Culture potential and population structure of the indigenous oysters Striostrea margaritacea and Saccostrea cucullata in South Africa

• Main Author: Keightley, Jenna
• Other Authors: Jackson, Susan, Von der Heyden, Sophie, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
• Format: Thesis
• Language: English
• Published: Stellenbosch : Stellenbosch University 2016
• Subjects: Oyster culture > South Africa; Striostrea margaritacea > South Africa > Genetics; Saccostrea cucullata > South Africa > Genetics; Striostrea margaritacea > South Africa > Diversity; Saccostrea; cucullata > South Africa > Diversity; Spat settlement > Effect of harmful algal blooms on; UCTD; Pacific; Westbrook; Crassostrea gigas; Pacific oyster
• Online Access: http://hdl.handle.net/10019.1/100416

Thesis (MSc)--Stellenbosch University, 2016. ENGLISH ABSTRACT: Oyster culture has a long standing history with mankind and movement of indigenous oysters, in South Africa, dates back to the 1600s. Crassostrea gigas (the Pacific oyster) accounts for 80% of global oyster culture and is the sole oyster species cultured in South Africa. Marine environments are vulnerable to invasion, not only by the introduced species but also their associated epifaunal organisms and parasites, as well as the potential for intraspecific disease transmission between introduced and indigenous species. The culture of indigenous oysters, within their range, could reduce these risks as well as relieve commercial harvesting pressure on the current wild stocks. Of South Africa’s five indigenous oysters the two most palatable ones were chosen for this study, Striostrea margaritacea (Cape rock oyster) and Saccostrea cucullata (Natal rock oyster). To develop a new culture species requires knowledge of population densities, distribution, biology, growth rates, and settlement success. To minimize the potential impact of such mariculture, genetic structure and diversity should also be examined. This study focused on genetic structure and diversity, as well as spat settlement and the impact of a Harmful Algal Bloom on spat settlement. Samples of S. margaritacea were taken from five equidistant locations throughout the species’ range in South Africa, from the Breede River to Westbrook in KwaZulu-Natal; the same was done for S. cucullata from three equidistant locations from Mtakatye in the Eastern Cape up to Umdloti in KwaZulu-Natal. Genetic analyses assessed the CO1 and 16S mtDNA gene regions and both showed that S. margaritacea populations have relatively high genetic diversity and high levels of gene flow along South Africa’s coastline (Fst>0.02, p>0.05 in both cases). The populations that were thought to be S. cucullata have a high level of fixation between populations for CO1 and 16S (Fst>0.86 in both cases, p<0.01); the fact ...