Search Results (8)

The Iberian barbel (Luciobarbus bocagei Steindachner, 1864) and the Iberian nase (Pseudochondrostoma polylepis Steindachner, 1864) are two potamodromous species that migrate upstream in freshwater environments to reproduce. Thus, river fragmentation is a major threat to these species, and fish passes are one of the most-used mitigation measures to restore the longitudinal connectivity of impounded rivers, enabling these species to reach upstream spawning sites. Since 2013, the fish pass installed in the Coimbra dam (Mondego River) has been equipped with a video-recording system to continuously monitor fish passage. Based on visual count data between 2013 to 2015, a total of 61,965 movements of Iberian barbel (up- and downstream) and a total of 138,207 movements of Iberian nase (up- and downstream) were registered, with the migratory upstream movements of nase occurring over a wider period (i.e., January to December) relative to what is described in the literature. The analysis conducted to evaluate the temporal variability in the size of fish using the fish pass showed significant differences between the studied months for both species in both migratory directions; upstream-moving barbel showed a bigger body length in May, and nase showed bigger body lengths in the months of May, June and November. Boosted Regression Trees were used to identify the environmental variables that triggered these movements, with water temperature and flow being, overall, two of the most important variables for both species in both migratory directions. This study updates the relatively scarce available information concerning these species migrations, including movement activity and the associated peaks, size-structure characterization during the migratory periods, and the identification of environmental variables that seem to trigger Iberian barbel and nase movements. Full article

Pseudochondrostoma willkommii, called Guadiana nase in the Iberian Peninsula, is an endemic cyprinid that lives in the middle stretches of rivers and is also common in still water. According to the literature, spawning occurs in April, after upstream migration while looking for shallow waters with a current and coarse substratum. There are no previous studies about captive breeding of this species, even though it has been a common species in the Guadiana River basin for years. Now, Guadiana nase populations are declining due to allochthonous fish introductions, river fragmentation, and pollution. The main objective of this study was the natural reproduction of Pseudochondrostoma willkommii in captivity. Guadiana nase captive breeding was started in 2017 at the Vegas del Guadiana fish farm; fish were captured in the wild by electrofishing and kept in spawning ponds with a natural photoperiod and temperature regime, with spawning substrates and without previous hormonal treatment. Guadiana nase spawned in captivity beginning in the first year. Spawning took place in still water, using the coarse substratum areas; no current was provided in the pond. It started in March and continued in April; at least two batches of larvae were recorded. The number of fingerlings was quite variable in different years; final juvenile fish densities ranged from 1.78 to 90.39 fish/m³ and were not correlated with the initial number of spawners. Better results were obtained the sooner we introduced spawners to the pond, which enabled proper acclimatization and more complex habitat conditions. Spawners gathered in groups, except in the ponds with the lowest densities, where they were never in groups and showed agonistic behavior. This agonistic behavior did not affect reproduction success. Full article

The introduction of invasive alien species (IAS) is a severe problem in ecosystems worldwide, heavily impacting biodiversity and especially endemic species. This situation is especially worrying in the Iberian Peninsula, since Spain and Portugal’s rivers and lakes host an outstanding richness of endemic freshwater species. Ignorance about IAS presence and distribution is a serious problem that hampers its management. Regarding invasive fish species, difficulties in sampling and studying the ichthyofauna of lentic and deep waters, where many IAS inhabit, comprise some of the reasons for this lack of knowledge. In this study, we sampled the fish community of ten impounded waters in Navarre (Ebro River Basin, Spain) using multi-mesh gillnets. Four sampling points were dams located in rivers, and the remaining points were ponds. One of these ponds had a direct connection with a water channel, and another was found in a flood plain, so it connects with a nearby river in floods. The remaining ponds did not have a direct connection to any major river. A total of 14 fish species were detected (9 of which were IAS (64.3%)), with 3383 specimens collected (56% IAS). Only one of the analyzed dams did not contain IAS. Numerically, the most abundant fish was the exotic bleak (Alburnus alburnus) (almost 44% of the captures), followed by the native Ebro nase (Parachondrostoma miegii) (23.4%). The most widely distributed IAS were the common carp (Cyprinus carpio) and the bleak, which appeared in 70% and 60% of the sampling stations, respectively. IAS in dams accounted for 50% of the total species found and represented 21.3% of fish abundance. On the other hand, 64.3% of species in ponds were IAS, reaching 68.3% of fish abundance. This percentage increased when analyzing only the ponds without a natural connection with rivers or canals, where IAS introduction would be anthropic. IAS species in these points represented 71.4% of total fish species and 92.5% of the abundance of fish. Full article

Histopathology has been used as a very useful tool to provide information on the severity of tissue damage, injuries, and organ functionality. Thus, this work aimed to assess whether seasonal variations (summer and winter) in water quality had consequences on the liver histology of Iberian barbel (Luciobarbus bocagei) and Douro nase (Pseudochondrostoma duriense). The research was carried out in the Vilariça River, a tributary of the Sabor River in Portugal, which is used as spawning grounds by these endemic cyprinids. The liver histopathological changes, assessed through a semi-quantitative system, allowed the identification of 13 histopathological changes located in the hepatic parenchyma, bile duct, and blood vessels. The histopathological changes with a higher prevalence in both species were vacuolization of hepatocytes, endothelial rupture, necrosis, fibrosis, and degenerative vacuolization. The results showed that the severity degree of liver histological alterations ranged between moderate and severe, and the major severity degree was observed in L. bocagei, in the summer season, and at the sampling points located in the downstream and middle stream. The canonical analysis indicated that the exposure of fish to metals may increase the potential risk of liver damage. Thus, in the summer, the high concentrations of Fe, Cu, Zn, As, and Mn justified the prevalence of the biliary duct epithelial detachment, in both species, and the hyperplasia of biliary epithelium, in L. bocagei. In the winter, the high TSS and Cd, Ni, and Cr concentrations justified the prevalence of congestion of blood vessels and degenerative vacuolization in both species. The higher hepatosomatic index of fish caught in the winter was due to the high presence of degenerative vacuolization and hepatocyte vacuolization. The severity of liver histopathological changes reflected differences in the type of contaminants in different seasons and sampling periods, and was thus proven as a valuable indicator of water quality. Full article

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 (Touvedo, Portugal), allows potamodromous fish—Iberian barbel (Luciobarbus bocagei), Northern straight-mouth nase (Pseudochondrostoma duriense) and brown trout (Salmo trutta fario)- to migrate upstream. Most fish (79.5%) used the lift between summer and early-fall. Water temperature was the most significant predictor of both cyprinids’ movements, whereas mean daily flow was more important for trout. Movements differed according to peak-flow magnitude: nase (67.8%) made broader use of the lift in the absence of turbined flow, whereas a relevant proportion of barbel (44.8%) and trout (44.2%) passed when the powerhouse was operating at half (50 m³s⁻¹) and full-load (100 m³s⁻¹), respectively. Size-selectivity found for barbel and trout could reflect electrofishing bias towards smaller sizes. The comparison of daily abundance patterns in the river with fish lift records allowed the assessment of the lift’s efficacy, although biological requirements of target species must be considered. Results are discussed in the context of management strategies, with recommendations for future studies. Full article

Endemic freshwater fish from semiarid environments are among the most threated species in the world due to water overexploitation and habitat fragmentation problems. Stepped or pool-type fishways are used worldwide to reestablish longitudinal connectivity and mitigate fish migration problems. Many of them are being installed or planned in rivers of semiarid environments, however, very few studies about fish passage performance through pool-type fishways has been carried out to date on these regions. The present work focuses on the passage performance of two potamodromous cyprinids endemic of these regions, with different ecological and swimming behavior: southern Iberian barbel (Luciobarbus sclateri) and Iberian straight-mouth nase (Pseudochondrostoma polylepis). These are assessed in two of the most common types of stepped fishways: vertical slot and submerged notch with bottom orifice fishways. Experiments were carried out during the spawning season in the Segura River (southeastern Spain), using a passive integrated transponder (PIT) tag and antenna system. Ascent success was greater than 80%, with a median transit time lower than 17 minutes per meter of height in all trials, and for both species and fishway types. Results show that both types of fishways, if correctly designed and constructed, provide interesting alternatives for the restoration of fish migration pathways in these regions. Full article

One of the movement barriers that fish populations must overcome for migration success in the upper basin of Tormes river (Salamanca, Spain) is a 20 m high dam. The design of its pool and weir fishway for potamodromous fishes (mostly Iberian barbel—Luciobarbus bocagei—and Northern straight-mouth nase—Pseudochondrostoma duriense) to overcome the obstacle was improved in 2013. The aim of this study was to assess the efficiency of the fishway using FDX passive integrated transponder (PIT)-Tags inserted into the fish and PIT-Tag detection antennas at the fishway. During several sampling events, 7113 barbel and nase individuals were tagged and released at the point of capture along the basin (2538 and 4575 of which were tagged downstream and upstream, respectively). PIT-Tag Detection Antennas close to the top and bottom of the fishway monitored tagged fish continuously for 10 months (from March to December 2017), to analyze the performance of the fishway. Upstream passage efficiency was greater for barbel (60% and 25% for barbel and nase, respectively). Differences in passage efficiency between species may be due to differences in their size. Mean length for barbels attempting to pass was 336 mm (±47 mm) while for nases was 143 mm (±26 mm). Moreover, both the number of attempts to pass and ascend time for nases were higher than for barbels. Entrance efficiency was low (3.5% and 10.8% for barbel and nase, respectively), although 2017 was a very dry year, thus these results are most likely influenced by flow rates. Therefore, the fishway has proved to be functional but is actually poor for efficiency purposes, especially for small fish. Full article

A repulsive effect, that some induced primary stimuli, like sound and light, is known to be provoked in fish behavior. In the present study, two strobe light frequencies, 350 flashes/minute and 600 flashes/minute, were tested in laboratorial conditions, using three native freshwater fish species of northern Portugal: Brown trout (Salmo trutta), Northern straight-mouth nase (Pseudochondrostoma duriense) and Iberian barbel (Luciobarbus bocagei). The results showed a differential repulsive behavior of the fish species to light stimulus, and particularly to a frequency of 600 flashes/minute. S. trutta presented the most repulsive behavior, whereas the L. bocagei showed less repulsion to the light stimulus. No relevant differences were found between pre-test and post-assessments, confirming a rapid recovery of natural fish behavior after the deterrent effect. The results highlighted the potential of behavioral barriers, particularly in salmonid streams, based on strobe light stimulus. Full article