Modelling the variation in larval dispersal of marbled rock crab Pachygrapsus marmoratus in the Gulf of Cadiz

Rita T. Pires1, Maria Pan1, Alvaro Peliz2, Antonio Miguel P A Santos1, Dmitri Boutov3 and Antonina Dos Santos4, (1)Instituto Português do Mar e da Atmosfera (IPMA), Lisbon, Portugal, (2)IDL-Instituto Dom Luiz Faculty of Science Univ. Lisboa, Lisboa, Portugal, (3)University of Lisbon, (4)Instituto Português do Mar e da Atmosfera
Abstract:
Pachygrapsus marmoratus is a common coastal crab occurring in rocky shores of the northeastern Atlantic and Mediterranean. Information on the planktonic larval phase for this species is still incomplete. However, for the first six zoeal stages a long larval duration of around 30 days was observed. Larvae are released in the intertidal area and exported to the shelf in order to complete their development.

In situ data obtained during an oceanographic survey along the southern Portuguese coast in August 2010 consisting on CTD casts and plankton hauls were analyzed. The first five zoeal stages and megalopae were captured and results showed a progressively wider distribution towards offshore through the larval development with megalopae being found close to the coast. A modelling approach was employed to explain the mechanisms used by megalopae (last larval phase) to return to adult habitats. Their vertical distribution, oceanic circulation of the area and the points of larval release were integrated in the model to understand the influence of vertical migrations on the dispersal range of Pachygrapsus larvae.

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