, greater fingerling production is achieved in freshwater or slightly saline (2‰ to 5‰) waters. Maximum salinity tolerance in tilapia appears to be reached at a total length of 50 to 70 mm. Acclimation of tilapia from freshwater to saline water appears best accomplished by increasing salinity from 2.5-5‰ daily until the desired salinity is reached, although some producers acclimate more rapidly. Season, choice of culture species, source of tilapia fingerlings, market, and management/logistical considerations of tilapia-marine shrimp polyculture are discussed. Along the Pacific coast of Central America, polyculture of tilapia and marine shrimp may be limited to 6 to 7 months each year during and immediately following the rainy season depending on the tilapia species. Tilapia can be stocked directly into ponds or into cages placed in ponds, supply canals or drain canals. Both cage culture of tilapia in shrimp farm supply canals, and polyculture of tilapia and shrimp in production ponds are being implemented on shrimp farms in Latin America. Management systems have been developed for this polyculture where either tilapia or shrimp is the principal culture species.

This abstract was excerpted from the original paper, which was published in IV Symposium on Aquaculture in Central America: Focusing on Shrimp and Tilapia, D.E. Alston, B.W. Green, and H.C. Clifford (Editors), 22-24 April 1997, pp. 85-93.

Semi-intensive shrimp pond management and quality of effluents

David Teichert-Coddington and Bartholomew Green, Department of Fisheries and Allied Aquacultures, Auburn University, Alabama, 36849

Delia Martinez and Eneida Ramirez, Laboratorio de Calidad de Aqua, La Lujosa, Choluteca, Honduras

John Harvin, Wayne Toyofuku, and Rafael Zelaya, Grupo Granjas Marinas, San Bernardo, Choluteca, Honduras

29 May 1997, CRSP Research Report 97-108

Abstract A collaborative research program was established in Choluteca, Honduras, in 1993 to establish a baseline of estuarine water quality in the shrimp producing regions and to study the impact of pond management on effluent water quality. Participants in the program included Auburn University AL, the Ministry of Natural Resources, Government of Honduras, the National Association of Honduran Aquaculturists (ANDAH), Pan-American Agricultural School at Zamorano, Honduras, and the Federation of Export Producers (FPX). This report summarizes studies on effluent quality from ponds and makes associations between pond management and effluent quality.

This abstract was excerpted from the original paper, which was published in IV Symposium on Aquaculture in Central America: Focusing on Shrimp and Tilapia, D.E. Alston, B.W. Green, and H.C. Clifford (Editors), 22-24 April 1997: 203-204.

The Pond Dynamics/Aquaculture CRSP-sponsored proceedings of the third conference on the culture of tilapias at high elevations in Africa *

Karen Veverica, Editor, Department of Fisheries and Allied Aquacultures, Auburn University, Alabama 36849

11 June 1997, CRSP Research Report 97-109

Abstract This was the third conference of its kind to be held for Rwanda, Burundi, and Kivu province in the east part of Zaire. High elevation was understood to be greater than 1,000 meters. During the conference, country reports were presented describing the extension service and providing technical data following a list of points included in the conference invitation. Technical papers on rice-fish culture and extension strategy were presented from Burundi. Papers on rabbit-fish culture, composting regimes, elevation-related tilapia production and tilapia-clarias polyculture were presented from Rwanda. Kivu province presented a paper on the Zaire Peace Corps fish culture sustainable extension service. Attendees included ministry personnel, university professors, FAO personnel, university students, Peace Corps volunteers, station managers, model farmers, extension and training specialists, and some trainees.

The organization and operation of the extension services in all three countries were compared. Fish culture extension has been assured mainly by Peace Corps volunteers in Zaire, with very few Zairian counterparts on hand. In Rwanda, although some Peace Corps volunteers have recently commenced activities in fish culture, Rwandese extension agents are responsible for all fish culture extension. Burundi is in the midst of re-vamping its fish culture extension service. It previously relied on Peace Corps volunteers but now has funding to train its own extension agents. However, Burundi presently has a freeze on hiring for government jobs and has opted to use extension agents already working in other domains such as forestry. A very lively discussion of the advantages and disadvantages of each country's extension service took place. All three countries have active farmer training programs.

(The foregoing is the first two paragraphs of the publication's Executive Summary.)

This abstract was excerpted from the original article which was published as CRSP Research Report 97-109 by the Program Management Office of the Pond Dynamics/Aquaculture Collaborative Research Support Program (PD/A CRSP)

* This article can be obtained directly from PD/A CRSP.

The CRSPs: International Collaborative Research Support Programs

John M. Yohe, Pat Barnes McConnell, Hillary S. Egna, John Rowntree, Jim Oxley, Roger G. Hanson, David Cummins, Avanelle Kirksey

11 June 1997, CRSP Research Report 97-110

Abstract The Collaborative Research Support Programs (CRSPs) are communities of U.S. Universities, U.S. Agency for International Development (USAID) and USAID missions, and developing countries national agriculture research systems (NARS), other U.S. federal agencies, international agricultural research centers (IARCs), private agencies, industry, private voluntary organizations (PVOs), and other developing country institutions. Their scientists, in close collaboration with one another and for the mutual benefits of their programs, carry out agricultural research and training around identified constraints to food production, storage, marketing, and consumption. More specifically, they include components which address food and agricultural policy/planning, natural resource management, plant and animal improvement (including basic genetics, biodiversity, applied genetics and biotechnology), plant and animal physiology and improved production practices, plant and animal protection, socio-economic and socio-cultural factors influencing production and consumption patterns; cultural constraints to technology adoption and development; and improved food processing, household food security and human nutrition. Through shared resources, peer review and institutional support, these communities of scientists and institutions give emphasis to the needs of small scale producers and the rural and urban poor.

(The foregoing is the introductory paragraph to the book chapter identified above.)

This abstract was excerpted from the original publication, which is Chapter 19 in Disease Analysis through Genetics and Biotechnology: Interdisciplinary Bridges to Improved Sorghum and Millet Crops, 1995. J.F. Leslie and R.A. Frederiksen (Editors), Iowa State University Press, pp. 321-338.