Water management and wise use of wetlands: enhancing productivity

Lakes and reservoirs are affected by human interventions mainly by eutrophication. Changes in morphology are less common, although siltation and local alterations to the riparian zone can result from urbanisation,marina construction and deforestation. In lakes and particularly reservoirs used for water supply and power generation, rapid drawdown can occur that damages riparian vegetation and fish populations.

Technical efficiency of freshwater pond polyculture production in selected asian countries : estimation and implication

The research documented in this article estimates the levels and determinants of farm-level technical efficiencies (TE) in freshwater pond polyculture systems in China, India, Thailand, and Vietnam. The levels of country-specific TE were estimated for different production intensity levels by estimating stochastic production frontier functions involving the model for technical inefficiency effects. The results were compared with estimates from past studies of aquaculture TE. It was found that yield, input levels, and TE increases in line with intensity levels.

Survival of Clarias gariepinus fry in earthern ponds: effects of composts and leaks

To inform decisions on improving the yields of African catfish Clarias gariepinus fingerlings in earthen ponds, the hypothesis that composts and leaks were partly responsible for usually low and variable fry survivals was tested, through comparison of treatments and simple regression. The occurrence of amphibians was significantly higher (P<0.05) and survival of fry was significantly lower (P<0.02) in ponds with composts than in those without.

Roles of ponds in integrated agriculture-aquaculture systems

The effects of adding an aquaculture pond to existing farming operations on nutrient use efficiency and productivity were explored. Ponds can be used to cycle nutrients from agricultural by-products such as manures and composted grasses. The production from ponds using agricultural by-products was similar to that of ponds receiving formulated pellets. The largest fraction of the nutrients fed to ponds accumulated in the sediment. Pond sediments were rich in nitrogen and potassium, but only contained small amounts of soluble reactive phosphorous.

Rhizons improved estimation of nutrient losses because of seepage in aquaculture ponds

Seepage represents one of the largest water losses in static ponds accounting for about 30-70% of total pond water losses. This short communication describes a novel meth¬od in which a similar principle as in Masuda and Boyd (1994) is applied to obtain seepage water di¬rectly. It is standard methodology developed in soil science to sample soil moisture from the vadous zone. The method involves the use of small suction probes called rhizons Agrisearch Equipment.

Rapid growth and bioturbation activity of the sea cucumber Holothuria scabra in earther ponds

Sea cucumbers are valuable export products. Technology on their culture is expanding rapidly to help meet market demand in China, and to help relieve exploited fisheries. The sandfish. Holothuria scabra, is the most valued of tropical species. It is the focus of a restocking research project in New Caledonia, funded by ACIAR, provincial governments and the government of France. Sandfish are deposit-feeding detritivores of shallow muddy/sandy habitats, thus earthen ponds provide suitable conditions.

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