12 Habitat 3D Complexity Effects on the Processes Structuring . . .
187
2002) that are in medium density (around 20 individuals m
−2 ) (Hoffmann et al.
1992).
It has been reported worldwide that infralittoral habitats are subject to strong modification due to anthropogenic pressures (Coll et al. 2010), such as water pollution,
coastal urbanization, boat anchoring, dredging, date mussel fisheries, or invasive
species (Claudet and Fraschetti 2010). Macrophytes-formed habitats have not been
spared. For instances, Mediterranean Cystoseira dominated assemblages have been
reported to regress (Thibaut et al. 2005; Mangialajo et al. 2007; Sala et al. 2011).
They are generally replaced by habitats with reduced architectural complexity, such
as Dictyotales-dominated assemblages (smaller ribbon-like macrophytes), algal turfs
or barren-grounds (over-grazed area where dominated by encrusting corallinales).
These habitat shifts induce strong modification in compositions and configurations
of seascapes, and ultimately in their whole ecological functioning (Ryall and Fahrig
2006; Claudet and Fraschetti 2010).
12.3 Complex Macrophyte-Formed Habitats Are Nursery
for Many Fish Species
Fish assemblages usually exhibit different patterns of composition and abundances
between habitats. Differences are usually larger when focusing only on postsettlement juveniles (hereafter called ‘juveniles’) due to their more specific habitat
requirements (Harmelin-Vivien et al. 1995; Cheminée et al. 2013). The habitat(s) that host(s) higher than average densities of juveniles have a nursery role
for the considered species (excluding the possible lack of connectivity with adult
habitats), and are therefore very important for populations renewals (Beck et al.
2001).
Many studies carried worldwide in coastal temperate seascapes reported that
macrophyte-formed habitats play the nursery role for many fish species. Examples
include Ecklonia and Carpophyllum (Phaeophycea) forests of temperate rocky reefs
of New Zealand (see Box 1; Jones 1984), Cystoseira forests of temperate rocky reefs
of the Mediterranean (see Box 2; Cheminée et al. 2013) and the Mediterranean temperate Posidonia oceanica seagrass meadows (see Box 3; Guidetti 2000). However,
it is worth noting that other less complex habitats play also the nursery role for some
other species (e.g. Box 2). Hence, fish juvenile assemblage structure depends on
the structure of macrophyte assemblage. We develop in the following sections how
architectural complexity of macrophyte-formed habitats can affect the ecological
processes structuring fish assemblages.
187
2002) that are in medium density (around 20 individuals m
−2 ) (Hoffmann et al.
1992).
It has been reported worldwide that infralittoral habitats are subject to strong modification due to anthropogenic pressures (Coll et al. 2010), such as water pollution,
coastal urbanization, boat anchoring, dredging, date mussel fisheries, or invasive
species (Claudet and Fraschetti 2010). Macrophytes-formed habitats have not been
spared. For instances, Mediterranean Cystoseira dominated assemblages have been
reported to regress (Thibaut et al. 2005; Mangialajo et al. 2007; Sala et al. 2011).
They are generally replaced by habitats with reduced architectural complexity, such
as Dictyotales-dominated assemblages (smaller ribbon-like macrophytes), algal turfs
or barren-grounds (over-grazed area where dominated by encrusting corallinales).
These habitat shifts induce strong modification in compositions and configurations
of seascapes, and ultimately in their whole ecological functioning (Ryall and Fahrig
2006; Claudet and Fraschetti 2010).
12.3 Complex Macrophyte-Formed Habitats Are Nursery
for Many Fish Species
Fish assemblages usually exhibit different patterns of composition and abundances
between habitats. Differences are usually larger when focusing only on postsettlement juveniles (hereafter called ‘juveniles’) due to their more specific habitat
requirements (Harmelin-Vivien et al. 1995; Cheminée et al. 2013). The habitat(s) that host(s) higher than average densities of juveniles have a nursery role
for the considered species (excluding the possible lack of connectivity with adult
habitats), and are therefore very important for populations renewals (Beck et al.
2001).
Many studies carried worldwide in coastal temperate seascapes reported that
macrophyte-formed habitats play the nursery role for many fish species. Examples
include Ecklonia and Carpophyllum (Phaeophycea) forests of temperate rocky reefs
of New Zealand (see Box 1; Jones 1984), Cystoseira forests of temperate rocky reefs
of the Mediterranean (see Box 2; Cheminée et al. 2013) and the Mediterranean temperate Posidonia oceanica seagrass meadows (see Box 3; Guidetti 2000). However,
it is worth noting that other less complex habitats play also the nursery role for some
other species (e.g. Box 2). Hence, fish juvenile assemblage structure depends on
the structure of macrophyte assemblage. We develop in the following sections how
architectural complexity of macrophyte-formed habitats can affect the ecological
processes structuring fish assemblages.