Browsing by Author "Yokwana, Sibusiso"

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    Genetic stock assessment of the Blue Bream, Pachymetopon aeneum (Pisces: Sparidae), a South African linefishery species, using microsatellite markers.
    (University of Fort Hare, 2024-07) Yokwana, Sibusiso; Gouws, G.; Vine, N.G.
    The blue bream (Pachymetopon aeneum) is a valuable species in South Africa's line fishery sector, necessitating effective management to ensure its preservation. This study utilised eight microsatellite markers to analyse the genetic diversity and structure of blue bream populations, providing insights to inform better management strategies. Microsatellites were selected for their effectiveness in assessing genetic diversity within and between populations below the species level. Given the species' vulnerability to overexploitation due to slow growth, late maturity, and protogynous hermaphroditism a comprehensive genetic stock assessment is critical. Samples were collected from 27 locations across the species' range between 2009 and 2015 by DAFF, fishing observers, and the Oceanographic Research Institute. These samples, recorded with details such as location, date, size, weight, and reproductive stage, were grouped into seven regions for robust analyses. This study aimed to determine the genetic diversity and structure of P. aeneum populations. DNA was extracted from samples, and eight microsatellite loci were amplified using fluorescently-dyed primers. Fragment analysis was conducted using the SANGER sequencer, and the fragment lengths were scored using the GeneMapper software, with quality control performed in Microchecker. Hardy-Weinberg equilibrium was assessed using Arlequin 3.5. Genetic diversity and population structure analyses were performed with GenAlex 6.5, Arlequin, and STRUCTURE 2.3.4. The results indicated high levels of genetic diversity and low inbreeding, suggesting random mating across the distribution range. AMOVA, PCoA, and Bayesian assignment identified two subpopulations. Relatedness and population assignment analyses supported these findings. Isolation by distance analysis showed no significant association between pairwise genetic differentiation and geographic distance. The evidence of two subpopulations suggests that management strategies for P. aeneum should be reconsidered. Further investigation with a larger sample size is recommended. Additionally, fishing trends should be monitored, as excessive local harvesting could impact the entire stock.