Abstract
We investigate the transport dynamics of decapod larvae in the Canary-African coastal transition zone (C-ACTZ), where larval assemblages are poorly known. In August 1999, during the FAX99 cruise, the waters downstream of the Canary Island archipelago displayed intense mesoscale activity, with numerous cyclonic and anticyclonic eddies as well as upwelling filaments. Our results illustrate a close relationship between these mesoscale oceanographic structures and the distribution of decapod larvae, using both field observations and Lagrangian transport modelling. Analysis of plankton samples shows that larvae of pelagic species were excluded from filament waters, whereas larvae of neritic species were heterogeneously distributed, suggesting that the C-ACTZ is a mixing area where larvae originating from both the Canary Islands and the African coast may be present at the same time. This finding was supported by the simulations, which suggested that the larvae collected in the offshore waters south of Gran Canaria came mainly from the African population (between Cape Bojador and Cape Juby) during early August, whereas during the second half of August the targeted area was dominated by larvae released from Fuerteventura populations. Our observations introduce new insights into our understanding of marine population connectivity, the dispersal pathways of the terrestrial biota, and general biogeography in the region.
Highlights
Larval transport is a key factor for dispersal capabilities of marine species (Pineda et al 2007)
Several multidisciplinary surveys have increased the understanding of oceanographic processes in the Canary-African Coastal Transition Zone (C-ACTZ), as well as their influence on the plankton community and fish larvae, but no attention has been paid to other taxonomic larval groups
We study the transport of decapod larvae related to the complex filament-eddy system of August 1999 in the C-ACTZ described by Barton et al (2004)
Summary
Larval transport is a key factor for dispersal capabilities of marine species (Pineda et al 2007). Oceanographic structures such as eddies and filaments are associated with strong transports that influence larval fate Studying these structures allows us to detect potential connectivity routes between distant populations, which are a useful tool for managing commercial species, designing marine protected areas, and monitoring the spread of invasive species (Underwood and Keough 2001). Remote sensing and field observations of temperature and chlorophyll have revealed that cyclonic and anticyclonic eddies are sequentially spun off from several islands in the Canary Archipelago all year long (Hernández-Guerra et al 1993, Jiménez et al 2008, Piedeleu et al 2009) These eddies are generated as a perturbation of the southwestward-flowing Canary Current by the island’s topography (Arístegui et al 1997, Sangrà et al 2007), favoured by the trade winds through Ekman pumping in the islands’ wakes (Barton et al 2000). Eddies contribute to the larval retention of neritic species that have been advected from their island populations (Lobel and Robinson 1988, Rodríguez et al 2001, Torres et al 2014)
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