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On the role of the polychaete Dendronereis spp. i the transmission of white spot syndrome virus in shrimp ponds
Desrina, Haryadi - \ 2014
Wageningen University. Promotor(en): Johan Verreth; Just Vlak, co-promotor(en): Marc Verdegem. - Wageningen : Wageningen University - ISBN 9789462570856 - 181
polychaeta - witte-vlekken-syndroom-virus - garnalen - ziekteoverdracht - visvijvers - garnalenteelt - voer - reservoir hosts - aquacultuur - white spot syndrome virus - shrimps - disease transmission - fish ponds - shrimp culture - feeds - aquaculture
White spot syndrome virus (WSSV) is by far the most devastating shrimp virus. Control measures have lowered the WSSV incidence to various degrees, but the pathogen remains plaguing shrimp culture worldwide. Continuous exposure may cause WSSV to adapt and infect non-crustacean benthic fauna in ponds such as polychaetes, hence, extending WSSV host range to maintain virus persistence in ponds. Dendronereis spp. (Pieters 1854) are ubiquitous Nereid polychaetes in shrimp ponds in Indonesia and part of the shrimp’s natural diet. This thesis aimed to investigate the possible role of Dendronereis spp. in the transmission of WSSV in shrimp ponds. The significance of the findings may provide new insight on the persistence of WSSV in the pond environment and novel strategies for disease management. The investigation started with a survey to determine the occurrence of WSSV in Dendronereis spp. in Indonesia, followed by subsequent laboratory observations to determine the role of Dendronereis spp. in white spot syndrome disease development. Field surveys in selected ponds in two research locations in Indonesia, the Mahakam delta (East Kalimantan) and the vicinity of Semarang (Central Java), showed that WSSV infection in Dendronereis spp. is quite common. Point prevalence of WSSV infected Dendronereis spp. was 44 ± 27% (± SD). The average prevalence in Mahakam delta was 73 ± 22% and in Java 26 ± 38%. This result implied that WSSV-infected Dendronereis spp. are widely distributed. WSSV replicated in the gut of naturally-infected Dendronereis spp. as detected in cell nuclei via immunohistochemistry (IHC) using monoclonal antibodies and via RT-PCR to detect the viral mRNA. These experiments showed that Dendronereis spp. are natural and susceptible hosts of WSSV. WSSV was transmitted from naturally infected Dendronereis spp. to Litopenaeus vannamei (Boone 1931) through the oral route and further to new naïve shrimp showing natural transmission of WSSV from polychaetes to shrimp. This indicates that the transmission of WSSV from polycheates to shrimp is possible. An experiment using Hediste diversicolor (O.F. Müller 1776) as a more amenable alternative model animal to study WSSV infection in polychaetes showed that this polychaete was not susceptible to WSSV infection using methods commonly used to induce infection in shrimp. In ponds, WSSV infection incidence in Dendronereis spp. correlated positively with Dendronereis spp. density and with the proportion of WSSV infection in shrimp. Findings of the present study underscore that Dendronereis spp., as ubiquitous and resident animals in the shrimp ponds can be reservoir hosts of WSSV and responsible for disease transmission. However, further studies are needed to obtain a better understanding of the importance of Dendronereis spp in WSSV epidemiology in and beyond shrimp ponds.
Zomerziekten in de visvijver
Haenen, O.L.M. - \ 2013
Aquacultuur 28 (2013)4. - ISSN 1382-2764 - p. 24 - 26.
visvijvers - visteelt - viskwekerijen - visziekten - virusziekten - bacterieziekten - fish ponds - fish culture - fish farms - fish diseases - viral diseases - bacterial diseases
Met het stijgen van de watertemperatuur in het voorjaar komt ook het metabolisme van de vis op gang. Veel vissoorten paaien bovendien in het voorjaar of de vroege zomer, dus ook hormonaal verandert er van alles. Dit hoort bij een natuurlijke gang van zaken maar geeft ook stress aan de vis. Stress is een basis voor ziekte. Welke ziekten kunnen we zoal aantreffen in de buitenvijver met het stijgen van temperatuur naar zomerse waarden?
Tegen de stroom in (interview met Arjan Palstra)
Ramaker, R. ; Palstra, A.P. - \ 2013
Resource: weekblad voor Wageningen UR 8 (2013)8. - ISSN 1874-3625 - p. 14 - 15.
kweekvis - aquacultuur - zwemmen - beweging - viskwekerijen - visvijvers - dierlijke productie - vissen - diergedrag - diergezondheid - farmed fish - aquaculture - swimming - movement - fish farms - fish ponds - animal production - fishes - animal behaviour - animal health
Vet, gestrest en ongezond. Veel kweekvissen zijn hopeloos uit vorm. Dat is niet alleen slecht voor de vis, maar ook voor de kweker. De oplossing is simpel: vis moet zwemmen.
Myxidium giardi, een myxospore parasiet van wilde paling
Engelsma, M.Y. ; Haenen, O.L.M. - \ 2012
Aquacultuur 27 (2012)4. - ISSN 1382-2764 - p. 33 - 35.
palingen - palingteelt - visteelt - myxidium giardi - parasieten - protozoa - visziekten - visvijvers - eels - eel culture - fish culture - parasites - fish diseases - fish ponds
In Nederland is de myxospore parasiet Myxidium giardi in mei 2005 in beeld gekomen bij palingen in fuiken op het IJsselmeer. Op palingkwekerijen in broedhuizen komt de parasiet doorgaans niet voor, wel in vijversystemen.
Ideotyping integrated aquaculture systems to balance soil nutrients.
Muendo, P.N. ; Stoorvogel, J.J. ; Verdegem, M.C.J. ; Mora Vallejo, A.P. ; Verreth, J.A.J. - \ 2011
Journal of Agriculture and Rural Development in the Tropics and Subtropics 112 (2011)2. - ISSN 1612-9830 - p. 157 - 168.
channel catfish ponds - farming systems - economic-performance - fish ponds - chemical fertilizers - water-quality - nitrogen - manure - cattle - flows
Due to growing land scarcity and lack of nutrient inputs, African farmers switched from shifting cultivation to continuous cropping and extended crop area by bringing fragile lands such as river banks and hill slopes into production. This accelerated soil fertility decline caused by erosion, harvesting and insufficient nutrient replenishment. We explored the feasibility to reduce nutrient depletion by increasing nutrient utilization efficiencies, while diversifying and increasing food production through the development of integrated aquaculture – agriculture (IAA). Considering the climatic conditions prevailing in Kenyan highlands, aquaculture production scenarios were ideotyped per agro-ecological zone. These aquaculture production scenarios were integrated into existing NUTrient MONitoring (NUTMON) farm surveydata for the area. The nutrient balances and flows of the resulting IAA-systems were compared to present land use.The effects of IAA development on nutrient depletion and total food production were evaluated. With the development of IAA systems, nutrient depletion rates dropped by 23–35%, agricultural production increased by 2–26% and overall farm food production increased by 22–70%. The study demonstrates that from a bio-physical point of view, the development of IAA-systems in Africa is technically possible and could raise soil fertility and total farm production. Further studies that evaluate the economic feasibility and impacts on the livelihood of farming households are recommended.
Het monitoren van kwantiteit en kwaliteit van afvalwater van pangasiusvijvers in Vietnam
Heijden, P.G.M. van der; Poelman, M. ; Bosma, R. - \ 2011
Aquacultuur 26 (2011)4. - ISSN 1382-2764 - p. 7 - 12.
afvalwater - viskwekerijen - aquacultuur - visteelt - visvijvers - monitoring - vietnam - waste water - fish farms - aquaculture - fish culture - fish ponds
In 2010 hebben twee Vietnamese onderzoeksinstituten onder begeleiding van Wageningen UR het inkomende water en het water dat de vijvers van vier pangasiuskwekerijen verlaat, maandelijks bemonsterd en de gemonitord. Doel was om een simpele methode te vinden om hoeveelheid en kwaliteit van het afvalwater te meten om hiermee bedrijven en organisaties die betrokken zijn bij certificering van kwekerijen te kunnen adviseren. De effecten van de kwekerijen op het milieu vormen een onderdeel van de certificering en dienen door de kwekerijen geregeld gemeten te worden. In dit artikel wordt verslag gedaan van de resultaten van deze studie.
C/N ratio control and substrate addition for periphyton development jointly enhance freshwater prawn Macrobrachium rosenbergii production in ponds
Asaduzzaman, M. ; Wahab, M.A. ; Verdegem, M.C.J. ; Huque, S. ; Salam, M.A. ; Azim, M.E. - \ 2008
Aquaculture 280 (2008)1-4. - ISSN 0044-8486 - p. 117 - 123.
fish ponds - aquaculture - systems - culture - israel
The present research investigated the effect of carbon/nitrogen ratio (C/N ratio) control in ponds with or without substrate addition for periphyton development on production of giant freshwater prawn. C/N ratios of 10, 15 and 20 were investigated in 40 m¿ 2 ponds stocked with 2 prawn juveniles (5.023 ± 0.02 g) m¿ 2 with or without added substrates for periphyton development. The various treatment combinations of C/N ratio and periphyton substrate addition are abbreviated as `CN10¿, `CN15¿, `CN20¿, `CN10 + P¿, `CN15 + P¿ and `CN20 + P¿, P representing periphyton substrate. A locally formulated and prepared feed containing 30% crude protein with C/N ratio10 was applied. Tapioca starch was used as carbohydrate source for manipulating C/N ratio and applied to the water column separately from the feed. Increasing the C/N ratio from 10 to 20 reduced (P <0.001) the total ammonia-nitrogen (TAN), nitrite¿nitrogen (NO2¿N) and nitrate¿nitrogen (NO3¿N) in water column and total Kjeldahl nitrogen (TKN) in sediment. The addition of substrates only influenced the NO2¿N concentration in the water column (P <0.001). Increasing the C/N ratio raised the total heterotrophic bacterial (THB) population in the water column, sediment and periphyton (P <0.001). It also increased the dry matter (DM), ash free dry matter (AFDM), and chlorophyll a content of periphyton (P <0.001). The lowest specific growth rate (SGR), the highest food conversion ratio (FCR), and the lowest protein efficiency ratio (PER) were recorded in treatment CN10 (P <0.05). The addition of substrates did not influence size at harvest (P > 0.05) but improved the survival from 62.8 to 72% (P <0.001). Increasing the C/N ratio from 10 to 20 increased the net yield by 40% and addition of substrate increased the net yield by 23%. The combination of C/N ratio control and substrate addition increased the net yield by 75% from 309 (CN10) to 540 (CN20 + P) kg ha¿ 1 (120 days)¿ 1. This 75% higher production concurred with (1) a lower inorganic nitrogen content in the water column, (2) a higher THB abundance supplying additional single cell protein to augment the prawn production, and (3) an improved periphyton productivity and quality.
De bijdrage van visvijvers aan de nutriënthuishouding op gemengde kleinschalige landbouwbedrijven
Verdegem, M.C.J. ; Muendo, P.N. - \ 2007
Aquacultuur 22 (2007)1. - ISSN 1382-2764 - p. 26 - 32.
agrarische bedrijfsvoering - gemengde landbouw - voedingsstoffenbalans - visvijvers - visteelt - voedingsstoffenbeschikbaarheid - experimenteel veldonderzoek - toegepast onderzoek - farm management - mixed farming - nutrient balance - fish ponds - fish culture - nutrient availability - field experimentation - applied research
Vijvers kunnen een aanzienlijke bijdrage leveren aan de nutriëntenkringloop op gemenge landbouwbedrijven. Het integreren van water- en landgebonden productie in gemengde bedrijven kan leiden tot een verhoogde efficiëntie van het nutriëntengebruik. Bij evaluatie van de visteelt wordt vaak alleen gekeken naar de oogst zonder aandacht voor andere voordelen van visteelt zoals waterbeschikbaarheid of efficiëntie van nutriëntengebruik. Bovendien verkiezen boeren vaak geformuleerde voeders, hoewel het voordeel voor de oogst hiervan niet evident is in de gemiddelde eenvoudige onbeluchte vijvers. Een onderzoeksproject is gestart om mogelijkheden voor verbetering in kaart te brengen
The role of a fish pond in optimizing nutrient flows in integrated agriculture-aquaculture farming systems
Nhan, D.K. - \ 2007
Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Marc Verdegem. - [S.l.] : S.n. - ISBN 9789085047391 - 162
visvijvers - aquacultuur - landbouw - bedrijfssystemen - duurzaamheid (sustainability) - voedingsstoffen - kringlopen - recycling - optimalisatie - vietnam - geïntegreerde bedrijfssystemen - fish ponds - aquaculture - agriculture - farming systems - sustainability - nutrients - cycling - optimization - integrated farming systems
In the Mekong delta, the Vietnamese government promoted integrated agriculture-aquaculture (IAA) farming systems as an example of sustainable agriculture. An important advantage of IAA-farming is the nutrient linkage between the pond and terrestrial components within a farm, which allows to improve resource use efficiency and income while reducing environmental impacts. This study monitored and analyzed water use in and nutrient flows through ponds that are part of an IAA-farming system. The goal was to improve the nutrient management of ponds which in turn lead to improved water and nutrient use efficiency of the whole IAA-farm. The study included three main parts: (1) understanding the context and characteristics of IAA-systems (chapters 2 and 3), (2) analyzing the performance of IAA-systems, suggesting and testing improvements (chapters 4 and 5), and (3) recommending procedures for the continuous upgrading of existing IAA-farming systems (chapter 6). The research was done on-farm in freshwater areas of the Mekong delta and followed a Participatory Learning in Action approach. Different multivariate statistical methods were applied for data analysis. At community and household level, results showed that the type of IAA-farming systems applied was determined by a mixture of bio-physical, technological and socio-economic factors (chapter 2). Three major IAA-systems were identified: (1) low-input fish farming in fruit-dominated area (system 1), (2) medium-input fish farming (system 2), and (3) high-input fish farming (system 3) in rice-dominated areas. System 1 was commonly practiced in a rural and intensive fruit production area with fertile soils, while systems 2 and 3 were more frequent in peri-urban and in rice production areas with less fertile soils. In the study areas, poor farmers usually did not adopt IAA-farming. With good market accessibility, richer farmers tended to intensify fish farming. The principal factors why farmers did not start aquaculture were the inappropriateness of the technology available, lack of capital, insufficient land holding, poor access to extension services, limited farm management, and a fear of conflicts associated with pesticide use on crops. The main motivations to practice IAA-farming were increased farm resource uses, which resulted in improved income, a better supply of foods for home consumption and a reduction of the environmental impacts from the farming. In low- and medium-input ponds, nutrient inputs, the accumulation of nitrogen (N), organic carbon (OC) and phosphorus (P) and environmental impacts were closely linked (chapter 3). Parameters related to nutrients input levels and water exchange rates in ponds explained most of the variability between farms. Parameters linked to agro-ecological sites, pond physical properties and livestock or human excreta inputs explained most of the remaining variability. A combination of these variables allowed to characterize three indicative integrated systems: (1) the low water-exchange-rate ponds in the fruit-dominated area, (2) the low water-exchange-rate ponds in the rice-dominated area receiving home-made feed, and (3) the high water-exchange-rate ponds in the rice-dominated areas receiving excreta. These systems concurred to a large extend with the systems identified on the basic of the community and household survey. In the rice-dominated area with deep ponds, more livestock or human wastes were supplied, and high water exchange rates were practiced. In these ponds, large excreta-OC loads reduced dissolved oxygen and increased total phosphorus concentrations in the water column and nitrogen, organic carbon and phosphorus accumulation in the sediments. In the rice-dominated area with wide ponds, more home-made feed was applied and low water-exchange rates were practiced, which resulted in a high phytoplankton biomass and primary productivity. On the contrary, in the fruit-dominated area fish were grown in shallow and narrow ditches with a low phytoplankton biomass and only a small fraction of the nutrient input accumulated in the sediments. The water and nutrient budgets of a selected number of ponds, representing either low or high water-exchange systems were determined (chapter 4). The sluice-gate water inflow and outflow largely dominated the total pond water budgets, accounting for 72-97% of the total water budget. On-farm livestock manures were the most important nutrient source for ponds. High water-exchange rate ponds received larger quantities of livestock and/or human excreta and had significantly higher volumes of water passing through ponds than low water-exchange rate ones. Only 5-6% of the total N, OC and P inputs were retained in the harvested fish, but 18-91% accumulated in the pond sediments, the rest was lost through pond water discharges. Fish yields and the quantity of nutrients accumulating in the sediments increased with increasing on-farm nutrient input levels at the cost of higher nutrient discharges. Its was concluded that farmers need to manage water and nutrient flows between the pond and the other IAA-farm components with the goals to maximize productivity and profitability while minimizing nutrient discharges of the farm as a whole. Excreta were the principle type of nutrient input applied to ponds in the study areas. Therefore, the economic and nutrient discharge tradeoffs stemming from the use of livestock and human excreta were analyzed (chapter 5). Data collected during three consecutive production years were combined in the analysis. Results showed that increased excreta input levels resulted in lower dissolved oxygen concentrations, higher water exchange rates practiced, and increased discharge of chemical oxygen demand (COD), N, P and total suspended solids (TSS). Fish yields and the accumulation of N, OC and P in pond sediments, however, increased with increasing excreta input levels. Through regression analysis, it was predicted that with an input of 5 kg N ha-1 day-1, a fish yield of 8379 kg and an economic return of 52 million VND ha-1 yr-1 will be obtained while about 2057 kg COD, 645 kg N, 213 kg P and 39203 kg TSS ha-1 yr-1 will be discharged from the farm. At this input level, about 9% of input-N will be retained in harvested fish, 52% will accumulate in the sediments and 39% will be discharged. Further development of IAA-farming practices should focus on reducing nutrient discharges while maintaining favorable economic returns. In brief, this study demonstrated that the adoption of one type of IAA-system by farmers is determined by a mixture of factors at different scales ranging from the individual pond to community or village level. Within each IAA-system, the pond fulfils multiple roles, in part influenced by the existing resource base, agricultural development pathways and the household's goals and aspirations. An important function of ponds is the trapping and storage of nutrients for subsequent reuse within IAA-systems, which otherwise would be lost. Optimizing nutrient storage in ponds also concurs with best management practices from an environmental and economic point of view. The key challenge to the further development and optimization if IAA-farming is to balance economic, environmental and social interests within a highly dynamic setting of the Mekong delta today.
Fishponds in farming systems
Zijpp, A.J. van der; Verreth, J.A.J. ; Quang Tri, Le; Mensvoort, M.E.F. van; Bosma, R.H. ; Beveridge, M.C.M. - \ 2007
Wageningen : Wageningen Academic Publishers - ISBN 9789086860135 - 311
visvijvers - visteelt - bedrijfssystemen - geïntegreerde systemen - landbouw - duurzaamheid (sustainability) - kringlopen - fish ponds - fish culture - farming systems - integrated systems - agriculture - sustainability - cycling
Throughout the last century, specialisation and intensification were buzz words for farmers in the Western world. However, this approach has not resulted in sustainable development as evidenced by the fact that scientists now need to create technologies to reduce negative impacts. In this book we demonstrate that an alternative exists. Case studies from Bangladesh, Thailand, and Vietnam show that integration and diversification increase both farm productivity and farmers' incomes. By adopting a participatory approach, farmers and scientists identified a range of technologies that strengthen the positive impacts of integrated aquaculture-agriculture systems for the environment. This book is a collection of refereed papers on a controversial subject in agricultural development. Arguing that sustainability of fish culture in ponds needs a new paradigm - feed the pond to grow fish - two chapters focus on nutrient cycling in such systems. Another chapter makes the case for breeding Nile tilapia for resource poor farmers and presents practical options to avoid the pitfalls that arise from natural tilapia mating in low-input ponds. The book contains chapters on livelihood and development aspects and ends with a general discussion completing the picture of the integrated aquaculture-agriculture systems. Overall it composes a review which addresses one of the key issues of the new century: how to sustainably produce food without compromising environmental integrity.
Mixed culture of tilapia (Oreochromis niloticus) and freshwater prawn (Macrobrachium rosenbergii) in periphyton-based ponds
Uddin, S. - \ 2007
Wageningen University. Promotor(en): Johan Verreth; M.A. Wahab, co-promotor(en): Marc Verdegem. - [S.l.] : S.n. - ISBN 9789085046424 - 208
oreochromis niloticus - tilapia - macrobrachium rosenbergii - steurgarnalen - visvijvers - substraten - vegetatie - prestatieniveau - dierlijke productie - aquacultuur - prawns - fish ponds - substrates - vegetation - performance - animal production - aquaculture
Decomposition of high protein aquaculture feed under variable oxic conditions
Torres Beristain, B. ; Verdegem, M.C.J. ; Kerepeczki, E. ; Verreth, J.A.J. - \ 2006
Water Research 40 (2006)7. - ISSN 0043-1354 - p. 1341 - 1450.
anaerobic ammonium oxidation - organic-matter - nitrogen transformations - flooded soil - fish ponds - nitrification - management - bacteria - marine - carbon
The microbial decomposition of nitrogen-rich organic matter in aquaculture ponds is affected by the oxic-anoxic conditions gradient at the soil¿water interface as well as by resuspension practices. To investigate these interactions, the decomposition of a 49% protein fish feed was analyzed in 10 marine lab-scale systems with different exposures to aerobic and anaerobic conditions. The degree of coupling between oxic and anoxic conditions in the system had a strong effect on product accumulation and loss from the culture system. Pure oxic or anoxic conditions proved to be less favorable than mixed aerobic¿anaerobic systems with respect to the metabolites accumulated in the system. Short 15-min resuspension events and a continuous alternation of oxic and anoxic conditions at 12-h time intervals proved to be the best options to minimize the accumulation of organic matter in the systems. The correct coupling of aerobic¿anaerobic conditions in space and time is a key to maintain a good water quality condition for the cultured animals and also to improve the decomposition and recycling of organic matter, reducing the environmental impact from the effluents
Fingerponds: managing nutrients and primary productivity for enhanced fish production in Lake Victoria's wetlands, Uganda
Kaggwa, R.S. - \ 2006
Wageningen University. Promotor(en): P. Denny, co-promotor(en): A.A. van Dam; F. Kansiime. - [S.l.] : S.n. - ISBN 9085044987 - 202
aquacultuur - visteelt - visvijvers - wetlands - kleine landbouwbedrijven - voedingsstoffen - mest - duurzaamheid (sustainability) - visproductie - uganda - geïntegreerde bedrijfssystemen - strategieën voor levensonderhoud - aquaculture - fish culture - fish ponds - small farms - nutrients - manures - sustainability - fish production - integrated farming systems - livelihood strategies
Fingerponds: seasonal integrated aquaculture in East African freshwater wetlands : exploring their potential for wise use strategies
Kipkemboi, J. - \ 2006
Wageningen University. Promotor(en): P. Denny, co-promotor(en): A.A. van Dam. - [S.l.] : S.n. - ISBN 9780415416962 - 168
aquacultuur - visteelt - visvijvers - wetlands - kleine landbouwbedrijven - milieueffect - bestaan - duurzaamheid (sustainability) - kenya - geïntegreerde bedrijfssystemen - strategieën voor levensonderhoud - aquaculture - fish culture - fish ponds - small farms - environmental impact - subsistence - sustainability - integrated farming systems - livelihood strategies
The role of fish ponds in the nutrient dynamics of mixed farming systems
Muendo, P.N. - \ 2006
Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Marc Verdegem; Jetse Stoorvogel. - [S.l. ] : S.n. - ISBN 9085044596 - 120
visvijvers - gemengde landbouw - voedingsstoffen - aquacultuur - visproductie - bedrijfssystemen - landbouwbijproducten - kringlopen - fish ponds - mixed farming - nutrients - aquaculture - fish production - farming systems - agricultural byproducts - cycling
Food web interactions and nutrients dynamics in polyculture ponds
Rahman, M.M. - \ 2006
Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Marc Verdegem; Leo Nagelkerke. - [S.l. ] : S.n. - ISBN 9085044472 - 157
karper - labeo - voedselwebben - visvijvers - voedingsstoffen - visteelt - aquacultuur - visproductie - ecologie - waterkwaliteit - voer - diergedrag - plassen - bangladesh - carp - food webs - fish ponds - nutrients - fish culture - aquaculture - fish production - ecology - water quality - feeds - animal behaviour - ponds
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 effect of carbohydrate addition on water quality and the nitrogen budget in extensive shrimp culture systems
Hari, B. ; Kurup, B.M. ; Varghese, J.T. ; Schrama, J.W. ; Verdegem, M.C.J. - \ 2006
Aquaculture 252 (2006)2-4. - ISSN 0044-8486 - p. 248 - 263.
penaeus-monodon fabricius - dietary-protein - aquaculture systems - high-intensity - fish ponds - management - juveniles - nutrient - bacteria - exchange
Water quality and shrimp production were monitored in extensively managed ponds which were fed a 25% (P25) or 40% (P40) dietary protein, each diet complemented with or without carbohydrate (CH) addition. The experiment was carried out in 6-m3 concrete tanks, with a mud bottom and stocked with 7 post larvae (PL 20) of Penaeus monodon per m2. Tapioca flour was used as carbohydrate source. CH addition reduced total ammonia nitrogen (TAN) and nitrite–nitrogen (NO2-–N) in the water column and TAN in the sediment (P <0.001). CH addition also increased the total heterotrophic bacterial (THB) count in water column and sediment (P <0.05). Lower specific growth rate (SGR) and higher feed conversion ratio (FCR) were recorded in P25, compared to all other treatments (P <0.05). The 160 g m- 2 shrimp yield in treatment P25 + CH was similar to the 157 g m- 2 yield in treatment P40, which was much higher than the 114 g m- 2 yield in treatment P25 (P <0.001). CH addition to treatment P40, did not result in a higher yield (P > 0.05). The protein efficiency ratio (PER) was higher (P <0.001) in treatment P25 + CH compared to other treatments. Survival of the shrimps was not affected by treatment (P > 0.05). A system nitrogen budget revealed that 16% to 21% of the total nitrogen input was retained in the shrimp, 0.22% to 0.49% in the water, 67% to 71% in the sediment, and 2.1% to 2.7% was lost through water exchange. The quantity of nitrogen not retained in shrimp biomass to produce 1 kg of shrimp ranged between 109.2 and 164.0 g N. The total water based N-loss (final pond water N + exchange N-loss) from an extensive type of shrimp culture system was within the range of 2.7% to 3.2% of the total input nitrogen. The percentage non-retained nitrogen was reduced by CH addition (P <0.01). In summary, CH addition to the water column under extensive shrimp culture conditions (1) increased the nitrogen retention in harvested shrimp biomass (2) reduced the demand for feed protein (3) reduced the concentration of TAN and NO2-–N in the pond, and (4) reduced nitrogen discharge making extensive shrimp farming more ecologically sustainable and economically viable.
Short Communication. Rhizons improved estimation of nutrient losses because of seepage in aquaculture ponds
Muendo, P.N. ; Stoorvogel, J.J. ; Gamal, N.E. ; Verdegem, M.C.J. - \ 2005
Aquaculture Research 36 (2005)13. - ISSN 1355-557X - p. 1333 - 1336.
fish ponds - water - phosphorus - hydrology - nitrogen - budgets - shallow - lake
Afbraak van organisch materiaal en bacteriële biomassa in aquacultuur productiesystemen
Verdegem, M.C.J. ; Torres Beristain, B. - \ 2005
Aquacultuur 2 (2005). - ISSN 1382-2764 - p. 15 - 19.
aquacultuur - visteelt - viskwekerijen - visvijvers - waterkwaliteit - organische verbindingen - anaërobe afbraak - aquaculture - fish culture - fish farms - fish ponds - water quality - organic compounds - anaerobic digestion
Ophoping van mest, voerresten en ander organisch materiaal kan in de vijverteelt tot waterkwaliteitsproblemen leiden. In het laboratorium van de Leerstoelgroep Visteelt en Visserij, Wageningen Universiteit, is de afgelopen jaren onderzoek gedaan naar de omstandigheden die de afbraak van mest, voerresten en ander organisch materiaal bepalen. Dit artikel vat enkele resultaten samen