Transport pathways of decapod larvae under intense mesoscale activity in the Canary-African coastal transition zone: implications for population connectivity

Abstract

Summary: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.Keywords: decapod larvae; C-ACTZ; upwelling filament; eddy; Lagrangian transport; connectivity.Vías de transporte de larvas de decápodos en condiciones de intensa actividad mesoescalar en la región de transición canario-africana: implicaciones para la conectividad poblacional Resumen: Investigamos la dinámica del transporte de larvas de decápodos en la región de transición canario-africana (C-ACTZ), donde el conocimiento sobre las asociaciones de larvas es escaso. En agosto de 1999, durante la campaña FAX99, las aguas al sur del Archipiélago Canario mostraron una intensa actividad mesoescalar a modo de numerosos remolinos ciclónicos y anticiclónicos, así como de filamentos de afloramiento. Nuestros resultados ilustran una relación estrecha entre las estructuras oceanográficas mesoescalares y la distribución de larvas de decápodos tanto mediante observaciones in situ como modelos de transporte larvario. El análisis de las muestras de plancton mostró la práctica ausencia de larvas de especies pelágicas en aguas asociadas al filamento de afloramiento, mientras que las larvas de especies neríticas mostraron una distribución heterogénea, lo que indica que la C-ACTZ es una zona de mezcla donde larvas con origen canario y africano pueden coexistir simultáneamente. Las simulaciones apoyaron estos patrones de distribución y sugieren que las larvas presentes en aguas abiertas al sur de Gran Canaria llegaron principalmente desde poblaciones africanas a principios de agosto, mientras que durante la segunda mitad del mes fueron larvas liberadas desde las poblaciones de Fuerteventura, las que dominaron la región d...

Seasonality of planktonic crustacean decapod larvae in the subtropical waters of Gran Canaria Island, NE Atlantic

“…This species is one of the most abundant of the mesopelagic community in Canary Island waters (Ariza et at. 2015), although its larval stages have also been collected in September (FAX99 cruise, Landeira et al 2017), and October-November (CANARIAS 9110 cruise, Landeira et al 2009), suggesting a longer spawning season than that observed in the present study.…”

“…Moreover, C. crangon is an epibenthic shrimp that preferably inhabits soft-sediment in estua-rine habitats (Holthuis 1980) that do not exist in the Canary Islands. It is possible that this larva reached the Gran Canaria coast transported by upwelling filaments from Africa, as has been suggested by Landeira et al (2017), but with the available data it is not possible to support this hypothesis.…”

“…This larval form was described by dos Santos (1999) from plankton specimens collected south of Portugal in July. It has also been observed in the NW African upwelling, where it was transported towards the ocean during a strong filament event in August-September 1999 (Landeira et al 2017). The only callianassid species reported for the Canary Islands are Pestarella tyrrhena (Petagna, 1792) (González and Quiles 2003) and Pestarella candida (Moro et al 2014), which are also present off NW Africa and Portugal (d'Udekem D'Acoz 1999).…”

“…In open waters, the larval abundance is usually very low, but there is a clear physical/biological coupling between mesoscale oceanographic activity and decapod larvae distribution. Eddies generated downstream of the archipelago when the Canary Current impinges upon the island topography (Hernández-Guerra et al 1993, Sangrà et al 2007) act as oceanic retention zones for larvae of neritic species (Landeira et al 2010(Landeira et al , 2017. Furthermore, it has been observed that filaments of upwelled waters originating over the continental shelf transport larvae from the African coast towards the ocean, indicating that they provide a conduit to the islands that connects populations (Brochier et al 2011.…”

Updating changes in the Iberian decapod crustacean fauna (excluding crabs) after 50 years

“…Accurate faunistic analysis of fishery discards may also become an increasing source of biodiversity knowledge that may help to understand biogeographic patterns and dynamic changes in distribution, including early detection of allochtonous and invasive species (Gorelli et al 2016, Anjos et al 2018. Another interesting and necessary activity, which is also carried out in some areas, is the study of meroplanktonic larvae in relation to hydrographic currents and climate change, because it improves knowledge of specific composition and biocenoses, and can explain the presence of new records and the increase of the biogeographical range of some species (Torres 2015, Landeira et al 2017, Landeira and Lozano-Soldevilla 2018. (Holthuis, 1961) 18…”