Using a continuous riverscape survey to examine the effects of the spatial structure of functional habitats on fish distribution

Abstract

To fill the gap between microhabitat and landscape scale habitat models for freshwater fish, it is becoming increasingly common practice to adopt a continuous view of riverscapes, thus allowing a better understanding of the processes in place at the river management level (segments of 1À100 km). The aim of this study was to test the effects of the spatial structure of habitat on fish distribution at this scale. Inferred habitat relationships were generated using spatial metrics adapted from landscape ecology. These were calculated for two species of multi-habitat cyprinid fish in a 25-km long segment of the Seine River. A spatially continuous survey was then designed to acquire fish sampling data relating to the riverscape. Explanatory models were devised to quantify the extent to which environmental and spatial variables could describe fish distribution patterns. Spatially continuous sampling of feeding habitats at dawn and dusk provided greater understanding of the spatial distribution of common barbel (Barbus barbus, L.) and nase (Chondrostoma nasus, L.). Fish observations were aggregated longitudinally in neighboring feeding habitat patches, with the highest abundance found in patches with the best local conditions. The species were present for large feeding patches, as well as for a higher proximity index for those patches. This result emphasized the importance of the supplementation of feeding habitats. By quantifying spatial habitat relationships using spatial metrics, it was possible to identify the best suited configuration of functional habitats to the needs of shoals. At present, most conservation work focuses on restoring local habitats. There is also growing interest in large-scale fish management, which has been encouraged by the advent of metapopulation theory. This study highlights the need for greater work at a third, intermediate scale that is no less significant: restoring daily and seasonal movements between functional habitats.

Modelling the dispersal of riverine fish larvae: from a raster-based analysis of movement patterns within a racetrack flume to a rheoreaction-based correlated random walk (RCRW) model approach

“…The nase carp (C. nasus) is a widespread and characteristic riverine cyprinid species in Central and Eastern Europe (Lelek 1987) and is considered as a target species in many studies (Le Pichon et al 2016;Hauer et al 2008;Keckeis et al 1996) for European rivers. During the last century, its populations declined drastically due to pollution, river regulation, and damming (Kirchhofer 1996;Peň áz et al 1996;Lusk and Halačka 1995).…”

Modelling functional fish habitat connectivity in rivers: A case study for prioritizing restoration actions targeting brown trout

“…Furthermore, the map‐based approach may be more suitable than graph‐based dendritic network approaches (Saura & Torné, ; Segurado, Branco, Avelar, & Ferreira, ; VanLooy et al, ) to account for longitudinal and lateral movements along the riverscape and the 2D physical heterogeneity of rivers. These features are of great importance as they allow continuous mapping of habitat variability in a context relevant to particular species and life stages at the intermediate scale of management actions (Le Pichon et al, ) that cannot be substituted by discrete data typically obtained from sampling multiple smaller reaches (Fausch et al, ; White et al, ). Moreover, the continuous approach presented here could be complementary with large‐scale riverscape approaches, using network drainage lines, for species such as wild salmon whose life cycle involves movements across large geographic areas (Whited et al, ).…”

“…In rivers and streams, the spatial and temporal variation of flow velocity, bed morphology, vegetation and temperature contribute to creating and maintaining a dynamic mosaic of habitat patches (Pringle et al, ; Statzner, ). The resulting heterogeneity provides a variety of complementary functional habitats for fish (Le Pichon, Tales, Gorges, Baudry, & Boët, ; Schlosser, ). The spatial configuration of complementary habitats and the connectivity between them affects fish dispersal and migration, which in turn have an impact on the spatial variation in genetic diversity, community composition and metapopulation dynamics (Fullerton et al, ).…”

Patterns of riparian policy standards in riverscapes of the Oregon Coast Range

“…Though the riverscape concept has informed new ideas in ecological research (Falke et al 2013, Pichon et al 2016, its foundation in the broader field of landscape ecology also included social considerations of land-use policy and management (Wiens 2002). The current U.S. policy framework for resource management divides ecosystems into individual components, e.g., air, water, land, or individual species, each managed by numerous state and federal agencies with varied management goals (Marcus 1980, Wood 2013).…”