Distribution of brown trout (Salmo truttaLinnaeus, 1758) (Teleostei: Salmonidae) in its southwesternmost European limit: possible causes

Abstract

Andalusian brown trout populations represent the southwestern limit of this species in Europe, show a high genetic diversity, are subjected to extreme habitat conditions and environmental alterations, and are very sensitive to extinction. However, there is a lack of scientific studies on them. A necessary first step to preserve them is to describe their spatial distribution. We detected the species in eastern Andalusia along almost 710 km of rivers, finding 38 populations inhabiting streams and reservoirs in the upper reaches of three basins (Guadalquivir, Segura and South) in an altitude range between 200 and 2200 m above sea level. Populations are constrained by natural causes in their upper limits, and by anthropogenic causes in their lower limits (mainly related to water management). Currently, the populations are very isolated in protected areas (62% of their distribution) or downstream of those areas (32%), and a range displacement towards higher altitudes compared with their distribution in the nineteenth century is observed.

Driving factors of synchronous dynamics in brown trout populations at the rear edge of their native distribution

“…From the distribution limits of brown trout in the southernmost basins of the Iberian Peninsula (Larios‐López, Tierno de Figueroa, Alonso, et al, 2015), the spatial structure of the local populations in the study region was identified through a detailed field study that searched for any physiographic feature that prevents the population connection between watercourses inhabited by the species (Table S2).…”

“…During 2008 and 2009, intense habitat mapping was conducted on foot with the aims of locating (a) the upper and lower limits reached by trout populations in the studied rivers (Larios‐López, Tierno de Figueroa, Alonso, et al, 2015) and (b) impassable obstacles (waterfalls, dams, etc.) present in their channels (Table S2).…”

“…The southeastern Iberian Peninsula is home to the southernmost populations of brown trout ( Salmo trutta Linnaeus, 1758) in Europe, showing exclusively resident forms (Larios‐López, Tierno de Figueroa, Alonso, & Nebot, 2015). These populations have been classified as endangered (Franco Ruíz & Rodríguez de los Santos, 2001) and exhibit exceptional local characteristics: (a) high genetic diversity with new haplotypes that were recently discovered (Almodóvar, Nicola, Leal, & Elvira, 2010), (b) a high degree of population isolation between basins and even among rivers (Larios‐López, Tierno de Figueroa, Alonso, et al, 2015), and (c) the most extensive spawning period described for this species to date (from early October through late April or early May, see Larios‐López, Tierno de Figueroa, Galiana‐García, Gortázar, & Alonso, 2015). According to the authors, these characteristics emerged as a result of these populations remaining isolated since the last glacial period, evolving in parallel with the development of the current Mediterranean climate.…”

Fish and mussels: Importance of fish for freshwater mussel conservation

“…Changes in distribution, phenology, population structure and dynamics of freshwater fish have been described or predicted in response to climate change (Comte, Buisson, Daufresne, & Grenouillet, 2013;Comte, Murienne, & Grenouillet, 2014;Harrod, Graham, & Mallela, 2009;Kovach et al, 2016;Nakano, Kitano, & Maekawas, 1996;Xenopoulos et al, 2005), and they have the potential to alter fishmussel interactions. For example, increasing temperatures might negatively affect cold-water stream fishes like salmonids that are near the edge of their distribution, which may contribute to their extirpation or shift their distribution to more suitable areas at higher latitudes or altitudes (Larios-López, Tierno De Figueroa, Alonso-Gonzalez, & Nebot Sanz, 2015). According to Almodóvar, Nicola, and Benigno (2012), warming will lead to the widespread decline of brown trout (Salmo trutta, Salmonidae) across Iberian Peninsula, an area that represents the southern limit of the species distribution.…”

The effect of large predators on the decomposition rate and the macroinvertebrate colonization pattern of leaves in a Mediterranean stream

“…The study took place from the 1st of December 2014 to the 16th of January 2015. Common trout, Salmo trutta , was present in the experimental reach (Larios‐López, Tierno de Figueroa, Alonso‐González, & Nebot Sanz, , Larios‐López personal communication). Due to the small size and relatively shallow depth of the studied reach, large trout are very scarce or absent; therefore, small individuals dominate the trout population (Larios‐López, based on an unpublished study using electrofishing performed between 2006 and 2014).…”