Efectos de las puntas de caudal hidroeléctricas (hidropuntas) en las poblaciones de trucha común (Salmo trutta) de ríos pirenaicos

[spa] Las puntas de caudal de origen hidroeléctrico (hidropuntas) provocan cambios de distinta intensidad y alcance, a todos los niveles de organización de los ecosistemas fluviales donde tienen lugar. No hay en condiciones naturales, una situación comparable y por tanto no hay ni especies ni ecosistemas específicamente adaptados a ella. Comprender en profundidad la magnitud de los efectos es la única opción para poder definir y llevar a la práctica, medidas eficaces y equilibradas entre la producción de energía hidroeléctrica y la conservación de los ecosistemas fluviales. Esta Tesis Doctoral pretende mejorar el conocimiento sobre los efectos de las hidropuntas en las poblaciones de trucha (Salmo trutta) de ríos pirenaicos de la vertiente mediterránea. Para ello se ha estudiado la dinámica poblacional, la movilidad y la alimentación de la trucha en un tramo con hidropuntas, comparándolo con uno de control y otro de referencia más alejado pero dentro de la misma cuenca. Los resultados obtenidos indican que las hidropuntas tienen una influencia directa y muy significativa sobre la organización del cauce y el hábitat físico, lo que a su vez determina cambios en las densidades de trucha, especialmente de alevines (disminución de frezaderos, condiciones hidráulicas desfavorables,…). Estos efectos, no obstante, se atenúan río abajo, especialmente cuando se incorporan tributarios con aporte de carga sedimentaria. Se ha constatado también que la estructura demográfica de la trucha en tramos sujetos a hidropuntas es más estable al paso de crecidas naturales de cierta entidad. Las poblaciones de trucha de los tramos altos de los ríos Flamisell y Noguera Pallaresa tienen un carácter marcadamente sedentario a lo largo del año. El 76,8% de ejemplares realizan movimientos inferiores a 20 m y solo un 3,6% los realizan superiores a 200 m. Las hidropuntas no parece que influyan directamente sobre los patrones de movilidad de las truchas. Sí que se observan diferencias considerables en la amplitud de los movimientos relacionados con la época de freza, significativamente mayores en el tramo de hidropuntas, sin duda debido a la falta de zonas aptas para la freza. A escala de una hidropunta, la movilidad de las truchas es mayor durante la primera mitad de la punta de caudal, especialmente en sentido río arriba. Coincide con el incremento de la deriva de macroinvertebrados y se manifiesta como el momento de mayor ingesta de alimentos por parte de las truchas. En general, en el tramo con hidropuntas las truchas presentaron mayor tasa de consumo de alimentos y una dieta más generalista y heterogénea, lo que indica un comportamiento alimentario oportunista. Las hidropuntas no parecen causar impactos negativos directos en la alimentación de la trucha adulta. De acuerdo con los resultados obtenidos, algunas actuaciones sobre el hábitat físico en tramos con hidropuntas como la incorporación de gravas, la restitución de zonas de freza, la creación de refugios, etc., pueden contribuir sustancialmente a la conservación de las poblaciones de trucha de estos tramos sometidos a un régimen de caudales altamente fluctuante.[cat] Les puntes de cabal d'origen hidroelèctric (hidropuntes) provoquen canvis de diferent intensitat i abast, a tots els nivells d'organització dels ecosistemes fluvials on tenen lloc. No hi ha en condicions naturals, una situació comparable i per tant no hi ha ni espècies ni ecosistemes específicament adaptats a ella. Comprendre en profunditat la magnitud dels efectes és l'única opció per poder definir i portar a la pràctica, mesures eficaces i equilibrades entre la producció d'energia hidroelèctrica i la conservació dels ecosistemes fluvials. Aquesta tesi doctoral pretén millorar el coneixement sobre els efectes de les hidropuntas en les poblacions de truita (Salmo trutta) de rius pirinencs del vessant mediterrani. Per això s'ha estudiat la dinàmica poblacional, la mobilitat i l'alimentació de la truita en un tram amb hidropuntes, comparant-lo amb un de control i un altre de referència més allunyat però dins de la mateixa conca. Els resultats obtinguts indiquen que les hidropuntes tenen una influència directa i molt significativa sobre l'organització de la llera i l'hàbitat físic, el que al seu torn determina canvis en les densitats de truita, especialment d'alevins (disminució de zones de fressa, condicions hidràuliques desfavorables, ...). Aquests efectes, però, s'atenuen riu avall, especialment quan s'incorporen tributaris amb aportació de càrrega sedimentària. S'ha constatat també que l'estructura demogràfica de la truita en trams subjectes a hidropuntas és més estable al pas de crescudes naturals de certa entitat. Les poblacions de truita dels trams alts dels rius Flamisell i Noguera Pallaresa tenen un caràcter marcadament sedentari al llarg de l'any. El 76,8% d'exemplars realitzen moviments inferiors a 20 m i només un 3,6% els realitzen superiors a 200 m. Les hidropuntes no sembla que influeixin directament sobre els patrons de mobilitat de les truites. Sí que s'observen diferències considerables en l'amplitud dels moviments relacionats amb l'època de fresa, significativament majors en el tram de hidropuntas, sens dubte a causa de la manca de zones aptes per a la fresa. A escala d'una hidropunta, la mobilitat de les truites és major durant la primera meitat de la punta de cabal, especialment en sentit riu amunt. Coincideix amb l'increment de la deriva de macroinvertebrats i es manifesta com el moment de major ingesta d'aliments per part de les truites. En general, en el tram amb hidropuntes les truites van presentar una major taxa de consum d'aliments i una dieta més generalista i heterogènia, la qual cosa indica un comportament alimentari oportunista. Les hidropuntes no semblen causar impactes negatius directes en l'alimentació de la truita adulta. D'acord amb els resultats obtinguts, algunes actuacions sobre l'hàbitat físic en trams amb hidropuntes, com ara la incorporació de graves, la restitució de zones de fresa, la creació de refugis, etc. poden contribuir substancialment a la conservació de les poblacions de truita d'aquests trams sotmesos a un règim de cabals altament fluctuant.[eng] Peak flows of hydroelectric origin (hydropeaking) lead to changes of different intensity and scope at all levels of organization of fluvial ecosystems where they occur. In natural conditions, there is no comparable situation and therefore no species or ecosystems are specifically adapted to it. A deep understanding of the magnitude of the effects is the only option in order to define and implement effective and balanced measures between hydroelectric power production and the conservation of river ecosystems. This Doctoral Thesis aims to improve the knowledge of the effects of hydropeaking on populations of brown trout (Salmo trutta) of the Pyrenean rivers in the mountain Mediterranean catchments. To do so, the population dynamics, mobility and feeding of the brown trout have been studied in a stretch with hydropeaking, comparing it with a control stretch and another benchmark stretch further away but still within the same watershed. The results obtained show that hydropeaking has a direct, significant influence on the organization of the watercourse and the physical habitat, which in turn determines changes in brown trout population densities, especially of juveniles (fewer spawning grounds, unfavourable hydraulic conditions,...). These effects, however, are attenuated downstream, especially when tributaries contribute sedimentary load. It has also been found that the demographic structure of brown trout in stretches of river subject to hydropeaking is more stable in front of the occurrence of natural flooding of a certain magnitude. The brown trout populations in the upper sections of the Flamisell and Noguera Pallaresa rivers have a markedly sedentary character throughout the year. A 76.8% of specimens move less than 20 m and only 3.6% move further than 200 m. Hydropeaking does not seem to directly influence brown trout mobility patterns. However, considerable differences are observed in the breadth of movements associated with the spawning season, being significantly higher in the section of hydropeaking, doubtless due to the lack of areas suitable for spawning. On the scale of a hydropeak, the mobility of the brown trout is greater during the first half of the flow peak, especially in the upstream direction. It coincides with the increase of macroinvertebrate drift and manifests itself as the time of greatest food intake by brown trout. In general, in the stretch with hydropeaking the brown trout had a higher rate of food consumption and a more general and heterogeneous diet, indicating opportunistic feeding behaviour. Hydropeaking does not seem to cause direct negative impacts on adult brown trout feeding. According to the results obtained, acting on the physical habitat in stretches with hydropeaking as the incorporation of gravel, restoring spawning grounds, the creation of shelters, etc., may contribute substantially to the conservation of the populations of brown trout in these stretches with a highly fluctuating flow regime

Effects of pulsed discharges from a hydropower station on summer diel feeding activity and diet of brown trout (Salmo trutta Linnaeus, 1758) in an Iberian stream.

The influence of pulsed discharges associated with hydroelectric power generation (i.e. hydropeaking) on feeding activity and diet composition of adult brown trout (Salmo trutta) was studied during the summer by comparing two sites: upstream (control site) and downstream from a power plant (hydropeaking site). Twenty fish were captured from each study site by electrofishing at 4-hour intervals for two consecutive days and stomach contents were collected with pulsed gastric lavage. Hydropeaking events affected brown trout feeding behaviour as well as prey availability. Feeding intensity, measured by the stomach Fullness Index, showed pronounced variations with maximum values after flow pulses, which were linked to variations in prey availability because of increased drift rates of invertebrates. In contrast, brown trout living at the control site showed smoother variations in feeding activity not linked to invertebrate drift. Overall, brown trout at the hydropeaking site had higher food consumption rates and a more generalist and heterogeneous diet than trout from the control site, indicating an opportunistic feeding behaviour during flow pulses. Therefore, the hydrological disturbance caused by hydropeaking did not appear to cause direct negative impacts on feeding of adult brown trout. However, reduced trout density and imbalanced size structure in the hydropeaking site were detected, requiring further research to clarify the spatial influence of hydropeaking on other factors that could negatively affect brown trout populations

Hydropeaking effects on movement patterns of brown trout (Salmo trutta L.)

Radiotelemetry was used to investigate seasonal movement and home range of brown trout Salmo trutta (size range 188–420 mm fork length, N = 30) in two reaches of the Noguera Pallaresa River (Ebro Basin, north‐east Spain) subjected to different flow regulation schemes. NP‐1 reach is a bypassed section with near natural flow conditions, whereas the downstream reach NP‐2 is subjected to daily pulsed flow discharge (i.e., hydropeaking) from an upstream hydropower station. Significant differences in home range size (95% kernel estimates) and seasonal movement pattern between study reaches were found. Mean home range size was (μ ± SE) 112.1 ± 11.5 m in the bypassed reach NP‐1 and increased significantly in the hydropeaking reach NP‐2 up to 237.9 ± 37.2 m. There was a large individual variability in fish home range size within reaches. Most of the seasonal differences in fish movement among reaches were associated with the spawning season. Pulsed discharge events in NP‐2 during daytime in summer (lasting about 3 hr and increasing water flow from 1 to 20 m3/s) did not cause significant displacements in either upstream or downstream direction during the duration of the event. Our results highlight the importance of habitat connectivity in hydropeaking streams due to the need of brown trout to move large distances among complementary habitats, necessary to complete their life cycle, compared with unregulated or more stable streams.Financial support was provided by the Biodiversity Conservation Plan of ENDESA, S.A. (ENEL Group). Carles Alcaraz acknowledges support from CERCA Programme (Generalitat de Catalunya)

Movements and dispersal of brown trout (Salmo trutta Linnaeus, 1758) in Mediterranean streams: influence of habitat and biotic factors

Dispersal is a critical determinant of animal distribution and population dynamics, and is essential information for management planning. We studied the movement patterns and the influence of habitat and biotic factors on Mediterranean brown trout (Salmo trutta) by mark-recapture methods in three headwater streams of the Ebro Basin (NE Iberian Peninsula). Fish were sampled by electrofishing on five occasions over 18–24 months and movements of over 3,000 individually tagged trout (age 1+ onwards) were recorded. Most of the tagged fish exhibited limited movement and were recaptured within 100 m from the initial capture section. Small seasonal differences in the movement pattern were observed, but in two of the streams, displacement distances increased prior the spawning period in autumn. The frequency distributions of dispersal distances were highly leptokurtic and skewed to the right and fitted well to a two-group exponential model, thus trout populations were composed of mobile and stationary individuals, the latter being the predominant component in the populations (71.1–87.5% of individuals). The mean dispersal distances, for fish captured at least in three sampling events, ranged 20.7–45.4 m for the stationary group and 229.4–540.5 m for the mobile group. Moving brown trout were larger than non-moving individuals and exhibited higher growth rates in two of the streams. Habitat features were not consistently linked to movement rates, but there were some interaction effects between stream and habitat characteristics such as depth, cover and water velocity.info:eu-repo/semantics/publishedVersio

Movements and dispersal of brown trout (Salmo trutta Linnaeus, 1758) in Mediterranean streams: influence of habitat and biotic factors

Dispersal is a critical determinant of animal distribution and population dynamics, and is essential information for management planning. We studied the movement patterns and the influence of habitat and biotic factors on Mediterranean brown trout (Salmo trutta) by mark-recapture methods in three headwater streams of the Ebro Basin (NE Iberian Peninsula). Fish were sampled by electrofishing on five occasions over 18–24 months and movements of over 3,000 individually tagged trout (age 1+ onwards) were recorded. Most of the tagged fish exhibited limited movement and were recaptured within 100 m from the initial capture section. Small seasonal differences in the movement pattern were observed, but in two of the streams, displacement distances increased prior the spawning period in autumn. The frequency distributions of dispersal distances were highly leptokurtic and skewed to the right and fitted well to a two-group exponential model, thus trout populations were composed of mobile and stationary individuals, the latter being the predominant component in the populations (71.1–87.5% of individuals). The mean dispersal distances, for fish captured at least in three sampling events, ranged 20.7–45.4 m for the stationary group and 229.4–540.5 m for the mobile group. Moving brown trout were larger than non-moving individuals and exhibited higher growth rates in two of the streams. Habitat features were not consistently linked to movement rates, but there were some interaction effects between stream and habitat characteristics such as depth, cover and water velocity

Differential metabolic profiles associated to movement behaviour of stream-resident brown trout (Salmo trutta)

The mechanisms that can contribute in the fish movement strategies and the associated behaviour can be complex and related to the physiology, genetic and ecology of each species. In the case of the brown trout (Salmo trutta), in recent research works, individual differences in mobility have been observed in a population living in a high mountain river reach (Pyrenees, NE Spain). The population is mostly sedentary but a small percentage of individuals exhibit a mobile behavior, mainly upstream movements. Metabolomics can reflect changes in the physiological process and can determine different profiles depending on behaviour. Here, a non-targeted metabolomics approach was used to find possible changes in the blood metabolomic profile of S. trutta related to its movement behaviour, using a minimally invasive sampling. Results showed a differentiation in the metabolomic profiles of the trouts and different level concentrations of some metabolites (e.g. cortisol) according to the home range classification (pattern of movements: sedentary or mobile). The change in metabolomic profiles can generally occur during the upstream movement and probably reflects the changes in metabolite profile from the non-mobile season to mobile season. This study reveals the contribution of the metabolomic analyses to better understand the behaviour of organisms.This study has been supported and financed by the Biodiversity Conservation Plan of ENDESA, S.A. (ENEL Group)

Population trends and current status of the endangered Pyrenean sculpin

The status of Pyrenean sculpin Cottus hispaniolensis was assessed in the Spanish part of the Garonne drainage on the basis of its distribution and abundance from 2001 to 2016. Population trends showed a progressive reduction in range extension and density, exacerbated by a severe spate occurred in 2013. However, C. hispaniolensis was resilient to this natural disturbance by compensating for mortality with increasing recruitment. Both occurrence and density of Pyrenean sculpin showed a positive correlation with coarse substrates. Riverine habitat deterioration, mainly channelization, presence of dams and flow regulation are the main factors threatening sculpin populations. Several management measures are proposed

Adaptation of the European Fish Index (EFI+) to Include the Alien Fish Pressure

The European Fish Index EFI+ is the only fish-based multimetric index for the assessment of the ecological status of running waters that is validated and thus applicable across most countries of the European Union. Metrics of the index rely on several attributes of the species present in the fish assemblage, irrespective of their native/alien status. The abundance of alien fish, together with other anthropogenic impacts, is one of the most important threats to the conservation of native fish and ecosystem health and is also an indicator of degraded stream conditions. Therefore, to improve the performance of the EFI+ in regions with high incidence of alien species, the EFI+ was adapted to include alien fish pressure as a new metric that reflects the number of alien species as well as the proportional abundance of alien individuals. The application of the adapted index (A-EFI+) is illustrated with data from several Iberian Mediterranean basins and showed similar or stronger correlations than the original EFI+ with anthropogenic pressure (land-use variables and alterations in hydrology and river morphology) and with other regional fish indices. EFI+ has been invaluable to intercalibrate fish indices across Europe, and A-EFI+ is similar but explicitly includes alien pressure, thus helping to provide a more comprehensive assessment of ecosystem health and to communicate it to society.Financial support was provided by the Spanish Ministry of Science, Innovation and Universities (MCIN/AEI/10.13039/501100011033) and the European Union (NextGenerationEU/PRTR) through projects PID2019-103936GB-C21, TED2021-129889B-I00 and RED2022-134338-T.info:eu-repo/semantics/publishedVersio