José Maria Santos

University of Lisbon | UL · Forest Research Centre (CEF)

River artificial fragmentation is arguably the most imperilling threat for freshwater- dependent fish species. Fish need to be able to freely move along river networks as not only spawning grounds but also refuge and feeding areas may be spatially and temporally separated. This incapacity of free displacement may result in genetic depletion of some...

River ecosystems are exposed to a multitude of stressors, including increasing pesticide runoff driven by precipitation and irrigation. Pyrethroids are the fourth major group of insecticides in use worldwide and have extremely negative effects on aquatic fauna. In this study, we aimed to assess the effects of an acute 2 h sub-lethal exposure to dif...

Fish represent a quarter of all vertebrates and 40% of those are freshwater-related species, the second most threatened animal group. These species are, at least for a significant part of their life cycle, limited to occur in rivers, i.e., hierarchic and dendritic networks where flow imposes a directionality. Data collected from the International U...

Unlabelled: Research on how intermittent water releases from hydropower plants affect the early life stages of fish has advanced in the last years, focusing not only on the direct impacts of rapid flow changes (hydropeaking), but also on the short-term fluctuations in water temperature (thermopeaking). Flow and thermal fluctuations caused by hydro...

Despite the growing literature on the topic of freshwater fish invasion, few studies employed a comprehensive analysis of the stages characterizing the invasion process (i.e. invasion pathway), thereby demanding a deeper knowledge to avoid incomplete and unbiased conclusions and give support to adequate management strategies. The aim of the present...

Rivers have always been closely related with society development wich has resulted in a a high degree of human induced impacts forced upon freshwaters. Among all the pressures, river network fragmentation by artificial barriers is considered one of the most damaging, especially for freshwater fish species that see their longitudinal movements impar...

Freshwater fish species are the second most threatened animal group while the richest among European vertebrates. The International Union for Conservation of Nature (IUCN) Red List contains information on species’ populations, distribution, ecology and threats, setting the foundation for a comprehensive evaluation of species extinction risk. Using...

Dammed Fish is a research project that aims to evaluate and propose solutions and tools to inform river network connectivity management to improve fish biodiversity and to enhance biotic quality of European rivers. For this purpose, river network connectivity management needs guidance to choose the best available solutions within a frame of ongoing...

The need to increase hydropower production to reduce CO2 emissions, while supporting the development of self-sustainable fish populations in a cost-effective way, protect biodiversity and restore water-related ecosystems is urgent and recognized in the UN Agenda 2030 and in the recently launched European Green Deal. Despite the growing awareness of...

Freshwater fish species comprise 40% of all fish diversity and provide multiple ecosystem ser-vices. Recently, several populations of this faunal group have faced declines and range contrac-tions due to several threats. The Red List of Threatened Species, established by the International Union for Conservation of Nature (IUCN), is the most comprehe...

Special Session: Ecohydraulics 2021: Novel methods to investigate flow-biota interactions numerically, in the lab and in the field Abstract Rivers are affected by a vast number of artificial barriers that block fish movements within river networks, preventing several freshwater dependent fish species from completing their life cycle. Fish need to b...

Hydropeaking negatively affects fish assemblages, but knowledge gaps still constrain our ability to rank and mitigate the impacts of different hydropower operation regimes at particular power plants. This is especially relevant for species and rivers for which the effects of hydropeaking are less investigated, such as the Iberian Cypriniformes and...

Rivers are experiencing increasing anthropogenic pressures and salinity has shown to affect freshwater fish behaviour, potentially disrupting ecological processes. In this study, the aim was to determine the sub-lethal effects of salinization on freshwater fish behaviour, using a widespread native cyprinid species, the Iberian barbel (Luciobarbus b...

Climate change represents a major challenge for the management of native fish communities in Mediterranean rivers, as reductions in discharge may lead to a decrease in passability through small barriers such as weirs, both in temporary and perennial rivers. Through hydraulic modelling, we investigated how discharges from a large hydropower plant in...

Many types of fish passage facilities have been built worldwide to mitigate river fragmentation by instream barriers and partially restore upstream movements of fish. Among these, fish lifts are a design that enables fish to pass through high-head obstacles (>15 m height) and can be considered the most cost-effective fishway. However, fishways may...

Comprising 25% of vertebrates and 40% of all fish diversity, freshwater fish species are among the most threatened animal groups. The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is the most comprehensive system for evaluating species risk of extinction and provides information on the species’ populations, di...

Freshwater ecosystems are disproportionally important for biodiversity conservation, as they support more than 9% of known animal species while representing less than 1% of the Earth’s surface. However, the vast majority of the threats (99%, or 826 out of 837) identified by the International Union for Conservation of Nature Red List of Threatened S...

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment area...

Diversos estudos têm reportado sérias alterações nas comunidades piscícolas fortemente relacionadas com a presença de barreiras transversais ao longo dos cursos de água. Comparativamente com o conhecimento sobre os impactes nas populações piscícolas dos grandes empreendimentos hidráulicos, como as barragens, os pequenos açudes (< 5 m de altura) têm...

Requalification of low-head ramped weirs through the addition of substrates (retrofitting) has attracted attention in recent years. However, few studies are available on how this measure affects the negotiation of ramped weirs by fish. This study aimed to assess the performance of an experimental ramped weir (3.00 m long with 10% slope; 0.30 m head...

Pool-type fishways have been increasingly tested to improve fish passage performance and minimize migration delays. Designing cost-effective fishways is essential for a trade-off between water uses and successful longitudinal connectivity restoration. The multislot fishway (MSF) concept, which operates with 30–50% lower discharge than a vertical sl...

Fishway research has long focused on post-establishment assessments to optimize fish passage efficiency. Model-based optimization with the use of hydrodynamic-habitat models (HHMs) has rarely been employed to investigate passage suitability based on key hydraulic variables. In this study, a vertical slot fishway was designed, the hydraulic properti...

A participatory monitoring programme of an exceptional modification of urban soundscapes during Covid-19 containment.

Environmental changes due to non-native species introductions and translocations are a global concern. Whilst understanding the causes of bioinvasions is important, there is need for decision-support tools that facilitate effective communication of the potential risks of invasive non-native species to stakeholders. Decision-support tools have been...

Climate and land-use change drive a suite of stressors that shape ecosystems and interact to yield complex ecological responses, i.e. additive, antagonistic and synergistic effects. Currently we know little about the spatial scale relevant for the outcome of such interactions and about effect sizes. This knowledge gap needs to be filled to underpin...

Freshwater ecosystems have been severely damaged worldwide by a multitude of human pressures, such as pollution, nutrient enrichment, damming or overexploitation, and this has been more intense over the past five decades. It is therefore important that the impacts of such stressors can be effectively detected, monitored and assessed in order to pro...

Heatwaves, which can be defined as increases of at least 5 °C in air temperature for more than five consecutive days for a specified reference period, are expected to become more frequent under the ongoing climate change, with freshwater organisms being particularly vulnerable to high temperature fluctuations. In Mediterranean-climate areas, depend...

The Iberian barbel (Luciobarbus bocagei) is one of the most common cyprinids in the Iberian Peninsula, whose migratory routes are often hampered by anthropogenic barriers. Fishways might be an effective mitigation measure if they integrate designed operational characteristics that account for the biomechanical requirements of this species. Understa...

Rivers have been intensively degraded due to increasing anthropogenic impacts from a growing population in a continuously developing world. Conflict demands on freshwater resources, exacerbated by climate change, present a difficult dilemma for scientists and managers: until when and how much can a river (and its natural flow regime) be altered, wh...

River fragmentation by large hydropower plants (LHP) has been recognized as a major threat for potamodromous fish. Fishways have thus been built to partially restore connectivity, with fish lifts representing the most cost-effective type at high head obstacles. This study assessed the effectiveness with which a fish lift in a LHP on the River Lima...

The addition of substrates to small instream obstacles, like low-head ramped weirs, has been considered a useful management solution to retrofit those structures and enhance fish passage. Substrate dimensions and spatial arrangement, together with discharge, and consequently water depths, appear as important factors for the creation of hydrodynamic...

Os pequenos açudes rampeados constituem um dos obstáculos fluviais mais comuns aos movimentos das espécies piscícolas. A transponibilidade destas estruturas, em que a água passa sobre as mesmas, mas não gera uma queda vertical, é sobretudo afetada pelo comprimento e declive da respetiva rampa. Contudo, a contribuição relativa destes fatores raramen...

Os pequenos açudes rampeados constituem um dos obstáculos fluviais mais comuns aos movimentos das espécies piscícolas. A transponibilidade destas estruturas, em que a água passa sobre as mesmas, mas não gera uma queda vertical, é sobretudo afetada pelo comprimento e declive da respetiva rampa. Contudo, a contribuição relativa destes fatores raramen...

Low-head ramped weirs are one of the most common small engineered structures present in Iberian rivers. Fish passability of these obstacles, where water passes over but does not generate a waterfall, is primarily related to ramp length and slope. However, the relative contribution of these factors has seldom been investigated. This study aims to as...

Numerous anthropogenic stressors impact rivers worldwide. Hypoxia, resulting from organic waste releases and eutrophication, occurs very commonly in Mediterranean rivers. Nonetheless, little is known about the effects of deoxygenation on the behavior of Mediterranean freshwater fish. To fill this knowledge gap, we assessed the impact of three diffe...

Low-head ramped weirs are a common instream obstacle to fish movements. Fish passability of these structures, where water passes over but does not generate a waterfall, is primarily related to ramp length and slope, but their relative contribution has seldom been considered. This study aims to assess the passage performance of a potamodromous cypri...

Wildfires are a common phenomenon in Mediterranean regions that is becoming increasingly frequent and severe, causing several environmental concerns, of which ash runoff represents an important source of disturbance for aquatic organisms, in particular for fishes. Studies on the behavioural response of fishes to wildfire ash runoff are scarce and s...

New engineering solutions are required to minimise the effects of an increasing number of anthropogenic barriers on watercourses. Longitudinal connectivity must be provided through fishways to allow free passage for the whole fish community. Recently, a multislot fishway (MSF) was developed, with two consecutive vertical slots that divide the overa...

The Iberian native freshwater fish fauna consists of 69 species (Ordeix & Casals, in prep), and almost all of them (95.7%) clearly migrate during their life cycle. Their migratory movements are extensive in time, and influenced by the large variation in seasonal river discharge and water temperature that is characteristic of the Mediterranean clima...

Contrary to the vast literature on dams, much less is known about the effects of small weirs on fish movements. This study aims to evaluate the upstream and downstream passage of the Iberian barbel (Luciobarbus bocagei), when facing a small broad-crested experimental weir with varying widths of the weir crest (W) and discharges (Q). Nine configurat...

Stream salinization is a great environmental hazard being aggravated by anthropogenic disturbances. Harmful conditions, as increasing salinity in freshwater systems, may negatively affect river fish fauna and possibly influence fish behaviour, such as boldness and/or cerebral lateralization. Salinity has been proven to affect behavioural expression...

Freshwater fish from the Mediterranean region are amongst the most threatened species worldwide due to increasing river degradation. Because of such threats, the number of river restoration projects has greatly increased. However, they are seldom planned with inputs from the species' life history, often resulting in erroneous practices that failed...

In Mediterranean regions and other areas with water scarcity, discharge-efficient passage systems are required to reestablish longitudinal connectivity to migratory fish. The present study compares the passage performance of the Iberian barbel (Luciobarbus bocagei), a potamodromous cyprinid, negotiating two different types of vertical slot fishways...

Background. Hybridization may drive speciation and erode species, especially when intrageneric sympatric species are involved. Five sympatric Luciobarbus species—Luciobarbus sclateri (Günther, 1868), Luciobarbus comizo (Steindachner, 1864), Luciobarbus microcephalus (Almaça, 1967), Luciobarbus guiraonis (Steindachner, 1866), and Luciobarbus steinda...

The presence of small weirs, far more numerous than dams, have altered the river systems and negatively affected fish communities, mainly by disturbing fish movements. However, contrarily to the vast literature on dams, much less is known about the effects of small weirs on fish movements. This study aims to evaluate the upstream passage performanc...

River ecosystems are most often subject to multiple co-occurring anthropogenic stressors. Mediterranean streams are particularly affected by water scarcity and organic loads that commonly lead to a simultaneous reduction in flow and increasing depletion of dissolved oxygen. In the present study, the single and combined effects of water scarcity (fl...

Most fishway studies are conducted during the reproductive period, yet uncertainty remains on whether results may be biased if the same studies were performed outside of the migration season. The present study assessed fish passage performance of a potamodromous cyprinid, the Iberian barbel (Luciobarbus bocagei), in an experimental full-scale verti...

Inúmeros estudos têm reportado sérias alterações nas comunidades piscícolas fortemente relacionadas com a presença de barreiras transversais ao longo dos cursos de água. Mesmo os pequenos açudes, considerados como barreiras a priori permeáveis à movimentação dos peixes, podem provocar sucessivas perdas de conectividade com consequências negativas n...

The cover image, by S.D. Amaral et al., is based on the Research Article To swim or to jump? Passage behaviour of a potamodromous cyprinid over an experimental broad-crested weir, DOI 10.1002/rra.3232.

Environmental flows remain biased toward the traditional biological group of fish species. Consequently, these flows ignore the inter-annual flow variability that rules species with longer lifecycles and therefore disregard the long-term perspective of the riverine ecosystem. We analyzed the importance of considering riparian requirements for the l...

Physical stressors, such as man-made obstacles, are considered one of the main causes that negatively affect freshwater fish. Even small weirs may impact fish populations, including potamodromous cyprinids, by partially or totally blocking upstream migratory movements. Some studies have addressed the effect of key hydraulic parameters on upstream m...

Endemic freshwater fish from the Mediterranean region are among the most threatened species in the world owing to increasing river degradation. Because of such threats, the number of river restoration projects has greatly increased. However, they are seldom planned with consideration of the species' life history, often resulting in erroneous practi...

Poster presented in the 10 Symposium for European Freshwater Sciences. Olomouc (Czech Republic), 2 – 7 July.

In Mediterranean rivers, water scarcity is a key stressor with direct and indirect effects on other stressors, such as water quality decline and inherent oxygen depletion associated with pollutants inputs. Yet, predicting the responses of macroinvertebrates to these stressors combination is quite challenging due to the reduced available information...

Adequately designed vertical slot fishways (VSF) mitigate the impact of anthropogenic obstructions onfish migrations. Until now, most studies on VSF were conducted focusing on high priority species, partic-ularly salmonids, while other species, such as cyprinids, have received less attention. In Mediterraneanrivers, where water availability is a pr...

Environmental flows remain biased toward the traditional biological group of fish species. Accordingly, these flows ignore the inter-annual flow variability that rules species with longer life cycles, thereby disregarding the long-term perspective of the riverine ecosystem. We analyzed the influence of considering riparian requirements for the long...

River fragmentation due to artificial barriers directly impacts fish communities by limiting migratory movements. This work aims to understand how small barriers affect the movements of a potamodromous cyprinid species – the Iberian barbel (Luciobarbus bocagei (Steindachner, 1864)) – in a 5.6 km upstream segment of a stream impacted only by the pre...

The presence of small weirs, far more numerous than dams, has increased habitat fragmentation on rivers worldwide. This study aims to evaluate the upstream passage performance of a potamodromous cyprinid, the Iberian barbel (Luciobarbus bocagei), over an experimental broad-crested weir by varying key-hydraulic parameters. Fish passage success was s...