Browsing by Author "Van Schalkwyk, Hester Josina"

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    Assessment of yield traits between family groups of the cultured abalone (Haliotis midae) in South Africa
    (Stellenbosch : Stellenbosch University, 2012-03) Van Schalkwyk, Hester Josina; Brink, Danie; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
    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.