River Continuity Restoration and Diadromous Fishes: Much More than an Ecological Issue

Abstract

Ecosystem fragmentation is a serious threat to biodiversity and one of the main challenges in ecosystem restoration. River continuity restoration (RCR) has often targeted diadromous fishes, a group of species supporting strong cultural and economic values and especially sensitive to river fragmentation. Yet it has frequently produced mixed results and diadromous fishes remain at very low levels of abundance. Against this background, this paper presents the main challenges for defining, evaluating and achieving effective RCR. We first identify challenges specific to disciplines. In ecology, there is a need to develop quantitative and mechanistic models to support decision making, accounting for both direct and indirect impacts of river obstacles and working at the river catchment scale. In a context of dwindling abundances and reduced market value, cultural services provided by diadromous fishes are becoming increasingly prominent. Methods for carrying out economic quantification of non-market values of diadromous fishes become ever more urgent. Given current challenges for rivers to meet all needs sustainably, conflicts arise over the legitimate use of water resources for human purposes. Concepts and methods from political science and geography are needed to develop understandings on how the political work of public authorities and stakeholders can influence the legitimacy of restoration projects. Finally, the most exciting challenge is to combine disciplinary outcomes to achieve a multidisciplinary approach to RCR. Accordingly, the co-construction of intermediary objects and diagrams of flows of knowledge among disciplines can be first steps towards new frameworks supporting restoration design and planning.

Toward a roadmap for diadromous fish conservation: the Big Five considerations

“…Moreover, global change may profoundly alter hydrological patterns in the future, for instance through increased winter and reduced summer runoff in several major European river catchments (Schröter et al 2005). Hydrological management, including development related to navigation, drainage, and hydropower, will therefore need to be adapted, potentially impacting aquatic habitat connectivity (and consequently diadromous fish) to an even greater degree (Limburg and Waldman 2009;Drouineau et al 2018a).…”

Comparison of coarse‐resolution rapid methods for assessing fish passage at riverine barriers: ICE and SNIFFER protocols

“…As a result, new methods have been developed to measure the alteration of connectivity induced by anthropogenic barriers in lotic systems. Common to methods is the inherent difficulty in assessing barrier passability—the dynamic component of river connectivity (Bourne, Kehler, Wiersma, & Cote, ; Kemp & O Hanley 2011; Nunn & Cowx, ; Drouineau et al, ), and in particular the difficulty in developing cost‐ and time‐effective coarse‐resolution methods that can be implemented at the catchment scale or larger.…”

“…Fragmentation of habitats has been identified as one of the five main factors of biodiversity loss along with pollution, overexploitation of natural resources, invasive species, and climate change (Fahrig, ). The main cause of connectivity loss for migratory fish species (diadromous and potamodromous) in riverine systems are man‐made structures, such as dams, weirs, and culverts for road crossings, which act as physical barriers to both fish passage and sediment transport (Doehring, Young, & McIntosh, ; Hall, Jordaan, & Frisk, : Gargan et al, ; Drouineau et al, ). Although many of these barriers can be eliminated (De Leaniz, ) or mitigated by modification (Dodd, Cowx, & Bolland, ), this process can often be expensive, and budgetary constraints tend to restrict the amount of restoration that can occur (Poplar‐Jeffers et al, ).…”

“…Within SACs, Conservation Objectives, specific to the species, are developed. Impaired passage is a significant issue for migratory fish species listed in the Habitats Directive, for example, Atlantic salmon, twaite and allis shad, and the sea and river lamprey (Castro‐Santos, Shi, & Haro, ; Drouineau et al, ; Lucas, Bubb, Jang, Ha, & Masters, ) and also nonmigratory fish species (Benitez, Matondo, Dierckx, & Ovidio, ). The Water Framework Directive identifies the importance of longitudinal connectivity for ecological quality in rivers, both for upstream and downstream movement of aquatic organisms and for sediment transport and renaturalization of constrained rivers.…”

Adjustive ecological restoration through stakeholder involvement: a case of riparian landscape restoration on privately owned land with public access

“…In fact, disagreements over restoration may reflect differences in protection interests, e.g. birds versus plants, between protection interests and recreational interests, or between different types of natural value (Marttila et al ; Drouineau et al ; Paudyal et al ). Conflicts may also abound over concrete, yet perhaps less tangible values, such as aesthetic values (Gobster et al ) or concerns over place attachment and loss of meaning (Drenthen ) versus more psychological values such as cooperation (Miles et al ) and building of a conscience of so‐called ecological citizenship (Light ).…”