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Towards Assessment of Welfare in Africal Catfish, Clarias Gariepinus : = the First Step.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Towards Assessment of Welfare in Africal Catfish, Clarias Gariepinus :/
Reminder of title:	the First Step.
Author:	Rueda, Pablo Almazan.
Description:	1 online resource (161 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 83-02, Section: B.
Contained By:	Dissertations Abstracts International83-02B.
Subject:	Trout. -
Online resource:	click for full text (PQDT)
ISBN:	9798516025617

Towards Assessment of Welfare in Africal Catfish, Clarias Gariepinus : = the First Step.
Rueda, Pablo Almazan.

Towards Assessment of Welfare in Africal Catfish, Clarias Gariepinus :the First Step. - 1 online resource (161 pages)

Source: Dissertations Abstracts International, Volume: 83-02, Section: B.

Thesis (Ph.D.)--Wageningen University and Research, 2004.

Includes bibliographical references

During the past three decades, aquaculture has expanded, diversified and intensified. To increase production under farm conditions, the most common practice has been to increase the number of fish per culture unit and/or to increase growth rate by improving feeds, feeding strategies and optimising water quality. Secondary practices are to manipulate photoperiod and/or light intensities. All these efforts strongly focused on the improvement of productivity, but little attention has been paid on the question how and if the animal could cope with these new husbandry conditions. Welfare issues gained only very recently some interest in fish farming. Public apprehension about intensive fish culture has not reach the high levels of concern as it has for the pig and poultry industry. However, animal welfare pressure groups have suggested that current farming practices may compromise fish welfare as well. There are several factors that may affect welfare in fish. Animals will respond at different levels when they are subject to environmental conditions which impaired their welfare status: varying from endocrine changes to atypical behaviour. The overall objective of this thesis is to determine the effect of different environmental factors on social behaviour of the African catfish (Clarias gariepinus) and the results of this social behaviour in relation to stress response, feed intake, and growth. In this thesis we hypothesise that environmental factors play a major role in the expression of behaviour and performance of the African catfish (Clarias gariepinus).The first step of this study (Chapter 2) focused on the development of base line data on the behaviour of the African catfish (Clarias gariepinus) under inormali and standardised conditions. In this part, behaviour patterns, such as swimming activity, air breathing, aggression (as scars and/or wounds on body), and stereotypes were described and used as a reference for the following chapters. In the second part of this thesis (Chapters 3, 4 and 5), various husbandry conditions were screened for being potential stressors and thus affecting the fish welfare. In addition to the main effect of the studied husbandry factor, there was also attention paid to the occurrence of interaction effects between different husbandry factors. In Chapter 3, the effects of feeding method (continuous by self-feeders vs. twice a day hand feeding), light intensity (15 vs. 150 lux), photoperiod (continuous light vs. 12D:12L) and their interactions on water quality and growth of juvenile African Catfish (Clarias gariepinus) were studied. Feeding method influenced water quality. Suspended solid production was almost doubled in self-fed fish compared with those fed by hand fed. TAN production was influenced by light intensity, being higher under 15 lux compared to 150 lux. Despite of the similar growth, self-fed fish demanded more feed compared to hand fed fish. Based on the performance data, juvenile African catfish (C. gariepinus) seemed to be insensitive to light intensity but were influenced by photoperiod. A 12D:12L photoperiod increases growth and feed consumption compared with 0D:24L.In Chapter 4 the same husbandry factors as in Chapter 3 were assessed but now in relation to the behaviour of the fish. Fish under continuous light and at high light intensity spent more time swimming, were more aggressive and consequently had more scars on the body than fish under 12D:12L photoperiod and at low light intensity. A good correlation between swimming activity and aggression and/or scars on the body was found.In Chapter 5 stocking density, photoperiod and light intensity were assessed. High stocking density (2500 fish.m-3) increased growth, swimming activity, and reduced FCR, aggression and the occurrence of stereotypes compared to low stocking density (250 fish.m-3). High stocking density also showed to have an influence on plasma cortisol and glucose levels.Based on the results in Chapters 3, 4 and 5 (behavioural, physiological and performance responses to the imposed husbandry conditions), stocking density and photoperiod were selected for more detailed assessment in Chapter 6 and 7, respectively. Different photoperiod regimes (24D:0L, 18D:06L, 12D:12L and 06D:18L) were studied in Chapter 6. Short periods of light or no light (6L:18D and 0L:24D) resulted in an increased growth compared to extended periods of light (18L:6D and 12L:12D). Fish kept at longer periods of light (12L:12D and 18L:6D) showed an increased swimming activity, more aggression (injuries on the body), and higher blood plasma levels of lactate, free fatty acids, and cortisol compared to fish kept at shorter periods of light (0L:24D and 6L:18D). As the hours of light increased during the 24 h cycle, data suggested that the fish became more stressed and aggressive. In Chapter 7, the effects of group size as well as available swimming area on the fishis behaviour, stress response and growth were assessed. African catfish (Clarias gariepinus) improved growth, increased swimming activity, and reduced aggression, stereotypes and cortisol levels when the group size increased (fish per tank). Reducing the available swimming area reduced the growth and the swimming activity and increased blood plasma cortisol levels. Differences in nutrient partitioning and behaviour suggested that fishis maintenance cost was higher in fish at the restricted space and/or low stocking density due to agonistic behaviour and/or exposure to stress. The term istocking densityi, defined as the number of fish per unit of space, cannot be used as a criterion to evaluate or compare systems.This thesis proved that small changes in husbandry conditions, such as reduced hours of light during 24 h and low light intensity might improve general conditions for the African catfish (Clarias gariepinus). Furthermore contrary to the general belief, ihighi stocking density reduced aggression and improved growth in African catfish. The current results may be helpful to solve some problems of aggression, improve growth and reduce physiological responses to stress in the African catfish culture. On the other hand, assessing the welfare of the African catfish is a hard task, especially because results can be contradictory. Measurement of a single parameter, such as behaviour, physiological levels or performance parameter is not sufficient for an objective assessment of welfare. A combination of these three types of parameters mentioned above might help to understand fish welfare, but precautions must be taken in order to prevent erroneous conclusions.This thesis is the first step towards assessment of welfare in the African catfish.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798516025617Subjects--Topical Terms:

1465323
Trout.
Index Terms--Genre/Form:

554714
Electronic books.

Towards Assessment of Welfare in Africal Catfish, Clarias Gariepinus : = the First Step.
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245 1 0 $a Towards Assessment of Welfare in Africal Catfish, Clarias Gariepinus : $b the First Step.
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500 $a Source: Dissertations Abstracts International, Volume: 83-02, Section: B.
500 $a Advisor: Verreth , J. A.J. ;Schrama, J. W.
502 $a Thesis (Ph.D.)--Wageningen University and Research, 2004.
504 $a Includes bibliographical references
520 $a During the past three decades, aquaculture has expanded, diversified and intensified. To increase production under farm conditions, the most common practice has been to increase the number of fish per culture unit and/or to increase growth rate by improving feeds, feeding strategies and optimising water quality. Secondary practices are to manipulate photoperiod and/or light intensities. All these efforts strongly focused on the improvement of productivity, but little attention has been paid on the question how and if the animal could cope with these new husbandry conditions. Welfare issues gained only very recently some interest in fish farming. Public apprehension about intensive fish culture has not reach the high levels of concern as it has for the pig and poultry industry. However, animal welfare pressure groups have suggested that current farming practices may compromise fish welfare as well. There are several factors that may affect welfare in fish. Animals will respond at different levels when they are subject to environmental conditions which impaired their welfare status: varying from endocrine changes to atypical behaviour. The overall objective of this thesis is to determine the effect of different environmental factors on social behaviour of the African catfish (Clarias gariepinus) and the results of this social behaviour in relation to stress response, feed intake, and growth. In this thesis we hypothesise that environmental factors play a major role in the expression of behaviour and performance of the African catfish (Clarias gariepinus).The first step of this study (Chapter 2) focused on the development of base line data on the behaviour of the African catfish (Clarias gariepinus) under inormali and standardised conditions. In this part, behaviour patterns, such as swimming activity, air breathing, aggression (as scars and/or wounds on body), and stereotypes were described and used as a reference for the following chapters. In the second part of this thesis (Chapters 3, 4 and 5), various husbandry conditions were screened for being potential stressors and thus affecting the fish welfare. In addition to the main effect of the studied husbandry factor, there was also attention paid to the occurrence of interaction effects between different husbandry factors. In Chapter 3, the effects of feeding method (continuous by self-feeders vs. twice a day hand feeding), light intensity (15 vs. 150 lux), photoperiod (continuous light vs. 12D:12L) and their interactions on water quality and growth of juvenile African Catfish (Clarias gariepinus) were studied. Feeding method influenced water quality. Suspended solid production was almost doubled in self-fed fish compared with those fed by hand fed. TAN production was influenced by light intensity, being higher under 15 lux compared to 150 lux. Despite of the similar growth, self-fed fish demanded more feed compared to hand fed fish. Based on the performance data, juvenile African catfish (C. gariepinus) seemed to be insensitive to light intensity but were influenced by photoperiod. A 12D:12L photoperiod increases growth and feed consumption compared with 0D:24L.In Chapter 4 the same husbandry factors as in Chapter 3 were assessed but now in relation to the behaviour of the fish. Fish under continuous light and at high light intensity spent more time swimming, were more aggressive and consequently had more scars on the body than fish under 12D:12L photoperiod and at low light intensity. A good correlation between swimming activity and aggression and/or scars on the body was found.In Chapter 5 stocking density, photoperiod and light intensity were assessed. High stocking density (2500 fish.m-3) increased growth, swimming activity, and reduced FCR, aggression and the occurrence of stereotypes compared to low stocking density (250 fish.m-3). High stocking density also showed to have an influence on plasma cortisol and glucose levels.Based on the results in Chapters 3, 4 and 5 (behavioural, physiological and performance responses to the imposed husbandry conditions), stocking density and photoperiod were selected for more detailed assessment in Chapter 6 and 7, respectively. Different photoperiod regimes (24D:0L, 18D:06L, 12D:12L and 06D:18L) were studied in Chapter 6. Short periods of light or no light (6L:18D and 0L:24D) resulted in an increased growth compared to extended periods of light (18L:6D and 12L:12D). Fish kept at longer periods of light (12L:12D and 18L:6D) showed an increased swimming activity, more aggression (injuries on the body), and higher blood plasma levels of lactate, free fatty acids, and cortisol compared to fish kept at shorter periods of light (0L:24D and 6L:18D). As the hours of light increased during the 24 h cycle, data suggested that the fish became more stressed and aggressive. In Chapter 7, the effects of group size as well as available swimming area on the fishis behaviour, stress response and growth were assessed. African catfish (Clarias gariepinus) improved growth, increased swimming activity, and reduced aggression, stereotypes and cortisol levels when the group size increased (fish per tank). Reducing the available swimming area reduced the growth and the swimming activity and increased blood plasma cortisol levels. Differences in nutrient partitioning and behaviour suggested that fishis maintenance cost was higher in fish at the restricted space and/or low stocking density due to agonistic behaviour and/or exposure to stress. The term istocking densityi, defined as the number of fish per unit of space, cannot be used as a criterion to evaluate or compare systems.This thesis proved that small changes in husbandry conditions, such as reduced hours of light during 24 h and low light intensity might improve general conditions for the African catfish (Clarias gariepinus). Furthermore contrary to the general belief, ihighi stocking density reduced aggression and improved growth in African catfish. The current results may be helpful to solve some problems of aggression, improve growth and reduce physiological responses to stress in the African catfish culture. On the other hand, assessing the welfare of the African catfish is a hard task, especially because results can be contradictory. Measurement of a single parameter, such as behaviour, physiological levels or performance parameter is not sufficient for an objective assessment of welfare. A combination of these three types of parameters mentioned above might help to understand fish welfare, but precautions must be taken in order to prevent erroneous conclusions.This thesis is the first step towards assessment of welfare in the African catfish.
520 $a Gedurende de afgelopen drie decennia heeft de visteelt zich uitgebreid, veranderd en geOntensifeerd. De stijging in productie op praktijkbedrijven is voornamelijk gerealiseerd door verhoging van het het aantal vissen per teelteenheid en/of door stijging van de groeisnelheid door het verbeteren van voer, voederstrategieIn en optimalisatie van de water kwaliteit. Daarnaast zijn ook fotoperiode en lichtintensiteit gebruikt om de productie te sturen. Alle deze inspanningen richtten zich sterk op de verbetering van de productiviteit. Er is echter weinig aandacht besteed aan de vraag Uf en hoe de vissen zich konden aanpassen aan deze nieuwe houderijcondities. Pas sinds kort krijgt het vraagstuk van dierwelzijn aandacht in de aquacultuursector. Daarbij is de aandacht en zorg voor dierenwelzijn in de visteelt nog lang niet zo intens als in de varkens- en pluimveeindustrie. Echter dierwelzijnsgroeperingen suggereren dat onder de huidige teeltcondities ook het welzijn van de vissen mogelijk niet optimaal is. Er zijn meerdere factoren die het welzijn van vissen kunnen beOnvloeden. Dieren reageren op verschillende manieren wanneer zij onderworpen worden aan omstandigheden die hun welzijnsstatus nadelig beinvloedt: variIrend van endocriene veranderingen tot atypisch gedrag. Het algemene doel van dit proefschrift is te bepalen in welke mate verschillende omgevingsfactoren het (sociale) gedrag van de Afrikaanse meerval (Clarias gariepinus) beOnvloeden en hoe dit (sociale) gedrag bijdraagt aan de reactie op stress, voer opname en groei. De onderliggende werkhypothese was dat omgevingsfactoren een belangrijke rol spelen in de uitdrukking van gedrag en groeiprestatie van de Afrikaanse meerval (Clarias gariepinus).Het eerste deel van deze studie (Hoofdstuk 2) concentreerde zich op de ontwikkeling van een set referentiegegevens m.b.t. het gedrag van de Afrikaanse meerval (Clarias gariepinus) onder inormalei en gestandaardiseerde omstandigheden. In dit deel werden gedragsparameters, zoals zwem-activiteit, lucht ademhalen, aggressie (als littekens en/of wonden op het lichaam), stereotiep gedrag, beschreven en gebruikt als een referentie voor de daaropvolgende hoofdstukken.In het tweede deel van dit proefschrift (Hoofdstukken 3, 4 en 5) werden verschillende houderijcondities doorgelicht en werd onderzocht of deze mogelijk een stressor zijn voor de vis en dus het welzijn van de vis treffen. In Hoofdstuk 3 werden de effecten van voedermethode (continue voedering door middel van pendel voedering versus tweemaal per dag met de hand voederen), lichtintensiteit (15 versus 150 lux), fotoperiode (continu licht versus 12D:12L) en hun onderlinge interactie op waterkwaliteit en groei van jonge Afrikaanse meerval (Clarias gariepinus) bestudeerd. De methode van voederen beOnvloedde de waterkwaliteit. De productie van zwevende stofdeeltjes in het water werd bijna verdubbeld bij pendel voedering in vergelijking tot de handgevoederde vissen. TAN productie werd beOnvloed door lichtintensiteit en was hoger bij 15 lux dan bij 150 lux. Ondanks een vergelijkbare groei, was het voerverbruik bij pendel gevoerde vissen hoger dan bij handgevoerde vissen. Gebaseerd op de productieparameters, bleek jonge Afrikaanse meerval (C. gariepinus) ongevoelig te zijn voor lichtintensiteit, maar wel voor verandering in de fotoperiode. Een fotoperiode van 12D:12L resulteerde in een hogere groei en voerverbruik ten opzichte van 0D:24L (continue belichting)..In Hoofdstuk 4 werden dezelfde houderijfactoren als in Hoofdstuk 3 bestudeerd, maar nu ten aanzien van hun invloed op het gedrag van de vis. Vissen verkerend in continu licht en in hoge lichtintensiteit besteedden meer tijd aan zwemmen, waren agressiever en hadden meer littekens op het lichaam dan vissen verkerend in een 12D:12L fotoperiode en lage lichtintensiteit. Zwemactiviteit bleek sterk gecorreleerd te zijn met de mate van aggressie en/of littekens op het lichaam.In Hoofdstuk 5 werden dichtheid, fotoperiode en licht intensiteit bestudeerd. Bij een hoge dichtheid (2500 fish.m-3) was de groei en zwemactiviteit hoger en de voedselconversie, agressie en de frequentie van stereotiep gedrag lager dan bij lage dichtheid (250 fish.m-3). De dichtheid beOnvloedde ook de bloedplasma concentraties van cortisol en glucose.Gebaseerd op de resultaten in Hoofdstukken 3, 4 en 5 werden dichtheid en fotoperiode geselecteerd voor een meer gedetailleerde studie in respectievelijk Hoofdstukken 6 en 7. In Hoofdstuk 6 werden verschillende fotoperiodes (24D:0L, 18D:06L, 12D:12L en 06D:18L) bestudeerd. Korte periodes van licht of geen licht (6L:18D en 0L:24D) resulteerden in een toename van de groei vergeleken met langere periodes van licht (18L:6D en 12L:12D). Bij deze langere periodes van licht vertoonden de vissen ook een toename in zwemactiviteit, meer aggressie (verwondingen op het lichaam) en hogere bloedplasma niveaus van lactaat, vrije vetzuren en cortisol vergeleken met vissen die gehouden werden onder kortere periodes van licht (0L:24D en 6L:18D). Wanneer het aantal uren licht gedurende een etmaal stijgt, leken de vissen meer gestresst en agressief te worden.In Hoofdstuk 7 werden de effecten van groepsgrootte en van de beschikbare zwemruimte bestudeerd op het gedrag van de vissen, de stressresponse en de groei. Bij Afrikaanse meerval (Clarias gariepinus) verbeterde de groei, nam zwemactiviteit toe en verminderde aggressie, stereotiepe gedragingen en cortisol niveaus naarmate de groepsgrootte toenam (aantal vissen per tank). Het verminderen van beschikbare zwemruimte verminderde de groei en de zwemactiviteit en liet bloedplasma cortisol niveaus toenemen. Verschillen in nutriIntbesteding en gedrag suggereerden dat de onderhoudsbehoeften aan voer van de vissen hoger waren bij vissen in beperkte ruimte en/of lage teeltdichtheid tengevolge van agonistisch gedrag en/of blootstelling aan stress. De benaming iteeltdichtheidi, gedefinieerd als het aantal vissen per eenheid ruimte, kan niet gebruikt worden als een criterium om systemen te evalueren of te vergelijken.Dit proefschrift heeft aangetoond dat kleine veranderingen in houderijcondities, zoals een verminderd aantal uur licht gedurende 24 uur en lage lichtintensiteit, de algemene omstandigheden voor de Afrikaanse meerval (Clarias gariepinus) kunnen verbeteren. In tegenstelling tot de algemeen heersende opvatting, verminderde een ihogei teeltdichtheid aggressie en verbeterde het de groei in Afrikaanse meerval. De hier gepresenteerde resultaten kunnen nuttig zijn om sommige aggressieproblemen op te lossen, groei te verbeteren en fysiologische reacties op stress te verminderen in de teelt van deze soort. Aan de andere kant is het bepalen van welzijn van de Afrikaanse meerval een moeilijke opgave, voornamelijk omdat resultaten tegenstrijdig kunnen zijn. Het meten van een enkele parameter, zoals gedrag, een fysiologische bloedparameter of een productieparameter, is niet voldoende om tot een objectieve beoordeling van het welzijn van vissen te komen. Een combinatie van deze drie soorten parameters zou echter wel kunnen helpen om het welzijn van vissen te begrijpen. Voorzichtigheid blijft echter noodzakelijk om geen verkeerde conclusies te trekken.Dit proefschrift kan daarom beschouwd worden als een eerste stap in de richting van de beoordeling van het welzijn van Afrikaanse meerval.
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