Effects of feeding pelleted versus non-pelleted defatted rice bran on Nile tilapia Oreochromis niloticus production and water quality in ponds

P. Perschbacher and R. Lochmann, Aquaculture/Fisheries Center, Department of Aquaculture and Fisheries, University of Arkansas at Pine Bluff, P.O. Box 4912, Pine Bluff, AR 71611 USA

15 July 2000, CRSP Research Report 00-146

Abstract Effects of pelleted versus non-pelleted defatted rice bran on fish production and water quality were evaluated at the Aquaculture Research Station, University of Arkansas at Pine Bluff. Mixed-sex Nile tilapia (Oreochromis niloticus) were stocked at 2.3/m^-2 into each of six 0.04-ha earthen ponds. Largemouth bass (Micropterus salmoides) were added at 0.17/m^-2 for population control. Defatted rice bran was fed to fish at 2% body weight daily. After 169 days, tilapia harvests averaged 2,924 kg/ha in pellet-fed and 3,031 kg/ha in loose bran-fed treatments (a non-significant difference). Stocked fish comprised an average of 52% and 39%, respectively, in these treatments, and approached a significant difference (P=0.2). Average amounts of inorganic fertilizer required to maintain chlorophyll a levels of 100-150 mg/m^-3 were significantly different at 736 and 1,108 kg/ha in pelleted and loose bran treatments, respectively.

This abstract was excerpted from the original paper, which was published in Asian Fisheries Science, 12(1999):49-55.

Sound policies for food security: The role of culture and social organization

Joseph J. Molnar, Dept of Agricultural Economics and Rural Sociology, Auburn University, AL 36849-5406 USA

15 July 2000, CRSP Research Report 00-147

Abstract Culture conditions the ability to organize and to provide food security, but social organization is the immediate source of policies that prevent food insecurity or determine what happens when it does occur. Weather, war, terrorism, conflict, overpopulation, environmental degradation, corruption, and faulty policies have been identified as causes of food insecurity. Perhaps most of the blame for food insecurity should go to faulty policies or poor implementation of sound policy. This article identifies reasons for both kinds of failure that are linked to culture and social organization. The central task of government is to allow the food system to manage its own affairs, but policies must be ready to guide action when market, crop, or policy failures create food insecurity among those with no other means of coping with adversity.

This abstract was excerpted from the original paper, which was published in Review of Agricultural Economics, 21(2):489-498.

Integrated cage culture in ponds: Concepts, practice and perspectives

Yang Yi and C. Kwei Lin, Aquaculture and Aquatic Resources Management Program, School of Environment, Resources and Development, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand

15 July 2000, CRSP Research Report 00-148

Abstract The integrated cage culture in ponds refers to the system in which high valued species are stocked in cages suspended in ponds while filter-feeding species are stocked in open water outside the cages. While the caged fish are fed with high protein diets, the open-pond fish are solely dependent on the natural foods generated from cage wastes.

The following advantages make the integrated cage culture in ponds attractive and promising:
(1) Wastes derived from high protein diets of caged fish are reused as a valuable nutrient source to generate natural foods for open pond fish.
(2) Nutrients in wastes derived from cages are recovered thus reducing nutrients contained in effluents, which are usually released directly or indirectly to the surrounding environment, causing accelerated eutrophication in those waters.
(3) It is used in polyculture ponds to confine costly high protein diets to caged high valued species to achieve higher economic returns.
(4) It is used in sub-tropical or temperate regions, where tropical fish species cannot overwinter, to make full use of growing seasons and make management such as fish harvest easy and convenient.
(5) This system makes it possible to fatten large fingerlings with high protein diets in cages and nurse fry with natural foods derived from cages wastes in open water in a single pond, which could allow small-scale farmers with one pond to maximize fish production and profitability.

The integrated cage culture in ponds has been practiced in caged catfish-open pond tilapia and caged large tilapia-open pond small tilapia. Encouraging results have been achieved from the above trials.

This abstract was excepted from the original paper, which was published in I.C. Liao and C.K. Lin (Editors), Proceedings of the First International Symposium on Cage Aquaculture in Asia. Asian Fisheries Society, Manila, pp. 217-224.

An overview of freshwater cage culture in Thailand

C. Kwei Lin and K. Kaewpaitoon, Aquaculture and Aquatic Resources Management Program, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand

15 July 2000, CRSP Research Report 00-149

Abstract Despite its long history and a large number of rivers and reservoirs in Thailand, cage culture contributed only 0.3% of 200,000 tons in total fish production from freshwater aquaculture. Over the last decade, the peak of annual fish production from freshwater cages reached 2,700 tons in 1991 and declined since to a minimum of 600 tons in 1995. Although cage culture takes place in various habitats such as river, reservoirs, irrigation canals and large ponds, its predominant habitats are in flowing waters. Among a dozen of cultured species, red snakehead (Channa micropeltes), catfish (Pangasius spp.), marble goby (Oxyeleotris marmoratus) and tilapia (Oreochromis spp.) topped the list. The production of those species fluctuated drastically resulting mainly from deteriorating water quality, competing for trash fish feed, changing market value, and shifting culture practices. However, disease and fingerling supply caused the reduction and limitation in culture of the most valued marble goby. Recently, the cage culture of tilapia has gained great popularity in certain parts of the country. Cage culture has been a small-scale, artisanal operation with little research and technical innovation. Further development of cage cultures in freshwater lies on ecologically sound multiple uses of reservoirs and flowing waters. In addition, integration of intensive cage culture with semi-intensive species in ponds should also be promoted.

This abstract was excerpted from the original paper, which was published in I.C. Liao and C.K. Lin (Editors), Proceedings of the First International Symposium on Cage Aquaculture in Asia. Asian Fisheries Society, Manila, pp. 237-242.

Effects of shrimp farming on the hydrography and water quality of El Pedregal and San Bernardo Estuaries, Gulf of Fonseca, Honduras*

George H. Ward, Jr., Center for Research in Water Resources, The University of Texas at Austin, Austin, Texas 78712 USA

15 July 2000, CRSP Research Report 00-150

Abstract Intensive data collection and a modeling study have been underway for the past several years addressing two of the channel estuaries draining into the Gulf of Fonseca, Estero El Pedregal and Estero San Bernardo. Data have been compiled on the shrimp farm configurations, exchange rates, and effluent chemistry. Temperature, salinity, and dissolved oxygen profiles have been measured in the estuary channels during both rainy and dry seasons. Physiographic, hydrographic, and meteorological data have been obtained to supplement the estuary data. This report examines the assimilative capacity of these estuaries with respect to dissolved oxygen (DO). The oxygen demand of organics is measured by biochemical oxygen demand (BOD). Shrimp farm BOD loadings were estimated from effluent data and exchange. A transport model for salinity and DO in the estuaries was applied to predict the tidal-mean and section-mean concentrations of salinity and DO. The model predictions of DO–based on 1995 BOD loadings–were satisfactory. Future loadings based upon full shrimp farm development along these two estuaries were then input to determine the resulting DO under these conditions. It was found that the 1995 configuration is already pressing the carrying capacity of both systems, and the DO will be worse at full development. Shrimp farms placed farther upstream than about 20 km from the mouth will most likely have excessive impact on the DO in the estuary, which is exacerbated under dry–season conditions. Negative impacts of a specific farm can be ameliorated by reducing or eliminating pond discharges during the dry season and by reducing the level of water exchange employed. This work needs to be extended to address additional water quality parameters and to incorporate larger spatial scales, especially to establish the interaction between different estuaries draining into Fonseca.

This abstract was excerpted from the original article which was published as CRSP Research Report 00-150 by the Information Management and Networking Component of the Pond Dynamics/Aquaculture Collaborative Research Support Program (PD/A CRSP).

* The full version of this report is available as a 1.2 Mb PDF file. It can also be ordered in hard copy format.