Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 12 / 12

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    Invloed van transport op de stressfysiologie van marktwaardige Afrikaanse meerval en Europese paling
    Vis, J.W. van de; Schram, E. ; Boerrigter, J. ; Manuel, R. ; Heul, J.W. van der; Bos, R. van den; Hofman, A.R.T. ; Ros, N.A.M. ; Lambooij, E. ; Flik, G. - \ 2013
    IJmuiden : IMARES Wageningen UR (Rapport / IMARES Wageningen UR C100/13) - 28
    stressfysiologie - clarias gariepinus - european eels - transport - laesies - bloedplasma - visserij - dierenwelzijn - stress physiology - clarias gariepinus - european eels - transport - lesions - blood plasma - fisheries - animal welfare
    Het onderzoek was gericht op effecten van praktijkgerichte transportcondities van marktwaardige Afrikaanse meerval (Clarias gariepinus) en Europese paling (Anguilla anguilla) op de relevante fysiologische parameters in het bloedplasma (cortisol, glucose en niet-veresterde vrije vetzuren) en mogelijke laesies van de huid.
    Beproeven apparaat bedwelmen van meerval voor de praktijk
    Vis, J.W. van de; Burggraaf, D. ; Abbink, W. ; Pol-Hofstad, I. ; Reimert, H. ; Lambooij, E. - \ 2013
    Yerseke : IMARES (Rapport / IMARES Wageningen UR C097/13) - 17
    aquacultuur - clarias gariepinus - bedwelmen - elektrisch verdoven - dierenwelzijn - dierlijke productie - kweekvis - diergezondheid - aquaculture - clarias gariepinus - stunning - electronarcosis - animal welfare - animal production - farmed fish - animal health
    Het doel van dit project was vaststellen of apparatuur voor elektrisch bedwelmen en vervolgens doden van de meervalsoorten in de praktijk aan het gestelde welzijnscriterium voldoet. Het welzijnscriterium voor elektrisch bedwelmen is dat de bewusteloosheid en gevoelloosheid onmiddellijk moeten worden opgewekt zonder dat deze vissoorten weer bijkomen. Het onderzoek richtte zich op de implementatie van elektrisch bedwelmen van Afrikaanse meerval (Clarias gariepinus) en een kruising van A. meerval en Vundu meerval (Heterobranchus longifilis) (Claresse meerval). Om dit doel te bereiken werden testen uitgevoerd met een eerste ontwerp en een omgebouwde versie van de apparatuur voor het bedwelmen en doden van beide vissoorten.
    Hoe giftig is nitraat voor Afrikaanse meerval?
    Schram, E. ; Roques, J.A.C. ; Abbink, W. ; Vries, P. de; Bierman, S.M. ; Vis, J.W. van de - \ 2012
    Aquacultuur 27 (2012)6. - ISSN 1382-2764 - p. 6 - 11.
    clarias gariepinus - clarias - recirculatie aquacultuur systemen - recirculatiesystemen - aquacultuur - nitraat - nitraatstikstof - voeropname - toxiciteit - clarias gariepinus - clarias - recirculating aquaculture systems - recirculating systems - aquaculture - nitrate - nitrate nitrogen - feed intake - toxicity
    In een recirculatiesysteem kan de nitraatconcentratie hoog oplopen. Hoe hoog mag de nitraatconcentratie worden zonder dat dit negatieve effecten heeft op de vissen? IMARES onderzocht dit in samenwerking met de Radbaoud Universiteit Nijmegen voor Afrikaanse meerval. Conclusie: nitraat is niet ongevaarlijk. Tot 140 mg nitraatstikstof per liter lijken meervallen weinig hinder te ondervinden. Wordt de concentratie hoger dan daalt de voeropname en groei behoorlijk.
    Aquaculture Stewardship Council (ASC) ontwikkeltraject meerval : een inventarisatie
    Poelman, M. ; Rothuis, A.J. ; Bosma, R.H. - \ 2012
    Aquacultuur 27 (2012)1. - ISSN 1382-2764 - p. 9 - 15.
    clarias - clarias gariepinus - aquacultuur - certificering - kwaliteitscontroles - viskwekerijen - clarias - clarias gariepinus - aquaculture - certification - quality controls - fish farms
    Om een Aquaculture Stewardship Council (ASC) gecertificeerd product te krijgen is een standaard nodig, waaraan getoetst kan worden. Deze standaard geeft certificeerders een referentiekader. Pas als een standaard aanwezig is, kunnen producten gecertificeerd worden.
    Het effect van verhoogde ammonia concentratie in het water op fysiologie, groei en voeropname van Afrikaanse meerval (Clarias gariepinus)
    Schram, E. ; Roques, J. ; Abbink, W. ; Spanings, T. ; Vries, P. de; Bierman, S.M. ; Vis, J.W. van de; Flik, G. - \ 2010
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C026/10) - 29
    aquacultuur - clarias gariepinus - ammoniak - nadelige gevolgen - effecten - dierfysiologie - voeropname - dierenwelzijn - aquaculture - clarias gariepinus - ammonia - adverse effects - effects - animal physiology - feed intake - animal welfare
    IMARES onderzocht het effect van de ammoniaconcentratie in het kweekwater op groei, voeropname en fysiologie van Afrikaanse meerval (Clarias gariepinus). Het doel van dit onderzoek was het vaststellen van de maximale ammoniaconcentratie (grenswaarde) waarbij geen negatieve effecten op welzijn van de vis en de productie waar te nemen zijn.
    De relatie tussen waterkwaliteit en welzijn bij Afrikaanse meerval en tong op Nederlandse viskwekerijen
    Abbink, W. ; Blanco Garcia, A. ; Heul, J.W. van der; Gool, A.C.M. van; Schram, E. ; Vis, J.W. van de - \ 2009
    Yerseke : IMARES (Rapport / IMARES Wageningen UR nr. C109/09) - 39
    waterkwaliteit - dierenwelzijn - viskwekerijen - clarias gariepinus - tong (vis) - visteelt - water quality - animal welfare - fish farms - clarias gariepinus - dover soles - fish culture
    Het doel van deze literatuurstudie is het beschrijven van de mogelijke knelpunten in de relatie tussen het welzijn van vissen en de waterkwaliteit in recirculatiesystemen (RAS), gespecificeerd op de Afrikaanse meerval (Clarias gariepinus) en tong (Solea solea). Hiernaast is bij een tongkwekerij en bij twee meervalkwekerijen een studie uitgevoerd naar de waterkwaliteit. De resultaten tonen aan dat de temperatuur, pH en zuurstofconcentratie van het water constant zijn. Het TAN-niveau (Total Ammonia Nitrogen) laat een variabel beeld zien bij de meervalkwekerijen, bij de tongkwekerij is het TAN-niveau constant laag.
    Welfare of African catfish : effects of stocking density
    Nieuwegiessen, P.G. van de - \ 2009
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama. - [S.l.] : S.n. - ISBN 9789085049869 - 137
    clarias gariepinus - dierenwelzijn - bezettingsdichtheid - stressreactie - dierfysiologie - diergedrag - leeftijd - visteelt - aquacultuur - clarias gariepinus - animal welfare - stocking density - stress response - animal physiology - animal behaviour - age - fish culture - aquaculture
    The general aim of this thesis was to determine the impact of stocking density on welfare indicators in African catfish, Clarias gariepinus, cultured in a recirculating aquaculture system. The following factors were studied: 1) the effects of stocking density on physical, physiological, and behavioural responses of African catfish, 2) how age mediates the effects of stocking density on physical, physiological, and behavioural responses of African catfish, 3) the potential effects of chemical alarm cues on the welfare of farmed African catfish, and 4) the fitness consequences of different coping strategies in intensive husbandry systems
    Individual variation in growth of African catfish Clarias gariepinus: a search for explanatory factors
    Matos Martins, C.I. de - \ 2005
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama. - Wageningen : - ISBN 9789085043065 - 166
    clarias gariepinus - groei - variatie - lichaamsafmetingen - voedingsgedrag - dierenwelzijn - voeropname - stressreactie - genetische variatie - visteelt - clarias gariepinus - growth - variation - body measurements - feeding behaviour - animal welfare - feed intake - stress response - genetic variation - fish culture
    Among farmed animals, fish exhibit the largest individual variation in growth, yet most of the studies reporting data on growth do not take individual variation into account. Usually a mean value is considered and although the variation around the mean is also mentioned, it is generally viewed as a sort of "statistical noise". The importance of individual variation in growth should not be underestimated since it has important consequences for water quality, aggression, stress levels, farm management, selection programmes, etc. Among the factors responsible for growth variation, social hierarchy is often considered as the most important. Social hierarchies may induce behavioural inhibition and stress on subordinate fish, affecting their feed intake, feed efficiency and as a consequence reducing their growth. However, for most fish species there is no unambiguous proof that individual differences in feed intake, feed efficiency and growth result from social hierarchies. Some studies suggest that inherent (genetic) factors may also cause the variation in growth.

    The general aim of this study was to understand the underlying factors responsible for the individual variation in growth of African catfish Clarias gariepinus . The following factors were investigated: 1) if individual variation in growth is mainly a consequence of social hierarchies, 2) the contribution of individual differences in feed intake and feed efficiency to the individual differences in growth and 3) the contribution of feeding behaviour and stress response in explaining individual differences in feed efficiency.

    Chapters 2 and 3 investigated the importance of social hierarchy as an explanatory factor for the individual variation in growth of African catfish. The growth performance, behaviour (feeding behaviour, aggression levels) and stress response between groups of low-, medium- and heavy- weight fish were compared. Chapter 2 showed that low-weight fish do not exhibit increased growth rates in the absence of heavier fish. Apparently, the growth differences were not induced by social hierarchies where the larger fish suppress the growth of smaller fish. Instead, this study suggests that feeding behaviour is a crucial factor. Heavier fish exhibit feeding behaviours that may give advantage when feed is limited, such as being more active swimmers, spending more time at the feeding areas and eating their meal faster than low-weight fish. These differences in behaviour may result in growth variation, as found in this study.

    Chapter 3 showed that the aggression and stress levels did not increase in heterogeneous (weight) groups as compared with homogeneous (weight) groups. Furthermore, low-weight fish did not exhibit a higher number of skin lesions and higher stress levels when reared in heterogeneous groups as compared with low-weight fish reared in homogeneous groups. These results suggested that low-weight fish were not behaving as subordinates and heavy fish as dominants.

    To further investigate the importance of inherent differences in growth variation, a set of experiments were designed using individually housed fish. Housing fish individually enabled the study of individual differences in the absence of social interactions and to measure individual feed intake accurately. This raised the question whether the results obtained from housing fish individually could be representative of a group housing situation. Chapter 4 compared the growth performance, feeding behaviour and stress response of isolated and non-isolated fish. This study suggested that in African catfish feed intake is stimulated by the presence of conspecifics resulting in higher feed intake and growth rates. However, isolation per se seems not to act as a stressor in the short term or to affect the stress response, probably because periods of isolation are part of the African catfish lifestyle. In addition, Chapter 5 compared the growth of fish housed individually and afterwards in a group. The average growth of individually housed fish was lower than fish in group housing. However, slow and fast growing fish under individual housing remained slow and fast growing fish, respectively, under group housing. This suggests that the different growth rates observed when fish are housed individually are a characteristic of the individual and not simply a consequence of isolation.

    Chapters 5 to 7 used individually housed fish to supply experimental data on inherent factors responsible for individual variation in growth. Chapter 5 quantified individual differences in performance traits and feeding behaviour and focused on the repeatability of such individual differences when fish were fed ad libitum. Fish exhibited pronounced individual variation in growth (CV = 52.8 %), in feed intake (34.3 %) and in total feeding time (>100 %). The repeatability estimates were 0.55 for growth, 0.70 for feed intake, 0.49 for feed efficiency and 0.81 for total feeding time. These high repeatability estimates suggested that individual differences in growth, feed intake/efficiency and feeding behaviour are consistent over time and therefore probably inherent. Individual differences in growth were explained mainly by individual differences in feed intake (~85 %). Individual differences in feeding behaviour were shown to be related to feed efficiency, measured as residual feed intake (i.e., the difference between actual feed intake and that predicted from mean observed requirements for growth and maintenance). With increasing total feeding time, the maintenance requirements also increased suggesting that slow eaters have higher maintenance costs. Chapter 6 tested whether individual differences in feeding behaviour explained the differences in growth rate by affecting feed efficiency, using restrictively fed fish. This study showed that despite the low variation in initial body weight (6.5 %) and in cumulative feed consumption (7.5 %) over the experimental period, catfish exhibited high variation in final body weight (18.1 %), specific growth rate (17.2 %) and feed conversion ratio (27.9 %), suggesting that individual variation in growth/feed efficiency is important in determining growth. This individual variation may be related to individual differences in protein/fat deposition since faster growing fish deposited more protein and less fat than slower growing fish. Pronounced individual differences in feeding behaviour (reaction towards feed and time spent eating) were also observed and correlated to individual differences in growth/feed efficiency. Fast eaters were the fast growers.

    Chapter 7 presented two experiments to investigate individual differences in basal and post-stress levels of glucose, lactate and cortisol and their relation to individual differences in feed efficiency. There was a pronounced individual variation in both basal and post-stress levels of plasma glucose, lactate and cortisol. Basal levels of glucose, lactate and cortisol did not contribute significantly to explain differences in feed efficiency. However, glucose levels obtained after a stress test (netting) could explain differences in feed efficiency by 1.3 % in experiment 1 and 5.9 % in experiment 2. In experiment 2, the cortisol levels obtained after the stress test also explained part of the differences in feed efficiency (8.7 %). Apparently, high stress responders are less efficient fish. The stress response probably adds to differences in maintenance costs, thereby affecting the feed efficiency.

    The findings of this thesis are discussed and the main conclusions are presented in Chapter 8 . The importance of social hierarchy in explaining individual growth variation should be considered species-dependent. In addition, social hierarchy should not be accepted a priori as the major cause of individual growth variation without previous investigation. The results of this thesis suggested that in African catfish the individual variation in growth is not the result of marked dominance-subordinance relationships. Instead, genetic-based differences in feed intake, feed efficiency, feeding behaviour and stress response seem to play a role in explaining growth variation in African catfish. In practical terms, one may question the use of grading in this species as grading is done under the assumption that it disrupts an existing social hierarchy. Furthermore, the results of this thesis called for the development of selection programmes in African catfish. Selecting for feed efficiency (residual feed intake) is a promising direction to pursue. The most efficient fish (low residual feed intake) were shown to be fast eaters and low stress responders which may be advantageous under aquaculture conditions.

    It was also concluded that individual differences in feed intake and feed efficiency (residual feed intake) contributed ~85 and ~15 %, respectively, to the individual differences in the growth of African catfish. Individual differences in feeding behaviour (total feeding time) and stress response (plasma glucose and cortisol after an acute stress) contributed to explain variation in residual feed intake (maintenance requirements) up to 8.7 %.

    Despite the results obtained in this thesis, our understanding of the causes of growth variation in African catfish is far from being complete. The challenge is to find the mechanisms responsible for this variation and how they are related to the individual differences in behaviour and stress response found in this thesis
    Towards assessment of welfare in Africal catfish, Clarias gariepinus: the first step
    Almazán Rueda, P. - \ 2004
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama. - [S.l.] : S.n. - ISBN 9789058089410 - 152
    clarias gariepinus - diergedrag - dierenwelzijn - stress - stressreactie - visvoeding - groei - lichtregiem - bezettingsdichtheid - bloedanalyse - visteelt - aquacultuur - clarias gariepinus - animal behaviour - animal welfare - stress - stress response - fish feeding - growth - light regime - stocking density - blood analysis - fish culture - aquaculture
    Semen collection and preservation in African catfish, Clarias gariepinus
    Viveiros, A. - \ 2002
    Wageningen University. Promotor(en): E.A. Huisman; J. Komen; H. Woelders. - S.l. : S.n. - ISBN 9789058085610 - 144
    clarias gariepinus - vissen - visteelt - sperma - strippen - spermaconservering - cryopreservering - hormonen - geneesmiddelenbehandeling - voortplantingsstoornissen - genetische bronnen van diersoorten - clarias gariepinus - fishes - fish culture - semen - stripping - semen preservation - cryopreservation - hormones - drug therapy - reproductive disorders - animal genetic resources

    Stock improvement using quantitative and molecular genetics is an essential part of nowadays production of farm animals and fish. To achieve this in aquaculture, germplasm of both parental sexes should be obtained in a life-saving manner. In captivity, male African catfish, Clariasgariepinus , do not release semen under abdominal massage and have to be sacrificed to obtain sperm from the macerated testes. Of course, this is regarded as a major constrains by the catfish farming sector. Against this background, the research of the present thesis had a two-pronged approach and aimed (a) to induce semen release and facilitate stripping of semen under abdominal massage, and (b) to optimize protocols for cryopreserving semen of the African catfish. To facilitate hand-stripping of semen, several maturational hormones that increase plasma gonadotropin levels and drugs that stimulate contractions of the reproductive tract, such as oxytocin, were tested. The response to some of these treatments was compared between normal males and males that possessed undeveloped seminal vesicles - a possible block of the sperm flow during abdominal massage. Based on the results, it is unlikely that catfish males kept in captivity are not strippable because of a lack of gonadotropin surge. Fertile semen was hand-stripped from males that possessed undeveloped seminal vesicles but not from normal males, suggesting that seminal vesicles actually block the sperm flow during hand-stripping. However, stripping was possible only after treatment with pituitary extract. Oxytocin may play a role in sperm transport in catfish, but more research is needed to optimize dose and latency time. To optimize protocols for semen cryopreservation, different cryoprotectors, cooling rates and temperatures at which plunging into liquid nitrogen occurred, were evaluated. Catfish semen showed good tolerance to freezing and thawing. Hatching rates similar to the fresh semen were obtained with semen frozen in 10% methanol, at a cooling rate of -2, -5 or -10ºC/min to -40ºC and plunged into liquid nitrogen as soon as semen temperature reached -38ºC. Samples plunged into liquid nitrogen from a semen temperature above -30ºC or below -50ºC produced decreasing hatching rates. Post-thaw semen could be diluted at least 200 times without loosing fertilization capacity. Cryopreservation of semen is a valuable tool for selection and conservation of genetic diversity in catfish species.

    Onderzoek naar grondsmaak bij Afrikaanse meerval met behulp van een 'Electronic nose'
    Kamstra, A. ; Heul, J.W. van der; Scheerman, P. - \ 1998
    ijmuiden [etc.] : RIVO - 15
    clarias gariepinus - smaak - smaakonderzoek - taste - taste research
    A dynamic simulation model for growth of the African catfish, Clarias gariepinus (Burchell 1822)
    Machiels, M.A.M. - \ 1987
    Agricultural University. Promotor(en): E.A. Huisman; F.W.T. Penning de Vries. - s.l. : Machiels - 110
    visteelt - zoet water - siluridae - silurus - clarias - ictalurus - groei - computersimulatie - simulatie - simulatiemodellen - clarias gariepinus - fish culture - fresh water - siluridae - silurus - clarias - ictalurus - growth - computer simulation - simulation - simulation models - clarias gariepinus

    In the early '70 it was tried to identify new fish species for aquaculture in Africa. Amongst the most promising candidates was the African catfish. Clariasgariepinus (Burchell 1822). It is an omnivorous fish. which means a wide feeding spectrum. The fish is a partial air breather, so the oxygen concentration in the water is no strongly limiting factor, which facilitates high density culture.

    To provide the basis for a production programme of any species the various phases of its culture process must be elaborated. First of all methods for reproduction have to be established to ensure a reliable supply of fingerlings. Secondly raising of fingerlings to fish of marketable size is a field of major importance.

    An important question in fattening of fish is what to feed how much. The amount and the composition of the fish diet have a pronounced effect on growth rate and feed conversion. The conversion process of feed nutrients into fish biomass is influenced by a number of biotic and a-biotic factors like for instance body weight, maturity, water temperature and water quality. Many experiments are required to perform dose-respond relationships for the amount of feed and the weight gain at different temperatures, different weight classes and various diet compositions. To reduce these efforts developing a growth model may be helpful.

    In this study an explanatory growth model is developed to gain knowledge about the influence of various factors on the growth process. The quantitative equations of the model describe the processes at the underlying levels of growth, the intermediate metabolism and biochemistry. These equations reflect our understanding and knowledge of the relationship in the real system.

    To carry out the simulation the state variable approach is used. All rates of change between small time lags are calculated from the conditions of the system at time of start and if necessary from data in the past. The state of the system can be calculated by semi-parallel integration over the small time interval. From these new circumstances the calculations are repeated.

    The model calculations start with the amount of various digested nutrients. The digestion rate of the various nutrients depends on the eating rate, the diet composition and the digestion efficiency. The resulting amino acids. fatty acids and mono sacharides (glucose) are the building blocks for biosynthesis of new biomass. Apart from the composition of digested nutrient the conversion process of feed nutrients into fish biomass also depends on the composition of the biomass. Because the glycogen content in fish is very low it is assumed that glucose and fatty acids are converted to fat. The amino acids are used for the biosynthesis of protein. Since fish has to maintain its body composition within certain limits, more or less amino acids are used for other purposes via gluconeogenesis, depending the diet composition.

    Using the biochemical pathways, as given in the literature. of biosynthesis and other metabolic processes a molecular reaction equation can be made, giving the substrate required for any particular end product. The reaction equations generally include ATP and other recycling intermediates for energy transformations. The final equations for the most complex substrate and end products represent the efficient conversion possible, given the biochemical "machinery". The conversion process is easily expressed in terms of weight of substrate and end products formed. The reactions also include the gas exchange.

    The new fish biomass formed by biosynthesis is not all weight gain, because part of the biomass is broken down for respiration purposes. Respiration is determined by the total metabolic rate. The total metabolic rate is the sum of the routine metabolic rate at fasting conditions, the metabolic rate due to feed intake and assimilation and the metabolic rate for the biosynthesis of biomass. The ratio at which body fat and protein are oxidized for respiration is set to depend on the body composition in order to avoid unrealistic body compositions.

    The change in the amounts of different body constituents is calculated as the difference between biosynthesis and breakdown for respiration. When the protein gain is known, fresh weight gain is calculated with a relation between body weight and protein content. The fat gain is considered to affect the body composition only. The fat and the water content of fish biomass show a strong negative correlation.

    Feed consumption by the fish is determined by the daily feed ration. Since at high feeding levels a difference between amount of feed consumed and amount of feed provided may occur, a relation between maximum consumption and fish weight at different temperatures is incorporated in the model in order to limit the weight gain in such circumstances. In the model, the maximum feed intake by the fish is also controlled by the composition of both the fish biomass and the diet. Fat fish can consume less feed than a leaner fish of the same weight. A fish will also eat less in case of a carbohydrate rich diet.

    The input needed for the calculations are body weight and fat content of the fish. amount and composition of the feed and the water temperature. The output of the model includes fresh weight gain. protein gain. fat gain, oxygen consumption, carbon dioxide production and ammonia production.,

    During its development the model was tested by comparing the model output with experimental results which were not used during the calibration procedure.

    Firstly a comparison was made with results of an experiment were a diet with a fixed composition was offered to different weight classes of C . gariepinus at 3 temperatures and 5 feeding levels. A second comparison was made with result of an experiment were diets with different composition were fed to the fish. The model estimates the effects of feeding level, feed composition (in particular protein and fat content) and temperature on growth and growth composition reasonably well. The test results indicate that C . gariepinus utilises the feed nutrients at maximum biochemical efficiency. It became also apparent that the fish regulates its maximum feed intake by the fat content of the biomass. Because there were no data available to support this hypothesis. an experiment was carried out to determine the effects of body composition on growth and feed intake. In this experiment it was shown that feeding a diet to lean or fat fish, resulted in a higher maximum gain for lean fish due to a higher maximum feed intake level. Below the maximum gain, fat fish showed a slightly better feed conversion. It is likely, that C . gariepinus regulates its maximum feed intake. besides by lipostatic mechanisms. also by glucostatic mechanisms, because the maximum feed intake levels of a carbohydrate rich diet (54 %) were lower than the maximum intake levels of a low carbohydrate diet. The implications of these finding are of great practical value. The production results can be influenced by changing the biomass composition of the fish through different feeding strategies or diet compositions.

    Finally, the model was used to calculate the performance of C . gariepinus , fed with differently formulated diets. The output of the model was compared with the results of an experiment were C . gariepinus was fed with diets containing different protein sources of plant and animal origin. The model is suited to predict the effect of nutrient supply on growth and growth composition of C . gariepinus . For feed formulation purposes it seems possible to calculate a ranking order of different protein ingredients to be included in the fish diet.

    Limitations of the model are found for the prediction of growth at high feed intake levels. Emphasis must be given to find adequate relations for feed intake regulation at the upper limits of growth and/or feed intake, because the model is very sensitive for changes in the maximum feed Intake level.

    The model can be easily adopted for simulating growth of other fish species. Other possible applications are research and teaching on the principles of fish growth and nutrition, development and evaluation of new diets for various production methods and. in combination with a model of the physical culture system, economic analysis of real farm results.

    Check title to add to marked list

    Show 20 50 100 records per page

     
    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.