Green Crabs and the Marine Invasive Atlas

18 March 2014 - 1:09pm — anonymous spotter

One of our latest alien invasive species is the European Green Shore Crab (Carcinus maenas).

To date it has been recorded from the Table Bay and Hout Bay harbours.

There is a concern that they will both leave the harbours for the surrounding shoreline and invade other harbours along our coastline.

This is a key invasive species that needs to be tracked. So please can all i-spotters keep a good look out for anything similar to this species. Upload them onto iSpot and researchers at UCT will verify their ID.

An ideal observation for this species (or indeed, any crab) can be seen at http://ispot.org.za/node/243127 - note the three views:
a top view showing carapace and spines,
a bottom view showing the legs and bases, &
a frontal view showing the mouth and claws.

The European Green Shore Crab can be identified by:
* 5 spines either side of eyes;
* 3 bumps between the eyes.

The adult carapace width can reach 80mm.
Colour ranges from orange, green and brown to purple.
Swimming paddles are not present on the rear legs.

The Green Crab Survey is the first step in establishing a Marine Invasive Atlas.
SeaKeys also includes a group of scientists working on marine alien and invasive species. We request the public to photograph and report potential introduced species as well. More details - especially on what is need to identify the species - will become available as the project rolls out.

In the meantime, let no crab be safe. If you see it - put it on iSpot!

(picture and ID features courtesy of ClovaJurk on iSpot)