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P. Thiriet et al.
habitat. Considering that this active choice is a behavior that appeared thanks to
natural selection, the chosen habitat shall be the one with the highest probability of
growing and surviving until reproduction (Morris 2011). Therefore, the two classes
of processes, differential mortality and active habitat selection, are both mediated
by differential habitat quality in term of food availability and predation rate (Hindell
et al. 2000). The highest quality habitat minimize mortality rate by offering the tradeoff between foraging and safety (Anholt and Werner 1998; Dahlgren and Eggleston
2000).
12.5 Architectural Complexity of Macrophyte-Formed Habitats
Interact with Processes
12.5.1 Foraging Success
Food supply is one of the basic needs for any heterotrophic organism. Food gives
the energy, nutrients and vitamin needed to keep body-functioning, growth and
development, and reproductive potential. Individuals experiencing starvation lose
fat and muscle mass (decrease in condition) in order to keep vital systems. Growth
and development of juveniles may be altered (Heck et al. 2003) as well reproductive
potential of adults (Ordines et al. 2009). Energy deficiency reduces physical abilities
and ultimately results in death. Low food availability may therefore causes direct
mortality of post-settlement juveniles or indirect mortality through (a) a reduction of
size-at-age making longer the period of vulnerability toward size-selective predation
(“the bigger is better” hypothesis, Heck and Orth 1980; Levin et al. 1997), and (b) a
reduction of their physical abilities to escape predator attack (Levin et al. 1997).
Availability of food resources depends on their quantity and their accessibility,
which are both affected by macrophytes. Plants architecture (e.g. degree of branching) and densities affect the structure of benthic macroinvertebrate assemblages.
In several regions worldwide, habitats made up structurally complex macrophytes
harbor higher diversity and abundances of macroinvertebrates (Parker et al. 2001;
Chemello and Milazzo 2002; Christie et al. 2009; Hansen et al. 2010). These habitats may therefore be particularly suitable as feeding grounds for invertebrate feeders
such as many demersal fishes. However, it has been suggested that extremely high
structural complexity may alter fishes’foraging efficiency through physical constraint
(Stoner 1982; Heck and Orth 1980). Another characteristic potentially affecting invertebrate accessibility is the rigidity of macrophytes. A very flexible canopy is more
sensitive to water movement and its constantly back-and-forth may limit access for
fishes to understory invertebrates (Levi 2004).
P. Thiriet et al.
habitat. Considering that this active choice is a behavior that appeared thanks to
natural selection, the chosen habitat shall be the one with the highest probability of
growing and surviving until reproduction (Morris 2011). Therefore, the two classes
of processes, differential mortality and active habitat selection, are both mediated
by differential habitat quality in term of food availability and predation rate (Hindell
et al. 2000). The highest quality habitat minimize mortality rate by offering the tradeoff between foraging and safety (Anholt and Werner 1998; Dahlgren and Eggleston
2000).
12.5 Architectural Complexity of Macrophyte-Formed Habitats
Interact with Processes
12.5.1 Foraging Success
Food supply is one of the basic needs for any heterotrophic organism. Food gives
the energy, nutrients and vitamin needed to keep body-functioning, growth and
development, and reproductive potential. Individuals experiencing starvation lose
fat and muscle mass (decrease in condition) in order to keep vital systems. Growth
and development of juveniles may be altered (Heck et al. 2003) as well reproductive
potential of adults (Ordines et al. 2009). Energy deficiency reduces physical abilities
and ultimately results in death. Low food availability may therefore causes direct
mortality of post-settlement juveniles or indirect mortality through (a) a reduction of
size-at-age making longer the period of vulnerability toward size-selective predation
(“the bigger is better” hypothesis, Heck and Orth 1980; Levin et al. 1997), and (b) a
reduction of their physical abilities to escape predator attack (Levin et al. 1997).
Availability of food resources depends on their quantity and their accessibility,
which are both affected by macrophytes. Plants architecture (e.g. degree of branching) and densities affect the structure of benthic macroinvertebrate assemblages.
In several regions worldwide, habitats made up structurally complex macrophytes
harbor higher diversity and abundances of macroinvertebrates (Parker et al. 2001;
Chemello and Milazzo 2002; Christie et al. 2009; Hansen et al. 2010). These habitats may therefore be particularly suitable as feeding grounds for invertebrate feeders
such as many demersal fishes. However, it has been suggested that extremely high
structural complexity may alter fishes’foraging efficiency through physical constraint
(Stoner 1982; Heck and Orth 1980). Another characteristic potentially affecting invertebrate accessibility is the rigidity of macrophytes. A very flexible canopy is more
sensitive to water movement and its constantly back-and-forth may limit access for
fishes to understory invertebrates (Levi 2004).