The WorldFish Center Quarterly
Vol.27, No. 3 &4 (July - December 2004)

From drawing board to dining table: The success story of the GIFT project
M.V. Gupta and B.O. Acosta

As compared to crops and livestock, the genetic enhancement of fish is in its infancy. While significant progress has been achieved in the genetic improvement of temperate fish such as salmonids, no efforts were made until the late 1980s for the genetic improvement of tropical finfish, which account for about 90 percent of global aquaculture production.

This paper traces the history of the Genetic Improvement of Farmed Tilapia (GIFT) project initiated in 1988 by the WorldFish Center and its partners for the development of methods for genetic enhancement of tropical finfish using Nile tilapia (Oreochromis niloticus) as a test species. It also describes the impacts of the project on the adoption of these methods for other species and the dissemination of improved breeds in several countries in Asia and the Pacific.

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Dietary Phytase: An ideal approach for a cost effective and low-polluting aquafeed
K. Baruah, N.P. Sahu, A.K. Pal and D. Debnath

Global fishmeal production from wild-catch sources cannot continue to increase indefinitely; suitable alternatives have to be found for sustainable aquaculture. Plant-based aquafeed seems to be the ideal alternative to this, but has its own limitations. Plant ingredients are rich in phytic acid, which reduces the bioavailability of nutrients like minerals and protein to the fish, thereby causing aquaculture pollution. Dietary phytase treatment reduces the aquaculture pollution by improving the bioavailability of nutrients, and reduces the feed cost as evident from poultry and piggery. Phytase activity is highly dependent upon the pH of the gut. Unlike mammals, fish are either gastric or agastric, and hence, the action of dietary phytase varies from species to species. In this article, the authors attempt to summarise various effects of phytase on nutrient utilization, growth of fish and aquatic pollution.

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Utilization of trawl bycatch in Gujarat (India)
A.A. Zynudheen, G. Ninan, A. Sen and R. Badonia

Bycatch from trawlers forms a significant quantity of the total marine fish landings along the northwest coast of India, particularly in the state of Gujarat, which contributes about 23 percent of the total marine fish landings in the country. This paper discusses the composition of this bycatch, its significance in terms of nutritional value, its present utilization pattern and the scope for improvement.

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Padal fishing - A unique fi shing method in the Ashtamudi Estuary of Kerala (south India)
J.V. Thomas and B.M. Kurup

Bush park fishing / padal fishing is an indigenous fishing method widely employed in the Ashtamudi estuary of Kerala (south India). An artificial reef made from twigs and leaves of trees is planted in the shallow areas of the estuary. The aim is to harvest fish that find shelter in these structures for the purpose of feeding and breeding. Though the State Department of Fisheries has banned this method of fishing in the inland waters of Kerala, 400 padals are operating in this estuary. About 300 of them are anchored in the western parts of the estuary (west Kayal). Fish are harvested in the padals at monthly intervals almost round the year and this results in the destruction of a sizeable quantity of juveniles and sub-adults of the commercially important fishes, such as Pearl spot and mullets, from the estuary. These padals pose a major threat to the sustainability of the fishery resources of this estuary and, therefore, need to be phased out by providing alternative occupations for the fishermen who are dependant on the padals.

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Antibacterial marine bacterium deter luminous vibriosis in shrimp larvae
T.J. Abraham

Inhibitory activity of a marine pigmented bacterium - Alteromonas sp. - isolated from Penaeus monodon Fabricius larva against pathogenic and environmental isolates of Vibrio harveyi was studied. All the isolates were inhibited to varying degrees by Alteromonas sp. in vitro. The antibacterial substance produced by the Alteromonas sp. was soluble in organic solvent and closely bound to the external surface of bacterial cells. The antibacterial Alteromonas sp., when allowed to colonize on shrimp larvae, suppressed the activity of V. harveyi M3 and reduced mortality of P. monodon larvae in vivo.

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The relationship of shell dimensions and shell volume to live weight and soft tissue weight in the mangrove clam, Polymesoda erosa (Solander, 1786) from northern Australia
R. Gimin, R. Mohan, L.V. Thinh and A.D. Griffiths

Shell dimensions (length, height, width) and shell volume were evaluated as estimators of growth for Polymesoda erosa in northern Australia. Each parameter was a good estimator when applied to live weight (r2 values of 76-96 percent), but not to soft tissue weight (wet, dry, or ash-free dry weight) (r2 values of 13-32 percent). The b value for shell volume to weight relationship of clams collected during the dry season (June to October) was signifi cantly different than for those collected in the wet season (February to April).

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Economics and management strategies for restocking sandfish in Vietnam
H.V. Strehlow

This paper assesses the costs and benefits of a proposed project for restocking sandfish (Holothuria scabra) in Khanh Hoa Province, Vietnam. It identifies the key stakeholders, institutional framework, management and financing required for its implementation. The recommended management strategy includes a 50 percent harvest at optimum size. Limiting the number of boats fishing an area, possibly through licensing, can control the number of sandfish removed. The easiest way to prevent harvesting of undersized sandfish is to control the size of processed sandfi sh from processors. The potential benefits of restocking are shown by the rapid changes in selected indicators, particularly the net present value, the internal rate of return, and the benefit-cost ratio. Probability analysis is used to estimate the uncertainties in the project calculations. Based on a conservative estimate, the restocking of sandfish is expected to be profitable, although cost-benefit analyses are sensitive to the survival of restocked sandfish and their progeny, and the number of boats fishing for sandfish in the release area.

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Diet composition and food habits of demersal and pelagic marine fishes from Terengganu waters, east coast of Peninsular Malaysia
Z. Bachok, M.I. Mansor and R.M. Noordin

Fish stomachs from 18 demersal and pelagic fishes from the coast of Terengganu in Malaysia were examined.The components of the fishes’ diets varied in number, weight, and their frequency of occurrence. The major food items in the stomachs of each species were determined using an Index of Relative Importance. A “conceptual” food web structure indicates that fish species in the study area can be classified into three predatory groups: (1) predators on largely planktivorous or pelagic species; (2) predators on largely benthophagous or demersal species; and (3) mixed feeders that consume both pelagic and demersal species.

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Impact pathway analysis for research planning: The case of aquatic resources research in the WorldFish Center
R. Briones, M.M. Dey, M. Ahmed, I. Stobutzki, M. Prein and B.O. Acosta

In line with its mandate of poverty reduction and sustainable development, the WorldFish Center is orienting its research towards high impact scientific activity. Identifying such activities is the task of prospective impact assessment, in turn based on impact pathway analysis. The paper describes a framework for analyzing benefits from aquatic resources research, the relevant research categories, pathways to impact by category, and indicators along each pathway that can be estimated in order to quantify probable research impact.

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