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.

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Effect of vitamin B12 and taurine on the alleviation of nutritional anaemia in common sole (Solea solea)
Kals, Jeroen ; Blonk, Robbert J.W. ; Mheen, Henk W. van der; Schrama, Johan W. ; Verreth, Johan A.J. - \ 2019
Aquaculture Nutrition 25 (2019)2. - ISSN 1353-5773 - p. 456 - 465.
anaemia - haematocrit - haemoglobin - sole (Solea solea) - taurine - vitamin B12
Sole fed commercial pellets develop a nutritional anaemia. This study assessed the impact of dietary B12 and taurine on the haematocrit (Hct) and haemoglobin (Hb) level and mineral absorption in anaemic sole. Anaemic sole was fed one of four diets. Diets were equal regarding mineral, amino acid and macronutrient composition and formulated, according to a two by two factorial design: two B12 (0.34 vs. 1.9 mg kg dm) and two taurine levels (3.5 vs. 7.6 mg kg dm−1). The feeding level was restricted and equal for all diets. Hct and Hb levels in anaemic sole are influenced by dietary B12. A “high” level of B12 increases the Hct and Hb level. An increasing level of taurine suppresses the stimulating effect of the “high” level of B12. The applied B12 and taurine levels were unable to completely alleviate the anaemia in sole. Nevertheless, sole needs high dietary levels of B12 to alleviate anaemia. The impact of B12 and taurine on Hb and Hct was not related to a change in the absorption of iron. A “high” level of B12 positively affected the absorption of chromium and a high level of taurine negatively affected the absorption of cobalt in sole.
Monitoring klimaateffect van NL agroproductie : verkenning van behoeften en ideeën om het klimaateffect geïntegreerd te meten
Blonk, Hans ; Reijs, Joan ; Vellinga, Theun - \ 2018
Gouda : Wageningen Economic Research - 19
The development of a sole diet based on the composition of ragworm
Kals, Jeroen - \ 2017
Wageningen University. Promotor(en): J.A.J. Verreth, co-promotor(en): J.W. Schrama; R.J.W. Blonk. - Wageningen : Wageningen University - ISBN 9789463431804 - 136
dover soles - annelida - fish feeding - anaemia - haemoglobin - fish culture - aquaculture - tong (vis) - annelida - 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.

Decreasing the overall environmental impact of the Dutch diet : how to find healthy and sustainable diets with limited changes
Kramer, Gerard F.H. ; Tyszler, Marcelo ; Veer, Pieter van 't; Blonk, Hans - \ 2017
Public Health Nutrition 20 (2017)9. - ISSN 1368-9800 - p. 1699 - 1709.
Fossil energy use - Greenhouse gas emissions - Land occupation - Linear programming - Minimal changes - Sustainable diets

Objective: To find diets optimised on nutrition and environmental impact close to the current Dutch diet and to identify the most effective and acceptable options for mitigating environmental impact. Design: Linear programming was used to optimise diets of Dutch men and women aged 9–69 years, divided into ten age–gender groups. The analysis included nutrient composition, a metric for popularity and life cycle assessments of 207 food products. Greenhouse gas emissions, fossil energy use and land occupation were used to calculate a weighted score for the overall environmental impact. Optimised diets were solutions that minimised changes to the current diet while satisfying all nutritional constraints, with stepwise reductions in environmental impact. Setting: The Netherlands. Subjects: Dutch children and adults aged 9–69 years. Results: Meat was always reduced. Vegetable, fruit and dairy contents remained similar, while bread, fatty fish and legumes increased. The extent of changes depended on age and gender. Beverages were not heavily reduced. Nutrients critical for the outcome were α-linoleic acid, retinol, Ca, Na, Se, dietary fibre, SFA, thiamin and Fe (women of childbearing age). Total protein, essential amino acids and carbohydrates were not critical. Conclusions: Reducing meat is the most effective option for lowering the environmental impact of diets in all age–gender groups. Reducing alcoholic and non-alcoholic beverages is another option. Leaving out fish and dairy products are not. The differences in nutritional requirements related to age and gender have a significant effect on the composition of the optimised diets.

Feeding ragworm (Nereis virens Sars) to common sole (Solea solea L.) alleviates nutritional anaemia and stimulates growth
Kals, J. ; Blonk, R.J.W. ; Palstra, A.P. ; Sobotta, Tim ; Mongile, Fulvio ; Schneider, O. ; Planas, J.V. ; Schrama, J.W. ; Verreth, J.A.J. - \ 2017
Aquaculture Research 48 (2017)3. - ISSN 1355-557X - p. 752 - 759.
solea-solea l - nereis virens Sars - growth - anaemia - hepcidin - gene expression
Common sole fed with commercial pellets develop anaemia and are restricted in their growth performance. The anaemia can be the result of a difference in feed intake, a nutritional deficiency, an inflammatory response to infection or combinations of these aspects. In this study, it was investigated whether feeding ragworm would alleviate the anaemia and stimulate growth. Sole were fed one of three diets: a commercial feed, a commercial feed treated with ragworm extract or chopped ragworm. By comparing groups, three hypotheses were tested: (1) feeding ragworm alleviates the anaemia and positively affectS the sole’s metabolic performance reflected in feed intake, feed efficiency and growth; (2) anaemia is alleviated by a higher feed intake when feeding ragworm and (3)
anaemia is caused by an inflammatory response to infection. The sole fed with a commercial diet suffered from anaemia. Feeding sole with ragworm alleviated the anaemia as the average haematocrit level nearly doubled in these fish as
compared to fish fed pellets. Investigation of the expression of genes in the liver indicated that the anaemia in sole fed pellets is a nutritional anaemia and not an anaemia due to an inflammatory response. Sole fed ragworm showed improved
growth which may be a consequence of the higher haematocrit levels in these fish increasing their oxygen carrying capacity. Addition of ragworm extract to the pellets levelled the feed intake between pellets and ragworm, but did not
improve the anaemic state of sole and had only a limited effect on growth
Mussel (Mytilus edulis L.) and ragworm (Nereis virens, Sars) both alleviate anaemia in common sole (Solea solea L.) : short communication
Kals, Jeroen ; Blonk, Robbert J.W. ; Mheen, Henk W. van der; Schrama, Johan W. ; Verreth, Johan A.J. - \ 2017
Aquaculture Research 48 (2017)3. - ISSN 1355-557X - p. 1338 - 1341.
Anaemia - Heme - Mussel - Ragworm - Sole - vitamin B12
Effect of iron source on the alleviation of nutritional anaemia in common sole (Solea solea)
Kals, J. ; Blonk, R.J.W. ; Mheen, Henk van der; Schrama, J.W. ; Verreth, Johan - \ 2016
In: Book of Abstracts of the 67th Annual Meeting of the European Federation of Animal Science. - Wageningen : Wageningen Academic Publishers (Book of abstracts 22) - ISBN 9789086862849 - p. 256 - 256.
Effect of different iron sources on the alleviation of nutritional anaemia in common sole (Solea solea)
Kals, J. ; Blonk, R.J.W. ; Mheen, H.W. van der; Schrama, J.W. ; Verreth, J.A.J. - \ 2016
Aquaculture 451 (2016). - ISSN 0044-8486 - p. 266 - 270.
Sole fed commercial pellets suffers from a nutritional anaemia. The hypotheses tested are: (1) the nutritional anaemia in sole fed commercial pellets is caused by an iron deficiency; (2) the assumed iron deficiency is due to inadequate absorption of iron; (3) an increase in absorption due to a higher bioavailability of heme or iron chelates will alleviate anaemia in sole and (4) haematocrit (Hct) and haemoglobin (Hb) are expected to follow the iron absorption patterns. In addition, we estimated the absorption of copper, cobalt, chromium, manganese, molybdenum and zinc in order to evaluate possible interaction between available iron sources and the absorption of other divalent minerals. Sole were fed four diets, each with a different iron source: iron sulphate, iron methionate, iron proteinate or heme. Feeding was restricted and equal for all diets. At the start of the experiment, sole reared on commercial pellets had average values of Hct, Hb and the hepatosomatic index of 12.5%, 19.6 g.l- 1 and 1.13%, respectively. The values at the end of the experiment did not differ from the values at the start and were not affected by the source of iron. The apparent absorption coefficients (AAC) of iron, manganese, zinc, cobalt, chromium and molybdenum, except for copper, were unaffected by the iron sources. Yet, the iron absorption was high for all sources tested. The AAC of copper was 15–22% higher in sole fed the diet with heme. The use of the different iron sources, including heme, did not affect Hct and Hb in anaemic sole. The high absorption of iron and copper in sole fed heme did not affect Hct and Hb, which suggests that the nutritional anaemia in sole is not an iron nor a copper deficiency anaemia.
Feeding ragworm (Nereis virens Sars) increases haematocrit and haemoglobin levels in common sole (Solea solea L.) : Short Communication
Kals, J. ; Blonk, R.J.W. ; Mheen, H.W. van der; Schrama, J.W. ; Verreth, J.A.J. - \ 2016
Aquaculture Research 47 (2016)10. - ISSN 1355-557X - p. 3346 - 3349.
no abstract
Duurzaamheid, communicatie en veiligheid : verslag van de landelijke bijeenkomst 'Kenniskringen Visserij en duurzaamheid'
Zaalmink, W. ; Smith, S.R. ; Steenbergen, J. ; Trapman, B.K. ; Valk, O.M.C. van der - \ 2015
LEI Wageningen UR (Rapport / LEI Wageningen UR 2015-160) - 25 p.
visserij - duurzaamheid (sustainability) - biobrandstoffen - communicatie - familiebedrijven, landbouw - veiligheid - coöperaties - nederland - fisheries - sustainability - biofuels - communication - family farms - safety - cooperatives - netherlands
Op 6 juni 2015 vond op Fort IJmuiden een landelijke bijeenkomst plaats van het project Kenniskringen Visserij. Het doel van deze dag was te komen tot een uitwisseling van kennisvragen over verschillende visserij gerelateerde thema’s. Het programma bestond uit een plenaire bijeenkomst en uit een aantal zogenoemde cafébijeenkomsten. Bij elke cafébijeenkomst was een relevante expert aanwezig, die de bijeenkomst inleidde. Hierna konden de aanwezigen vragen aan de expert en aan elkaar stellen. Dit verslag is een samenvatting van de uitspraken die door de deelnemers en experts op deze dag gedaan zijn rond de thema’s: 1. Duurzaamheid en de visser als onderzoeker (expert: Bas Haring, volksfilosoof) 2. Communicatie (expert: Marissa Tanis, GoMaris) 3. Fuel of the future (expert: Dirk Kronemeijer) 4. Veiligheid aan boord (expert: Cor Blonk) 5. Coöperaties (expert: Thomas Højrup)
Genetic improvement of percids
Blonk, R.J.W. ; Komen, J. - \ 2015
In: Biology and Culture of Percid Fishes / Kestemont, P., Dabrowski, K., Summerfelt, R.C., Springer Netherlands - ISBN 9789401772266 - p. 699 - 722.
Breeding programme - Genetics - Inbreeding - Percids - Selection

During the past years, breeding programs for aquaculture have shown fast development. Globally, economically highly relevant species have experienced implementation of large scale breeding programs and it is impossible to imagine life today without them as they significantly improve production and profitability of enterprises. However, there are still many aquatic species cultured that rely on wild broodstock and for which there is no breeding program. The reasons for not having breeding programs are diverse: The knowledge to execute a breeding program is often not available, and more importantly, breeding programs are considered expensive. Costs for separate family rearing systems, testing environments, extensive tagging etc. are often limiting. Farming of percids is a new sector where pioneering farmers have to develop rearing systems, reproduction methodology, fish feeds, etc., all at the same time. Especially in such cases, low-cost methods are required to get their business up and running. For this reason, many farms consider the foundation of a basic breeding program as their least concern, only to reduce costs. However, we argue that there are good reasons to start with selective breeding at the very start of an aquaculture enterprise. In the next chapters, the principles of selective breeding programs will be described. This includes a basic description of the concept of estimating the heritable components of the phenotypic appearance of fish. Next the most commonly used selection methods and their implication for percids will be discussed. The potential traits for selection that should be relevant in percid culture are reviewed. Some insights into the optimisation of breeding programs and an overview of basic breeding program management will be presented. We present an outline of how to maintain genetic diversity within cultured stocks, with a special focus on limiting rates of inbreeding while selecting. Finally, some insights on how to manage costs and benefits of breeding programs are discussed.

Fokkerij op ziekteresistentie van Japanse oesters
Kamermans, P. ; Engelsma, M.Y. ; Peene, F. ; Blonk, R.J.W. - \ 2015
Yerseke : IMARES (Rapport / IMARES Wageningen UR C025/15) - 28
ziekteresistentie - dierveredeling - oesters - nederland - oesterteelt - schaal- en schelpdierenteelt - disease resistance - animal breeding - oysters - netherlands - oyster culture - shellfish culture
Het oesterherpesvirus OsHV-1 µvar veroorzaakt hoge sterfte onder Japanse oesters in de Nederlandse kweekgebieden. De oestersector ondervindt problemen van deze sterfte. In deze studie is geïnventariseerd of een fokprogramma waarbij oesters geselecteerd worden op resistentie tegen het oesterherpesvirus en vervolgens worden voortgeplant in een hatchery uitkomst kan geven voor deze problematiek. Ook is bekeken of een fokprogramma gebruikt kan worden ter verbetering van groei en conditie van oesters.
Forced sustained swimming exercise at optimal speed enhances growth of juvenile yellowtail kingfish (Seriola lalandi)
Palstra, A.P. ; Mes, D. ; Kusters, K. ; Roques, J.A.C. ; Flik, G. ; Kloet, K. ; Blonk, R.J.W. - \ 2015
Frontiers in Physiology 5 (2015). - ISSN 1664-042X - 11 p.
trout oncorhynchus-mykiss - salmon salmo-salar - salvelinus-alpinus l - bass morone-saxatilis - rainbow-trout - atlantic salmon - seriola-lalandi - arctic charr - muscular development - disease resistance
Swimming exercise at optimal speed may optimize growth performance of yellowtail kingfish in a recirculating aquaculture system. Therefore, optimal swimming speeds (U-opt in m s(-1) or body lengths s(-1), BL s(-1)) were assessed and then applied to determine the effects of long-term forced and sustained swimming at U-opt on growth performance of juvenile yellowtail kingfish. Uopt was quantified in Blazka-type swim-tunnels for 145, 206, and 311 mm juveniles resulting in values of: (1) 0.70 m s(-1) or 4.83 BL s(-1), (2) 0.82 m s(-1) or 3.25 BL s(-1), and (3) 0.85 m s(-1) or 2.73 BL s(-1). Combined with literature data from larger fish, a relation of U-opt (BL s(-1)) = 234.07(BL)(-0.779) (R-2 = 0.9909) was established for this species. Yellowtail kingfish, either forced to perform sustained swimming exercise at an optimal speed of 2.46 BL s(-1) ("swimmers") or allowed to perform spontaneous activity at low water flow ("resters") in a newly designed 3600 L oval flume (with flow created by an impeller driven by an electric motor), were then compared. At the start of the experiment, ten fish were sampled representing the initial condition. After 18 days, swimmers (n = 23) showed a 92% greater increase in BL and 46% greater increase in BVV as compared to resters (n = 23). As both groups were fed equal rations, feed conversion ratio (FCR) for swimmers was 1.21 vs. 1.74 for resters. Doppler ultrasound imaging showed a statistically significant higher blood flow (31%) in the ventral aorta of swimmers vs. resters (44 +/- 3 vs. 34 +/- 3 mL min(-1), respectively, under anesthesia). Thus, growth performance can be rapidly improved by optimal swimming, without larger feed investments.
In- and outdoor reproduction of first generation common sole Solea solea under a natural photothermal regime: Temporal progression of sexual maturation assessed by monitoring plasma steroids and gonadotropin mRNA experssion
Palstra, A.P. ; Blok, M.C. ; Kals, J. ; Blom, E. ; Tuinhof-Koelma, N. ; Dirks, R.P. ; Forlenza, M. ; Blonk, R.J.W. - \ 2015
General and Comparative Endocrinology 221 (2015). - ISSN 0016-6480 - p. 183 - 192.
Reproduction of many temperate fishes is seasonal and maturation and spawning of gametes are under photothermal control. Reproductive success of first generation (G1) common sole Solea solea in captivity has been low. In this study, the sexual maturation status has been assessed during the prespawning months in G1 sole that were housed (a) outdoor under the natural photoperiod and temperature, or (b) indoor under artificial photothermal induction. Maturation was assessed in male and female G1 broodstock in November as controls, after which the remaining population was divided over two outdoor flow-through tanks placed in a pond and two indoor recirculating aquaculture system (RAS) tanks. Subsequently, maturation status (gonadosomatic index GSI and plasma levels of testosterone T and 17ß-estradiol E2) was assessed in one tank for each condition in January, February and during spawning in early April, while fish in the other tank were not disturbed in achieving reproductive success. Quantitative real-time PCR was performed to determine species-specific gonadotropin mRNA expression in females. Successful G1 spawning and egg fertilisation occurred in all experimental tanks. Gonadal development was similar under both conditions. Higher E2 and T levels were found in indoor housed females. Gonadotropin expression revealed similar profiles between outdoor and indoor housed females. G1 sole could be reproduced in the outdoor tanks under the natural photoperiod and in the indoor tanks under artificial simulation of this regime that includes a potentially crucial chilling period of 2–3 months at 5–7 °C.
Cost effectiveness of options to reduce greenhouse gas emissions in the Dutch dairy sector
Pol, A. van den; Blonk, H. ; Dolman, M.A. ; Evers, A.G. ; Haan, M.H.A. de; Reijs, J.W. ; Sebek, L.B. ; Vellinga, Th.V. ; Wemmenhove, H. - \ 2014
Dairy farming contributes significantly to emissions of greenhouse gases (GHG). Approximately two-thirds of the emissions in the Dutch dairy chain occur on farms. The other one-third occurs in the supply and processing sectors. There are many mitigation options. Some cost money, while others save money. Obviously, the latter are the most appealing. The aim of this study was to provide insight into the cost effectiveness of mitigation options in the Dutch dairy chain. At the farm level, a cost/benefit analysis has been conducted for CO2, N2O and CH4, based on available studies and the expertise of the project team. The results have been scaled up to the sector level. Cost-effective options are sometimes implemented autonomously, but often there are farm-specific barriers like ‘uncertainty on the impact’ or ‘lack of current focus’. According to expert judgement, the Dutch dairy chain emission of 16.5 Mton CO2 equivalents can be reduced by 1-2 Mton due to farm measures. If only the cost effective options are considered, approximately 40% of this emission reduction can be realised. About 90% of the options can be implemented at relatively limited costs. The potential reductions in the supply and processing sector are estimated to be, respectively, 1 and 2 Mton CO2 equivalents. By combining options on farm level and in the rest of the dairy chain, a clear reduction in GHG emissions can be attained. Successful implementation of mitigation options benefits from cooperation between all stakeholders: farmers, industry, government agencies, universities and research institutes.
Genetic Analysis of Shape in Trout, using image analysis
Komen, J. ; Blonk, R.J.W. ; Sae-Lim, P. - \ 2014
We used digital images of rainbow trout (lateral view) to fit an ellipse around the circumference of the fish. The values for L and H, obtained from the ellipse, were used to calculate ellipticity as (L-H)/(L+H), and the surface area of the fish as p*1/2 L*1/2H. Heritability of ellipticity and surface area at age 8 months was 0.23 and 0.21. Surface area had near-unity genetic correlation with body weight at same age. Genetic correlations of ellipticity with body weight and surface area were -0.55 and -0.56. Genetic correlation of ellipticity with harvest weight at 14 months was -0.49. Estimates of ellipticity are comparable with those of Nile tilapia and common sole. We conclude that when shape is important, ellipticity should be included in the breeding goal, with a weight that reflects the desired direction of change in shape
Replacement of soybean meal in compound feed by European protein sources : effects on carbon footprint
Boer, H.C. de; Krimpen, M.M. van; Blonk, H. ; Tyszler, M. - \ 2014
Lelystad : Wageningen UR Livestock Research (Livestock research report 819) - 46
eiwitbronnen - voedingswaarde - koolstof - emissie - voer - varkens - eiwitleverende planten - sojabonen - protein sources - nutritive value - carbon - emission - feeds - pigs - protein plants - soyabeans
The overall aim was to investigate if soybean products from South American can be replaced by protein sources produced in Europe in a sustainable way. Based on data from literature, and based on the systematics of the FeedPrint programme, the nutritional value and the carbon footprint (CFP) of these protein sources is determined. These protein sources are used in feed optimizations of a starter diet for pigs, thereby maintaining the nutritional value of the diet. Subsequently, the CFP of the grower diet is calculated. The results and conclusions will be discussed in this report.
Forced sustained swimming exercise at optimal speed to enhance growth performance of yellotail kingfish (Seriola lalandi)
Mes, D. ; Kloet, K. ; Blonk, R.J.W. ; Palstra, A.P. - \ 2014
In: Book of abstractsof the International Congress on th Biology of Fish. - - p. 162 - 162.
Juvenile yellowtail kingfish were either forced to perform sustained swimming exercise at an optimal speed of 2.46 body-lengths per second (‘swimmers’) or allowed to perform spontaneous activity at low water flow (‘resters’) in a 3,600 L oval-shaped flume with flow created by an impeller driven by an electric motor. At the start of the experiment, ten fish were sampled as controls (346±6mm, 504±27g). After 18 days, swimmers (n=23; 385±4mm, 735±23g) showed a 92% greater increase in body-length and 46% greater increase in body-weight as compared to resters (n=23; 367±5mm, 661±32g). As both groups were fed equal portions, the feed conversion ratio (FCR) for swimmers was 1.21 and lower than 1.74 for resters. Using Doppler ultrasound imaging, we found a 31% higher blood flow in the ventral aorta of swimmers vs. resters (respect. 44±3 ml/min vs. 34±3 ml/min, under anaesthesia). This study shows that growth performance can be rapidly improved by optimal swimming, even without larger feed investments.
Analyse Bouwstenen Nationaal Strategisch Plan Aquacultuur
Blonk, R.J.W. ; Beukers, R. ; Duijn, A.P. van; Burg, S.W.K. van den; Mheen, H.W. van der - \ 2014
Yerseke : IMARES (Rapport / IMARES Wageningen UR C092/14) - 33
visserijbeleid - aquacultuur - strategisch management - marktanalyse - stimulansen - toekomst - nederland - innovaties - kennisoverdracht - fishery policy - aquaculture - strategic management - market analysis - incentives - future - netherlands - innovations - knowledge transfer
Door de verwachte groei van de wereldbevolking, de groeiende consumptie, en het achterblijven van de productie zal het verschil in vraag en aanbod voor vis, schaal- en schelpdieren steeds groter worden. Tegelijkertijd heeft de visserijsector ook binnen de EU steeds meer moeite om aan de stijgende vraag voor deze producten te voldoen. Om de kloof tussen vraag en productie van vis, schaal- en schelpdieren te verkleinen, en niet te afhankelijk te worden van importen, zet de EU in op het stimuleren van de aquacultuursector. Volgens de nieuwe beleidsrichting in het Europees Fonds voor Maritieme Zaken en Visserij (EMFZV) dient de ontwikkeling van aquacultuur binnen de EU zich te richten op productie- en afzetverhoging door innovaties op techniek en kennis. Het rapport bestaat uit een marktanalyse en een analyse van de belangrijkste uitdagingen en interventies die nodig zijn om het perspectief van de Nederlandse aquacultuursector te vergroten. De bevindingen zijn gebaseerd op een combinatie van literatuuronderzoek en interviews met stakeholders binnen de Nederlandse aquacultuursector.
In- and outdoor reproduction of first generation common sole under a natural photothermal regime: Temporal progression of sexual maturation determined by plasma steroids, genome sequencing and pituitary gonadotropin expression
Palstra, A.P. ; Blok, M.C. ; Kals, J. ; Blom, E. ; Tuinhof-Koelma, N. ; Dirks, R.P. ; Forlenza, M. ; Blonk, R.J.W. - \ 2014
Introduction Reproduction of many temperate fishes is seasonal and the maturation and spawning of their gametes is under photothermal control. Reproductive success of first generation (G1) common sole Solea solea has been low. This restricts domestication and consequently economic viability of commercial culture. In this study, we have investigated the photothermal effects on the sexual maturation during the prespawning months in G1 sole that were a) outdoor housed under the natural photothermal regime, or b) indoor housed under artificial photothermal induction. Methods Maturation status was assessed in male and female G1 broodstock in November as controls, after which the remaining population was divided over two outdoor tanks placed in a pond and two indoor recirculating aquaculture system (RAS) tanks. Repeatedly maturation status was assessed for male and female fish in one tank for each condition in January, February and during spawning in early April, while the other tank was untouched not to disturb the fish in achieving reproductive success. Maturation status was assessed by determining the gonadosomatic index (GSI) and blood plasma steroid levels. The sole genome was sequenced in order to retrieve gonadotropin sequences and perform quantitative real-time PCR in females. Results and Discussion Successful mass spawning and egg fertilisation occurred in all experimental outdoor and indoor tanks and gonadal development was similar for males and females under both conditions. Higher E2 and T levels were found in indoor housed females which may have caused differences in vitellogenesis as also indicated by lower hepatosomatic indices. The expression of common glycoprotein unit a (gpa), fshß and lhß revealed similar temporal expression profiles between outdoor and indoor housed females but the latter showed less individual variation. Conclusion G1 sole was reproduced successfully at large scale in captivity, both in outdoor pond tanks as in indoor RAS tanks. The results indicate the importance of the natural photothermal regime in inducing sexual maturation in sole, as in temperate fish species in general. Specifically, a significant cold period (2-3 months at 5-7 °C) may be permissive for the action of FSH which levels will subsequently decrease and LH levels increase during rising temperatures towards spawning. The sole genome will be instrumental in unraveling its maturation and reproduction impairment under captive conditions in future studies.
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