174
A. Cheminée et al.
sand. This is a matter of necessary conciliation between environmental priorities and
economic priorities linked to bathing activities. Once such guarantees are acquired
(k), this seascape approach to management will again require (m) the maintenance
of connectivity between the nurseries situated outside the protected area and the
adult habitats: the feasibility of these migrations of young white seabream recruits
has been confirmed by recent studies (Di Franco et al. 2012) showing the capacity
of recruits to migrate from the nurseries towards the adult habitats over distances
of more than 10 km. Furthermore, it is necessary to dispose of a sufficient quantity
of nurseries (m). If this is not the case, two options may be envisaged, both in the
core protected area and in the area without statutory protection: firstly, the causes
of the lack of nurseries may be of recent origin (n), for example if they have been
partly degraded by pollution events (e.g. alteration of the macrophyte-formed forests
of Cystoseira) or the reshaping of beaches (alteration of the heterogeneous shallow
bottoms with rocks). In this case, the managing authority may envisage measures of
restoration (o) in order to re-establish the characteristics of the micro-habitats and
thus the nursery value of these habitats. Or the causes of the lack of nurseries may
be historical (p) and irremediable, for example in the case of destruction by harbour
construction (for details, see Box 2); compensatory measures may then be envisaged
in order to replace the lost nurseries (q). At the conclusion of this process, both in
areas with and without statutory protection, once the nurseries of each species of
interest have been identified (characteristics) and localised (cartography) and their
quantity and connectivity with adult habitats is satisfactory and preserved, the next
stage is to take care of the management of the adult populations themselves (r); in
our case study, within the core area, in addition to the general regulations for the sea
(respect of size of catches, etc.), the special core area regulations and the no-catch
areas (ZNP and ZPR) provide a basis for managing the adult habitat and populations.
In the adjacent maritime area (AMA), operations such as the construction of artificial
reefs in the bay of Prado also play a role.
Box 1: Importance of the ‘three-dimensional structure’ of the seascape
and its habitats with regard to their nursery value: examples at various
spatial scales
The work of August (1983) offers a basis for defining the structuring of the
seascape; the structure of the seascape is the result of several components that
may be perceived at different scales: (1) at landscape scale: its ‘heterogeneity’,
which reflects (a) its composition (number of distinct units) and (b) their organization (i.e. the degree of fragmentation and their relative positions); (2) within
a given unit (a habitat): its ‘heterogeneity’ (subdivision in micro-habitats) and
its ‘complexity’, which reflects the three-dimensional architecture of the habitat (e.g. the degree of stratification of the erect macrophytes, or the degree
of ramification of the arborescent strata). This structuring of the landscape
(heterogeneity + complexity) influences the patterns of abundance of the organisms living there via the processes described by Thiriet et al. (this volume)
A. Cheminée et al.
sand. This is a matter of necessary conciliation between environmental priorities and
economic priorities linked to bathing activities. Once such guarantees are acquired
(k), this seascape approach to management will again require (m) the maintenance
of connectivity between the nurseries situated outside the protected area and the
adult habitats: the feasibility of these migrations of young white seabream recruits
has been confirmed by recent studies (Di Franco et al. 2012) showing the capacity
of recruits to migrate from the nurseries towards the adult habitats over distances
of more than 10 km. Furthermore, it is necessary to dispose of a sufficient quantity
of nurseries (m). If this is not the case, two options may be envisaged, both in the
core protected area and in the area without statutory protection: firstly, the causes
of the lack of nurseries may be of recent origin (n), for example if they have been
partly degraded by pollution events (e.g. alteration of the macrophyte-formed forests
of Cystoseira) or the reshaping of beaches (alteration of the heterogeneous shallow
bottoms with rocks). In this case, the managing authority may envisage measures of
restoration (o) in order to re-establish the characteristics of the micro-habitats and
thus the nursery value of these habitats. Or the causes of the lack of nurseries may
be historical (p) and irremediable, for example in the case of destruction by harbour
construction (for details, see Box 2); compensatory measures may then be envisaged
in order to replace the lost nurseries (q). At the conclusion of this process, both in
areas with and without statutory protection, once the nurseries of each species of
interest have been identified (characteristics) and localised (cartography) and their
quantity and connectivity with adult habitats is satisfactory and preserved, the next
stage is to take care of the management of the adult populations themselves (r); in
our case study, within the core area, in addition to the general regulations for the sea
(respect of size of catches, etc.), the special core area regulations and the no-catch
areas (ZNP and ZPR) provide a basis for managing the adult habitat and populations.
In the adjacent maritime area (AMA), operations such as the construction of artificial
reefs in the bay of Prado also play a role.
Box 1: Importance of the ‘three-dimensional structure’ of the seascape
and its habitats with regard to their nursery value: examples at various
spatial scales
The work of August (1983) offers a basis for defining the structuring of the
seascape; the structure of the seascape is the result of several components that
may be perceived at different scales: (1) at landscape scale: its ‘heterogeneity’,
which reflects (a) its composition (number of distinct units) and (b) their organization (i.e. the degree of fragmentation and their relative positions); (2) within
a given unit (a habitat): its ‘heterogeneity’ (subdivision in micro-habitats) and
its ‘complexity’, which reflects the three-dimensional architecture of the habitat (e.g. the degree of stratification of the erect macrophytes, or the degree
of ramification of the arborescent strata). This structuring of the landscape
(heterogeneity + complexity) influences the patterns of abundance of the organisms living there via the processes described by Thiriet et al. (this volume)