Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The abalone Haliotis midae is the most important aquaculture species in South
Africa. The industry is dependent on export to Far Eastern markets in a variety
of forms, including live, frozen, canned or dried. The species is considered
undomesticated in the sense that the current commercial broodstock has been
obtained from natural populations through a process of random collection.
Global competition has necessitated the South African industry to introduce a
genetic improvement program to increase biological productivity and financial
profitability.
The objective of this study was to assess the genetic variation and to estimate
key parameters in terms of growth and yield related traits, between family
groups that form part of the breeding program. The study reports on heritability
estimates of growth rate (0.14 ± 0.05), canning yield (0.08 ± 0.03), and drip loss
during live export (0.03 ± 0.02). The high genetic correlation (0.94 ± 0.34)
between shell length and live weight enables industry to utilise either weight or
shell length as a criteria during operational practices such as sorting, grading
and harvesting. The correlation of 0.85 ± 0.01 between live weight and canning
loss indicates that animals that weigh more have a lower dressing percentage.
Based on these low heritability values obtained for yield related traits it is
recommended not to include these traits in the selection program at this stage.
The findings of the study were however, compromised by the availability of a
limited number of family groups, the age differences between families and the
effect of different locations on the variance in phenotypes. Further investigation
is needed to confirm the credibility of the results. / AFRIKAANSE OPSOMMING: Die perlemoen Haliotis midae is die belangrikste akwakultuurspesie in Suid
Afrika. Die industrie is afhanklik van uitvoere na markte in die Verre Ooste. ‘n
Verskeidenheid van produkte word uitgevoer, insluitend lewendige, gevriesde,
gedroogte en verblikte perlemoen. Die spesie word as ongedomestikeerd
beskou aangesien die huidige teeldiere op ‘n lukrake wyse uit natuurlike
populasies versamel is. Globale kompetisie het die Suid Afrikaanse industrie
genoodsaak om ‘n genetiese verbeteringsprogram in werking te stel om
sodoende die biologiese produktiwiteit en finansiële winsgewendheid te
verbeter.
Die studie poog om genetiese variasie in groei en opbrengsverwante kenmerke
tussen familiegroepe wat deel uitmaak van die teelprogram te ondersoek.
Oorerflikheid van groeitempo (0.14 ± 0.05), opbrengs na verblikking (0.08 ±
0.03), en vogverlies na lewendige uitvoer (0.03 ± 0.02) is beraam. Die hoë
korrelasie (0.94 ± 0.34) tussen gewig en skulplengte stel die industrie in staat
om beide massa en skulplengte as kriteria te geruik tydens operasionele
praktyke van sortering, groepering en oes. Die korrelasie van 0.85 ± 0.01
tussen gewig en verlies na verblikking dui aan dat swaarder diere ‘n laer
uitslagpersentasie het.
As gevolg van die lae oorerflikheidswaardes vir opbrengsverwante kenmerke
word daar aanbeveel dat hierdie kenmerke nie op hierdie stadium ingesluit word
in die seleksieprogram nie. Resultate is egter beïnvloed deur ‘n beperkte aantal
familie groepe, ouderdomsverskille tussen families en die effek van verskillende lokaliteite op die variansie in die fenotipes. Verdere ondersoeke is nodig om die
geloofwaardigheid van die bevindinge te bevestig.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17781 |
| Date | 03 1900 |
| Creators | Van Schalkwyk, Hester Josina |
| Contributors | Brink, D., Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 81 p. : ill., map |
| Rights | Stellenbosch University |
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