Restoration of native Atlantic salmon runs in northern Spain: do costs outweigh benefits?

Abstract

Atlantic salmon stocks in northern Spain are at the southern range of the species distribution. As such they are likely more vulnerable to environmental change and human disturbance. The Nalon-Narcea River salmon is one such population in Asturias, Spain. The river is dammed throughout the watershed with few fish passage facilities. However, angling data show that salmon returns are consistent although the population is relatively small. We have employed one tributary as a model, the River Trubia. Although some problems of agriculture and industrial pollution have been detected downstream, an upstream habitat evaluation suggests that adequate spawning and juvenile habitat exists. The regional Government has proposed to construct fishways for allowing upstream passage of salmon. This would potentially increase salmon production, but there are also some concerns like increased hybridization of salmon and trout which is already evident downriver and which previous work suggests will increase as salmon colonize new habitat, and potential changes in fishing regulations as salmon distributions shift upriver and away from traditional angling areas. Here, we present an overview of ecological and social aspects of salmon habitat restoration in the River Nalon-Narcea that we hope will provide solutions that balance costs and benefits and may be applicable to other anadromous populations. RÉSUMÉLa restauration du saumon de l'Atlantique natif fonctionne dans le nord de l'Espagne : les coûts dépassent-ils les avantages ?Les stocks de saumon atlantique dans le nord de l'Espagne sont à la limite sud de la distribution de l'espèce. Comme tels, ils sont probablement plus vulnérables aux changements environnementaux et aux perturbations humaines. Le saumon de la rivière Nalon-Narcea est une de ces populations dans les Asturies, en Espagne. La rivière est endiguée, avec quelques passes à poissons. Toutefois, les données de pêche montrent que les retours de saumon sont bons bien que la population soit relativement faible. Nous avons employé un affluent comme modèle, la rivière Trubia. Bien que certains problèmes de pollution agricole et

Environmental DNA for freshwater fish monitoring: insights for conservation within a protected area

“…One of the benefits of eDNA is allowing to monitor more sites in a faster and cheaper manner ( Deiner et al, 2016 ; Bista et al, 2017 ), screening environments for potential species from which ground truthing (i.e., electrofishing or netting in the present case) can be conducted later to verify. The river part studied here exhibits a good habitat for salmonids ( Juanes et al, 2011 ). The sampling points where rainbow trout eDNA was found had 161.17 ERUs and the best water quality.…”

“…In the streams (river headwaters) brown trout ( Salmo trutta) are the only native fish species, because two consecutive impassable dams ( Fig. 1 ) impede the arrival of native migratory European eel ( Anguilla anguilla ) and Atlantic salmon ( Salmo salar ), which occur downstream ( Juanes et al, 2011 ). There is a rainbow trout fish farm located in one of the headwater streams in a zone denominated Veneros ( Fig.…”

“…Three measures of depth and width were taken within the 20-meter transect at each sampled site. From these data, the total amount of juvenile salmonid (‘rearing’) habitat units were estimated for each site based on the model described by Juanes et al (2011) . All profile variables were considered to assign a percentage of juvenile’s habitat to each sampling point.…”

Expansion of Non-Native Brown Trout in South Europe May Be Inadvertently Driven by Stocking: Molecular and Social Survey in the North Iberian Narcea River

“…This methodology has been described in a previous work [ 26 ]. Briefly, river users (principally anglers) were interviewed on the Narcea River banks while fishing or other activities, employing an Open Response Questionnaire, with open-ended questions where the participants can explain themselves using their own words.…”

“…We present here the results obtained for the questions: “Trends observed in local Salmonid populations during the last years”, and “Solutions suggested for improving/conserving the status of Salmonid populations”. We compared these results with those obtained in 2004 for the same questions (50 interviews in the Narcea River; [ 26 ]). In addition, in 2012 the presidents of the five local fishermen associations that collaborate in stocking the Narcea-Nalón River basin (namely Asociación de Pescadores Las Mestas del Narcea, Sociedad de Pescadores Fuentes del Narcea, Sociedad de Pescadores El Banzao, Sociedad de Pescadores Amigos del Nalón, Asociación Allerana de Pescadores El Maravayu) were interviewed in order to know the official opinion of their Association regarding the importance of the hatchery stock origin (native versus non native).…”