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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    Next-generation salmonid alphavirus vaccine development
    Hikke, M.C. - \ 2016
    Wageningen University. Promotor(en): Just Vlak, co-promotor(en): Gorben Pijlman. - Wageningen : Wageningen University - ISBN 9789462577404 - 159
    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.

    Thermal regime, predation danger and the early marine exit of sockeye salmon Oncorhynchus nerka
    Katinic, P.J. ; Patterson, D.A. ; Ydenberg, R.C. - \ 2015
    Journal of Fish Biology 86 (2015)1. - ISSN 0022-1112 - p. 276 - 287.
    british-columbia - atlantic salmon - temperature - water - river - populations - mortality - migration - pacific - energetics
    Marine exit timing of sockeye salmon Oncorhynchus nerka populations on the Haida Gwaii Archipelago, British Columbia, Canada, is described, with specific focus on Copper Creek. Marine exit in Copper Creek occurs¿>¿130¿days prior to spawning, one of the longest adult freshwater residence periods recorded for any O. nerka population. Copper Creek presents an easy upstream migration, with mild water temperatures (7 to 14°¿ C), short distance (13·1¿km) and low elevation gain (41¿m) to the lake where fish hold prior to spawning. An energetic model estimates that
    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.
    Comparison of endogenous loss and maintenance need for minerals in rainbow trout (Oncorhynchus mykiss) fed fishmeal or plant ingredient-based diets
    Antony Jesu Prabhu, P. ; Kaushik, S.J. ; Mariojouls, C. ; Surget, A. ; Fontagné-Dicharry, S. ; Schrama, J.W. ; Geurden, I. - \ 2015
    Fish Physiology and Biochemistry 41 (2015)1. - ISSN 0920-1742 - p. 243 - 253.
    salmon salmo-salar - true phosphorus digestibility - fingerling channel catfish - biliary copper excretion - juvenile chinook salmon - phytate soybean meals - atlantic salmon - magnesium requirement - potassium requirement - fresh-water
    Mineral needs as affected by changes in dietary protein and oil sources were studied in rainbow trout. Duplicate groups (n = 30 fish per replicate) of rainbow trout (initial BW: 37 g) were fed either a fish meal/fish oil-based (M) or a complete plant ingredient (V)-based diet at four graded ration (R) levels [apparent satiation (AS), R75, R50 and R25 % of AS]; one treatment group was maintained under starvation. The feeding trial lasted 12 weeks at a water temperature of 17 °C. Dietary intake, apparent digestibility and initial and final whole-body composition data were used to calculate mineral gain which was regressed against digestible mineral intake (both expressed as mg or µg kg-0.8 day-1). Starvation loss (SL), endogenous loss of fed fish (ELF, y-intercept at x = 0) and point of intake for zero balance (PZB, x-intercept at y = 0) were used as estimates of maintenance requirements. SL provided the lowest estimate, ELF provided the net requirement of a mineral for maintenance and PZB provided the digestible dietary intake required to meet maintenance (SL
    Salmonid alphavirus glycoprotein E2 requires low temperature and E1 for virion formation and induction of protective immunity
    Hikke, M.C. ; Braaen, S. ; Villoing, S. ; Hodneland, K. ; Geertsema, C. ; Verhagen, L. ; Frost, P. ; Vlak, J.M. ; Rimstad, E. ; Pijlman, G.P. - \ 2014
    Vaccine 32 (2014)47. - ISSN 0264-410X - p. 6206 - 6212.
    pancreas disease virus - atlantic salmon - monoclonal-antibodies - insect cells - salar l - replicon - line
    Salmonid alphavirus (SAV; also known as Salmon pancreas disease virus; family Togaviridae) causes pancreas disease and sleeping disease in Atlantic salmon and rainbow trout, respectively, and poses a major burden to the aquaculture industry. SAV infection in vivo is temperature-restricted and progeny virus is only produced at low temperatures (10–15 °C). Using engineered SAV replicons we show that viral RNA replication is not temperature-restricted suggesting that the viral structural proteins determine low-temperature dependency. The processing/trafficking of SAV glycoproteins E1 and E2 as a function of temperature was investigated via baculovirus vectors in Sf9 insect cells and by transfection of CHSE-214 fish cells with DNA constructs expressing E1 and E2. We identified SAV E2 as the temperature determinant by demonstrating that membrane trafficking and surface expression of E2 occurs only at low temperature and only in the presence of E1. Finally, a vaccination-challenge model in Atlantic salmon demonstrates the biological significance of our findings and shows that SAV replicon DNA vaccines encoding E2 elicit protective immunity only when E1 is co-expressed. This is the first study that identifies E2 as the critical determinant of SAV low-temperature dependent virion formation and defines the prerequisites for induction of a potent immune response in Atlantic salmon by DNA vaccination.
    Steroids accumulate in the rearing water of commercial recirculating aquaculture systems
    Mota, V.C. ; Martins, C.I. ; Eding, E.H. ; Canário, A.V.M. ; Verreth, J.A.J. - \ 2014
    Aquacultural Engineering 62 (2014). - ISSN 0144-8609 - p. 9 - 16.
    rainbow-trout - noninvasive measurement - pleuronectes-platessa - treatment plants - atlantic salmon - free cortisol - waste-water - testosterone - fish - 17-alpha,20-beta-dihydroxy-4-pregnen-3-one
    Little information is available on steroid concentrations in the rearing water of aquaculture systems and whether they accumulate in recirculating aquaculture systems (RAS). Therefore this study aimed at determining (1) the concentrations and variation of cortisol and sex steroids in RAS, (2) the contribution of fish rearing conditions to steroid concentrations in seven commercial RAS. Each RAS was sampled twice at three different points: (1) make-up water; (2) influent and (3) effluent of the rearing unit. The results showed significant higher steroid concentrations in the influent and effluent when compared with the make-up water. On average cortisol concentration was 15.7% higher in the effluent when compared with the influent. Mean steroid concentrations in the rearing unit effluent varied between: 3.8–217.0 ng/L for cortisol, 3–12.5 ng/L for testosterone, 0.9–7.1 ng/L for 11-ketoteststerone and 1.8–12.8 ng/L for 17,20ß-dihydroxypregn-4-en-3-one. Stocking density, Total Ammonia-Nitrogen concentration and orthophosphate-P concentration (a measure of make-up water usage) showed a positive correlation with sex steroids in the water. The steroid concentrations from the present study were orders of magnitude lower than initial estimations indicating a water treatment efficiency of >99%. The results suggest that an intensification of fish production through decrease of make-up water use and increase of stocking density will lead to a build-up of steroids in the water. Although intensification is critical for the economical success of RAS, this ultimately could affect fish performance as steroids accumulates in the water of RAS at levels that can potentially be detected by some fish species.
    Post-prandial changes in plasma mineral levels in rainbow trout fed a complete plant ingredient based diet and the effect of supplemental di-calcium phosphate
    Antony Jesu Prabhu, P. ; Schrama, J.W. ; Mariojouls, C. ; Godin, S. ; Fontagné-Dicharry, S. ; Geurden, I. ; Surget, A. ; Bouyssiere, B. ; Kaushik, S.J. - \ 2014
    Aquaculture 430 (2014). - ISSN 0044-8486 - p. 34 - 43.
    salmon salmo-salar - fecal phosphorus excretion - european sea-bass - low fish-meal - oncorhynchus-mykiss - atlantic salmon - fresh-water - channel catfish - dicentrarchus-labrax - tricalcium phosphate
    Post-prandial changes in plasma mineral levels and utilisation of minerals in rainbow trout fed complete plant ingredient based diets with or without supplemental di-calcium phosphate (DCP) were studied over an 8 week period. Three diets were used: diet M was FM and fish oil (FO) based diet (control); diets VP0 and VP + (V diets) were completely based on plant derived protein and lipid sources. One of the V diets (VP +) was supplemented with DCP to supply 5 g kg- 1 dry matter available phosphorus (P); while the other diet (VP0) was not supplemented with DCP. Change in dietary protein source significantly affected the post-prandial pattern in plasma levels of P (p <0.05), Ca (p <0.007), Mg (p <0.001) and Zn (p <0.03). Area under the curve analysis indicated that compared to VP0, DCP supplementation in VP + improved plasma levels of P (p <0.01) and K (p <0.05); Cu (p <0.002), Se (p <0.009) and Zn (p <0.001) levels were reduced while Ca, Mg and Fe levels were unaffected (p > 0.05). Based on measurement of apparent digestibility, growth and whole body composition analyses, mineral balances were established showing that supplementation of DCP led to significant increase in whole body P concentration and P retention in VP +, comparable to fish fed diet M with significantly (p <0.05) reduced faecal and non-faecal P losses. There was improved post-absorptive retention (as % of available intake) of Ca (p <0.05), Mg (p <0.05) and K (p <0.05) in VP + compared to VP0. Utilisation of Cu (p <0.05) and Zn (p <0.01) was negatively affected. DCP supplementation to complete plant ingredient based diet increased the post-prandial plasma levels, whole body concentration and utilisation of macro-minerals (P, Ca, Mg and K) whereas that of micro-minerals especially Zn and Cu were negatively affected.
    Temporal structure of sound affects behavioural recovery from noise impact in European seabass
    Neo, Y.Y. ; Seitz, J. ; Kastelein, R.A. ; Winter, H.V. ; Cate, C. ten; Slabbekoorn, H. - \ 2014
    Biological Conservation 178 (2014). - ISSN 0006-3207 - p. 65 - 73.
    zebrafish danio-rerio - seismic air-guns - dicentrarchus-labrax - fish distribution - startle response - atlantic salmon - high-intensity - rainbow-trout - teleost fish - marine fish
    Human activities in and around waters generate a substantial amount of underwater noise, which may negatively affect aquatic life including fish. In order to better predict and assess the consequences of the variety of anthropogenic sounds, it is essential to examine what sound features contribute to an impact. In this study, we tested if sounds with different temporal structure resulted in different behavioural changes in European seabass. Groups of four fish were exposed in an outdoor basin to a series of four sound treatments, which were either continuous or intermittent, with either consistent or fluctuating amplitude. The behavioural changes of the fish were analyzed by a video-tracking system. All sound treatments elicited similar behavioural changes, including startle responses, increased swimming speed, increased group cohesion and bottom diving. However, with all other sound conditions being the same, intermittent exposure resulted in significantly slower behavioural recovery to pre-exposure levels compared to continuous exposure. Our findings imply that the temporal structure of sound is highly relevant in noise impact assessments: intermittent sounds, such as from pile driving, may have a stronger behavioural impact on fish than continuous sounds, such as from drilling, even though the latter may have higher total accumulated energy. This study urges regulatory authorities and developers to pay more attention to the influence of temporal structure when assessing noise impacts. However, more studies are needed to examine other sound parameters and to determine the generality of our observations in other species and in other outdoor water bodies
    Effects of Pro-Tex on zebrafish (Danio rerio) larvae, adult common carp (Cyprinus carpio) and adult yellowtail kingfish (Seriola lalandi)
    Boerrigter, J.G.J. ; Vis, J.W. van de; Bos, R. van den; Abbink, W. ; Spanings, T. ; Zethof, J. ; Louzao Martinez, L. ; Andel, W.F.M. van; Lopez-Luna, J. ; Flik, G. - \ 2014
    Fish Physiology and Biochemistry 40 (2014)4. - ISSN 0920-1742 - p. 1201 - 1212.
    artemia-franciscana larvae - heat-shock factor-1 - atlantic salmon - stress-response - expression - l. - heat-shock-protein-70 - hsp70 - fish - enhancement
    Aquaculture practices bring several stressful events to fish. Stressors not only activate the hypothalamus–pituitary–interrenal-axis, but also evoke cellular stress responses. Up-regulation of heat shock proteins (HSPs) is among the best studied mechanisms of the cellular stress response. An extract of the prickly pear cactus (Opuntia ficus indica), Pro-Tex, a soluble variant of TEX-OE®, may induce expression of HSPs and reduce negative effects of cellular stress. Pro-Tex therefore is used to ameliorate conditions during stressful aquaculture-related practices. We tested Pro-Tex in zebrafish (Danio rerio), common carp (Cyprinus carpio L.) and yellowtail kingfish (Seriola lalandi) exposed to aquaculture-relevant stressors (thermal stress, net confinement, transport) and assessed its effects on stress physiology. Heat shock produced a mild increase in hsp70 mRNA expression in 5-day-old zebrafish larvae. Pro-Tex increased basal hsp70 mRNA expression, but decreased heat-shock-induced expression of hsp70 mRNA. In carp, Pro-Tex increased plasma cortisol and glucose levels, while it did not affect the mild stress response (increased plasma cortisol and glucose) to net confinement. In gills, and proximal and distal intestine, stress increased hsp70 mRNA expression; in the distal intestine, an additive enhancement of hsp70 mRNA expression by Pro-Tex was seen under stress. In yellowtail kingfish, Pro-Tex reduced the negative physiological effects of transport more efficiently than when fish were sedated with AQUI-S®. Overall, our data indicate that Pro-Tex has protective effects under high levels of stress only. As Pro-Tex has potential for use in aquaculture, its functioning and impact on health and welfare of fish should be further studied.
    Differences between intestinal segments and soybean meal-induced changes in intestinal mucus composition of common carp Cyprinus carpio L.
    Marel, M.C. van der; Propsting, M.J. ; Battermann, F. ; Jung-Schroers, V. ; Hubner, A. ; Rombout, J.H.W.M. ; Steinhagen, D. - \ 2014
    Aquaculture Nutrition 20 (2014)1. - ISSN 1353-5773 - p. 12 - 24.
    salmon salmo-salar - perorally applied endotoxin - atlantic salmon - aeromonas-hydrophila - mucin glycoproteins - induced enteritis - distal intestine - skin mucus - in-vivo - adhesion
    The alimentary tract is a possible site where pathogens and toxins can enter. The alimentary tract is protected, amongst others, by mucus. In this study, tissue samples and crude mucus preparations from different parts of the intestinal tract of Cyprinus carpio (from intestinal bulb onto the hindgut) were examined using histological, histochemical and biochemical techniques. Furthermore, the response of the intestinal mucosal layer and intestinal mucus of C. carpio to acute soybean meal (SBM)-induced enteritis was investigated. In the present study, an indication for a different protein core of mucus high molecular weight glycoproteins (HMGs) for first and second segment could not be found. However, differences in mucus glycosylation could be found. Along the gut axis, the size of the major protein peaks were not similar, which can be caused by a different glycosylation. Also, differences in staining for the antimicrobial peptide beta-defensin 2 were found. Furthermore, changes in HMGs upon SBM diet were found similar to those found in inflammatory bowel disease (IBD) in humans. Initial changes include: changes in mucin composition, the presence of BD3 and of bacteria in internal organs. After the initial changes, all values measured returned back to the initial pre-SBM diet values.
    Oxidative and nitric oxide responses in carp macrophages induced by zymosan, MacroGard and selective dectin-1 agonists suggest recognition by multiple pattern recognition receptors
    Pietretti, D. ; Vera-Jimenez, N.I. ; Hoole, D. ; Wiegertjes, G.F. - \ 2013
    Fish and Shellfish Immunology 35 (2013)3. - ISSN 1050-4648 - p. 847 - 857.
    zebrafish danio-rerio - beta-glucan receptor - polymeric immunoglobulin receptor - cyprinus-carpio - atlantic salmon - rainbow-trout - differential expression - dietary beta-1,3-glucan - aeromonas-hydrophila - scavenger receptors
    ß-Glucans are glucose polymers that are found in the cell walls of plants, bacteria, certain fungi, mushrooms and the cell wall of baker's yeast. In mammals, myeloid cells express several receptors capable of recognizing ß-glucans, with the C-type lectin receptor dectin-1 in conjunction with Toll-like receptor 2 (TLR2), considered key receptors for recognition of ß-glucan. In our studies to determine the possible involvement of these receptors on carp macrophages a range of sources of ß-glucans were utilized including particulate ß-glucan preparations of baker's yeast such as zymosan, which is composed of insoluble ß-glucan and mannan, and MacroGard(®), a ß-glucan-based feed ingredient for farmed animals including several fish species. Both preparations were confirmed TLR2 ligands by measuring activation of HEK293 cells transfected with human TLR2 and CD14, co-transfected with a secreted embryonic alkaline phosphatase (SEAP) reporter gene. In addition, dectin-1-specific ligands in mammals i.e. zymosan treated to deplete the TLR-stimulating properties and curdlan, were monitored for their effects on carp macrophages by measuring reactive oxygen and nitrogen radicals production, as well as cytokine gene expression by real-time PCR. Results clearly show the ability of carp macrophages to strongly react to particulate ß-glucans with an increase in the production of reactive oxygen and nitrogen radicals and an increase in cytokine gene expression, in particular il-1ß, il-6 and il-11. We identified carp il-6, that was previously unknown. In addition, carp macrophages are less, but not unresponsive to selective dectin-1 agonists, suggesting recognition of ß-glucans by multiple pattern recognition receptors that could include TLR but also non-TLR receptors. Candidate receptors for recognition of ß-glucans are discussed.
    The Positive Impact of the Early-Feeding of a Plant-Based Diet on Its Future Acceptance and Utilisation in Rainbow Trout
    Geurden, I. ; Borchert, P. ; Balasubramanian, M.N. ; Schrama, J.W. ; Dupont-Nivet, M. ; Quillet, E. ; Kaushik, S.J. ; Panserat, S. ; Médale, F. - \ 2013
    PLoS ONE 8 (2013)12. - ISSN 1932-6203 - 9 p.
    salmon oncorhynchus-kisutch - atlantic salmon - amino-acids - epigenetic modifications - growth-performance - homing migration - body-composition - oil replacement - ration level - mykiss
    Sustainable aquaculture, which entails proportional replacement of fish-based feed sources by plant-based ingredients, is impeded by the poor growth response frequently seen in fish fed high levels of plant ingredients. This study explores the potential to improve, by means of early nutritional exposure, the growth of fish fed plant-based feed. Rainbow trout swimup fry were fed for 3 weeks either a plant-based diet (diet V, V-fish) or a diet containing fishmeal and fish oil as protein and fat source (diet M, M-fish). After this 3-wk nutritional history period, all V- or M-fish received diet M for a 7-month intermediate growth phase. Both groups were then challenged by feeding diet V for 25 days during which voluntary feed intake, growth, and nutrient utilisation were monitored (V-challenge). Three isogenic rainbow trout lines were used for evaluating possible family effects. The results of the V-challenge showed a 42% higher growth rate (P = 0.002) and 30% higher feed intake (P = 0.005) in fish of nutritional history V compared to M (averaged over the three families). Besides the effects on feed intake, V-fish utilized diet V more efficiently than M-fish, as reflected by the on average 18% higher feed efficiency (P = 0.003). We noted a significant family effect for the above parameters (P,0.001), but the nutritional history effect was consistent for all three families (no interaction effect, P.0.05). In summary, our study shows that an early shortterm exposure of rainbow trout fry to a plant-based diet improves acceptance and utilization of the same diet when given at later life stages. This positive response is encouraging as a potential strategy to improve the use of plant-based feed in fish, of interest in the field of fish farming and animal nutrition in general. Future work needs to determine the persistency of this positive early feeding effect and the underlying mechanisms.
    Unexpectedly high catch-and-release rates in European marine recreational fisheries: implications for science and management
    Ferter, K. ; Weltersbach, M.S. ; Strehlow, H.V. ; Graaf, M. de; Hammen, T. van der - \ 2013
    ICES Journal of Marine Science 70 (2013)7. - ISSN 1054-3139 - p. 1319 - 1329.
    salmon salmo-salar - atlantic salmon - length limits - circle hooks - mortality - anglers - fish - harvest - recall - norway
    While catch-and-release (C&R) is a well-known practice in several European freshwater recreational fisheries, studies on the magnitude and impact of this practice in European marine recreational fisheries are limited. To provide an overview of the practice and magnitude of C&R among marine recreational anglers in Europe, the existing knowledge of C&R and its potential associated release mortality was collected and summarized. The present study revealed that in several European countries over half of the total recreational catch is released by marine anglers. High release proportions of >60% were found for Atlantic cod (Gadus morhua), European sea bass (Dicentrarchus labrax), pollack (Pollachius pollachius), and sea trout (Salmo trutta) in at least one of the studied European countries. In the case of the German recreational Baltic Sea cod fishery, release proportions varied considerably between years, presumably tracking a strong year class of undersized fish. Reasons for release varied between countries and species, and included legal restrictions (e.g. minimum landing sizes and daily bag limits) and voluntary C&R. Considering the magnitude of C&R practice among European marine recreational anglers, post-release mortalities of released fish may need to be accounted for in estimated fishing mortalities. However, as the survival rates of European marine species are mostly unknown, there is a need to conduct post-release survival studies and to identify factors affecting post-release survival. Such studies could also assist in developing species-specific, best-practice guidelines to minimize the impacts of C&R on released marine fish in Europe.
    Bodybuilders met schubben (interview met A. Palstra)
    Palstra, A.P. - \ 2013
    Visionair : het vakblad van sportvisserij Nederland (2013)28. - ISSN 1569-7533 - p. 4 - 7.
    vissen - danio rerio - europese zalm - zwemmen - dierfysiologie - weerstand - stress - kweekvis - fishes - danio rerio - atlantic salmon - swimming - animal physiology - resistance - stress - farmed fish
    Een getrainde vis is een fitte vis, kan een adagium worden in het visonderzoek. Want vissen die genoeg zwemmen groeien harder, zijn minder stressgevoelig en beter bestand tegen ziekten. Hoe dat precies werkt wordt langzaam duidelijk.
    Adaptation Turning Points in River Restoration? The Rhine salmon case
    Bölscher, T. ; Slobbe, E.J.J. van; Vliet, M.T.H. van; Werners, S.E. - \ 2013
    Sustainability 5 (2013)6. - ISSN 2071-1050 - p. 2288 - 2304.
    atlantic salmon - climate-change - salar l - water - temperature - discharge - juvenile - habitat - basins - models
    Abstract: Bringing a sustainable population of Atlantic salmon (Salmo salar) back into the Rhine, after the species became extinct in the 1950s, is an important environmental ambition with efforts made both by governments and civil society. Our analysis finds a significant risk of failure of salmon reintroduction because of projected increases in water temperatures in a changing climate. This suggests a need to rethink the current salmon reintroduction ambitions or to start developing adaptive action. The paper shows that the moment at which salmon reintroduction may fail due to climate change can only be approximated because of inherent uncertainties in the interaction between salmon and its environment. The added value of the assessment presented in this paper is that it provides researchers with a set of questions that are useful from a policy perspective (by focusing on the feasibility of a concrete policy ambition under climate change). Thus, it offers opportunities to supply policy makers with practical insight in the relevance of climate change. Keywords: Atlantic salmon (Salmo salar); Rhine river; climate change; water temperature; adaptation turning points
    Quantifying dietary phosphorus requirement of fish – a meta-analytic approach
    Antony Jesu Prabhu, P. ; Schrama, J.W. ; Kaushik, S.J. - \ 2013
    Aquaculture Nutrition 19 (2013)3. - ISSN 1353-5773 - p. 233 - 249.
    trout oncorhynchus-mykiss - melanogrammus-aeglefinus l. - flounder paralichthys-olivaceus - large rainbow-trout - salmon salmo-salar - cyprinus-carpio l - mineral requirements - atlantic salmon - sea-bass - proximate composition
    A meta-analysis of available data on dose response to dietary phosphorus (P) in fish from over 70 feeding trials reported in 64 published studies covering over 40 species of fish was performed. Broken-line regression was used to model the data sets. The meta-analysis showed that estimated minimal dietary P level varies with the response criterion and that estimates should preferably be expressed in terms of available P than in terms of total P. Estimates based on whole-body P concentration (4.7 g available P kg-1 dry matter, DM) or vertebral P (5.2 g available P kg-1 DM) were greater than that for maximizing somatic weight gain (WG) (3.5 g available P kg-1 DM) or plasma P concentration (2.8 g available P kg-1 DM). P content of fish varies linearly with body mass (3.6 g kg-1 live weight). Use of ingredients rich in P or of diets with high basal P content or high levels of water P concentration can affect the estimations. Among the different response criteria tested, WG was found to be the most reliable and whole-body P concentration to be the most stringent criterion to estimate P requirement of a given fish species. Expressing available P requirement as g P per unit DM or digestible energy (DE) in the diet was equally effective, but expressing in terms of g P intake per kg BW0.8 per day would be more precise.
    The effect of tryptophan supplemented diets on brain serotonergic activity and plasma cortisol under undisturbed and stressed conditions in grouped-housed Nile tilapia Oreochromis niloticus
    Martins, C.I. ; Silva, P.I.M. ; Costas, B. ; Larsen, B.K. ; Santos, G.A. ; Conceicao, L.E.C. ; Dias, J. ; Overli, O. ; Höglund, E. ; Schrama, J.W. - \ 2013
    Aquaculture 400-401 (2013). - ISSN 0044-8486 - p. 129 - 134.
    trout oncorhynchus-mykiss - sole solea-senegalensis - neutral amino-acids - cod gadus-morhua - rainbow-trout - flesh quality - atlantic salmon - meat quality - preslaughter stress - interrenal activity
    Tryptophan (TRP) supplemented diets have been shown to have therapeutic effects in farmed animals including fish by modulating the activity of the neurotransmitter serotonin (5-hydroxytryptamine; 5-HT). The effects reported in fish have been obtained using individually-housed fish and include a reduction in stress response, aggression and stress-induced anorexia. In land farmed animals, TRP supplemented diets have also been shown to improve meat quality as a result of reduced stress during slaughter while in fish no data is currently available. This study aims at investigating whether short-term supplementation with TRP supplemented diets changes brain serotonergic activity and the stress response associated with slaughter handling in grouped-housed Nile tilapia Oreochromis niloticus. Adult fish (n = 108, 490.6 ± 4.0 g, 12 individuals per tank) were exposed to one of the three treatments (triplicates per treatment were used): control (0.48 g/100 g), TRP 4 × (1.87 g/100 g) and TRP 10 × (4.45 g/100 g) diets during 7 days. Afterwards, half of the fish in each tank were subjected to an acute stressor consisting of a combination of crowding and chasing, just prior to slaughter. The other half of the fish represented undisturbed conditions. Blood and brain samples were collected for cortisol and serotonergic activity analyses, respectively. Flesh quality was also assessed in both undisturbed and stressed fish for all treatments by measuring muscle pH and rigor mortis over a 72 h period. Results showed that the highest TRP supplemented diet (TRP 10 ×) induced a significant reduction in undisturbed plasma cortisol (10.57 ± 2.71 ng/ml) as compared to TRP 4 × (24.93 ± 3.19 ng/ml) and control diets (18.69 ± 2.94 ng/ml) and no effect on post-stress cortisol levels. After stress, the major 5-HT metabolite (5-hydroxyindoleacetic acid, 5-HIAA) was higher in the TRP 10 × (471.31 ± 60.95 ng/g) as compared to the other diets (TRP 4 ×: 313.52 ± 30.12 ng/g; control: 260.36 ± 19.65 ng/g). Stress before slaughter induced a significant increase in plasma cortisol (from 18.40 ± 1.76 ng/ml under undisturbed conditions to 80.34 ± 7.16 ng/ml), however, it was not sufficient to cause a faster deterioration of flesh quality. TRP supplement diets had also no effect on muscle pH and rigor mortis during the 72 h observation period. In conclusion, this study showed that only the highest levels of supplementation (10 × the control diet) affect serotonergic activity. However, these levels did not result in reduced stress responsiveness or improved flesh quality when an acute stressor is applied before slaughter. Therefore, these results underline the fact that effects of TRP on cortisol production are dose- and context-dependent, and further experiments are needed to determine under which conditions the optimal effect is obtained.
    Heritability of cortisol response to confinement stress in European sea bass dicentrarchus labrax
    Volckaert, F.A.M. ; Hellemans, B. ; Batargias, C. ; Louro, B. ; Massault, C. ; Houdt, J.K.J. Van; Haley, C. ; Koning, D.J. de; Canario, A.V.M. - \ 2012
    Genetics, Selection, Evolution 44 (2012). - ISSN 0999-193X
    tilapia oreochromis-niloticus - input earthen ponds - cyprinus-carpio l. - genetic-variation - rainbow-trout - disease resistance - body-weight - atlantic salmon - growth - traits
    Background: In fish, the most studied production traits in terms of heritability are body weight or growth, stress or disease resistance, while heritability of cortisol levels, widely used as a measure of response to stress, is less studied. In this study, we have estimated heritabilities of two growth traits (body weight and length) and of cortisol response to confinement stress in the European sea bass. Findings: The F1 progeny analysed (n = 922) belonged to a small effective breeding population with contributions from an unbalanced family structure of just 10 males and 2 females. Heritability values ranged from 0.54 (+/- 0.21) for body weight to 0.65 (+/- 0.22) for standard body length and were low for cortisol response i.e. 0.08 (+/- 0.06). Genetic correlations were positive (0.94) between standard body length and body weight and negative between cortisol and body weight and between cortisol and standard body length (-0.60 and -0.55, respectively). Conclusion: This study confirms that in European sea bass, heritability of growth-related traits is high and that selection on such traits has potential. However, heritability of cortisol response to stress is low in European sea bass and since it is known to vary greatly among species, further studies are necessary to understand the reasons for these differences.
    How to measure the economic impacts of changes in growth, feed efficiency and survival in aquaculture
    Kankainen, M. ; Setala, J. ; Berrill, I.K. ; Ruohonen, K. ; Noble, C. ; Schneider, O. - \ 2012
    Aquaculture Economics & Management 16 (2012)4. - ISSN 1365-7305 - p. 341 - 364.
    atlantic salmon - rainbow-trout - selection
    In this article we introduce a variety of bio-economic models that can be used to calculate the economic benefits associated with improved productivity in aquaculture. In the aquaculture industry, three important biological productivity factors are growth, survival and feed efficiency. The profitability of improving productivity factors, especially growth, is highly dependent upon the cost factor structure, production system, its constraints and other factors within the supply chain. Therefore we present a number of different bio-economical models that can be used to robustly assess the economic impacts in different production environments. These models are introduced with case examples across a range of aquaculture species and production systems. We calculate changes in profitability through a reduction in production costs and any potential increases in product price premiums via the use of weight dependent unit profit as the outcome in cost-benefit analysis, so that results may be expanded to cover different volumes.
    Molecular cloning and expression of two B-defensin and two mucin genes in common carp (Cyprinus carpio L.) and their up-regulation after B-glucan feeding
    Marel, M.C. van der; Adamek, M. ; Gonzalez, S.F. ; Frost, P. ; Rombout, J.H.W.M. ; Wiegertjes, G.F. ; Savelkoul, H.F.J. ; Steinhagen, D. - \ 2012
    Fish and Shellfish Immunology 32 (2012)3. - ISSN 1050-4648 - p. 494 - 501.
    gram-negative bacteria - salmo-salar l - disease resistance - immune-responses - atlantic salmon - secreted mucins - infection - fish - macrophages - microbiota
    In this study, we described the partial structure, mRNA tissue distribution and regulation of two carp mucin and two ß-defensin genes. This is the first description of these genes in fish. The genes might provide relevant tools to monitor feed-related improvements of fish health under aquaculture conditions. Carp mucin 2 and mucin 5B genes show a high similarity to their mammalian and avian counterparts. The carp ß-defensin 1 and ß-defensin 2 genes cluster together well with their piscine family members. The influence of a ß-glucan immunomodulant on the expression of these genes in mucosal tissues could be confirmed for the first time. Muc5B expression was significantly increased in the skin. For Muc2 no significant up- or down-regulation could be observed. Significantly higher expression levels of ß-defensin 2 in gills and both ß-defensin genes in skin were found. Thus, the mucosal system can be influenced by the addition of ß-glucans to the food
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