Polyculture of silver barb, Puntius gonionotus (Bleeker), Nile tilapia, Oreochromis niloticus (L.), and common carp, Cyprinus carpio L., in Vietnamese ricefields: feeding ecology and impact on rice and ricefield environment

Abstract

Rice production, ricefield environment and the feeding ecology offish were studied in an experiment conducted at a rice‐fish station in the Mekong Delta, Vietnam. In total, six treatments (three replicates) were investigated: four different polyculture combinations of small sized silver barb, Puntius gonionotus (Bleeker), Nile tilapia, Oreochromis niloticus (L.), and common carp, Cyprinuso carpio L.; one treatment with pre‐grown fingerlings; and a control treatment in which no fish were stocked. No insecticides or fungicides were utilized before or during the experiment. Frequent fertilization of the water and a low rice plant biomass during the early vegetative growth phase stimulated the development of phytoplankton and zooplankton. The total weed biomass was low (maximum = 5.3 g dry weight m−2) and not significantly (P < 0.05) different between the treatments. A major component of the silver barb diet consisted of rice plants and accessible grains. However, the introduction of silver barb only had a significant effect on the number of rice tillers in the ratoon crop and not on the paddy yield. The quantitative differences in the diets of tilapia and common carp were minimal: both species fed mostly on detritus. Ricefields without silver barb produced the highest paddy yield (3120 kg ha−1). The total yield of introduced fish increased after increasing the stocking density of silver barb from 319.9 to 494.1 kg ha‐1. The highest fish yield (541.8 kg ha‐1) was obtained by stocking pre‐grown fingerlings in the ricefields.

Growth performance of Trichogaster pectoralis Regan in intensively cultivated rice fields

“…Detritus was as important as aquatic vegetation in terms of frequency of occurrence, and was dominant in terms of volume (Ali 1994). Similar observations were made for O. niloticus in rice fields (Chapman & Fernando 1994; Haroon & Pittman 1997; Rothuis et al . 1998).…”

“…In experiments at the Co Do rice–fish research station, the maximum weed biomass obtained was just 5.31 g dry weight m −2 (Rothuis, Duong, Richter & Ollevier 1998), leaving little for T. pectoralis to eat. The little there is has to be shared with B. gonionotus , a macrophyte feeder.…”

“…It is therefore striking that B. gonionotus has a much higher SGR than T. pectoralis . In rice fields, B. gonionotus mainly feeds on plant material (Rothuis et al . 1998).…”

“…As the SGR of T. pectoralis remains low, it can be concluded that T. pectoralis does not feed on the abundant rice biomass. Its other main food items, zoo‐ and phytoplankton, are also lacking in rice fields, as the rice canopy shades the water surface (Rothuis et al . 1998).…”

Produção integrada de arroz irrigado e peixes

“…Resultados semelhantes foram relatados por ROTHUIS et al (1998), que constataram a necessidade de controle apenas de plantas daninhas aquáticas, quando a lâmina de água é mantida constante, evitando a infestação da área com gramíneas, reduzindo custos e o impacto ambiental pela aplicação de herbicidas.…”