Quantifying the effect of inbreeding on the growth and yield of Mozambique Tilapia (Oreochromis mossambicus) over three generations of repeated full-sib mating

Akinoshun, Kolawole M. (2015-12)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

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.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/97852
This item appears in the following collections: