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.

AQUAFARM van zuiveren naar oogsten
Verdonschot, P.F.M. - \ 2017
Aquafarm NL
afvalwater - waterzuivering - industriële grondstoffen - biobased economy - afvalwaterbehandeling - aquacultuur - biomassa productie - waste water - water treatment - feedstocks - waste water treatment - aquaculture - biomass production
Aquafarm ziet afvalwater als basis voor het produceren van hoogwaardige bouwstoffen, waarmee tegelijkertijd het water gezuiverd wordt.
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.

Mission report Kenya : scoping Mission Marine Fisheries Kenya
Hoof, Luc van; Steins, Nathalie A. - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C038/17) - 136
marine fisheries - food security - aquaculture - seaweeds - trade - kenya - zeevisserij - voedselzekerheid - aquacultuur - zeewieren - handel
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.

Passende beoordeling ten behoeve van experimentele oesterkweek op Windgat percelen in de Kom van de Oosterschelde
Kamermans, Pauline - \ 2017
Yerseke : Wageningen Marine Research (Wageningen Marine Research rapport C031/17) - 30
oesters - oesterteelt - aquacultuur - oosterschelde - oysters - oyster culture - aquaculture - eastern scheldt
Production efficiency of mussel bottom culture
Capelle, Jacob J. - \ 2017
University. Promotor(en): Aad Smaal; P.M.J. Herman, co-promotor(en): Jeroen Wijsman. - Wageningen : Wageningen University - ISBN 9789463430869 - 240
mussels - mussel culture - bottom culture - efficiency - population dynamics - culture techniques - biomass production - improvement - shellfish culture - aquaculture - mossels - mosselteelt - bodemcultuur - efficiëntie - populatiedynamica - kweektechnieken - biomassa productie - verbetering - schaal- en schelpdierenteelt - aquacultuur

Mussel bottom culture is an extensive type of aquaculture; it depends on natural resources for feed, seed and space. It consists of the translocation of seed from natural beds to designed culture areas, where mussel farmers try to improve production efficiency. Production efficiency is measured by the relative biomass production (RBP) expressed as units of biomass harvested from one unit of biomass seeded, it increases with mussel growth and decreases with mussel mortality. Mussel bottom culture makes use of nature and also depends on nature. Cultured mussels are subject to similar environmental factors that influence growth and mortality on natural mussel beds, with additional effects of anthropogenic factors. In this thesis we focus on dynamics of mussel beds and the impact and effectivity of culture activities on mussel production yield. The major objectives are stated as: (1) to better understand the population dynamics of subtidal mussel populations, (2) to analyze what factors determine production efficiency in mussel bottom culture and how this can be improved. On natural mussel beds mussels organise in patterns that enhance food delivery and resilience of the bed. On culture plots mussels are seeded in concentric seeding patterns. Seeding techniques concentrate mussels locally within the culture plot area, resulting in high local mussel densities; this increases competition and limits the spatial re-organisation of mussels in the bed. Consequently, seeding on culture plots is followed by a large size and density dependent seeding loss that ranges from about 40% for seed from fishery to 69% for smaller SMC seed. This loss was the major factor in determining the maximum RBP. Losses in the grow-out stage were substantially lower, a subsequent density dependent loss was found for smaller mussels (<30 mm), and a non-density dependent loss for larger mussels (>30 mm). Shore crab predation is an important factor contributing to the higher losses at seeding. The effect of shore crab predation on mussel biomass production is higher than expected from previous studies. In an experiment on an intertidal culture plot in the Oosterschelde (NL), we observed that shore crab predation peaks directly after seeding and accounted for 33% of the total losses within five weeks after seeding. Spatial patterns in the survival rates of natural mussel beds in the Wadden Sea show better seed survival in areas with intermediate salinity (mean annual salinity 17.5-22.5 mg l-1). This suggests that mussel survival is negatively related to sea star distribution, which is largely controlled by salinity. Natural beds that escape predation are found at lower salinities and mussels on these beds showed low growth rates, also because of a lower food quality in these areas. Mussel culture strongly affects the population dynamics of the subtidal mussel population, through relaying of mussels from natural mussel beds to culture plots. Culture plots are located in more saline regions of the Wadden Sea (mean annual salinity 25.8 mg l-1), compared to natural mussel beds. This activity increased mussel growth and survival because food quality on culture plots is high and predation is prevented. As a result, average biomass production is higher on culture plots than on natural mussel beds and this difference increases over time. A more efficient seed use on the available area, that can be obtained by reducing seeding losses will increase RBP, maximum biomass production and increases maximum profit. Our results suggest that this can be achieved by seeding homogeneously in low densities.

Aquaculture Innovation in Vietnam
Rurangwa, E. ; Baumgartner, U. ; Nguyen, H.M. ; Vis, J.W. van de - \ 2016
Yerseke : Wageningen Marine Research (Wageningen Marine Research report C097/16) - 28
aquaculture - innovations - tilapia - fishes - shrimps - crabs - vietnam - aquacultuur - innovaties - vissen - garnalen - krabben (schaaldieren)
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.

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.

Blauwe groei: duurzame bedrijvigheid opde Noordzee : perspectieven uit een scenarioanalyse
Burg, S.W.K. van den; Bolman, B.C. ; Borgstein, M.H. ; Valk, O.M.C. van der; Vos, B.I. de; Selnes, T. - \ 2016
Wageningen : LEI Wageningen UR (Nota / LEI Wageningen UR 2016-017) - 25 p.
energievoorraden - duurzame energie - aquacultuur - noordzee - toerisme - natuurbescherming - milieubeleid - beleid - regelingen - energy resources - sustainable energy - aquaculture - north sea - tourism - nature conservation - environmental policy - policy - regulations
Door een groeiend belang van nieuwe maritieme sectoren neemt de bestuurlijke drukte op zee toe. In dit project is een kwalitatieve scenarioanalyse uitgevoerd om te beschrijven hoe de gebeurtenissen zich in de toekomst kunnen ontvouwen, om risico’s te identificeren en om zo beslissers in staat te stellen over verschillende ontwikkelrichtingen te oordelen. De ontwikkelingen in de sectoren energie, aquacultuur en toerisme zijn ook van invloed op de (on)mogelijkheden voor natuurbeleid op zee. De mariene natuur zal zich moeten schikken naar deze ontwikkelingen. De trend van wet- en regelgeving voor individuele sectoren naar een meer geïntegreerde aanpak van alle sectoren, inclusief natuurbescherming, zet zich door.
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

ABSTRACT

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.

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
Paling op straat
Palstra, A.P. - \ 2015
Visionair : het vakblad van sportvisserij Nederland 10 (2015)38. - ISSN 1569-7533 - p. 34 - 36.
palingen - visconsumptie - japan - palingteelt - aquacultuur - eels - fish consumption - eel culture - aquaculture
Japanners eten graag paling. Het land kent zelfs speciale palingrestaurants. Het is daarom niet vreemd dat in Japan op grote schaal glasaal wordt opgekweekt.
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.
Visvernieuwers: interesse van Europese consumenten voor innovatie in het (kweek)visschap
Tacken, G.M.L. ; Dagevos, H. ; Reinders, M.J. - \ 2015
Aquacultuur 30 (2015)2. - ISSN 1382-2764 - p. 8 - 11.
visconsumptie - visproducten - voeding en gezondheid - gezondheidsvoedsel - dieetrichtlijnen - houding van consumenten - innovaties - kweekvis - consumentengedrag - aquacultuur - fish consumption - fish products - nutrition and health - health foods - dietary guidelines - consumer attitudes - innovations - farmed fish - consumer behaviour - aquaculture
Vis is gezond en veel consumenten beoordelen vis ook als zodanig. Toch is gezond als een kwaliteitsaspect van vis vaak geen doorslaggevende reden om voor vis te kiezen. Het voedingsadvies om vaker vis te eten krijgt onder veel Europese consumenten onvoldoende navolging. Het product vis heeft met gezond weliswaar een sterke troef in handen die gekoesterd moet worden, deze kwaliteit alleen schiet tekort om consumenten (meer) vis te laten eten. Productvernieuwing is een mogelijk hulpmiddel hierbij. Ter aanvulling op gezond, als 'klassieke' kernkwaliteit van vis, wordt binnen het Europese onderzoeksproject 'Diversity' gezocht naar innovatieve ideeën met aantrekkingskracht op hedendaagse consumenten, waarbij meer specifiek oog is voor vijf nieuwe kweekvissoorten.
Wettelijke Onderzoek Taken WOT-05 Visserijonderzoek; Werkafspraken en werkplan 2016
Verver, S.W. - \ 2015
IJmuiden : Centrum voor Visserijonderzoek (CVO rapport / Stichting DLO, Centrum voor Visserijonderzoek (CVO) 15.010) - 101
visserij - onderzoek - onderzoeksprojecten - aquacultuur - fisheries - research - research projects - aquaculture
Dit rapport beschrijft het werkplan voor 2016 voor het Wettelijke taken programma Visserij onderzoek van Wageningen UR. Wageningen UR voert voor het Ministerie van Economische Zaken (EZ) een aantal programma’s met Wettelijke Onderzoek Taken (WOT) uit. Binnen programma WOT-05 worden Wettelijke Onderzoek Taken uitgevoerd die betrekking hebben op het beheer van de visserij op zee, in Nederlandse kust- en binnenwateren en de aquacultuur. Het werkplan is een uitwerking van de Uitvoeringsovereenkomst en werkafspraken tussen het Ministerie van EZ en de Stichting Dienst Landbouwkundig Onderzoek (DLO), onderdeel van Wageningen UR, voor diensten vanwege wettelijke taken op het terrein van visserijonderzoek voor de periode 2011-2015.
Culturing soles on ragworms: growth and feeding behaviour
Ende, S.S.W. - \ 2015
University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama. - Wageningen : Wageningen University - ISBN 9789462575622 - 128
solea - soleidae - kweekvis - voeropname - groei - prooi - wormen - foerageren - voedingsgedrag - prestatieniveau - vijverteelt - aquacultuur - farmed fish - feed intake - growth - prey - helminths - foraging - feeding behaviour - performance - pond culture - aquaculture

Ende, S.S.W. (2015). Culturing soles on ragworms: Growth and feeding behaviour. PhD thesis, Wageningen University, The Netherlands.

Despite the high market demand and intensive research efforts since the 1960s commercial culture of common sole (Solea solea L.) has been unsuccessful. Problems related to availability and price of suitable raw materials (invertebrates) and the low tolerance to crowding have hampered the development of intensive sole culture. Alternative extensive pond cultures systems are currently explored where common sole can graze on natural food. The general aim of this study was to get insight into which factors limit growth of common sole foraging on ragworms in ponds. The results did not show any nutritional effects that may hamper the growth of common sole. At non-limiting conditions, i.e. when fed chopped ragworms and when housed in sediment free tanks, common sole showed higher food intake, higher growth rates and higher nutrient utilization efficiencies than when fed mussels or a formulated diet. The results however suggest that growth in a pond with ragworms was limited by reduced foraging capabilities of common sole. To explore this hypothesis, the effect of prey size, predator size and prey density were tested. Overall, intake of buried ragworms was reduced by more than half in contrast to intake of unburied ragworms. Intake of buried ragworms was reduced regardless of ragworm size or common sole size. Increasing ragworm density only resulted in satiation intake values in smaller common sole. Our results additionally indicate that the presence of common sole hampers ragworm performance in a pond. Ragworms reduced their feeding activities when receiving water from tanks which contained common sole and ragworms, i.e. when common sole could graze on ragworms. Results from this PhD study suggest that the growth of common sole in ponds is not limited by nutritional but by their foraging abilities. However, the results of this study are too incomplete to fully predict growth performance of common sole in a pond. Factors such as temperature, oxygen supply or feeding activity need to be investigated to make comprehensive growth predictions.

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