Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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The evaluation of energy in fish feed
Haidar, Mahmoud - \ 2017
University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama. - Wageningen : Wageningen University - ISBN 9789463438049 - 155
oreochromis niloticus - fish feeding - feed formulation - digestible energy - dietary protein - dietary fat - carbohydrates - growth - feed evaluation - fish culture - aquaculture - visvoeding - voersamenstelling - verteerbare energie - voedingseiwit - voedingsvet - koolhydraten - groei - voederwaardering - visteelt - aquacultuur

New and alternative plant ingredients are increasingly incorporated in fish feed due to the scarcity of captured fish and increased fishmeal and fish oil prices. As a result, current fish feeds are characterized by a highly variable ingredients composition, leading to a similar variability in the dietary macronutrients composition, especially the carbohydrates fraction. Appropriate formulation of the energy component in fish feeds requires information on nutrient digestibility, energy requirements for maintenance, and the efficiency of utilization of digestible energy for growth (kgDE). In fish feed formulation, the energy evaluation is based on digestible energy (DE) basis. The main assumptions of this DE system are that maintenance requirements and kgDE are independent of dietary factors. The main objective of this thesis was to evaluate and improve the DE system for Nile tilapia. Data showed that, opposite to what is assumed in literature and irrespective of the feeding level applied, an optimal digestible protein to digestible energy ratio (DP/DE) for young Nile tilapia could not be detected. In addition, it was expected that Nile tilapia would show a maximal protein deposition in relation to a wide range of DP/DE ratios, however, this was either observed. Further investigations showed that different body compartments/organs responded differently in terms of protein and fat composition as a result of changes in the dietary DP/DE ratio. In tilapia, viscera and the “rest” fraction (head, skin, fins and bones) were the main site for fat retention. In addition, protein content of fillets seems to be constant (about 17%) and not affected by dietary factors in Nile tilapia. In addition, the effect of using new plant ingredients in Nile tilapia diets was also investigated. The results showed that the ingredients composition had an effect on the maintenance requirements of Nile tilapia. Further, changes in the ratio of starch vs non starch carbohydrates revealed that energy retention was lower when more dietary fibers were included. In addition, the net energy retention differed also when the levels of digestible protein, fat and carbohydrates changed in the diets. The latter results proved that kgDE was not constant and was dependent on diet composition. All aforementioned results led us to calculate the energetic efficiencies of digestible protein, fat and carbohydrates for net energy retention. These estimated efficiencies were used to propose a net energy evaluation system being feasible for Nile tilapia.

The development of a sole diet based on the composition of ragworm
Kals, Jeroen - \ 2017
University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama; Robbert Blonk. - Wageningen : Wageningen University - ISBN 9789463431804 - 136
dover soles - annelida - fish feeding - anaemia - haemoglobin - fish culture - aquaculture - tong (vis) - visvoeding - anemie - hemoglobine - visteelt - aquacultuur

Scientifically, this study aimed to validate the potential of ragworm to alleviate anaemia in common sole and to identify the dietary requirements of common sole to alleviate this anaemia. At the same time it was aimed to explain part of the difference in growth between sole fed a commercial pellet and sole fed ragworm. Practically, this study aimed to develop a diet that achieves similar growth rates in sole as when fed ragworm. Sole fed commercial pellets developed nutritional anaemia. Feeding ragworm or mussel alleviates this nutritional anaemia. It is suggested that the ability of mussel or ragworm (meal) to alleviate anaemia and improve growth in sole can be explained by heme iron and high B12 levels. Yet, iron absorption in sole is high and independent of iron source. Still, heme increases the absorption of copper. The high absorption of iron and copper in sole fed heme does not affect the haematocrit (Hct) and haemoglobin (Hb) levels, which indicates the anaemia in sole is not an iron or a copper deficiency anaemia. The Hct and Hb levels in sole are affected by dietary B12. Yet, the applied levels are unable to alleviate the anaemia in sole induced by feeding commercial pellets. More options to alleviate the nutritional anaemia in common sole are discussed. Nutrients as vitamin C, B1, B2, B5 and a possible role of dietary EPO are discussed. It is suggested that the slow growth of pellet-fed sole might be due to the low Hct and Hb levels, which hampers the uptake of oxygen, and thus also the overall metabolic capacity, including the scope for growth. Discussed is a 7°C difference in the “optimal” temperature between sole fed ragworm and the 2nd generation pellet and that the “worm effect” is dependent on temperature. However, the growth rate of sole fed the 3rd generation pellet at 18.4°C was comparable to the growth rate of sole fed ragworm, which could not have been the consequence of increasing Hct and Hb levels as these were comparable to levels found in sole fed commercial pellets. Yet, B12 levels in blood plasma of sole are up to 200 times those of other (fish) species. Hence, we inferred on the possibility of a specific metabolic function of B12 in respiration in sole. In addition, the economic and practical impact of the improved growth rate in sole culture is discussed. Finally, several suggestions for future research are given.

Feeds, water quality, gut morphology and digestion in Nile tilapia (Oreochromis niloticus)
Trần Ngọc Thiên Kim, Kim - \ 2017
University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama; Arjen Roem. - Wageningen : Wageningen University - ISBN 9789463431484 - 127
tilapia - oreochromis niloticus - feeds - fish feeding - water quality - digestion - digestibility - intestines - morphology - fish culture - aquaculture - voer - visvoeding - waterkwaliteit - spijsvertering - verteerbaarheid - darmen - morfologie - visteelt - aquacultuur

Diet composition, ingredient and nutrients, are important to consider for maintaining intestinal functions. Studies on both positive (using feed additives) and negative effects (using high inclusion of plant ingredients) of fish feeds are numerous, however, between studies results are often highly variable, both in type of response and in significance. The central hypothesis of this study was that adverse environmental conditions may aggravate negative effects of plant ingredients on the intestinal functions to the extent that mild effects become severe and perceptible. To do so, dietary factors and environmental conditions were evaluated and the interaction between diet composition and environmental conditions were studied in Nile tilapia.

In Chapter 2, six common raw materials including hydrolysed feather meal (HFM), soybean meal (SBM), rice bran (RB), rapeseed meal (RM), sunflower meal (SFM) and dried distiller grains with solubles (DDGS) were chosen to determine the effect of nutrient digestibility, nitrogen/energy balance and changes in intestinal morphology. The study demonstrated that feed ingredients do have an impact on the alteration in intestinal parameters, but also on the nutrient digestibility and the nitrogen/energy balance. Although being well digested, soybean meal caused the most obvious alteration in the intestinal morphology. These alterations were not related to the nutrient digestibility nor to nitrogen/energy balance parameters. Soybean meal, causing the most alterations in the intestinal morphology, was further used in all subsequent chapters of this thesis.

Chapter 3 and 4 described the interaction between diet composition and environmental conditions on the intestinal functions. This was studied with two different environmental conditions, dissolved oxygen (Chapter 3) and salinity (Chapter 4). These two chapters evaluated whether suboptimal environmental conditions (low dissolved oxygen or elevated salinity in water) may interact with a soybean meal based diet in nutrient digestion and intestinal morphology of tilapia. The study demonstrated that environmental stressors can aggravate/reveal the negative intestinal morphology changes induced by a soybean meal based diet. However, these effects of adverse environmental conditions on the intestinal functions were not homogenously dispersed over the whole intestinal length. The effect of salinity on the intestinal morphology occurred predominantly in the distal intestine, whereas the effect of low oxygen concentration was more visible at the proximal intestine. Alterations in the intestinal morphology, as found in this study, have wider effects on the performance of the affected fish. In Chapter 3, the protein digestibility decreased under hypoxic conditions at week 8, which parallels with the time related alteration in intestinal morphology. Chapter 4 showed that when fish were raised at 15 ‰ salinity, nutrient digestibility increased; however, this positive effect decreased when the intestinal morphology changed. The study also found that the combined effect of a soybean meal based diet and hypoxia was stronger compared to the combination with elevated salinity. Therefore, the combination with hypoxia was further used in the next study of this thesis.

In Chapter 5, the combination of hypoxic condition and a soybean meal based diet was chosen to test the hypothesis that only under stressful conditions, the effects of feed additives can be noticed. The impact of two dietary organic acids, formic acid and butyric acid, on nutrient digestibility and intestinal morphology was determined under optimal (normoxia) and suboptimal conditions (hypoxia). The results showed that although organic acids did not significantly improve growth performance and nutrient digestibility under normoxic condition, they did so under hypoxic conditions. Fish fed organic acid supplemented diets all showed improvements in the morphology of intestine under normoxic conditions, and these effects were more enhanced under hypoxic conditions. This indicates that environmental conditions can alter the effect of organic acid on nutrient digestibility and intestinal morphology in tilapia.

Finally, Chapter 6 provided a synthesis of the main findings, and a reflection on the methodologies used in Chapters 2-5 as well as a discussion on the relevance of this study to aquaculture. It is concluded that although being well digested, soybean meal caused the most obvious alteration in intestinal morphology. The adverse environmental conditions aggravated negative effects of soybean meal based diets on the intestinal functions to the extent that mild effects become severe and visible. The negative effect on intestinal morphology of soybean meal in the diet is enhanced at low oxygen level and at elevated salinity. The effect of salinity on the intestinal morphology occurs predominantly in the distal intestine, whereas the effect of low oxygen concentration is more visible at the proximal intestine. The thesis indicated that the impact of organic acids on intestinal functions is dependent on environmental conditions, being more pronounced under challenging conditions (e.g. hypoxia). Therefore, studies on both positive (using feed additives) and negative effects (using high inclusion of plant ingredients) of dietary factors should be done under suboptimal conditions.

Optimization of breeding schemes for Nile tilapia (Oreochromis niloticus) in smallholder production systems in Kenya
Omasaki, Simion Kipkemboi - \ 2017
University. Promotor(en): Hans Komen, co-promotor(en): Johan van Arendonk; A.K. Kahi. - Wageningen : Wageningen University - ISBN 9789463431064 - 167
oreochromis niloticus - tilapia - breeding programmes - selective breeding - genetic improvement - small farms - sustainability - fish culture - aquaculture - kenya - veredelingsprogramma's - selectief fokken - genetische verbetering - kleine landbouwbedrijven - duurzaamheid (sustainability) - visteelt - aquacultuur

The aim of this thesis was to develop a sustainable low cost breeding program for Nile tilapia that addresses both genetic and economic aspects of smallholder fish farmers in Kenya. First, Analytical Hierarchy Process Technique was used to define a breeding goal based on farmer’s preferences for traits. Farmers’ preferences for traits differed significantly depending on income and market orientation. Low and medium income farmers preferred harvest weight (HW) while high income farmers preferred growth (GR) and survival (S) traits. Grouping farmers according to market objective (fingerling production or fattening) showed that fingerling producers preferred GR and S while fattening farmers preferred HW and S. Consensus preference values were obtained using weighted goal programming and these values were used to derive desired gains for a breeding goal that takes into account farmers’ diverse backgrounds and preferences for traits. Secondly, the existence of genetic variation for traits of interest was investigated. Substantial additive genetic effects for HW, GR and shape traits were present that can be exploited through selection under low input production system. Heritability estimates for HW, GR and shape were 0.21 ± 0.03, 0.26 ± 0.04 and 0.12 ± 0.03 for mixed sex (nucleus) respectively. The calculation of economic values for breeding goal traits revealed that economic values for GR differed depending on the definition of the breeding goal and that selection for feed efficiency is the key factor to economic profitability of Nile tilapia breeding programs. A significant genotype by environment re-ranking was found for GR between the mixed sex nucleus and monosex production environments. Genotype by environment interaction (G x E) led to lower genetic gain for GR in production environment. Incorporating sib information from monosex production environment into the selection index resulted in a more accurate estimation of breeding values which increased genetic gain in growth. Using desired gain approach, weights for desired gains in harvest weight, growth rate and survival were derived that maximized genetic gains for these breeding goal traits. It is concluded that these results can be used to develop a sustainable centralized breeding program. However, a reliable well planned and organized decentralized strategy for dissemination of genetically improved fry of Nile tilapia to farmers is paramount.

Matching breeding goals with farming systems to enhance the sustainability of fish farming
Besson, Mathieu - \ 2017
University. Promotor(en): Imke de Boer; Hans Komen, co-promotor(en): M. Vandeputte. - Wageningen : Wageningen University - ISBN 9789463430067 - 201
fish culture - sustainability - animal production - farming systems - models - feed conversion - breeding - growth rate - feed conversion efficiency - animal welfare - visteelt - duurzaamheid (sustainability) - dierlijke productie - bedrijfssystemen - modellen - voederconversie - veredelen - groeitempo - voederconversievermogen - dierenwelzijn

Fish farming is growing but is also facing challenges regarding economic viability and environmental sustainability. Selective breeding could enhance the sustainability of fish farming by changing animal performances. Thus, our aim was to develop sustainable breeding goals by using economic (EV) or environmental values (ENV) to weigh the traits to improve. EV and ENV represent the economic and environmental impacts of improving a trait. They were calculated using a bioeconomic model combined with a life cycle assessment. We showed that the EV and ENV of traits change with the factor constraining the production of the farm. It suggests that breeding goals should be finely tuned according to the limiting factor to maximize economic or environmental responses. In addition, we showed that improving feed conversion ratio is a major trait to improve because it always increases profit and decreases environmental impacts. We conclude that it is possible to develop breeding programs enhancing the sustainability of fish farming by improving the right trait in the right production system.

Improving sustainability of striped catfish (Pangasianodon hypophthalmus) farming in the Mekong Delta, Vietnam through recirculation technology
Nguyen, Nhut - \ 2016
University. Promotor(en): Johan Verreth, co-promotor(en): Marc Verdegem. - Wageningen : Wageningen University - ISBN 9789462579194 - 180
fish culture - recirculating aquaculture systems - aquaculture - fishes - nutrients - vietnam - visteelt - recirculatie aquacultuur systemen - aquacultuur - vissen - voedingsstoffen

The aim of this thesis was to document improvements in sustainability indicators of striped catfish (Pangasianodon hypophthalmus, Sauvage, 1878) production through the application of recirculation and waste treatment techniques. To be able to document improvements in sustainability, in each system studied the same set of twenty sustainability indicators were measured. Indicators related to the use of fingerlings, water, diesel oil, electricity, labor, chemicals and antibiotics.

Also, indicators related to nutrient utilization efficiencies and waste discharge were monitored. In addition, a sampling scheme, allowing to calculate organic matter, nitrogen, phosphorous and chemical oxygen demand mass balances covering a full production cycle and applicable in different production systems, was developed. Overall, from a sustainability point of view, striped catfish culture in ponds compared well to other important aquaculture species.

Although favorable, it was concluded that water, chemicals and antibiotics use, survival, and the amounts of waste discharged could be further reduced through recirculation and treatment of solid wastes. The realized improvements through RAS technology and waste treatment technology were quantified in lab or pilot scale experiments. Large improvements were realized for water, antibiotic and chemical use, survival, waste discharge and color grade of striped catfish fillets at harvest. In addition, in RAS, utilization efficiencies of nutrients supplied through feeding were improved.

Solid wastes removed from ponds or RAS could be partially re-used by making compost or producing methane for generating electricity. Another approach tested was the integration of a denitrification reactor in the recirculation system, which allowed to decompose solid waste and reduce nitrogen discharge. Denitrification in RAS did not affect fish growth, nutrient retention efficiencies and the quality of the fish fillets produced, and thus also improved sustainability of striped catfish farming.

In conclusion, application of recirculation and waste treatment techniques tested in this thesis improved the sustainability for striped catfish culture. The challenge remains to scale up RAS and waste treatment technology for striped catfish to the production volumes handled in outdoor ponds without raising production costs.

Economic analysis of technological innovations to improve sustainability of pangasius production in Vietnam
Ngoc, Pham Thi Anh - \ 2016
University. Promotor(en): Alfons Oude Lansink; Johan Verreth, co-promotor(en): Miranda Meuwissen. - Wageningen : Wageningen University - ISBN 9789462579880 - 141
fish production - fishes - innovations - economic analysis - sustainability - fish culture - vietnam - visproductie - vissen - innovaties - economische analyse - duurzaamheid (sustainability) - visteelt

In response to increasing concerns about sustainable production, a growing number of European customers expect seafood products to be certified, for example by the Aquaculture Stewardship Council (ASC) certification. Water purification technologies such as Recirculating Aquaculture Systems (RAS) could be a potential solution to reduce waste discharge and to improve water quality in fish ponds as a response to environmental regulations. In order to provide useful insights to consider investments in RAS, the overall objective of this thesis was to perform an economic analysis of technological innovations such as RAS to improve the sustainability of pangasius production in Vietnam.

This thesis first uses Data Envelopment Analysis to measure input- and output-specific technical and scale inefficiency of pangasius farmers in the traditional system and uses a bootstrap truncated regression to assess the impact of farmers’ demographics and farm characteristics on these technical inefficiencies. Second, the economic feasibility of RAS in pangasius farming is analysed using a capital budgeting approach and stochastic simulation accounting for uncertainty in key parameters. Next, key determinants influencing the adoption of RAS by pangasius farmers are investigated using a choice experiment. Finally, price transmission along the international supply chain of pangasius, from the Vietnamese farm to the Polish retail stage is analysed using a vector autoregressive error correction model framework.

The results show that inadequate management skills in using capital assets and improper methods for producing fish are the main challenges for enhancing the performance of Vietnamese pangasius production. Location of the farm in a saltwater intrusion area is positively associated with inefficiency of producing fish. The results suggest further that when shifting from the traditional system to RAS, the Net Present Value (NPV) of the investment in RAS is expected to substantially increase, for both medium (1-3 ha) and large (equal or greater than 3 ha) farms. Lack of trust in receiving a price premium, inadequate access to finance and uncertainty about the actual performance of RAS systems are constraints for the adoption of RAS. Finally, our study provides evidence that price signals at the Polish-Vietnamese retail stage were transmitted back to wholesale, export and Vietnamese pangasius farms stages.

Microbial interactions in the fish gut
Giatsis, Christos - \ 2016
University. Promotor(en): Johan Verreth, co-promotor(en): Marc Verdegem; Detmer Sipkema. - Wageningen : Wageningen University - ISBN 9789462578777 - 196
fishes - tilapia - larvae - microbial interactions - intestinal microorganisms - intestines - dynamics - fish feeding - probiotics - fish culture - aquaculture - vissen - larven - microbiële interacties - darmmicro-organismen - darmen - dynamica - visvoeding - probiotica - visteelt - aquacultuur

Aquaculture has realized considerable growth over the past years while the world demand on seafood has been increasing. As aquaculture intensifies, the production sector needs to tackle major bottlenecks such as suboptimal growth and high and unpredictable mortality, especially in larval cultures. Fish-microbe interactions are closely related to overall fish health. To obtain a healthy and resilient microbial community (MC), it is important to understand the underlying mechanisms of microbial colonization in the fish gut.

The goal of this thesis was to investigate the role of water and feed microbial communities on shaping gut communities during early development of Nile tilapia.

To determine the contribution of stochasticity to overall variation, we first characterized the spatio-temporal variation in MC composition between individuals reared within the same or in replicate recirculating or active suspension systems (RAS vs. AS). Highly similar MCs developed in the gut when larvae shared the same water and diet. Rearing larvae in replicate production systems resulted in significantly different gut communities indicating that compositional replication of the MCs of an ecosystem is not fully predictable. We found that mainly water MCs, and to a lesser degree feed MCs, were associated with changes in MCs. Thus, we could conclude that steering gut MCs can be possible through water MC management tailored on the specifications of the rearing system in use.

Next, the possibility of early life steering of gut communities via microbial manipulations of feed MCs was explored. We hypothesized that gut microbial composition is strongly shaped by selective pressures in the gut and by the MCs present in the water. Thus similar MCs should develop between treatments regardless of the dietary treatments. Fish larvae were fed either a control feed or the control feed containing MCs derived from aerobic, methanogenic or denitrifying sludge reactors. We found that gut microbiota shared a much higher number of operational taxonomic units (OTUs) with microbiota in sludge-based feeds than with water, resulting in distinct gut MCs between treatments. Our findings suggest that Nile tilapia gut MC has a certain plasticity, which makes it amenable to interventions through proper feed microbial management.

Subsequently, we tested the imprinting effect of early exposure to the probiotic Bacillus subtilis on shaping gut MC composition even after the administration of the probiotic discontinues. For this, we constrained the initial contact with microbes from the environment by producing axenic tilapia larvae, which were then exposed to normal husbandry conditions. Early life probiotic exposure affected gut MC composition during B. subtilis administration but also within the first two weeks after its administration stopped, thus indicating that early exposure to the probiotic strain via the water had a sustained impact on gut MC composition.

Finally, overall conclusions and practical implications of our results for aquaculture production were presented. A meta-analysis was also performed to examine (1) the phylogenetic similarity among gut MCs of the same and different fish species reared in different habitats, fed different diets and at different developmental stages and (2) the factors primarily shaping gut MCs. We showed that the selective pressure responsible in shaping gut MC composition highly depends on the host as gut communities clustered primarily together by host and to a lesser extent reflected differences in habitat and diet. The phylogenetic analysis of gut communities revealed a clear clustering by study thus indicating that manipulation of gut communities is conceivable. Study-to-study variation could be attributed to the methodology used for MC analysis highlighting also the importance of methodological uniformity when comparisons between studies are made.

Overall, this thesis provided fundamental knowledge on MC composition and development in aquaculture rearing systems. Although the insights generated by this thesis are still premature to fully explain, predict or steer MC composition, and though additional studies are needed, we believe that, in the long run, this approach will facilitate the development of safe and effective methods for manipulating gut microbial composition to promote fish health in aquaculture rearing systems.

Next-generation salmonid alphavirus vaccine development
Hikke, M.C. - \ 2016
University. Promotor(en): Just Vlak, co-promotor(en): Gorben Pijlman. - Wageningen : Wageningen University - ISBN 9789462577404 - 159 p.
alphavirus - atlantic salmon - rainbow trout - vaccine development - immunity - virology - fish culture - aquaculture - biotechnology - alfavirus - europese zalm - regenboogforel - vaccinontwikkeling - immuniteit - virologie - visteelt - aquacultuur - biotechnologie


Aquaculture is essential to meet the current and future demands for seafood to feed the world population. Atlantic salmon and rainbow trout are two of the most cultured aquaculture species. A pathogen that threatens these species is salmonid alphavirus (SAV). A current inactivated virus vaccine against SAV provides cross-protection against all SAV subtypes in salmonids and reduces mortality amongst infected fish. However, protection is not 100% and due to virus growth at low temperature, the vaccine production process is time consuming. In addition, the vaccine needs to be injected into the fish, which is a cumbersome process. The work described in this thesis aimed to increase the general knowledge of SAV and to assess current vaccine technologies, and to use this knowledge in designing next-generation vaccines for salmonid aquaculture.

An alternative cell line to support SAV proliferation was identified, however, the virus production time could not yet outcompete the current SAV production system. Making use of the baculovirus insect cell expression system, multiple enveloped virus-like particle (eVLP), and core-like particle (CLP) prototype vaccines were produced in insect cells at high temperature. An in vivo vaccination study showed, however, that these vaccines could not readily protect Atlantic salmon against SAV. The low temperature-dependent replication of SAV was attributed to the glycoprotein E2, and it was found that E2 only correctly travelled to the cell surface at low temperature, and in the presence of glycoprotein E1. The biological impact of this finding was confirmed in the development and in vivo testing of a DNA-launched replicon vaccine. The effective DNA-launched replicon vaccine was extended by delivery of the capsid protein in trans. It was hypothesized that viral replicon particles (VRP) were formed in vivo, which would cause an additional single round of infection and might further elevate the immune response in comparison to the replicon vaccine. A second animal trial indicated that the inclusion of capsid did not yet improve vaccine efficacy. This trial however did show that a DNA vaccine transiently expressing the SAV structural proteins provided superior protection over both replicon vaccines (with and without capsid).

In this thesis, some virus characteristics, such as the cause of temperature-dependency of SAV replication, of an unique aquatic virus were further explored. The production and in vivo testing of multiple next-generation vaccines defined the prerequisites for induction of a potent immune response in Atlantic salmon. A prototype DNA-launched replicon vaccine has shown potential for further development. The research described in this thesis contributes to the development of next-generation vaccines in the challenging area of fish vaccinology.

Scoping study Turkish Rainbow trout aquaculture
Schram, E. - \ 2016
IJmuiden : IMARES (Report / IMARES C005/16) - 19 p.
rainbow trout - recirculating aquaculture systems - fish culture - industry - stakeholders - companies - feasibility studies - turkey - regenboogforel - recirculatie aquacultuur systemen - visteelt - industrie - kapitaalvennootschappen - haalbaarheidsstudies - turkije
Een overzicht van de benodigde vergunningen en regelgeving voor de start van een viskweekbedrijf
Abbink, W. - \ 2016
Yerseke : IMARES (Rapport / IMARES C011/16) - 15 p.
vergunningen - visteelt - milieuwetgeving - wetgeving - overheid - kosten - permits - fish culture - environmental legislation - legislation - public authorities - costs
Het ministerie van EZ heeft IMARES Wageningen UR gevraagd om een overzicht te maken van de aanvraagprocedures voor benodigde vergunningen en bepalende regelgeving voor het opzetten van een viskweekbedrijf. In dit rapport zijn de procedures opgedeeld in de twee hoofdonderdelen Bouw en Milieu, en Dieren. De laatste jaren zijn met de invoering van de Wet algemene bepalingen omgevingsrecht (Wabo, 2010) en de Waterwet (2009) tientallen wetten en regelgevingen samengevoegd en geïntegreerd. Dit heeft onder andere geleid tot de omgevingsvergunning, milieuvergunning en watervergunning, die van belang zijn bij het starten van een viskweekbedrijf. Via online modules kan gecontroleerd worden welke vergunningen of onderdelen van de vergunningen nodig zijn (de vergunningcheck), en de aanvraag van de benodigde vergunningen verloopt ook via een van deze modules. De aanvraag wordt automatisch naar de bevoegde lokale of regionale overheid gestuurd, die deze afhandelt. Door al deze maatregelen zijn de procedures om de verschillende benodigde vergunningen aan te vragen sterk versimpeld. De inhoudelijke wet- en regelgeving is hiermee echter niet versimpeld, en door de sterke digitalisatie is het moeilijk om gespecialiseerde ambtenaren rechtstreeks te benaderen. Op het gebied van de dieren zijn de vergunningen en de regelgeving veelal nationaal en/of Europees georganiseerd, en fungeert in de meeste gevallen de nVWA als centraal orgaan waarbij de regelgevingen kunnen worden bestudeerd en vergunningen moeten worden aangevraagd. De duur en de kosten voor het verkrijgen van de vergunningen zijn sterk afhankelijk van de precieze vergunningen of onderdelen van vergunningen die nodig zijn, en van de gemeente waar de vergunningen worden aangevraagd. Het invullen van de vergunningcheck is hierbij de belangrijkste leidraad. Ondernemers moeten rekening houden met een procedure tijd van zes maanden.
De invloed van de concentratie vrij koolstofdioxide in het water op de prestaties van snoekbaars
Blom, E. ; Remmerswaal, Rene ; Janssen, Jac ; Schram, E. - \ 2015
IMARES (Rapport / IMARES C183/15) - 16 p.
snoekbaars - kooldioxide - concentratie - prestatieniveau - visteelt - viskwekerijen - aquacultuur - pike perch - carbon dioxide - concentration - performance - fish culture - fish farms - aquaculture
Het effect van een verhoogde ammoniak concentratie in het water op fysiologie, groei en voeropname van Europese paling (Anguilla anguilla)
Abbink, W. ; Blom, E. ; Pelgrim, Thamar ; Vries, P. de; Vis, J.W. van de; Schram, E. - \ 2015
Yerseke : IMARES (Rapport / IMARES C187/15) - 18 p.
european eels - ammoniak - dierfysiologie - groei - voeropname - visteelt - aquacultuur - dierenwelzijn - dierlijke productie - kweekvis - palingen - huisvesting, dieren - diergezondheid - ammonia - animal physiology - growth - feed intake - fish culture - aquaculture - animal welfare - animal production - farmed fish - eels - animal housing - animal health
Uit Je Eigen Stad
Heijden, P.G.M. van der - \ 2015
Aquacultuur 2015 (2015)2. - ISSN 1382-2764 - p. 17 - 24.
groenten - vis - bedrijven - voedselproductie - stadslandbouw - aquacultuur - visteelt - viskwekerijen - groenteteelt - aquaponics - innovaties - vegetables - fish - businesses - food production - urban agriculture - aquaculture - fish culture - fish farms - vegetable growing - innovations
In 2010 vatte drie ondernemers het plan op om bij de Rotterdamse Fruithaven een loods en het erom heen gelegen rangeerterrein een landbouwkundige bestemming te geven. Het duurde tot 2012 voordat voldoende kapitaal en vergunningen waren geregeld en met de aanleg van Uit Je Eigen Stad begonnen kon worden. Inmiddels is er veel bereikt (waaronder een werkend aquaponics systeem met een inhoud van 125 m3) en worden groente, tilapia, Afrikaanse meerval, paddenstoelen en kippen in het eigen restaurant en in Rotterdam en omgeving verkocht. Maar de medewerkers van Uit Je Eigen Stad rusten niet en gaan door met het testen en proberen van verschillende gewassen, productiewijzen, producten, markten en evenementen. We bezochten het bedrijf en spraken met Ivo Haenen.
Community based fish culture in the public and private floodplains of Bangladesh
Mahfuzul Haque, A.B. - \ 2015
University. Promotor(en): Leontine Visser, co-promotor(en): M.M. Dey. - Wageningen : Wageningen University - ISBN 9789462574533 - 166
stroomvlakten - visteelt - ontwikkelingsstudies - ontwikkelingseconomie - samenleving - huishoudens - bangladesh - zuid-azië - floodplains - fish culture - development studies - development economics - society - households - south asia

Seasonal floodplains are water bodies that retain water for 5-6 months during which they are suitable to grow fish and other aquatic animals. Out of 2.8 million ha of medium and deep-flooded areas, about 1.5 million ha are estimated to be suitable for Community-Based Fish Culture (CBFC). WorldFish had undertaken a five-year interdisciplinary action research project from 2005-2010 with the overall aim of enhancing the productivity of seasonally occurring floodwaters for the improved and sustained benefit of the livelihoods of the poor. My involvement in this project was as PhD Scholar from 2007-2009 for understanding the different and complex institutional arrangements and its overall impact of governing Community-Based Fish Culture in seasonal floodplains for the sustainable use and maximization of benefits to the targeted people of Bangladesh.

Six seasonal floodplains in different areas of Bangladesh were selected under the action research project implemented by the Department of Fisheries in collaboration with the Bangladesh Agricultural Research Council and the Bangladesh Fisheries Research Institute. For the action research which is the subject of this thesis, three seasonal floodplains were selected in the Brahamaputra, the Padma and the Teesta River Basins located at Mymensingh, Rajshahi and Rangpur districts, respectively. Another three floodplains were selected as control sites in the same river basins located near to the projects sites. The control sites were included in the economic study (Chapters 4 and 5) only. All the six floodplains belong to two types of ownership categories: public floodplains surrounded by private lands.

My thesis is broadly divided into a sociological and an economic part, mainly because of methodological differences. Chapter 2 and Chapter 3 discuss the institutional arrangements and the power and decision-making process of Community-Based Fish Culture management. Chapter 4 addresses the overall economic impact of technical and institutional arrangements of fish culture at both floodplain and household levels. We here employed a random effects model to estimate the impact of participation on fish income. Finally, in Chapter 5 the economic impact of community-based fish culture on expenditure inequality was measured at household level.

In the sociological part, three project floodplains covered the different institutional arrangements for managing the floodplains and maximizing their benefits to different classes of beneficiaries. Power relations between the various key actors or stakeholders were assessed who were directly or indirectly involved in the floodplain, and decision making processes in co-management practices were also studied at different institutional levels. Sociological research methods and techniques including semi-structured interviews, Focus Group Discussions, informal discussions with key informants, and
quantitative surveys were applied to gather data from Floodplain Management Committees, villagers and institutional stakeholders to investigate the use of the floodplain as a common property resource (CPR) and the processes of the formation of local institutions and organizations.

For the economic analysis of Chapter 4 and Chapter 5, three project floodplains and three control floodplains were selected for comparing the impact of the intervention at beneficiary level and also community level. Household survey data includes a baseline survey on socioeconomic information, three months monitoring on seasonal and monthly basis at community and household levels, as well as an assessment of the floodplains’ natural resource systems. The seasonal survey covered the changes in input use for crop production, changes in quality of output from the agricultural land and the effects of the intervention on crop production. A monthly survey on the 1st and 15th day of the month was conducted to capture the household consumption pattern, especially the frequency and quantity of fish and meat consumption.

Chapter 2 improves our understanding of the complex institutional relationships governing Community-Based Fish Culture in seasonal floodplains in Bangladesh. Formal institutional linkages between DoF, WorldFish Center and the Bangladesh Agricultural Research Council (BARC) played a key role in ensuring success. DoF is a government institution with establishments at different administrative levels. Institutional embedding of DoF through the Fishers Cooperatives (FMC) as implementing institutions appeared highly instrumental. Large numbers of people, including landless poor seasonal fishers, professional landowning fishers, and non-fishing landowners benefited from the successful implementation of the CBFC activities in the floodplains. The outcomes demonstrate a significant increase in income to all classes of beneficiaries through income sharing derived from their involvement in the fisheries cooperatives and fish culture.

In case 2 and case 3 the floodplains under private ownership privately owned land is inundated during the monsoon season; these floodplains are similar in size, with comparable percentages of beneficiaries and similar numbers of communities surrounding the floodplains. However, the distribution of beneficiaries among the classes differs with more landowners than landless seasonal fishers benefitting. FMCs normally allow these non-members to access the floodplains, but only to harvest un-stocked fish using local gears, considering the importance of fishing to their livelihood. This means that the CPR character of the management by the FMCs shows a certain permissiveness or permeable boundary regarding landless non-members under strict spatial and temporal conditions. Regulation and conservation thus guarantee the availability of un-stocked small fish in the floodplains with a high catch by artisanal gears which results in higher incomes and related benefits to the poorer households. Households who own land or ditches in the floodplains do not depend on un-stocked fish as they can have ponds to trap and harvest fish obtained in the wild. Additionally, during the dry season, they may use land in lowland areas for crop production.

Case 1 of the public floodplain surrounded by private lands differs most from the private floodplain cases. Here, the public area is leased out to fishers during the monsoon, including the private land owned by the affluent and politically influential stakeholders. The floodplain is larger than in the other two cases, but both the percentages of landless fishers and of landowners are lower, making the class of the landowning professional fishers the majority among the beneficiaries.

Generally, the rules and regulations that apply to public and privately owned floodplains are written down in a Memorandum of Understanding between DoF and the individual FMC’s in a non-judicial construction. In their regular meetings the FMCs also document the everyday practices of the rules related to fish culture and management in the minutes that are distributed among its members. It appears that in the three cases, comparable rules and regulations for fish culture are applied to the public and to the private floodplains in operational rules, collective choice rule and constitutional rule.

Benefit sharing of the fish production from the floodplains was agreed at the start of project activities by all stakeholders, but their commitment varied between the classes of beneficiaries and across the cases. A significant increase of income for different stakeholders was derived from their involvement in fish culture. In the public floodplain fishers received around 40% of net income increase and the landowners received almost 38% of net income increase, as they had to pay the lease money for the floodplain. But in private floodplain all classes of stakeholders deposited around 25% of their net income in a revolving fund. The fishers group got their income from the final harvesting of fish as they received 50% of the price of the harvest of un-stocked fish and 10-15% of the stocked fish. The landowners received 45-50% of income according to their land. The landless seasonal fishers had open access to the non-stocked fish during the monsoon. Finally, the users of the public as well as the private floodplains contributed a small portion of their income to social work, like the building of a mosque or a Hindu temple.

Chapter 3 firstly assessed the power relations between the various key actors or stakeholders who were directly or indirectly involved in floodplain fisheries in the three sites. Secondly, their shifting power relations and decision making process in co-management practices were studied in the different institutional contexts of the three research sites during WorldFish project intervention. Instead of merely listing the institutions involved, we studied the actual power practices and decisions making processes between the stakeholders in the three cases to gain insight in the different governance models used in CBFC in Bangladesh. Existing co-management arrangements are characterized by unequal power distribution among the different actors, often resulting in the marginalization of the professional fishers and the landless poor fishers. I differentiated between two types of power in the management of floodplain aquaculture and stakeholder involvement, namely a) the power to create rules and decision making procedures, and b) the power to resolve disputes and ensure compliance. The Floodplain Management Committee (FMC) reviews the rules and regulations formulated by the government to complement the vision and roles of the institution, and if there is a need, modify them. Rules and regulations governing access to the public and privately owned floodplains were developed by the Department of Fisheries (DoF) and the FMC. A similar set of rules and regulations was applied to the public and the privately owned floodplains for fish culture. Most of the rules were derived from the national fisheries law. The rules and regulations that were applied to the floodplain were written down in a Memorandum of Understanding between DoF and FMC. Examples are rules and regulations about membership, leadership, boundary and access, allocation, penalties, input, and conflict resolution that were enforced for the management of community based-fish culture.

Magistrate courts at local level in Bangladesh have the power to decide on penalties for offenders in case of violation of the Government Fisheries Act of 2010 (DoF 2013) in the management of fisheries and aquaculture including the floodplain; a range of penalties is stipulated in the Offences and Penalties paragraph of the Act. In addition, in the case of both public and private floodplains, leaders of customary organizations have the authority and power to confiscate illegal nets and penalize offenders by charging monetary fines.

Governance in the context of Community-Based Fish Culture (CBFC) management addresses the dominancy of the land-owning group, informal sets of norms and traditions, and the social network and power relationships between stakeholders. In the public floodplain governance processes resulting in the formation of a responsive, accountable leadership and representative membership appeared vital for the success of CBFC. But, the establishment of successful CBFCs in public floodplains demands continuous institutional support from agencies such as the Department of Fisheries, because an increase in production and income also increases the risk of elite capture, and the possibility of an exploitative. In the private floodplain, there was no specific governance system in place to manage access and use of the floodplains during the wet season, as opposed to the dry months when the lands of the floodplain could be used by individual households for crop production. Thanks to greater accountability of the leaders, and more equal representation of the different stakeholders including active leadership and a supporting role of DOF, leadership problems were few and easily solved. Downward accountability was well established in addition to many efforts by the project.

Chapter 4 examined the overall impact on households involved through the WorldFish project in community-based fish culture in seasonal floodplains, particularly with respect to fish production, consumption, and income generation. Qualitative as well as quantitative methods were deployed to examine the impact of Community-Based Fish Culture starting with a conceptual framework as to how positive impacts take effect. The overall fish production in the floodplains of the project appeared to have increased 274%. Due to project intervention introducing fish culture, 43% of the farmers used floodplain water to meet up irrigation needs instead of ground water and rice production increased by 18.9% for dry-season (Boro) rice and 28.9% for wet-season (Aman) rice in the project floodplain areas.

Increased income is an important economic incentive for the expansion of community-based fish culture in Bangladesh. Over that period, average income from fish production increased to USD 240 for all beneficiaries involved in the project, which is 237% higher than the income of beneficiaries in the control group. Results of the random effects model show that project-involved households significantly increased their fish income compared to the households of the control sites. Furthermore, total household income increased to about USD 175 per household for those who participated in the WorldFish project.

Fish availability increased in the project area from July to December. During these months approximately 68%-75% of the total fish consumption needs of the project beneficiaries could be fulfilled by the newly introduced fish culture in the floodplains. The consumption of nutritional food shows that per capita fish consumption of households in the project sites increased from 1.26 kg per capita per month in the baseline year to 2.31 kg per capita per month in 2009.

Apart from the direct effect on household income and food consumption, CBFC intervention also created the opportunity for employment, backward linkage, and access to market to sell harvested fish. Indirect benefits of the community based fish culture include reduced conflict; improved social capital and greater cooperation in the community.

Expenditure is a better measurement of welfare than income where most of the people are poor and struggle for food. In this study I therefore used data on expenditure instead of income. The results in Chapter 5 show that the CBFC project had a positive and significant impact on food expenditure, as well as on non-food (other basic needs) and overall total expenditure. The impact of CBFC on household expenditure and expenditure inequality was measured by using Propensity Score Matching (PSM) method and Gini decomposition. Results revealed that the overall average food expenditure per year per household (for panel estimation) increased due to participation in the CBFC project from USD 93 to USD 141. Project participants were able to spend significantly more on food compared to non-participants. In addition, expenditure on food was increasing year by year. Moreover, participant households were capable to spend more compared to non-participants on non-food items like cloth, health, education, housing, transport etc. (from USD 45 to USD 74 per year). This non-food expenditure also gradually increased per year. Finally, total household expenditure of CBFC project participants was between USD 134 and USD 215 per year higher than the total expenditure of control households, which implies a better livelihood of the households involved in the project.

Gini index of total expenditure was found to be 0.34 and 0.40 for the CBFC project and control households respectively, which indicate that expenditure was equally distributed among households, but that it is more equally distributed among the CBFC households as compared to the control households. The expenditure inequality difference between the CBFC project and the control sites was 0.06, which implies that the CBFC management system helped to distribute total expenditure more equally among the surrounding communities.

Policy advice

For better management of the floodplain beels, the government may apply a similar policy for better utilization of the resources and for the economic benefits of the beneficiaries. Accountability, sustainable management of the floodplains, proper marketing of fish and equity in the distribution of benefits of the floodplains have proven to increase the productivity and ensure the accessibility of the poor and landless farmers, as long as elite capture is controlled.

Taking all CBFC project lessons into consideration, the Bangladesh government could indeed make some changes to their floodplain /wetland policy in order to accommodate the poor fishers and the landless poor. Policy (re)formulation may be needed for the dissemination of the CBO-based fish culture approach to scale-up its impact. In order to establish the rights of the CBOs (under the leadership of fishers) there is a need for modification of the policy of leasing of public floodplains. The major issues to be included are to bring private and public floodplains under CBO management; to secure government support for the registration of the CBOs and the strengthening of the institution; to guarantee that CBOs obtain long term (10-15 years or more) lease of the public areas of the floodplains as priority; to support small infrastructure constructions in the outlet and inlets of the floodplains; and to develop a functional model for the scaling-up (influencing policy) and scaling-out of the CBO fish culture approach in Bangladesh.

Future research

To assess the effectiveness of the scaling-up of the innovation in Community-Based Fish Culture in public and private floodplains, using a CBO to CBO approach will have to be developed with the support and facilitation from formal institutions. This will be considered as the subject of future research.

Steroids accumulation in recirculating aquaculture systems
Mota, V.C. - \ 2015
University. Promotor(en): Johan Verreth, co-promotor(en): A.V.M. Cana´rio; C.I.M. Martins. - Wageningen : Wageningen University - ISBN 9789462575554 - 145 p.
steroïden - recirculatie aquacultuur systemen - prestatieniveau - bezettingsdichtheid - stress - ph - hydrocortison - testosteron - chemische communicatie - visteelt - viskwekerijen - steroids - recirculating aquaculture systems - performance - stocking density - hydrocortisone - testosterone - chemical communication - fish culture - fish farms
Minerals in fish: does the source matter?
Antony Jesu Prabhu, P. - \ 2015
University. Promotor(en): Johan Verreth, co-promotor(en): C. Mariojouls; S. Kaushik; Johan Schrama. - Wageningen : Wageningen University - ISBN 9789462574809 - 267
visvoeding - mineralen - voedingsstoffenbehoeften - mineraalmetabolisme - voer - minerale supplementen - groei - lichaamssamenstelling - visteelt - aquacultuur - fish feeding - minerals - nutrient requirements - mineral metabolism - feeds - mineral supplements - growth - body composition - fish culture - aquaculture
Investigation of a growth model incorporating density dependence for the mackerel management plan simulations
Brunel, T.P.A. - \ 2015
IJmuiden : IMARES (Report / IMARES Wageningen UR C134/15) - 12
trachurus - density dependence - growth - models - simulation models - fish culture - dichtheidsafhankelijkheid - groei - modellen - simulatiemodellen - visteelt
This report presents a framework to model density dependent growth for the North East Atlantic mackerel. The model used is the classical von Bertalanffy equation, but modified so that growth is reduced when stock size increases. The model developed was able to reproduce quite closely the trends in the observed historical weight-at-age data. This framework can therefore be incorporated in the simulation tool used for the mackerel management plan evaluation. But since the actual mechanisms through which stock size affects growth are not identified, density dependent growth should not be used as the base case scenario in simulations. However it can be used in sensitivity tests which can be conducted to assess the potential impact of density dependent growth on simulation output, such as Fmsy.
Bedwelmen aan boord
Sikkema, A. ; Vis, J.W. van de; Gerritzen, M.A. - \ 2015
Resource: nieuwssite voor studenten en medewerkers van Wageningen UR 9 (2015)15. - ISSN 1389-7756 - p. 12 - 13.
vissen - bedwelmen - slacht - dierenwelzijn - visserij - kweekvis - visteelt - wild gevangen vis - fishes - stunning - slaughter - animal welfare - fisheries - farmed fish - fish culture - wild caught fish
Wakker Dier voert de laatste weken actie tegen het onverdoofd slachten van vissen. Net als de kippen en varkens moeten de vissen worden verdoofd voor de slacht, vindt de actiegroep. Kan dat? De meeste kweekvis in Nederland wordt al verdoofd aan de slachtlijn, stellen Wageningse onderzoekers, maar de wilde vis uit de Noordzee nog niet. Om ook de schol en haring aan boord van het vissersschip verdoofd te kunnen slachten, is eerst meer onderzoek in het lab en op zee nodig.
Cooperative and uniform fish? : social interactions and variability in live body weight in the GIFT strain (Nile tilapia, Oreochromic niloticus) in Malaysia
Khaw, H.L. - \ 2015
University. Promotor(en): Johan van Arendonk, co-promotor(en): Piter Bijma; R.W. Ponzoni. - Wageningen : Wageningen University - ISBN 9789462572157 - 161
oreochromis niloticus - sociaal gedrag - lichaamsgewicht - variatie - genetische effecten - inteelt - kenmerken - heritability - genotype-milieu interactie - genotypische variatie - genetische verbetering - veredelingsprogramma's - visteelt - maleisië - social behaviour - body weight - variation - genetic effects - inbreeding - traits - genotype environment interaction - genetic variance - genetic improvement - breeding programmes - fish culture - malaysia


Khaw, HL. (2014). Cooperative and uniform fish? Social interactions and variability in live body weight in the GIFT strain (Nile tilapia, Oreochromic niloticus) in Malaysia. PhD thesis, Wageningen University, the Netherlands.

Social interactions are present everywhere in the living world. Such social interactions may lead to indirect genetic effects (IGE), which are heritable effects of an individual on trait values of the other individuals its interacts with. IGEs may affect the direction and magnitude of response to selection in breeding programs. Moreover, social interactions may affect variability of traits. In aquaculture, competition for resources inflates size variation within populations. In this thesis, we used the Genetically Improved Farmed Tilapia (GIFT; Oreochromis niloticus) strain to investigate the genetic basis for social interactions and variability in harvest weight for tropical finfish. Social interaction experiments were established for quantifying the genetic and non-genetic indirect effects on harvest weight in the GIFT strain. We found evidence for IGEs on harvest weight, and a negative direct-indirect genetic correlation, which suggesting heritable competitive interactions for harvest weight in GIFT. Hence, breeding schemes may need to be adapted to avoid an increase in competition. A stochastic simulation study was conducted to examine the effect of BLUP selection on the rate of inbreeding for socially affected traits. The rates of inbreeding for scenarios with IGEs were greater than for scenarios without IGE. Therefore, with IGEs there is a greater need for a selection algorithm that restricts the increase of mean kinship. In aquaculture industry, there is a wide range of commercial production environments, which may leads to genotype by environment (GxE) interaction, for example due to differential social interactions. The GIFT fish were tested in ponds and cages to study the GxE interaction. The genetic correlations between environments (0.73 to 0.85, for harvest weight and body measurements) indicate little GxE-interaction. The data collected from the social interaction experiments were also used to investigate the presence of genetic variation in uniformity for harvest weight. The genetic coefficient of variation for standard deviation of harvest weight (0.17) shows that uniformity of harvest weight is heritable and can be increased by selective breeding. In the General Discussion of this thesis, the uniformity study was extended to incorporate IGE. The result indicates that more cooperative fish are not necessary more uniform for harvest weight. Overall, our results suggest that genetic improvement in fish breeding programs can be increased by accounting for social interactions.

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