likely the case of several species in the Alboran Sea (Hidalgo et al. 2018), which are
structured in three Geographic Subareas (GSAs) for management and data compilation purposes.
Long-term connectivity (low genetic differentiation) is high in general terms in
the whole Alboran Sea. However, connectivity at short and middle temporal scale
(demographic connectivity) is currently a major challenge in the Alboran Sea that is
indeed highly species specific. Connectivity has two levels of implications in
populations and ecosystems: spatial management and temporal assessment. Spatial
management (e.g., no-take Marine Protected Areas, MPAs) is a key tool used in
marine conservation to enhance ecosystem resilience and reduce the decline of
fisheries resources. The effectiveness of an MPA (and network of MPAs) is highly
dependent on careful consideration of connectivity processes in their design (Muñoz
et al. 2018). In the Alboran Sea MPAs, east-west and along-shore connectivity are,
in addition to mesoscale and topographic-induced processes, of higher relevance
compared to potential north-south connectivity. MPAs were initially thought of as
the main conservation mechanisms for coastal ecosystems, while their importance as
a management measure to recover fish stocks at the continental shelf and slope is
increasing (e.g., European hake, Muñoz et al. 2018). However, one of the main
challenges with MPAs networks design is the general mismatch between fisheries
dependency and the larval supply provided by MPAs (Andrello et al. 2017), mainly
associated with local communities highly dependent on small-scale fisheries. This is
likely the case in the south Alboran Sea with comparatively less protected areas
compared to the north (e.g., Andrello et al. 2013). By contrast, in terms of fisheries
assessment, east-west and north-south connectivity provide a deep understanding of
both the spatial structure of populations beyond stock boundaries, and the influence
of hydrodynamic connectivity in the recruitment success (Hidalgo et al. 2019).
The three main harvested species potentially affected by hydrodynamic connectivity in the Alboran Sea are the European hake, the sardine, and the blakspot
seabream, for which ongoing research investigates cross-scale connectivity processes (Hidalgo et al. 2018). Each species represents a contrasting case study.
Sardine is currently assessed by Spain and Morocco as different stocks, while
hake is already assessed as a co-shared stock (General Fisheries Commission for
the Mediterranean). Sardine is a pelagic species with more coastal habitat compared
to hake. Their dispersion is sub-superficial and thus their potential north-south
connectivity is likely affected by the AJ (Fig. 12.8). Hake displays a deeper dispersal
and is less affected by the AJ, while the sluggishness of the flow in depth could
decrease the likelihood of effective north-south connectivity. Black-spot seabream
has a special and rather unknown life cycle. Most adults and spawners are fished in a
very small region in the Strait of Gibraltar and most of the spawning is assumed to
occur in the Strait, whereas larvae are thought to be mainly dispersed in the Alboran
Sea. Although populations in the Mediterranean display complex spatial structures
(e.g., Gargano et al. 2017; Hidalgo et al. 2019), any of these species consider still this
scenario.
Future projections and perspectives in terms of connectivity are difficult to
provide in the Mediterranean Sea due to uncertainties when dealing with mesoscale
480
J. Garcia-Lafuente et al.
structured in three Geographic Subareas (GSAs) for management and data compilation purposes.
Long-term connectivity (low genetic differentiation) is high in general terms in
the whole Alboran Sea. However, connectivity at short and middle temporal scale
(demographic connectivity) is currently a major challenge in the Alboran Sea that is
indeed highly species specific. Connectivity has two levels of implications in
populations and ecosystems: spatial management and temporal assessment. Spatial
management (e.g., no-take Marine Protected Areas, MPAs) is a key tool used in
marine conservation to enhance ecosystem resilience and reduce the decline of
fisheries resources. The effectiveness of an MPA (and network of MPAs) is highly
dependent on careful consideration of connectivity processes in their design (Muñoz
et al. 2018). In the Alboran Sea MPAs, east-west and along-shore connectivity are,
in addition to mesoscale and topographic-induced processes, of higher relevance
compared to potential north-south connectivity. MPAs were initially thought of as
the main conservation mechanisms for coastal ecosystems, while their importance as
a management measure to recover fish stocks at the continental shelf and slope is
increasing (e.g., European hake, Muñoz et al. 2018). However, one of the main
challenges with MPAs networks design is the general mismatch between fisheries
dependency and the larval supply provided by MPAs (Andrello et al. 2017), mainly
associated with local communities highly dependent on small-scale fisheries. This is
likely the case in the south Alboran Sea with comparatively less protected areas
compared to the north (e.g., Andrello et al. 2013). By contrast, in terms of fisheries
assessment, east-west and north-south connectivity provide a deep understanding of
both the spatial structure of populations beyond stock boundaries, and the influence
of hydrodynamic connectivity in the recruitment success (Hidalgo et al. 2019).
The three main harvested species potentially affected by hydrodynamic connectivity in the Alboran Sea are the European hake, the sardine, and the blakspot
seabream, for which ongoing research investigates cross-scale connectivity processes (Hidalgo et al. 2018). Each species represents a contrasting case study.
Sardine is currently assessed by Spain and Morocco as different stocks, while
hake is already assessed as a co-shared stock (General Fisheries Commission for
the Mediterranean). Sardine is a pelagic species with more coastal habitat compared
to hake. Their dispersion is sub-superficial and thus their potential north-south
connectivity is likely affected by the AJ (Fig. 12.8). Hake displays a deeper dispersal
and is less affected by the AJ, while the sluggishness of the flow in depth could
decrease the likelihood of effective north-south connectivity. Black-spot seabream
has a special and rather unknown life cycle. Most adults and spawners are fished in a
very small region in the Strait of Gibraltar and most of the spawning is assumed to
occur in the Strait, whereas larvae are thought to be mainly dispersed in the Alboran
Sea. Although populations in the Mediterranean display complex spatial structures
(e.g., Gargano et al. 2017; Hidalgo et al. 2019), any of these species consider still this
scenario.
Future projections and perspectives in terms of connectivity are difficult to
provide in the Mediterranean Sea due to uncertainties when dealing with mesoscale
480
J. Garcia-Lafuente et al.