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...
Main Authors: | , , |
---|---|
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
NISC
2016
|
Subjects: | |
Online Access: | http://www.ajol.info/index.php/ajms/article/view/141159 |
id |
ftjafricanj:oai:ojs.ajol.info:article/141159 |
---|---|
record_format |
openpolar |
spelling |
ftjafricanj:oai:ojs.ajol.info:article/141159 2023-05-15T15:58:31+02:00 Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition Keightley, J Heyden, S von der Jackson, S 2016-08-01 application/pdf http://www.ajol.info/index.php/ajms/article/view/141159 eng eng NISC http://www.ajol.info/index.php/ajms/article/view/141159/130890 http://www.ajol.info/index.php/ajms/article/view/141159 Copyright for articles published in this journal is retained by the publisher. African Journal of Marine Science; Vol 37, No 1 (2015); 89–98 1814-232X Cape rock oyster habitat suitability oyster invasivity shell density info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Peer-reviewed Article 2016 ftjafricanj 2017-03-05T06:28:11Z 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. Keywords: Cape rock oyster, habitat suitability, oyster invasivity, shell density Article in Journal/Newspaper Crassostrea gigas Pacific oyster AJOL - African Journals Online Pacific |
institution |
Open Polar |
collection |
AJOL - African Journals Online |
op_collection_id |
ftjafricanj |
language |
English |
topic |
Cape rock oyster habitat suitability oyster invasivity shell density |
spellingShingle |
Cape rock oyster habitat suitability oyster invasivity shell density Keightley, J Heyden, S von der 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. Keywords: Cape rock oyster, habitat suitability, oyster invasivity, shell density |
format |
Article in Journal/Newspaper |
author |
Keightley, J Heyden, S von der Jackson, S |
author_facet |
Keightley, J Heyden, S von der 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 |
publishDate |
2016 |
url |
http://www.ajol.info/index.php/ajms/article/view/141159 |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
Crassostrea gigas Pacific oyster |
genre_facet |
Crassostrea gigas Pacific oyster |
op_source |
African Journal of Marine Science; Vol 37, No 1 (2015); 89–98 1814-232X |
op_relation |
http://www.ajol.info/index.php/ajms/article/view/141159/130890 http://www.ajol.info/index.php/ajms/article/view/141159 |
op_rights |
Copyright for articles published in this journal is retained by the publisher. |
_version_ |
1766394274368192512 |