Wherever the hydrodynamic activity is intense, as in the upwelling regions where
preferred vital needs are met by small pelagic resources during their life cycle, the
probability of passive migration of ELHS is unavoidable. Offshore drift to the open
ocean can be detrimental for stock recruitment, as it occurs with the sardine in the
Iberian upwelling system (Guisande et al. 2001) or in the Canary region (Rodriguez
et al. 2006; Sanchez-Garrido et al. 2019). Only larvae that were enclosed in cyclonic
eddies that functioned as larval nursery grounds for neritic fish species appeared to
gather survival conditions (Rodriguez et al. 2006). Offshore drifting of anchovy
larvae has also been noted in the NW Mediterranean where important coastal
spawning grounds exist (Palomera et al. 2007). However, it has been still challenging to link the connectivity processes to the inter-annual variability of anchovy
populations in the Mediterranean Spanish coast (Ospina-Alvarez et al. 2015).
Anchovy post-larval stages with ages over 2 weeks, well beyond the post-flexion
stages, are routinely found in the bluefin tuna spawning grounds of the Balearic
Islands in the open ocean (Rodriguez et al. 2013), demonstrating their biological
sustainability during their advection from either of their original spawning sites.
In the Alboran Sea, the egg and larval connection includes inter-basin west-east
connectivity from the Gulf of Cadiz and may affect the population structure of
species. For instance, larvae of mesopelagic myctophid species from the Atlantic
spread over the Alboran Sea and tend to concentrate over the EAG and WAG (Rubin
1997). The distribution of sardine along the north coasts of the Alboran Sea shows
bimodal size frequency distributions with larger sizes in the westernmost area, which
suggests the incorporation of sardine individuals of the Atlantic (General Fisheries
Commission for the Mediterranean, Fisheries Assessment Data). The surface circulation pattern of the Alboran Sea previously described would confirm that the
western end of this basin is most likely to receive ELHS. The most resourceful
region in the Gulf of Cadiz is the shelf surrounding the Guadalquivir estuary (see
Fig. 12.1 for location) in terms of ichthyoplankton, zooplankton, and fisheries
(Baldo et al. 2006), where anchovy and sardine form the greater part of the ELHS.
Wind influences the environmental conditions in this area and also modulates the
dispersion of anchovy ELHS, with contrasting outcomes for easterly or westerly
(Catalan et al. 2006). Easterlies favor oligotrophic conditions in the anchovy
spawning grounds off the Guadalquivir estuary, which results detrimental to the
recruitment of anchovy in the area (Ruiz et al. 2006). Numerical simulations
(Catalan et al. 2013) confirm that larvae surviving over 10 days are able to reach
the nursery grounds in the Alboran Sea from those spawning grounds, and anticipated that changes in the anchovy population were dependent on the AJ dynamics.
PLD thus regulates the potential distributional range as a function of the survival
capabilities of the species.
The temporal extent of PLD depends on the species’ habitat, as inshore benthic
species have shorter PLD than species belonging to the pelagic domain (MacPherson
and Raventos 2006). Consequently, the former shows less distributional range. A
large fraction of the 62 species analyzed in this study showed a significant relationship of PLD with distributional range. Species belonging to the Sparidae family,
common in coastal habitats of the Mediterranean, whose ELHS belong to pelagic
12 Biophysical Processes Determining the Connectivity of the Alboran Sea Fish. . .
475
preferred vital needs are met by small pelagic resources during their life cycle, the
probability of passive migration of ELHS is unavoidable. Offshore drift to the open
ocean can be detrimental for stock recruitment, as it occurs with the sardine in the
Iberian upwelling system (Guisande et al. 2001) or in the Canary region (Rodriguez
et al. 2006; Sanchez-Garrido et al. 2019). Only larvae that were enclosed in cyclonic
eddies that functioned as larval nursery grounds for neritic fish species appeared to
gather survival conditions (Rodriguez et al. 2006). Offshore drifting of anchovy
larvae has also been noted in the NW Mediterranean where important coastal
spawning grounds exist (Palomera et al. 2007). However, it has been still challenging to link the connectivity processes to the inter-annual variability of anchovy
populations in the Mediterranean Spanish coast (Ospina-Alvarez et al. 2015).
Anchovy post-larval stages with ages over 2 weeks, well beyond the post-flexion
stages, are routinely found in the bluefin tuna spawning grounds of the Balearic
Islands in the open ocean (Rodriguez et al. 2013), demonstrating their biological
sustainability during their advection from either of their original spawning sites.
In the Alboran Sea, the egg and larval connection includes inter-basin west-east
connectivity from the Gulf of Cadiz and may affect the population structure of
species. For instance, larvae of mesopelagic myctophid species from the Atlantic
spread over the Alboran Sea and tend to concentrate over the EAG and WAG (Rubin
1997). The distribution of sardine along the north coasts of the Alboran Sea shows
bimodal size frequency distributions with larger sizes in the westernmost area, which
suggests the incorporation of sardine individuals of the Atlantic (General Fisheries
Commission for the Mediterranean, Fisheries Assessment Data). The surface circulation pattern of the Alboran Sea previously described would confirm that the
western end of this basin is most likely to receive ELHS. The most resourceful
region in the Gulf of Cadiz is the shelf surrounding the Guadalquivir estuary (see
Fig. 12.1 for location) in terms of ichthyoplankton, zooplankton, and fisheries
(Baldo et al. 2006), where anchovy and sardine form the greater part of the ELHS.
Wind influences the environmental conditions in this area and also modulates the
dispersion of anchovy ELHS, with contrasting outcomes for easterly or westerly
(Catalan et al. 2006). Easterlies favor oligotrophic conditions in the anchovy
spawning grounds off the Guadalquivir estuary, which results detrimental to the
recruitment of anchovy in the area (Ruiz et al. 2006). Numerical simulations
(Catalan et al. 2013) confirm that larvae surviving over 10 days are able to reach
the nursery grounds in the Alboran Sea from those spawning grounds, and anticipated that changes in the anchovy population were dependent on the AJ dynamics.
PLD thus regulates the potential distributional range as a function of the survival
capabilities of the species.
The temporal extent of PLD depends on the species’ habitat, as inshore benthic
species have shorter PLD than species belonging to the pelagic domain (MacPherson
and Raventos 2006). Consequently, the former shows less distributional range. A
large fraction of the 62 species analyzed in this study showed a significant relationship of PLD with distributional range. Species belonging to the Sparidae family,
common in coastal habitats of the Mediterranean, whose ELHS belong to pelagic
12 Biophysical Processes Determining the Connectivity of the Alboran Sea Fish. . .
475