Reassessing the invasion of South African waters by the European shore-crab Carcinus maenas

Reassessing the invasion of South African waters by the European shore-crab Carcinus maenas

The European shore-crab Carcinus maenas has been present in South Africa since 1983. Despite this species' international reputation as a biological invader, its distribution in this region has only been considered by three outdated 'snapshot surveys.' The present study is the most com...

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Bibliographic Details
Published in:African journal of marine science Vol. 39; no. 3; pp. 259 - 267
Main Authors: Mabin, CA, Wilson, JRU, Le Roux, JJ, Robinson, TB
Format: Journal Article
Language:English
Published: Grahamstown Taylor & Francis 25-10-2017
Taylor & Francis Ltd
Subjects:
Accumulators
Biological settlement
Carcinus maenas
Crabs
Crustaceans
Demographics
Demography
Detection
Harbors
harbour populations
Harbours
intertidal survey
Introduced species
invasive species
Marine crustaceans
marine invasions
Polls & surveys
population status
Populations
postlarval settlement
reproductive seasonality
Seasonal variations
Seasonality
subtidal survey
Surveys
South Africa
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Summary:The European shore-crab Carcinus maenas has been present in South Africa since 1983. Despite this species' international reputation as a biological invader, its distribution in this region has only been considered by three outdated 'snapshot surveys.' The present study is the most comprehensive to date, providing an update on the species' range and the first temporal assessment of its abundance and demographics. Along South Africa's Cape Peninsula and surrounding areas, C. maenas was absent from 12 intertidal sites surveyed, except for Sea Point, and no crabs were found during subtidal surveys along the open coastline. Subtidal harbour populations were recorded in the Cape Town harbours of Table Bay and Hout Bay (previously estimated as comprising approximately 164 200 and 6 500 individuals, respectively). Table Bay was surveyed monthly for one year, using baited traps, crab condos and postlarvae settlement collectors, to assess size distributions and reproductive seasonality of the crab. Reproductive females were recorded throughout most of the year. These results suggest that the harbour populations could be targeted by control programmes, but provide no strong evidence to support the initiation of management action during a particular season. The lack of detection of postlarval settlement, even among well-established populations, suggests this will not be a useful monitoring tool for detecting incursions.
ISSN:1814-232X
1814-2338
DOI:10.2989/1814232X.2017.1363818