Regional prediction of basin-scale brown trout habitat suitability

S Ceola,A Pugliese

doi:10.5194/piahs-364-26-2014

Abstract

Abstract. In this study we propose a novel method for the estimation of ecological indices describing the habitat suitability of brown trout (Salmo trutta). Traditional hydrological tools are coupled with an innovative regional geostatistical technique, aiming at the prediction of the brown trout habitat suitability index where partial or totally ungauged conditions occur. Several methods for the assessment of ecological indices are already proposed in the scientific literature, but the possibility of exploiting a geostatistical prediction model, such as Topological Kriging, has never been investigated before. In order to develop a regional habitat suitability model we use the habitat suitability curve, obtained from measured data of brown trout adult individuals collected in several river basins across the USA. The Top-kriging prediction model is then employed to assess the spatial correlation between upstream and downstream habitat suitability indices. The study area is the Metauro River basin, located in the central part of Italy (Marche region), for which both water depth and streamflow data were collected. The present analysis focuses on discharge values corresponding to the 0.1-, 0.5-, 0.9-empirical quantiles derived from flow-duration curves available for seven gauging stations located within the study area, for which three different suitability indices (i.e. ψ10, ψ50 and ψ90) are evaluated. The results of this preliminary analysis are encouraging showing Nash-Sutcliffe efficiencies equal to 0.52, 0.65, and 0.69, respectively.

Highlights

The natural streamflow regime of a river and the associated hydraulic features are considered a major controlling factor of stream ecological processes and functions (Power et al 1995, Poff et al 1997, Allan and Castillo 2007, Ceola et al 2013)
Habitat suitability curves are a tool widely employed in stream ecology to describe species habitat preferences: species behaviour and density distribution are expressed as a function of any generic environmental variable, such as flow velocity, water depth, river bed substrate and shear stress (Raleigh et al 1986, Vismara et al 2001, Ceola et al 2014)
The sub-basins closed at the gauging stations of Piobbico @ Biscuvio, Piobbico @ Candigliano, Foci, Cagli and Calmazzo present empirical values of brown trout habitat suitability that decrease from ψ10, to ψ50 and to ψ90

Summary

Introduction

The natural streamflow regime of a river and the associated hydraulic features are considered a major controlling factor of stream ecological processes and functions (Power et al 1995, Poff et al 1997, Allan and Castillo 2007, Ceola et al 2013). Habitat suitability curves are a tool widely employed in stream ecology to describe species habitat preferences: species behaviour and density distribution are expressed as a function of any generic environmental variable, such as flow velocity, water depth, river bed substrate and shear stress (Raleigh et al 1986, Vismara et al 2001, Ceola et al 2014). We present here an ecological extension of classical hydrological tools (e.g. flow-duration curves) coupled with a geostatistical regional model, such as Top-kriging, to assess the habitat suitability for brown trout (Salmo trutta) in a pre-alpine river basin (Metauro River, Italy). We employ a habitat suitability curve derived from data (Raleigh et al 1986) and estimate the temporal sequences of brown trout habitat suitability at the streamflow gauging stations. We develop a geostatistical model based on the Top-kriging technique (Skøien et al 2006, Archfield et al 2013, Pugliese et al 2013) to examine if a regionalization approach, widely employed in recent studies for the estimation of different hydrological indices in ungauged catchments, may be applied to an ecological context

Methods

Results

Conclusion