Current landscapes and legacies of land-use past: understanding the distribution of juvenile coho salmon (Oncorhynchus kisutch) and their habitats along the Oregon Coast, USA

The Oregon Coast landscape displays strong spatial patterns in air temperature, precipitation, and geology, which can confound our ability to detect relationships among land management, instream conditions, and fish at broad spatial scales. Despite this structure, we found that a suite of immutable or intrinsic attributes (e.g., reach gradient, drainage area, elevation, and percent weak rock geology of the catchments draining to each of our 423 study reaches) could explain much of the variation in pool surface area across the landscape and could contribute to an estimate of how many juvenile coho salmon (Oncorhynchus kisutch) one might expect to find in those pools. Further, we found evidence of differences in pool surface area across land ownership categories that reflect differing management histories. Our results also suggest that historical land and river management activities, in particular splash dams that occurred at least 50 years ago, continue to influence the distribution of juvenile coho salmon and their habitats today. Le paysage du littoral de l'Oregon presente un degre de structure spatiale eleve en ce qui concerne des caracteristiques du paysage comme la temperature de l'air, les precipitations et la geologie. Malgre cette structure sous-jacente, nous avons constate qu'une serie d'attributs immuables ou intrinseques comme, par exemple, le gradient des tronqons, la superficie drainee, l'elevation moyenne du bassin versant et le pourcentage de la geologie constitue de roches peu resistantes des reseaux hydrographiques se deversant dans chacun des 423 tronqons etudies, pourrait expliquer une bonne partie des variations de la superficie des fosses a l'echelle du paysage et pourrait aider a estimer le nombre de saumons cohos (Oncorhynchus kisutch) juveniles possiblement presents dans ces fosses. Nous avons egalement trouve des indices de variation de la superficie des fosses selon la categorie de propriete terrienne qui refletent differents historiques de gestion. Nos resultats donnent a penser que les activites passees de gestion des terres et des rivieres, en particulier le flottage de billots il y a au moins 50 ans, continuent a ce jour d'influencer la repartition des saumons cohos juveniles et leurs habitats. [Traduit par la Redaction]
Introduction Understanding the distribution of instream habitats and the density of fish within those habitats is essential for effective watershed management and conservation of depressed fish populations. For wide-ranging species [...]