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Change and diversity in smallholder rice-fish systems: Recent evidence and policy lessons from Bangladesh
Dey, M.M. ; Spielman, D.J. ; Haque, A.B.M.M. ; Rahman, M.S. ; Valmonte-Santos, R. - \ 2013
Food Policy 43 (2013). - ISSN 0306-9192 - p. 108 - 117.
fresh-water prawn - floodplain aquaculture - southwest bangladesh - culture-systems - constraints - polyculture - fisheries - adoption - impacts - fields
Efforts to unlock the genetic potential of both rice and fish, when combined with improvements in the management of rice-fish systems, can potentially increase agricultural productivity and food security in some of the poorest and most populous countries in Asia. In Bangladesh, estimates suggest that the country's potential rice-fish production system encompasses 2-3 million hectares of land. But despite three decades of research on biophysical and technical aspects of rice-fish systems, this potential has not been fully realized due to insufficient attention given to the social, economic, and policy dimensions of rice-fish system improvement. This paper provides a characterization of the diverse and changing nature of rice-fish systems in Bangladesh to shed new light on the economic viability of different rice-fish systems and recommend policy and investment options to accelerate the development of appropriate rice-fish technologies. Data are drawn from a novel subdistrict-level survey of fishery officers, a household/enterprise survey, focus group discussions, and a meta-review of the literature on aquaculture in the country, all of which were conducted in 2010-2011. Findings indicate that concurrent rice-fish systems, alternating rice-fish systems, and collectively managed systems offer considerable potential for increasing productivity and farm incomes in Bangladesh. Findings also suggest that while innovation in these rice-fish systems is being driven by households and communities, there is need for more supportive government policies and investments to enable further innovation. Policymakers need to develop effective regulations to promote feed and fish quality and quantity, for example. More rigorous analysis of the intended and unintended impacts of these policies and investments is also necessary. (C) 2013 Elsevier Ltd. All rights reserved.
Influence of periphyton substrates and rearing density on Liza aurata growth and production in marine nursery ponds
Richard, M. ; Maurice, J.T. ; Anginot, A. ; Paticat, F. ; Verdegem, M.C.J. ; Hussenot, J.M.E. - \ 2010
Aquaculture 310 (2010)1-2. - ISSN 0044-8486 - p. 106 - 111.
indian major carps - bacterial biofilm - fish production - grey mullet - polyculture - culture - phytoplankton - fertilization - aquaculture - community
The main objectives of this investigation were to test the effects of (i) the presence of periphyton substrates, (ii) rearing density and (iii) supplemental feeding with dry feed on the growth and production of golden mullet (Liza aurata) juveniles. Twenty-six 1 m2-cages were installed in a French marine pond from April till June 2008. Mullets were stocked in cages with or without substrate at a density of 0, 20, 40 or 60 individuals per cage. Each treatment was carried out in triplicate. In addition, 20 fish were put in three tanks and fed ad libitum with dry feed. The results showed that (i) although mullets were seen to graze on periphyton substrates, their presence did not affect mullet growth and production. In future studies, meshed substrates could be attached on hard structures to improve the efficiency of mullet grazing; (ii) individual growth was higher at low density due to a lower competition for space and food. Production increased with rearing density reflecting that food availability was not limiting in control cages; (iii) growth and net yield of mullets were lower in fed tanks than in natural ponds where food seemed to be more appropriate for wild mullet juveniles and where stress factors were lower. Finally, in contrast to the individual growth rate, the net fish yield in this experiment was greater than that recorded in other extensive and semi-intensive systems. It was equivalent to yields observed in other periphyton-based systems. Periphyton developed on the meshed walls of cages probably increased the natural productivity of the pond. As part of sustainable aquaculture development, the effluents of intensive farms could be exploited to produce periphyton on inflexible substrates and to rear mullet adults, which are more herbivorous than juveniles. This type of integrated system could be developed with other mullet species, such as Chelon labrosus or Mugil cephalus, whose growth rates are higher than L. aurata. Mullet production could be exploited by the sale of fillets and dried roe
Effects of intra- and interspecific competition on diet, growth and behaviour of Labeo calbasu (Hamilton) and Cirrhinus cirrhosus (Bloch)
Rahman, M.M. ; Verdegem, M.C.J. - \ 2010
Applied Animal Behaviour Science 128 (2010)1-4. - ISSN 0168-1591 - p. 103 - 108.
carp cyprinus-carpio - rohita hamilton - food competition - l. - ponds - fish - polyculture - preference - overlap - shoal
Effects of intra- and interspecific competition on diet, growth, grazing, swimming, resting and social behaviour of two carps calbasu (Labeo calbasu) and mrigal (Cirrhinus cirrhosus) were examined in single and mixed species treatments. Three treatments (tanks with 4 L. calbasu, 4 C. cirrhosus or 2 L. calbasu plus 2 C. cirrhosus) were randomly assigned to six 1m2 glass-walled aquaria, in which pond conditions were simulated. Overall, both species preferred feeding on benthic macroinvertebrates, spending the majority of its grazing time near the tank bottom. Intraspecific food competition affected L. calbasu more than interspecfic food competition. The opposite was true for C. cirrhosus which was more affected by L. calbasu than by intraspecific competition. L. calbasu broadened its selection of food items and increased grazing time in response to intense (intraspecific) food competition. This behaviour allowed L. calbasu to maintain its food intake and hence growth. In presence of L. calbasu, C. cirrhosus continued to feed mainly on benthic macroinvertebrates, not changing its feeding behaviour. Therefore, C. cirrhosus’ total food consumption and growth diminished in the presence of L. calbasu. In addition to food competition, direct interaction (interference competition from L. calbasu) also played an important role in the behaviour, diet, and growth rate of C. cirrhosus. From an ecological, economic and fish welfare point of view, it can be suggested that C. cirrhosus is deprived when cultured together with L. calbasu in aquaculture ponds.
Submersion time, depth, substrate type and sampling method as variation sources of marine periphyton
Richard, M. ; Trottier, C. ; Verdegem, M.C.J. ; Hussenot, J.M.E. - \ 2009
Aquaculture 295 (2009)3-4. - ISSN 0044-8486 - p. 209 - 217.
indian major carps - oreochromis-niloticus - artificial substrate - litopenaeus-vannamei - bacterial biofilm - stocking density - water-quality - polyculture - aquaculture - growth
Periphyton is an additional food source in African and Asian brackish and freshwater fish ponds. The present study was a preliminary assessment of periphyton development on artificial substrates in temperate marine ponds. The effects of submersion time, substrate type, water depth, and total or partial sampling methods on the quantity and quality of periphyton collected, were evaluated. Four types of substrate (W: wooden poles, S: smooth fiber-glass strips, m: mosquito screen (1 mm-mesh) and M: garden netting (5 mm-mesh)) were deployed in a marine pond, and periphyton was collected 15 and 30 days later. The total amount of periphyton per substrate unit was collected as one sample or as 5 sub-samples. Results showed that (i) periphyton biomass in a marine pond increased between day 15 and day 30, (ii) more periphyton was collected on mosquito screen than on wooden poles, fiberglass strips and garden netting, (iii) periphyton biomass increased with submersion depth, (iv) sub-sampling leads to an underestimate compared to whole unit sampling, and (v) a correction of periphyton weight must be carried out considering the dissolved inorganic salts present in periphyton samples from marine and brackish ponds. Whole substrate unit sampling using a tube and stopper is recommended to avoid underestimation of periphyton development. Finally, the autotrophic fraction in the periphyton communities was very low compared to periphyton developed on biodegradable substrates in fertilized tropical ponds. Studies on fertilization and use of biodegraded substrates (i.e. long-time submerged wood) are recommended to further optimize periphyton development in temperate marine ponds.
Effects of stocking density of freshwater prawn Macrobrachium rosenbergii and addition of different levels of tilapia Oreochromis niloticus on production in C/N controlled periphyton based system
Asaduzzaman, M. ; Wahab, M.A. ; Verdegem, M.C.J. ; Mondal, M.N. ; Azim, M.E. - \ 2009
Aquaculture 286 (2009)1-2. - ISSN 0044-8486 - p. 72 - 79.
extensive aquaculture - culture-systems - nile tilapia - substrate - growth - ponds - phytoplankton - polyculture
An on-station trial was conducted to evaluate the effect of stocking density of freshwater prawn and addition of different levels of tilapia on production in carbon/nitrogen (C/N) controlled periphyton based system. The experiment had a 2 × 3 factorial design, in which two levels of prawn stocking density (2 and 3 juveniles m¿ 2) were investigated in 40 m2 earthen ponds with three levels of tilapia density (0, 0.5 and 1 juveniles m¿ 2). A locally formulated and prepared feed containing 30% crude protein with C/N ratio close to 10 was applied considering the body weight of prawn only. Additionally, tapioca starch was applied to the water column in all ponds to increase C/N ratio from 10 (as in feed) to 20. Increasing stocking density of tilapia decreased the chlorophyll a concentration in water and total nitrogen in sediment, and increased the bottom dissolved oxygen. The concentrations of inorganic nitrogenous species (NH3¿N, NO2¿N and NO3¿N) were low due to maintaining a high C/N ratio (20) in all treatment ponds. Increasing prawn density decreased periphyton biomass (dry matter, ash free dry matter, chlorophyll a) by 3¿6% whereas tilapia produced a much stronger effect. Increasing stocking density of freshwater prawn increased the total heterotrophic bacterial (THB) load of water and sediment whereas tilapia addition decreased the THB load of periphyton. Both increasing densities of prawn and tilapia increased the value of FCR. Increasing prawn density increased gross and net prawn production (independent of tilapia density). Adding 0.5 tilapia m¿ 2 on average reduced prawn production by 12¿13%, and tilapia addition at 1 individual m¿ 2 produced a further 5% reduction (independent of prawn density). The net yield of tilapia was similar between 0.5 and 1 tilapia m¿ 2 treatments and increased by 8.5% with increasing stocking density of prawn. The combined net yield increased significantly with increasing stocking density of prawn and tilapia addition. The significantly highest benefit cost ratio (BCR) was observed in 0.5 tilapia m¿ 2 treatment but freshwater prawn density had no effect on it. Therefore, both stocking densities (2 and 3 juveniles m¿ 2) of prawn with the addition of 0.5 tilapia m¿ 2 resulted in higher fish production, good environmental condition and economic return and hence, polyculture of prawn and tilapia in C/N controlled periphyton based system is a promising options for ecological and sustainable aquaculture.
The potential of mixed culture of genetically improved farmed tilapia (GIFT, Oreochromis niloticus) and freshwater giant prawn (Macrobrachium rosenbergii) in periphyton-based systems
Uddin, S. ; Azim, M.E. ; Wahab, M.A. ; Verdegem, M.C.J. - \ 2006
Aquaculture Research 37 (2006)3. - ISSN 1355-557X - p. 241 - 247.
nile tilapia - substrate - phytoplankton - polyculture - growth - carps
The production performance of genetically improved farmed tilapia (GIFT, Oreochromis niloticus) and freshwater prawn (Macrobrachium rosenbergii) in periphyton-based systems were studied in farmers' ponds at Mymensingh, Bangladesh. Fifteen ponds (200-300 m2 area and 1.0-1.5 m in depth) were used to compare five stocking ratios in triplicate: 100% GIFT, 75% GIFT plus 25% prawn, 50% GIFT plus 50% prawn, 25% GIFT plus 75% prawn and 100% prawn. Ponds were stocked at a total density of 20 000 GIFT and/or prawn ha -1. Bamboo poles (mean diameter 6.2 cm and 5.5 pole m-2) were posted in pond bottoms vertically as periphyton substrate. Periphyton biomass in terms of dry matter (DM), ash-free DM and chlorophyll a were significantly higher in ponds stocked with prawn alone than in ponds with different combinations of GIFT and prawn. Survival of GIFT was significantly lower in ponds stocked with 100% GIFT (monoculture) whereas, that of prawn was significantly higher in its monoculture ponds indicating detrimental effects of GIFT on prawn's survival. Individual weight gains for both species were significantly higher in polyculture than in monoculture. The highest total fish and prawn yield (1623 kg GIFT and 30 kg prawn ha-1) over 125-140 days culture period was recorded in ponds with 75% GIFT and 25% prawn followed by 100% GIFT alone (1549 kg ha-1), 50% GIFT plus 50% prawn (1114 kg GIFT and 68 kg prawn ha-1), 25% GIFT plus 75% prawn (574 kg GIFT and 129 kg prawn ha-1) and 100% prawn alone (157 kg ha-1). This combination also gave the highest economic return. Therefore, a stocking ratio of 75% GIFT plus 25% prawn at a total density of 20 000 ha-1 appeared to be the best stocking ratio in terms of fish production as well as economics for a periphyton-based polyculture system
Exploring the trophic structure in organically fertilized and feed-driven tilapia culture environments using multivariate analyses
Muendo, P.N. ; Milstein, A. ; Dam, A. ; Gamal, N.E. ; Stoorvogel, J.J. ; Verdegem, M.C.J. - \ 2006
Aquaculture Research 37 (2006)2. - ISSN 1355-557X - p. 151 - 163.
oreochromis-niloticus - chemical fertilizers - aquaculture ponds - fish ponds - water - nitrogen - polyculture - phosphorus - manures - budgets
Reports of similar yields in manure and feed-driven tilapia culture environments raise questions on food utilization in these environments. The possibility that similar production rates are because of utilization of different foods was investigated using exploratory techniques of multivariate analyses. Using factor analysis, trophic pathways through which food becomes available to fish were explored, and using anova models, water quality, sediment quality and tilapia growth and yields were compared. Conceptual graphic models of the main ecological processes occurring in feed-driven and organically fertilized environments are presented and discussed. In both environments, autotrophic and heterotrophic pathways are important processes that result in the availability of natural foods that are utilized by the fish. Extrapolated fish yield data indicate that with equal nutrient input and stocking density, organically fertilized environments could achieve production rates similar to those in feed-driven environments. The general assumption that supplemental or complete foods are well utilized by tilapia in outdoor stagnant ponds remains challenged, and further research on tilapia feeding behaviour and food selection in feed-and organic fertilizer-driven environments is needed.
The effects of periphyton, fish and fertilizer dose on biological processes affecting water quality in earthen fish ponds.
Milstein, A. ; Azim, M.E. ; Wahab, M.A. ; Verdegem, M.C.J. - \ 2003
Environmental Biology of Fishes 68 (2003)3. - ISSN 0378-1909 - p. 247 - 260.
indian major carps - aquaculture - culture - hamilton - polyculture - biofilm
The potential of periphyton-based aquaculture in South Asia is under investigation in an extensive research program. This paper is a further analysis of data from four experiments carried out in that framework, to explore periphyton, fish and fertilizer dose effects on water quality. Factor analysis and ANOVA models applied to a data matrix of water quality parameters in ponds with and without artificial substrates (bamboo poles and kanchi sticks), with and without fish (filter feeders catla and rohu, with and without bottom feeder kalbaush), and with a standard or 50% increased fertilizer dose, allowed us to identify the underlying ecological processes governing this novel periphyton-based pond system, and construct conceptual graphic models of the periphyton-environment relationships observed. We clearly established that the phosphorus flow is mainly linked to phytoplankton activity in the water column and decomposition on the pond bottom, while nitrogen flow is mainly linked to autotrophic (photosynthesis) and heterotrophic (decomposition and nitrification) processes that take place in the periphyton in addition to the water column and pond bottom. Consequently, disruption of the pond bottom by bottom feeding fish primarily promoted phosphate cycling and phytoplankton, while periphyton development on the supplied substrates and fertilization mainly improved oxygen balance and nitrogen related processes developing in the water column. The use of bamboo poles led to better results than kanchi sticks, related to the greater autotrophic periphyton development on bamboo and to the larger surface of bamboo poles that facilitate fish grazing and periphyton dislodgment that in turn have a renewal effect on periphyton. Stocking bottom feeding fish produces a fertilizing effect through the food web that benefits the filter-feeding fish and that makes it unnecessary to increase the dose of inorganic and organic fertilizers applied to the ponds. Thus, the output of this analysis will help the fish farmers in resource constrained countries to improve their production in periphyton-based ponds just by choosing bamboo substrates, stocking a bottom feeder fish together with the filter feeders, and saving money on fertilizers.
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