Seasonal transboundary movements of Cape Hake (Merluccious Capensis) across the western coast of southern Africa
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Date
2018
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Publisher
University of Namibia
Abstract
This study was conducted to investigate the patterns of genetic differentiation of Cape hake (Merluccius capensis) across Southern Africa, using eight nuclear microsatellite markers to understand the seasonal movements of the two previously identified stocks. The aim of the project was to assess the position of the genetic break in two different temporal sampling events: summer months (February – March) and winter months (June – August) and to investigate the level of genetic diversity for 2017. Individual fishes were chosen randomly from a pool of samples, covering the distribution from the Cunene River Mouth, in northern Namibia, to Cape Town in South Africa. Six main sampling sites were chosen based on latitude and their relative position regarding known oceanographic breaks: Northern Namibia, Central Namibia, Southern Namibia, Orange River, Central West Coast and Southern West Coast. Total genomic DNA was extracted using a standard chlorophorm: isopropanol method of Backeljau, Dewachter &Winnepenninckx (1993). The Polymerase Chain Reaction (PCR) amplification of a fragment of the Control Region (CR) of the mtDNA was done for species validation. A total of 533 individuals were screened for genetic variation at eight nuclear microsatellite loci. The results shows an overall Fixation index (FST ) = 0.160 for summer and FST = 0.112 for winter, which were statistically significant different from zero (p<0.05). The overall genetic diversity was low, with expected heterozygosity (HE ) varying between 0.484 (southern West Coast) to 0.595 (southern Namibia), observed heterozygosity (HO) varied between 0.461 (Central West coast) to 0.537 (Central Namibia). Analyses of population distribution clines revealed differential seasonal movement across the Benguela region, with more northern migrants detected in the southern Benguela in the summer, and more southern migrants detected in northern Benguela in the winter. However, paired t-tests assessing statistical significance between population composition of summer and winter months were not statistically significant, suggesting that observed migration levels are low.
Description
A thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science in Biodiversity Management
Keywords
Cape hake, Merluccius capensis, Genetic deffrentiation, Benguela current