3.4.2 Curative Approach: Simulated Fish Response to the Restoration
of Degraded River Habitats
The freeware Anaqualand has been under development since 2002 at Irstea as a tool
to support the development of a ‘riverscape ecology’ approach that explicitly
considers connectivity in aquatic landscapes [29]. It was also designed to provide
helpful results to bridge research and management preservation. Longitudinal
and lateral connectivity for fish in rivers are modelled in 2D, through the calculation
of hydrographic or functional distances (expressed in functional km). Functional
connectivity is calculated according to the ‘least cost’ approach for which the
environment facilitates or prevents the movement of fish from one life cycle habitat
to another. This approach could be engaged to compare scenarios for the restoration
of physical and chemical barriers that fragment river networks, thus making it
possible to select priority actions and evaluate the relevance of restoration schemes
for ecological continuity [30].
Anaqualand was used in the context of a SAGE (water development and management plan). Outputs from the ProSe hydraulic model were used as input parameters in Anaqualand, providing a map of fish migration probabilities based on
participants’ management decisions. This tool helps the local water commission
(CLE) to define water resource management measures that take into account the
different uses of the river. Similarly, several scenarios for restoring the ecological
continuity of the Seine estuary to the Risle River for sea trout have been discussed
with the Fishing Federation of the department of Eure to prioritize their actions (see
Box 6).
Box 6
Modelling ecological continuity for sea trout under contrasting restoration
scenarios (Anaqualand model).
The Risle River is the most downstream tributary of the Seine estuary, close
to the Atlantic Ocean, and has a high potential for migratory species. It is
subject to tidal influence, and no physical barriers impede the migration of fish
up to Pont-Audemer, where there are a number of impassable obstacles. The
Fishing Federation of the Eure department wanted to compare the actual
ecological continuity of the Risle River (245 barriers) with 3 management
scenarios for 66 barriers distributed along the main course and 2 tributaries
(whereby 46 become passable and 20 are removed). In the short term, 21 initiatives are in preparation; in the medium term, 34 additional initiatives are
under discussion, and in the long term, 11 more are planned.
Anaqualand models the accessibility of the Risle River, from mouth to
headwaters (Fig. 7). The strong barrier effect for sea trout at Pont-Audemer is
clearly shown in the present state, as well as in the short-term scenario, since
no initiatives are envisaged in the near future for these most downstream
(continued)
400
C. Carré et al.
of Degraded River Habitats
The freeware Anaqualand has been under development since 2002 at Irstea as a tool
to support the development of a ‘riverscape ecology’ approach that explicitly
considers connectivity in aquatic landscapes [29]. It was also designed to provide
helpful results to bridge research and management preservation. Longitudinal
and lateral connectivity for fish in rivers are modelled in 2D, through the calculation
of hydrographic or functional distances (expressed in functional km). Functional
connectivity is calculated according to the ‘least cost’ approach for which the
environment facilitates or prevents the movement of fish from one life cycle habitat
to another. This approach could be engaged to compare scenarios for the restoration
of physical and chemical barriers that fragment river networks, thus making it
possible to select priority actions and evaluate the relevance of restoration schemes
for ecological continuity [30].
Anaqualand was used in the context of a SAGE (water development and management plan). Outputs from the ProSe hydraulic model were used as input parameters in Anaqualand, providing a map of fish migration probabilities based on
participants’ management decisions. This tool helps the local water commission
(CLE) to define water resource management measures that take into account the
different uses of the river. Similarly, several scenarios for restoring the ecological
continuity of the Seine estuary to the Risle River for sea trout have been discussed
with the Fishing Federation of the department of Eure to prioritize their actions (see
Box 6).
Box 6
Modelling ecological continuity for sea trout under contrasting restoration
scenarios (Anaqualand model).
The Risle River is the most downstream tributary of the Seine estuary, close
to the Atlantic Ocean, and has a high potential for migratory species. It is
subject to tidal influence, and no physical barriers impede the migration of fish
up to Pont-Audemer, where there are a number of impassable obstacles. The
Fishing Federation of the Eure department wanted to compare the actual
ecological continuity of the Risle River (245 barriers) with 3 management
scenarios for 66 barriers distributed along the main course and 2 tributaries
(whereby 46 become passable and 20 are removed). In the short term, 21 initiatives are in preparation; in the medium term, 34 additional initiatives are
under discussion, and in the long term, 11 more are planned.
Anaqualand models the accessibility of the Risle River, from mouth to
headwaters (Fig. 7). The strong barrier effect for sea trout at Pont-Audemer is
clearly shown in the present state, as well as in the short-term scenario, since
no initiatives are envisaged in the near future for these most downstream
(continued)
400
C. Carré et al.