Spelling suggestions: "subject:"mozambique tilapia"" "subject:"mozambique tilapias""
1 |
Growth regulation in the euryhaline tilapia, Oreochromis mossambicus effects of gonadal steroid hormones and salinity on the growth hormone/insulin-like growth factor-I axis /Riley, Lawrence G. January 2003 (has links)
Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 97-121).
|
2 |
An investigation of the survival level of Oreochromis mossambicus fry variably kept in a closed system : laboratory experiment /Asgodom, Mihretu T. January 2005 (has links)
Thesis (MPhil)--University of Stellenbosch, 2005. / On t.p.: Master of Philosophy in Livestock Industry Management (Aquaculture) Bibliography. Also available via the Internet.
|
3 |
Die morfologie, histologie en ultrastruktuur van die pankreas, lewer en galblaas van die algvoeder Oreochromis mossambicus (Peters)Geyer, Hendrik Jacobus 19 November 2014 (has links)
D.Sc. / Please refer to full text to view abstract
|
4 |
The ontogeny and morphology of the upper pharyngeal pad of Oreochromis mossambicus (Peters) and its possible role in the rearing of young01 September 2015 (has links)
Ph.D. / The declining marine fish catches and the increasing demand for farmed fresh water fishes are motivation for research and development of improved strains and techniques for the production of gynogenetic and triploid offspring of popular fresh water fishes ...
|
5 |
'n Vergelykende ondersoek van die morfologie en ultrastruktuur van die maag en maagwand van die algvoeder Oreochromis mossambicus (Peters) en die roofvis Hydrocynus forskahlii Cuvier19 November 2014 (has links)
D.Sc. / Please refer to full text to view abstract
|
6 |
A contribution to the biology of Tilapia mossambica Peters in Lake Sibaya, South AfricaBruton, Michael N January 1973 (has links)
An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Previous work on Tilapia in Lake Sibaya is reviewed. Apart from brief gillnet surveys, which recorded the species' presence, no research on T. mossambica had been performed at Lake Sibaya before the two-year study of Minshull who collected data on food preferences, depth distribution of juveniles and breeding biology of adults. The main physiographical features of the lake are outlined. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1-7 m deep. Adult fishes (over 8 cm SL) are usually absent from water deeper than 12 m and shallower than 0.5 m, whereas juveniles may occur at all depths, and fry only in very shallow water. T. mossambica inhabits the littoral in the warm and transition periods (August to April) but moves into deep water in the cool season (May to July). Exposed and sheltered shallow areas are utilised for different purposes by adult fishes, the former for nesting, and the latter for feeding and mouth-brooding. Habitat selection by males was governed by nest site selection. Habitat Nests were most common in sheltered, sparsely vegetated littoral and sublittoral areas, but also present in well-vegetated sheltered areas. Breeding females preferred sheltered littoral areas but ventured onto the terrace to release the young. Juvenile and fry T. mossambica inhabited shallow exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour of T. mossambica is described, and integrated with data on T. mossambica from other systems. The breeding season spans seven months. Shoaling takes place in shallow water probably as a means of protection. T. mossambica is an omnivorous feeder relying largely on diatoms. The main predator is probably the barbel Clarias gariepinus, but avian predators may be more important. A method whereby the time of formation of rings on the scales of T. mossambica is described. The fishes were found to reach maturity after one year at a length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 14 cm (females) and 17 cm (males). The maximum final size was about 24 cm SL. An estimate of the standing crop for fishes in the littoral and subiittoral areas of the eastern and southern shores of the south basin is given. The data were derived from a mark and recapture The biology of T. mossambica in Lake Sibaya as revealed by the present study is discussed with reference to data on the same and similar species in other systems. The utilis ation of the available resources in the lake by T. mossambica is commented upon, and reference is made to the significance of stunting, and the import ance of the retention of generalised characters for the successful habitation of the cyclically-renewed habitat of the littoral. Precocious breeding in T. mossambica is regarded as a functional adaptation which increases the proportion of fishes small enough to utilise the rich food resources in shallow water.
|
7 |
The effect of the pesticide, endosulfan, on hepatic cytochrome P-450, liver and gill ultrastructure, and selected haematological parameters of Oreochromis Mossambicus (Peters, 1852) (Pisces : Cichlidae)Quick, Arthur Joseph Rex January 1986 (has links)
Two possible ways in which fish may acclimate to prolonged exposure· to sublethal levels of endosulfan were investigated: induction of the hepatic monooxygenase system and changes in haematology. These studies also involved an examination of the ultrastructure of liver and gill tissue. Endosulfan caused none of the characteristic phenobarbital-type inductive effects on the liver of Oreochromis mossambicus. There was no increase in cytochrome P-450 levels, microsomal protein or hepatosomatic index. The reasons for the lack of induction are discussed. The effect of endosulfan on the following haematological parameters was determined: haemoglobin, erythrocyte count, microhaematocrit, mean erythrocyte volume and mean erythrocyte haemoglobin concentration. The only effect was an increase in erythrocyte count. The value of changes in haematological parameters as indicators of pollutioninduced anemia in the field is discussed. No changes in gill ultrastructure were noted although electron micrographs of liver tissue showed lesions in hepatocytes. The diagnostic value of pollution-induced pathological changes on cell ultrastructure are discussed. Recommendations are made with regard to future large scale application of pesticides on or near large water bodies
|
8 |
Behavioural, reproductive and growth studies on Oreochromis mossambicus (Peters 1852)Weber, Raimund Michael. January 2010 (has links)
A major obstacle facing the successful creation of an African aquaculture industry, based upon Oreochromids, is the irregular supply of good quality fish seed. There are several causative biological processes behind its irregular supply. The aim of this research was therefore to determine the basic requirements for the establishment and maintenance of a small breeding facility, for O. mossambicus. The goal was to make a unit that was simple and which could be easily replicated in rural, satellite aquaculture seed stations. The results obtained illustrate that a small reproduction unit can produce large quantities of healthy 90-day fry.
Asynchronous hatching of the eggs and spawning asynchrony in female Oreochromis mossambicus are two elements which negatively affect uniformity in the fry produced. Typical fish seed production uses large ponds partitioned into breeding allotments or a series of breeding pools. While the earthen ponds provide a substrate in which a nest can be excavated, its presence is not required for mating success in the closely related O. niloticus (Linneaus 1758). Female mate choice, as well as apparent fecundity, according to nest size has been clearly recorded in related cichlids but no investigations have been made as to nest size and spawning synchrony in O. mossambicus. The main focus of this investigation was to ascertain whether O. mossambicus would accept artificial nest substitutes in preference to their own constructed ones and secondly, whether different alternatives would elicit different levels of acceptance. The observed results indicate a ready acceptance for artificial nest alternatives, with nest lip height being prioritised by the fish . The implications thereof are discussed in relation to the potential for optimization of breeding arenas for O. mossambicus by the provision of artificial nests whose dimensions satisfy both male and female preferences.
In established communities, Oreochromis mossambicus display various complex and ritualised behaviours during stable and disruptive events. The aim of this research was primarily to produce a glossary of behaviours defining these interactions, particularly with reference to male-male behaviours. Three males and six females were allowed to acclimatise over one month, with various social groupings being established within the first few days. Results from this study illustrated not only a dynamic social structure, signaled via various chemosensory and visual methods, but also supported recent findings in apparent male-male courtship and the underlying
ii
causes. Furthermore, the observed male-male activity of the nestholder malesfirmly corroborate the current practice in aquaculture whereby only one male is allocated per breeding arena.
The use of artificial incubation of Oreochromis spp. eggs has become widespread in high intensity fish seed production. Various types of incubator exist, and their selection is dependent on the specific attributes of the egg to be incubated. Currently available incubators are typically of a funnel (up-flow) or round bottomed (down-flow) design. Neither permits easy access to the eggs, which is particularly important when dealing with poor quality water as is typically found in rural areas. The aim of this study was to devise and test an easy-to-use incubator, applicable to rural seed production projects, which offers advantages over currently available incubator types. The final design, WETNURSE Type II, offered improved hatching rates over Type I, with a mean hatching success of 75%. While falling short of the desired 80% success rate (Rana 1986), the various other benefits provided by the design justify further optimization and testing.
Three distinct populations of O. mossambicus, representing populations of inbred, randomly mated and genetically unknown (wild-caught) pedigree were analysed according to their food conversion efficiency (FCE). The intra- and inter-sample crosses were done with single males in order to produce half-sib progeny batches which allowed for the assessment of sire influences on the FCE of the progeny batches. The results show that the population of unknown pedigree is comparable to that of the randomly mating population, indicating the presence of sufficient genetic variation to permit further selection; the genetic contribution of the males to their respective progeny was insignificant in relation to that made by the female.
|
9 |
An analysis of population structure using microsatellite DNA in twelve Southern African populations of the Mozambique tilapia, Oreochromis mossambicus (Peters)Hall, Edward G. 12 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: DNA micro satellite loci express extensive allelic variation making them convenient markers for
research in many fields employing population genetic tools, including aquaculture and conservation
genetics. Twelve Oreochromis mossambicus populations from wild, captive and introduced sources
in Southern Africa were screened for genetic variation at ten CA repeat micro satellite loci. Three of
the loci - UNHI04, UNHlll, and UNH123 - were sufficiently well resolved to screen extensively
and were interpreted according to a model of Mendelian inheritance. Data was analyzed in terms of
genetic structure and levels of genetic variation, the effect of management regime in captivity
through successive generations on genetic diversity, and the nature of phylogenetic relationships
present between populations.
Exact tests, carried out using Monte Carlo type multiple resampling techniques, and F-Statistics
were used to detect and quantify genetic structure among the twelve populations. The Exact test X2
(P < 0.001), a FST of 0.27 (P < 0.001), eST of 0.26, RsT of 0.28, and a <l>ST of 0.17 all indicated
significant structuring among the populations. The evident genetic structuring endorsed the practice
of maintaining the populations as separate genetic stocks, in separate tanks, in order to preserve
unique genetic material for aquaculture strain development.
Populations also exhibited some significant deviations from Hardy Weinberg equilibrium
characterised by an overall reduced heterozygosity across the loci. In microsatellite studies, null
alleles are often suggested as major contributors to heterozygote deficits. To test for null alleles,
two controlled crosses of 0. mossambicus were made. The progeny from each cross were examined
for expected parental allelic ratios at the UNHI04, UNHlll and UNH123 loci. All three loci
presented evidence of possible null alleles.
Accelerated inbreeding and genetic drift through successive generations in captivity can reduce
heterozygosity and gene diversity. To investigate loss of diversity a sample taken from the
Bushmans population in 1999 (N = 25) was compared with a Bushmans 2000 sample (N = 36). The
comparison highlighted altered allele frequencies, a significant increase in average observed
heterozygosity and a non-significant change in average expected heterozygosity using the UNHI04
and UNH123 loci.
Calculation of genetic distances and phylogenetic comparisons between the populations provided
insight into the degree of management required in conserving genetic diversity in natural
populations of Mozambique tilapia. UPGMA and Neighbour-Joining techniques were used to
construct phylogenetic trees using Dm and ({)~)2 distance matrices. Clustering of populations
appeared to reflect geographic locality of the source populations, however certain populations were
not congruent with geography. Mantel tests were used to expose a possible association between
genetic distance matrices generated from each individual locus. An association would support a geographic background to population genetic structure. The Mantel tests did not provide conclusive
evidence. Mantel tests for association between the combined locus Dm and (81l)2 genetic distance
matrices and a geographic distance matrix were similarly non-significant.
Multi-dimensional scaling (MDS) plots of Euclidean distance values for Dm and (81l)2 matrices
presented a two-dimensional view of the genetic distance data. The degree of similarity with the
UPGMA and Neighbour-Joining tree-clustering pattern was higher for the (81l)2 than for the Dm
MDS plots. Scatter plots indicated a reliable non-linear correlation between Euclidean distance and
genetic distance for the two-dimensional MDS.
The micro satellite markers employed in this research provided molecular information needed for
complimenting a co-study on quantitative genetic evaluation of the twelve populations. The
quantitative co-study provided measures of average length and weight gain indices for the
populations based on progeny growth trials. No significant correlation of average heterozygosity
(gene diversity) with either average weight or length gain was found.
The significant genetic diversity and structure present between the twelve populations provided
rationale for implementing strategies to conserve natural 0. mossambicus populations as genetic
resources, and manage captive populations for long term maintenance of genetic diversity. / AFRIKAANSE OPSOMMING: Die verstaffing van groot alleliese variasie deur DNA mikrosateliete maak van hulle gerieflike
merkers vir navorsing in 'n verskeidenheid van velde wat gebruik maak van populasie genetiese
gereedskap, ingesluit akwakultuur en bewarings genetika. Twaalf 0. mossambicus populasies wat
verkry was vanuit die natuur, in gevangeneskap en ingevoerdes, van Suidelike Afrika was getoets
vir genetiese variasie by tien verskillende CA-herhalende mikrosateliet loci. Drie van die loci -
UNHI04, UNHlll en UNH123 - is op grootskaal getoets en volgens In model van Mendeliese
oorerwing geinterpreteer. Die data was ontleed volgens genetiese struktuur en vlakke van genetiese
variasie, die effek wat bestuur strategie in gevangeneskap op genetiese diversiteit in opeenvolgende
generasies uitgeoefen het, so wel as die aard van die filogenetiese verhoudings wat teenwoordig is
tussen die populasies.
"Exact" toetse is uitgevoer deur gebruik te maak van Monte Carlo tipe veelvuldige
hermonsterinsamelings tegnieke en F-statistieke is gebruik vir die deteksie en kwantifisering van
die genetiese struktuur tussen die twaalfpopulasies. Die Exact toets X2 (P < 0.001), 'n FST van 0.27
(P < 0.001), SST van 0.26, RsT van 0.28, en 'n <DST van 0.17 gee almal 'n indikasie van
betekenisvolle strukturering tussen die populasies. Die genetiese struktuur bevestig die beleid dat
die populasies behou moet word as aparte genetiese voorraad, in aparte tenke, om te verseker dat
die unieke genetiese materiaal behoue bly om akwakultuur variante te ontwikkel.
Populasies het ook betekenisvolle verskuiwings van die Hardy Weinberg ekwilibrium getoon, wat
gekarakteriseer word deur 'n algemene verlaging van heterosigositeit oor die loci. Nul allele word
dikwels aanbeveel om in mikrosateliet studies groot bydraes te maak tot hetersigotiese defekte. Om
vir nul allele te toets was twee gekontroleerde kruisings van 0. mossambicus gemaak. Die nageslag
van elke kruising was getoets vir verwagte ouer alleliese verhoudings by die UNHI04, UNHlll en
UNH123 loci. Al drie loci het getoon dat dit moontlike nul allele kan wees.
Versnelde inteling en genetiese drywing deur opeenvolgende generasies in gevangeneskap kan die
heterosigositeit en diversiteit verminder. Om die vermindering van diversiteit te toets was 'n
monster van die Busmans 1999 (N=25) populasie vergelyk met 'n monster van die Bushmans 2000
(N=36) populasie. Die vergelyking het veranderde alleel frekwensies, 'n betekenisvolle vermeerding
in gemiddelde waargeneemde heterosigositeit en 'n onbetekenisvolle verandering in gemiddelde
verwagte heterosigositeit getoon deur gebruik te maak van die UNHI04 en UNH123 loci.
Berekening van genetiese afstande en filogenetiese vergelykings tussen die populasies het nuwe
insig gegee oor die graad van bestuur wat nodig is om genetiese diversiteit in die natuurlike
populasies van 0. mossambicus tilapia te behou.UPGMA en Neighbour-Joining tegnieke was
gebruik om filogenetiese bome op te stel deur gebruik te maak van Dm en (OIl)2 afstand matrikse.
Populasie bondeling het geblyk om geografiese lokaliteit van die bron populasies te toon, alhoewel van die populasies nie met die geografiese lokaliteit ooreengestem het nie. Mantel toetse is gebruik
om 'n moontlike assosiasie tussen genetiese afstand matrikse wat verkry is van elke loci bloot te
stel. 'n Assosiasie sou 'n geografiese agtergrond tot populasie genetiese struktuur steun. Oortuigende
bewys is nie deur die Mantel toetse verskaf nie. Mantel toetse vir assosiasie tussen die
gekombineerde loci Dm en (OJ..l)2 genetiese afstand matrikse en In geografiese afstand matriks was
ook onbetekenisvol.
'n Tweedimensionele beskouing van die genetiese afstand data is voorgestel deur multidimensionele
skaal (MDS) grafieke van Euclidean afstand waardes van die Dm en (OJ..l)2 matrikse te
teken. Die graad van ooreenstemming met die UPGMA en Neighbour-Joining boom samevoeging
patroon was hoër vir die (OJ..l)2 as vir die DmMDS grafieke. Verspreiding grafieke het 'n vertroubare
nie-liniêre korrelasie tussen Euclidean afstande en genetiese afstande vir die twee-dimensionele
MDS grafieke getoon.
Die mikrosateliet merkers wat in die studie gebruik was het molekulêre informasie verskaf wat
nodig is vir 'n komplimentêre studie oor die kwantitatiewe genetiese evalueering van dié twaalf
populasies. Die kwantitatiewe studie het afmetings van gemiddelde lengte en gewig vermeerdering
van die populasies verskaf gebaseer op nageslag proewe. Geen betekenisvolle korrelasie van
gemiddelde hetersigositeit (geen diversiteit) was getoon met óf gemiddelde gewig óf lengte
vermeerdering.
Die betekenisvolle genetiese diversiteit en struktuur teenwoordig tussen die twaalf populasies het
rede gegee om strategieë te implimenteer om natuurlike 0. mossambicus populasies te konserveer
as genetiese bronne en om populasies in gevangeneskap te bestuur vir langtermyn instandhouding
van genetiese diversiteit.
|
10 |
Quantifying the effect of inbreeding on the growth and yield of Mozambique Tilapia (Oreochromis mossambicus) over three generations of repeated full-sib matingAkinoshun, Kolawole M. 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The effects of acute inbreeding on growth performance, yield and occurrence of deformity traits were studied in experimental full-sibling inbred populations of Mozambique tilapia Oreochromis mossambicus at three levels of inbreeding coefficients, namely F = 0.000, F = 0.250 and F = 0.375. The base population with F = 0.000 was established through the crossing of two geographically separated and genetically unrelated farm stocks. At each generation, the inbreeding depression indicated by body weight (BW), standard length (SL), specific growth rate (SGR) and yield were highly significant, but no linear relationship was found between level of inbreeding and inbreeding depression. Both condition factor (K) and the number of observed deformities appears not to be significantly affected by inbreeding at all three levels.
Over all, the average inbreeding depression at F = 0.250 and F = 0.375 respectively was found to be 46.5 percent and 46.6 percent for body weight (BW); 18.2 percent and 18.0 percent for standard length (SL); 21.8 percent and 20.3 percent for specific growth rate (SGR) and 5.752 percent and 8.940 percent for flesh yield. The outbred Control group differed significantly (P<0.05) from the six inbred family groups in terms of body weight (BW), standard length (SL), specific growth rate (SGR) and yield at all levels of inbreeding studied (F = 0.000, F = 0.250 and F = 0.375).
Average inbreeding depression for body weight (BW) amongst the six inbred families ranged from 39.6 to 54.2 percent at F = 0.250 (in Gen 2) and 45.6 to 47.3 percent at F = 0.375 (in Gen 3). The inbreeding depression coefficient for body weight (BW) per 10% increase in F, amongst the six inbred families, ranged from 15.9 to 21.7 percent at F = 0.250 and from 12.2 to 12.6 percent at F = 0.375.
Average inbreeding depression for standard length (SL) amongst the six inbred families ranged from 14.0 to 22.3 percent at F = 0.250 and from 17.2 to 18.4 percent at F = 0.375.
The inbreeding depression coefficient for standard length (SL) amongst the six inbred families ranged from 5.6 to 8.9 percent at F = 0.250 and from 4.6 to 4.9 percent at F = 0.375.
Average inbreeding depression for specific growth rate (SGR) amongst the six inbred families ranged from 17.9 to 27.9 percent at F = 0.250 and from 16.7 to 27.2 percent at F = 0.375. The inbreeding depression coefficient amongst the six inbred families ranged from 7.2 to 11.2 percent at F = 0.250 and from 4.5 to 7.3 percent at F = 0.375.
Average inbreeding depression for yield amongst the six inbred families ranged from 0.4 to 7.7 percent at F = 0.250 and from 8.5 to 10.2 percent at F = 0.375. The inbreeding depression coefficient for yield amongst the six inbred families ranged between 0.2 and 3.1 percent at F = 0.250 and from 2.3 to 2.7 percent at F = 0.375.
The condition factor (K) of the six inbred families showed no significant differences to the Control (P > 0.05) at all levels of inbreeding with K-values ranging from 1.42 to 2.85.
The occurrence of morphological deformities in all seven family groups including the Control showed no noticeable trend, with a random, nonlinear occurrence of fluctuating asymmetry observed at different inbreeding levels in O. mossambicus.
This study demonstrates that inbreeding has a significant negative effect on the production traits of Oreochromis mossambicus, especially growth. Results from this study emphasize the need to create awareness amongst small scale farmers of the importance of preventing uncontrolled inbreeding in production systems, as well as to monitor inbreeding levels during the process of dissemination of improved fish strains to small scale fish growers in developing countries, including Africa. / AFRIKAANSE OPSOMMING: Die gevolge van akute inteling op die groei prestasie, opbrengs en voorkoms van misvorming eienskappe bestudeer in eksperimentele full-broer ingeteelde bevolkings van Mosambiek tilapia Oreochromis mossambicus op drie vlakke van inteling koëffisiënte, naamlik F = 0,000, F = 0,250 en F = 0,375. Die basis bevolking F = 0,000 gestig deur die kruising van twee geografies geskei en geneties onverwant plaas aandele. Op elke generasie, die inteling depressie aangedui deur die liggaam gewig (BW), standaard lengte (SL), spesifieke groeitempo (SGR) en opbrengs was hoogs betekenisvol, maar geen lineêre verband is gevind tussen vlak van inteling en inteling depressie. Beide toestand faktor (K) en die aantal waargeneem deformiteite verskyn om nie beduidend beïnvloed deur inteling op al drie vlakke.
Oor alles is, die gemiddelde inteling depressie by F = 0,250 en F = 0,375 onderskeidelik gevind om 46,5 persent en 46,6 persent vir die liggaam gewig (BW) wees; 18,2 persent en 18,0 persent vir standaard lengte (SL); 21,8 persent en 20,3 persent vir spesifieke groeitempo (SGR) en 5,752 persent en 8,940 persent vir vlees opbrengs. Die outbred beheer betekenisvol verskil (P <0,05) van die ses ingeteelde familie groepe in terme van die liggaam gewig (BW), standaard lengte (SL), spesifieke groeitempo (SGR) en opbrengs op alle vlakke van inteling bestudeer (F = 0,000 , F = 0,250 en F = 0,375).
Gemiddeld inteling depressie vir die liggaam gewig (BW) onder die ses ingeteelde families gewissel 39,6-54,2 persent by F = 0,250 (in Gen 2) en 45,6-47,3 persent by F = 0,375 (in Gen 3). Die inteling depressie koëffisiënt vir die liggaam gewig (BW) per 10% toename in F, onder die ses ingeteelde families, het gewissel 15,9-21,7 persent by F = 0,250 en 12,2-12,6 persent by F = 0,375.
Gemiddeld inteling depressie vir standaard lengte (SL) onder die ses ingeteelde families gewissel 14,0-22,3 persent by F = 0,250 en 17,2-18,4 persent by F = 0,375. Die inteling depressie koëffisiënt vir standaard lengte (SL) onder die ses ingeteelde families gewissel 5,6-8,9 persent by F = 0,250 en 4,6-4,9 persent by F = 0,375.
Gemiddeld inteling depressie vir spesifieke groeitempo (SGR) onder die ses ingeteelde families gewissel 17,9-27,9 persent by F = 0,250 en 16,7-27,2 persent by F = 0,375. Die inteling depressie koëffisiënt onder die ses ingeteelde families gewissel 7,2-11,2 persent by F = 0,250 en 4,5-7,3 persent by F = 0,375.
Gemiddeld inteling depressie vir opbrengs onder die ses ingeteelde families het gewissel van 0,4-7,7 persent by F = 0,250 en 8,5-10,2 persent by F = 0,375. Die inteling depressie koëffisiënt vir opbrengs onder die ses ingeteelde families gewissel tussen 0,2 en 3,1 persent by F = 0,250 en 2,3-2,7 persent by F = 0,375.
Die toestand faktor (K) van die ses ingeteelde families het geen betekenisvolle verskille op die Beheer (P> 0,05) op alle vlakke van inteling met K-waardes wissel 1,42-2,85.
Die voorkoms van morfologiese afwykings in al sewe familie groepe, insluitend die beheer het geen merkbare neiging, met 'n ewekansige, nie-lineêre voorkoms van wisselende asimmetrie waargeneem op verskillende vlakke in inteling O. mossambicus.
Hierdie studie toon dat inteling het 'n beduidende negatiewe uitwerking op die produksie-eienskappe van Oreochromis mossambicus, veral groei. Resultate van hierdie studie beklemtoon die noodsaaklikheid om bewustheid onder kleinboere van die belangrikheid van die voorkoming van onbeheerde inteling in die produksie stelsels, sowel as om te monitor inteling vlakke tydens die proses van verspreiding van verbeterde vis stamme klein skaal vis produsente in ontwikkelende lande te skep, insluitend Afrika.
|
Page generated in 0.0598 seconds