Graciela G. Nicola

• PhD in Biology
• Senior Lecturer at Complutense University of Madrid

Stream-dwelling salmonids in the low-latitude and -altitude margins of their range are particularly threatened by climate change. However, they possess a variety of evolutionary, plastic, and behavioural mechanisms that provide resistance against rapid changes in their environment. Behavioural plasticity can be important under rapid environmental c...

Climate change is reducing the harvestable surplus that supports recreational fisheries, which, in turn, is affecting the resilience of exploited populations to the demographic and eco-evolutionary impacts of climatic changes. Consequently, total catch-and-release (C&R) fishing is a growing conservation strategy implemented to ensure the self-susta...

The European Union's (EU) environmental legislation establishes common measures to prevent the entry and spread of invasive non‐native species and to minimize their impacts. However, species that are native to at least one member state but non‐native and potentially invasive in others (NPIS) are in limbo because they are neither legally regulated a...

Atlantic salmon Salmo salar supports highly valuable commercial and recreational fisheries in Europe, but its stocks are currently overexploited and threatened by climate change. Its southernmost populations (in northern Spain) play a key role in conserving the species’ original genetic diversity, which is endangered due to decades-long (1970s to 1...

Freshwater fish biodiversity is experiencing an alarming decline worldwide. Understanding the main factors behind its deterioration is a key step for ecosystem restoration. In this work, large‐scale and long‐term data were used to identify the causes of the decline of native species richness in Castilla‐La Mancha. This region in central Spain cover...

The Southern Iberian spined-loach Cobitis paludica is an Iberian endemism threatened by human activities, including habitat destruction. For this reason, the development of conservation and the recovery plans for the species calls for a precise knowledge of its habitat requirements. Here, microhabitat use and selection patterns were investigated to...

Protected areas (PAs) are fundamental for global biodiversity conservation but many are not delivering their conservation potential. In particular, the European Natura 2000 (N2K)–the largest coordinated network of PAs in the world—has insofar proved insufficient to achieve the EU’s biodiversity conservation targets. Despite the adoption of innovati...

Aim Invasive alien species (IAS) can cause profound impacts on ecosystem function and diversity, human health, well-being and livelihoods. Climate change is an important driver of biological invasions, so it is critical to develop models and climate-driven scenarios of IAS range shifts to establish preventive measures. In this study, we analyse how...

The freshwater blenny Salaria fluviatilis is an endangered fish species with populations that are in rapid decline, largely owing to habitat degradation caused by human activity. This situation highlights the urgent need to develop measures for the conservation and recovery of the species based on a deep understanding of its specific habitat requir...

The European Commission has recently adopted its EU Biodiversity Strategy for 2030, which sets out an ambitious plan for reversing biodiversity loss, and preserving and restoring protected ecosystems. A central binding target is focused on enlarging the EU network of legally protected areas (Natura 2000, the largest global network of the world), an...

The European Natura 2000 (N2000) is the largest network of protected areas in the world. It was established to protect Europe’s most valuable and threatened species and habitats. While introduction pathways of invasive alien species (IAS) are strongly linked to human activities, they are not prohibited within N2000 sites, which makes them highly vu...

The European Natura 2000 (N2K) network of protected areas stands out as the main conservation strategy in the European Union to preserve biodiversity under the auspices of the Convention on Biological Diversity. The management of N2K sites is mainly focused on protecting the biological elements as Special Areas of Conservation for habitats or speci...

Climate change is impacting the composition and functioning of virtually every ecosystem on Earth, and disrupting the productivity of exploited ones. Species are rapidly adjusting to their changing environments through evolutionary and/or plastic phenotypic changes in behavioural, physiological, phenological and life‐history traits. Size‐selective...

Many Atlantic salmon Salmo salar populations in Europe are threatened by previous stocking with foreign hatchery strains. Temporal patterns of genetic characteristics of salmon from northern Spain, the southernmost European populations, were compared before and after species decline and heavy stocking with specimens from northern Europe. Eleven mic...

Historical data on the oceanic distribution and migration routes of southernmost Atlantic salmon Salmo salar populations from Europe are almost non-existent, as no rigorous tagging initiatives have been conducted. Here, we used stable isotope data (δ13C and δ15N) of historic scale collections to identify the potential marine feeding areas of the la...

Streamflow is a main driver of fish population dynamics and is projected to decrease in much of the northern hemisphere, especially in the Mediterranean region, due to climate change. However, predictions of future climate effects on cold-water freshwater fish populations have typically focused only on the ecological consequences of increasing temp...

Freshwater ecosystems constitute only a small fraction of the planet's water resources, yet support much of its diversity, with freshwater fish accounting for more species than birds, mammals, amphibians or reptiles. Fresh waters are, however, particularly vulnerable to anthropogenic impacts, including habitat loss, climate and land use change, pol...

Protected areas are considered effective tools to protect biodiversity from global change; however, their success against invasive alien species (IAS) is still quite unknown. The European Natura 2000 network (N2000) appears vulnerable to invasions as human activities are not prohibited, despite being the main drivers of biological invasions. This s...

The consistency of the global declining trend of Atlantic salmon (Salmo salar) populations suggests that climate-driven reduced survival and growth at sea are the main driving factors. The southernmost populations have experienced the greatest declines, consistent with harsher conditions in natal fresh waters. We analyzed temporal trends in Spanish...

Freshwater ecosystems constitute only a small fraction of the planet's water resources, yet support much of its diversity, with freshwater fish accounting for more species than birds, mammals, amphibians, or reptiles. Freshwaters are, however, particularly vulnerable to anthropogenic impacts, including habitat loss, climate and land use change, nut...

Harvesting alters demography and life histories of exploited populations, and there is mounting evidence that rapid phenotypic changes at the individual level can occur when harvest is intensive. Therefore, recreational fishing is expected to induce both ecological and rapid evolutionary changes in fish populations and consequently requires rigorou...

The abundance of Atlantic salmon is declining throughout its geographical area. Fisheries and global warming were assumed as main drivers of the decline, and recent studies suggest that habitat changes in freshwater is a third contributor. Southern populations experience the greatest decline, and face the highest risk of extinction as global warmin...

Territoriality is probably the most important ecological mechanism regulating densities in stream-living salmonids. Body size is typically regarded as the best predictor of territory size, but food abundance and competitor density may be key driving factors. However, a global analysis of literature data showed no clear patterns on the relative caus...

We used two different approaches involving two organizational levels and spatial scales to explore altitudinal and latitudinal variation in life histories of non-anadromous brown trout Salmo trutta. First, we studied the factors influencing the maturation of individuals from populations in northern Spain. Second, we explored the effects of altitude...

Free-living amoebae (FLA) include opportunistic pathogens such as Naegleria fowleri, Balamuthia mandrillaris, and the genera Sappinia and Acanthamoeba. In this study, a survey was conducted in order to evaluate the presence of potentially pathogenic amoebic strains in water samples collected from wells located in the western part of Guinea-Bissau....

Understanding the links between instream ecology and hydrology has become a critical task in contemporary river research and management. Habitat selection behaviour is a central dimension in applied ecology because it is a primary way that mobile organisms adapt to changing environmental conditions. Here, we analyzed brown trout habitat selection d...

Anthropogenic environmental change is causing unprecedented rates of population extirpation and altering the setting of range limits for many species. Significant population declines may occur however before any reduction in range is observed. Determining and modelling the factors driving population size and trends is consequently critical to predi...

Hybrids of invasive bleak Alburnus alburnus and native endemic calandino Squalius alburnoides complex and Southern Iberian chub Squalius pyrenaicus were found in the River Jarama (Tagus River basin, central Spain). Morphological analyses show that hybrids are intermediate in shape between the parent species. Molecular mitochondrial and nuclear anal...

Should a species be translocated? Uncertainty regarding the necessity and feasibility of many translocations complicates answering this question. Here, we review translocation projects, both published and unpublished. Our results indicate that most projects (1) addressed fewer than half of the basic criteria established for translocations and (2) w...

The Physical Habitat Simulation System (PHABSIM) still probably remains as the most widespread habitat method used to establish inflow standards or to link habitat temporal variations with fish population dynamics. However, statistical uncertainties around the PHABSIM main output, the weighted usable area (WUA) over discharge curves, are usually ig...

Current climate change exacerbates the environmental restrictions on temperate species inhabiting low latitude edges of their geographical ranges. We examined how temperature variations due to current and future climate change are likely to affect populations persistence of stream-dwelling brown trout Salmo trutta at the vulnerable southern periphe...

This study looks at the relative influence of water temperature and density dependence on the spatial variation in body size of 126 brown trout (Salmo trutta) cohorts from 12 Iberian rivers over a 12-year period. Mean cohort mass and length of age groups 0+ to 2+ varied significantly among sampling sites because of the concurrent effect of water te...

Should a species be translocated? Uncertainty regarding the necessity and feasibility of many translocations complicates answering this question. Here, we review translocation projects, both published and unpublished. Our results indicate that most projects (1) addressed fewer than half of the basic criteria established for translocations and (2) w...

1. Density-dependent growth has been widely reported in freshwater fishes, but the ontogenetic evolution of competition and its subsequent effects on growth through a life span remains unclear. 2. Patterns of competition can be described by integrating population abundance data with habitat-modelling results. Weighted usable area (WUA; m2 WUA ha−1)...

Territorial behaviour is often considered the main mechanism regulating salmonid populations and territory size regarded as the proximate factor that limits abundance, being mainly determined by body size. Despite the spatial requirements of young-of-the-year (YOY) brown trout, Salmo trutta, have been previously established, there is still a gap in...

Structure and composition of benthic macroinvertebrate assemblages were investigated during three consecutive years in six headwater streams that exhibit a high variation in environmental conditions, habitat structure and predatory pressure. We examined whether the abundance of functional feeding groups could be best predicted by the abundance of p...

Ayllón D, Almodóvar A, Nicola GG, Elvira B. Ontogenetic and spatial variations in brown trout habitat selection. Ecology of Freshwater Fish 2010: 19: 420–432. © 2010 John Wiley & Sons A/S Abstract – Habitat quality and quantity determine many biological processes and traits that directly affect the population dynamics of stream fishes. Understandin...

Habitat modelling results are extremely sensitive to the habitat suitability criteria (HSC) used in the simulations. HSCs are usually expressed as univariate habitat suitability curves, although such univariate approach has been long questioned, since overlooking interactions between hydraulic variables may misrepresent the complexity of fish behav...

Spatial variation in growth of stream-dwelling brown trout Salmo trutta was explored in 13 populations using a long-term study (1993-2004) in the Bay of Biscay drainage, northern Spain. The high variability in fork length (L(F)) of S. trutta in the study area was similar to the body-size range found in the entire European distribution of the specie...

Factors controlling brown trout Salmo trutta recruitment in Mediterranean areas are largely unknown, despite the relevance this may have for fisheries management. The effect of hydrological variability on survival of young brown trout was studied during seven consecutive years in five resident populations from the southern range of the species dist...

Abstract –  Feeding tactics, body condition and size structure of two populations of pumpkinseed Lepomis gibbosus from Cabañeros National Park (Guadiana River basin, central Spain) were compared to provide insight into the ecological requirements favouring levels of success/failure in relation to human intervention. Habitat, benthic macroinvertebra...

1. Population regulation was studied for seven consecutive years (1992–98) in five rivers at the periphery of the distribution of Salmo trutta , where the fish were living under environmental constraints quite different from those of the main distribution area. 2. Recruitment is naturally highly variable and the populations had been earlier classif...

Knowledge about the effects of captivity and environmental stress on fish populations is basic to culture them for ornamental, conservation or exploitation purposes. The aim of this study was to test how captivity affect morphological development of bilateral characters and whether levels of fluctuating asymmetry, morphological abnormalities and ec...

Hybrids of Barbus bocagei and Barbus comizo were found in the river Tagus, Madrid province, central Spain. Morphological univariate and multivariate analyses show that hybrids are intermediate in shape between the parent species. The potential causes of the hybridization are discussed.

Since its first record in a tributary of the Ebro basin in 1992, the bleak Alburnus alburnus has spread to almost the whole Iberian Peninsula. In this paper (based on electrofishing surveys in 598 localities), we provide information on the expansion of the bleak. We detail current distribution in the Ebro basin and the rivers of the Eastern Pyrenee...

Since its first record in a tributary of the Ebro basin in 1992, the bleak Alburnus alburnus has spread to almost the whole Iberian Peninsula. In this paper (based on elec-trofishing surveys in 598 localities), we provide information on the expansion of the bleak. We detail current distribution in the Ebro basin and the rivers of the Eastern Pyrene...

Spatial variation in Spanish populations of brown trout Salmo trutta was studied in 10 streams of contrasting environmental and biological characteristics based on data compiled over 7 years (1992–1998). Three of the streams had soft water (mean alkalinity as CaCO3 = 19.3 mg/L) supplied by granite catchments at elevations around 1,250 m above sea l...

1. A comprehensive analysis was carried out on the effects of stocking on the genetic structure of Iberian brown trout evolutionary lineages. Introgression and genetic diversity were estimated from allozyme results of 307 populations based on own data (180) and available literature (127). Stocking records, angling regulations and environmental feat...

During the spring of 2000 and 2001 there were two cyanobacterial bloom episodes in El Atazar reservoir (central Spain). They were attributed to the toxic cyanobacteria Planktothrix rubescens. The goal of the present study was to determine the possible effects and toxicity of these blooms on the fish community of the reservoir. The main objectives w...

Spanish brown trout, Salmo trutta L., populations are currently overexploited as a result of unsuitable management activities, and their genetic uniqueness is threatened by introgression of foreign genes because of stocking. In this study, the status and management of trout fisheries were reviewed and the effects of fishery management on abundance,...

Growth of brown trout Salmo trutta was analyzed based on 3 years of simultaneous temperature and growth data from seven streams of contrasting chemical and biological character. A laboratory-based growth model was employed to examine geographical variation in growth performance among wild populations. A sensitivity analysis of model predictions was...

1. Reproductive traits were studied in seven wild populations of resident brown trout in Spain. We examined whether growth, and certain environmental conditions such as water temperature or food abundance, could explain interpopulation variation in the reproductive characters. 2. The results indicated that nearby populations subjected to a wide var...

The genetic diversity of Spanish brown trout is currently threatened by stocking with exogenous brown trout from Central and Northern Europe. In the Douro River basin 25% of the analysed populations in the present study showed introgression by genes of hatchery origin. The mean introgression estimated by the single locus approach (S) varied from 0...

This paper presents a comprehensive review of the information currently available on the World Wide Web regarding Acipenser sturio L., 1758, featuring 113 selected sites concerning its conservation, biology, and related subjects. Web sites with additional information on other stur-geon species' conservation are also included. A Web page of links to...

A small hydroelectric power station was built in 1993 on the River Hoz Seca (Tagus basin, central Spain). Pre- and post-regulation studies provided the opportunity to test the early effects of this disturbance on the brown trout Salmo trutta L. population. Before and after comparisons of population density and biomass, age composition, growth and p...

The brown trout population of the River Gallo (central Spain) was monitored every two months during 1996 to determine the current impact of angling. To evaluate the influence of additional parameters, physical habitat and food availability were also studied. To assess fishing pressure, trout harvest and angling exploitation, a partial creel census...

Monitoring of fish communities in the middle-upper River Tagus was carried out from 1996. Owing to river regulation the original fluctuating and lotic condition of the river has been replaced by a mostly lentic environment. The native fish fauna consists of Anguilla anguilla and the Iberian endemics: Barbus bocagei, Barbus comizo, Chondrostoma poly...

The diet of largemouth bass, Micropterus salmoides, was investigated in the Natural Park of the Ruidera Lakes, Guadiana River basin, central Spain, where it has been stocked since 1963. Stomachs of 226 largemouth bass (fork length range 3.6 to 41.0 cm, mean 14.67 cm; weight range 0.8 to 1460 g, mean 97.48 g) were examined. The frequency of empty st...