Vertical and horizontal larval distribution of an offshore brachyuran crab, Monodaeus couchii, off the south coast of Portugal
Patricia N. Pochelon, Antonina dos Santos, A. Miguel P. Santos, Henrique Queiroga

A strong understanding of larval distribution and abundance is of major value in delineating the location and size of a breeding population of deep-sea species such as Monodaeus couchii. In this study, vertical distribution of the larvae of a brachyuran crab, M. couchii, was assessed during two week-long cruises conducted at the end of January 2006 and 2007 off the South Coast of Portugal. Larvae were collected by oblique plankton hauls with a Longhurst-Hardy Plankton Recorder from the surface to 300 m. Abundance and distribution of zoeae I and II were correlated during both years. For all stages, abundance decreased with depth during the day while it increased with depth at night; the larvae thus displayed reverse diel vertical migration. Abundance of zoeae I and II was correlated with chlorophyll a levels, whereas those of later stages were correlated with neither physical parameters (chlorophyll a, temperature or salinity) nor each other. An ontogenic shift in vertical distribution explained the results; earlier zoeal stages remain in the food-rich upper water column while later stages were not correlated with any physical parameters (i.e. chlorophyll a, salinity or temperature) and migrated to the bottom for settlement.

Keywords: diel vertical migration; crustacean; deep sea; invertebrate larva; vertical distribution; Monodaeus couchii; Iberian Peninsula
Contents of this volume Sci. Mar. 78(2) : 249-256 Back PDF
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