Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition
Successful aquaculture species are often chosen for their fast growth rates and fecundity, which are also characteristics of invasive species. The Pacific oyster Crassostrea gigas, which constitutes 80% of global oyster trade, has been confirmed as invasive in 17 of the 66 countries where it is cult...
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ftunstellenbosch:oai:scholar.sun.ac.za:10019.1/120891 2023-05-15T15:58:29+02:00 Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition Keightley, J. von der Heyden, S. Jackson, S. 2015-08-27T08:29:38Z 493992 bytes application/pdf http://hdl.handle.net/10019.1/120891 en eng NISC (Pty) Ltd and Taylor & Francis Keightley, J.; von der Heyden, S.; Jackson, S. (2015) Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition. African Journal of Marine Science, 37(1): 89-98 1814-232X http://hdl.handle.net/10019.1/120891 Cape rock oyster habitat suitability oyster invasivity shell density JournalArticles 2015 ftunstellenbosch 2021-08-31T00:09:41Z Successful aquaculture species are often chosen for their fast growth rates and fecundity, which are also characteristics of invasive species. The Pacific oyster Crassostrea gigas, which constitutes 80% of global oyster trade, has been confirmed as invasive in 17 of the 66 countries where it is cultured. The single study of its status in South Africa reported populations in six South Coast estuaries in 2001, dropping to three sites in 2003. We resurveyed these estuaries, visited others in the Eastern and Western Cape provinces, and sampled oyster tissue for molecular analyses of population structure. Pacific oysters have disappeared from Knysna and, following our collections, possibly also from the GouKou Estuary. Between 2003 and 2012, the Breede Estuary population decreased by 87%, from an estimated 184 206 to 23 760 individuals. Within this estuary, oysters 12 km upriver had denser shells and higher body condition indices than did those within 1.4 km of the river mouth, presumably reflecting higher availability of suspended organic matter. However, low salinity over most of the species’ range in the estuary probably inhibits recruitment. New populations of Pacific oysters in the Swartkops and Kaaimans estuaries urgently require monitoring and eradication. Haplotype (h) and nucleotide (π) diversities across all oyster populations sampled (h =0.2300 [SD 0.0595], π = 0.0006 [SD 0.0007]) were lower than those of co-occurring indigenous Cape rock oysters Striostrea margaritacea from the GouKou and Breede estuaries (h = 0.9076 [SD 0.0386], π = 0.00589 [SD 0.00347]). Pacific oysters either have been introduced to South African estuaries infrequently, or have experienced genetic bottlenecks following river floods or human exploitation, or both. Populations growing outside culture infrastructure are restricted to estuaries in the Eastern and Western Cape provinces, with no evidence of occurrence in fully marine shelf environments. Given the species’ considerable socio-economic importance, estuarine and coastal surveillance coupled with aquaculture zoning are required to integrate biodiversity and food security considerations. Other/Unknown Material Crassostrea gigas Pacific oyster Stellenbosch University: SUNScholar Research Repository Pacific |
institution |
Open Polar |
collection |
Stellenbosch University: SUNScholar Research Repository |
op_collection_id |
ftunstellenbosch |
language |
English |
topic |
Cape rock oyster habitat suitability oyster invasivity shell density |
spellingShingle |
Cape rock oyster habitat suitability oyster invasivity shell density Keightley, J. von der Heyden, S. Jackson, S. Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition |
topic_facet |
Cape rock oyster habitat suitability oyster invasivity shell density |
description |
Successful aquaculture species are often chosen for their fast growth rates and fecundity, which are also characteristics of invasive species. The Pacific oyster Crassostrea gigas, which constitutes 80% of global oyster trade, has been confirmed as invasive in 17 of the 66 countries where it is cultured. The single study of its status in South Africa reported populations in six South Coast estuaries in 2001, dropping to three sites in 2003. We resurveyed these estuaries, visited others in the Eastern and Western Cape provinces, and sampled oyster tissue for molecular analyses of population structure. Pacific oysters have disappeared from Knysna and, following our collections, possibly also from the GouKou Estuary. Between 2003 and 2012, the Breede Estuary population decreased by 87%, from an estimated 184 206 to 23 760 individuals. Within this estuary, oysters 12 km upriver had denser shells and higher body condition indices than did those within 1.4 km of the river mouth, presumably reflecting higher availability of suspended organic matter. However, low salinity over most of the species’ range in the estuary probably inhibits recruitment. New populations of Pacific oysters in the Swartkops and Kaaimans estuaries urgently require monitoring and eradication. Haplotype (h) and nucleotide (π) diversities across all oyster populations sampled (h =0.2300 [SD 0.0595], π = 0.0006 [SD 0.0007]) were lower than those of co-occurring indigenous Cape rock oysters Striostrea margaritacea from the GouKou and Breede estuaries (h = 0.9076 [SD 0.0386], π = 0.00589 [SD 0.00347]). Pacific oysters either have been introduced to South African estuaries infrequently, or have experienced genetic bottlenecks following river floods or human exploitation, or both. Populations growing outside culture infrastructure are restricted to estuaries in the Eastern and Western Cape provinces, with no evidence of occurrence in fully marine shelf environments. Given the species’ considerable socio-economic importance, estuarine and coastal surveillance coupled with aquaculture zoning are required to integrate biodiversity and food security considerations. |
format |
Other/Unknown Material |
author |
Keightley, J. von der Heyden, S. Jackson, S. |
author_facet |
Keightley, J. von der Heyden, S. Jackson, S. |
author_sort |
Keightley, J. |
title |
Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition |
title_short |
Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition |
title_full |
Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition |
title_fullStr |
Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition |
title_full_unstemmed |
Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition |
title_sort |
introduced pacific oysters crassostrea gigas in south africa: demographic change, genetic diversity and body condition |
publisher |
NISC (Pty) Ltd and Taylor & Francis |
publishDate |
2015 |
url |
http://hdl.handle.net/10019.1/120891 |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
Crassostrea gigas Pacific oyster |
genre_facet |
Crassostrea gigas Pacific oyster |
op_relation |
Keightley, J.; von der Heyden, S.; Jackson, S. (2015) Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition. African Journal of Marine Science, 37(1): 89-98 1814-232X http://hdl.handle.net/10019.1/120891 |
_version_ |
1766394227528302592 |