Stickleback fishes in the family Gasterosteidae have become model organisms in ecology and evolutionary biology. However, even in the case of the most widely studied species in this family - the three-spined stickleback (Gasterosteus aculeatus) - the worldwide phylogenetic relationships and colonization history of the different populations and lineages remain poorly resolved. Using a large collection of samples covering most parts of the species distribution range, we subjected thousands of single nucleotide polymorphisms to coalescent analyses in order to reconstruct a robust worldwide phylogeny of extant G. aculeatus populations, as well as their ancestral geographic distributions using Statistical-Dispersal Vicariance and Bayesian Binary MCMC analyses. The results suggest that contemporary populations originated from the Pacific Ocean in the Late Pleistocene, and the Atlantic was colonized through the Arctic Ocean by a lineage that diverged from Pacific sticklebacks ca 44.6 Kya. This lineage contains two branches: one that is distributed in the Mediterranean area, from the Iberian Peninsula to the Black Sea ('Southern European Clade'), and another that is comprised of populations from northern Europe and the east coast of North America ('Trans-Atlantic Clade'). Hence, the results suggest that the North American East Coast was colonized by trans-Atlantic migration. Coalescence-based divergence time estimates suggest that divergence among major clades is much more recent than previously estimated.

River regulation for hydroelectricity production results in rapid changes of flow and habitat features, but its effects in the movement patterns of freshwater fish are not well understood. Radiotelemetry was used to track Iberian barbel during a year cycle in non-regulated and regulated rivers. We applied a kernel density method to estimate and compare home range sizes of the two populations. Seasonal patterns of movement and the intra-annual variation in habitat preferences were also compared. Barbel inhabiting regulated river exhibit larger and more continuous home and core ranges, in opposition to the smaller and patchy areas used by fish inhabiting the non-regulated river. Seasonal movements of both populations were differentiated by the drought period. Barbel from the non-regulated river had to search for suitable refuges, with specific habitat characteristics, in which they remained aggregated during harsh summer conditions. Conversely, barbel from regulated river kept a continuous distribution along the river. This study contributes to the management of regulated rivers by providing insights about which flow components are more altered by hydropeaking operations and which are the most critical annual periods for fish movements. It also suggests several restoration actions, such as the protection of fish summer refuges, the restoration of large-scale temporal streamflow variability and the reduction of daily rates of discharge rise and fall, which should be continuously monitored in order to increase their efficiency and provide new knowledge.

Spatial variability in streamflow characteristics is responsible for a large range of habitat variations to which fish are adapted through life-cycle strategies and morphological adaptations. In this study, we compared the swimming performance and related morphology of two Iberian barbel populations from permanent and temporary rivers. The permanent river was characterised by its Atlantic influence with higher water availability and a more unstable and turbulent environment, contrasting with the lower discharge setting observed in the southern Mediterranean ecosystem during most of the hydrological year. Barbels from the permanent river exhibited a higher critical swimming speed (U crit ) associated with a more fusiform body shape, narrower head and caudal peduncle, lower body condition and longer and higher pectoral and dorsal fins, when compared with the population from the temporary watercourse. These results reflect a morphological response in a way to reduce hydrodynamic resistance and energy expenditure during locomotion that we hypothesise here to be related with the different hydrological regimes of the studied systems.

Decline in fish species populations due to river regulation by dams and weirs promoted the development of fishways, which are becoming one of the most common measures for the restoration of connectivity in rivers. Fishways efficiency can be species specific and thus monitoring and evaluation, and subsequent adjustments to design and hydraulic features, are required to inform potential users prior to installation. In this study we tested the applicability of electromyogram telemetry to study the swimming behavior of a cyprinid potamodromous species, the Iberian barbel Luciobarbus bocagei Steindachner, 1864, in an experimental pool-type fishway. In total, 24 barbels were used in the experiment, 12 of which were tagged with EMG radio transmitters equipped with electrodes that register muscle activity, while the other 12 untagged fish were used as control. For tagged fish, a relationship between swimming speed and EMG telemetry signals was developed in a swimming tunnel, which was later used to assess barbels swimming behavior within the experimental fishway. Tagged fish exhibited high passage success and anaerobic burst swimming was only required to move through the submerged orifices of the fishway. Barbels spent successively less time when transversing the pools in the upstream direction. Measured hydraulic variables that were related with barbels' swimming speed within the fishways were the water velocity, turbulent kinetic energy, turbulence intensity and, especially, the horizontal component of Reynolds shear stress, highlighting the importance of these parameters when designing pool-type fishways.

Many studies have assessed the effects of large dams on fishes but few have examined the effects of small obstacles. Fishes were sampled and environmental variables were characterized at 28 sites in two Iberian streams, 14 located immediately downstream, upstream and between five small obstacles at river Muge and 14 at river Erra, considered as the reference stream. Multivariate analysis indicated that habitat variables like current velocity and depth, but not physicochemistry, were mainly responsible for site groups' discrimination in both streams. The reference stream exhibited a longitudinal gradient of current velocity that, however, was not strong enough to cause significant changes in the fish assemblage's composition and structure. By successive and drastically repeating this gradient near each structure, the obstacles stream presented differences in fish fauna between the three site types. Lentic upstream sites presented higher density of limnophilic, omnivorous and exotic species, like gudgeon Gobio lozanoi, which are well adapted to this type of habitat. Downstream and between obstacles sites were characterized by the dominance of rheophilic and invertivorous taxa, especially barbel Luciobarbus bocagei. Richness metrics did not differ among site types, but diversity was higher in sites located between the obstacles away from its direct influence, where the habitat diversity was higher. Contrarily to upstream sites, downstream and between obstacles sites were similar in many of the studied features to the reference stream, implying that this type of structures cause a higher modification in the upstream fish community. This study suggests that the effects of small obstacles on habitat and fishes are similar, in some extent, to those reported for larger dams, providing important considerations for riverine ecosystem conservation efforts.

In 2011, a vertical‐slot fish pass was built at the Coimbra Açude‐Ponte dam (Mondego River, Portugal), approximately 45 km upstream from the river mouth. The performance of this infrastructure for sea lamprey passage was evaluated between 2011 and 2015 using several complementary methodologies, namely radio telemetry [conventional and electromyogram (EMG)], passive integrated transponder (PIT) telemetry and electrofishing surveys. During the study period, the electrofishing revealed a 29‐fold increase in the abundance of larval sea lamprey upstream of the fish pass. Of the 20 radio‐tagged individuals released downstream from the dam, 33% managed to find and successfully surpass the obstacle in less than 2 weeks, reaching the spawning areas located in the upstream stretch of the main river and in one important tributary. Fish pass efficiency was assessed with a PIT antenna installed in the last upstream pool and revealed a 31% efficiency, with differences between and within migratory seasons. Time of day and river flow significantly influenced the attraction efficiency of the fish pass, with lampreys negotiating it mainly during the night period and when discharge was below 50 m3 s−1. Sea lampreys tagged with EMG transmitters took 3 h to negotiate the fish pass, during which high muscular effort was only registered during passage, or passage attempts, of the vertical slots. The use of complementary methodologies provided a comprehensive passage evaluation for sea lamprey, a species for which there is a considerable paucity of valuable data concerning behavioural, physiological and environmental influences on obstacle negotiation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

The effects of river regulation on the hydrological cycle of a river and on the respective fish assemblage may differ according to dam operation purpose and type of river analysed. To assess the spatial and temporal variation of fish assemblages and their response to the hydrological changes caused by two different types of flow regulation, we selected three sampling sites in four rivers with different levels of regulation, two in a permanent river system and another two on a temporary one, which we sampled in four different annual seasons. In the permanent system, hydroelectrical regulation decreased hydrological variability, which affected fluvial specialist species, benefitting the generalist ones, and created a more homogeneous community that presented less intra-annual variation. In the temporary system, agricultural regulation caused an inversion of the hydrological cycle, maintaining a moderate flow volume throughout the drought period that benefited the introduced, generalist and more tolerant species. Monthly volume was recognized, in a temporal scale, as the most important hydrological feature for assemblages' structure, predicting the intra-annual variation of several ecological guilds. This study provides important considerations for dam management and riverine ecosystems conservation.

Streamflow variability, natural and human induced, has been suggested as a driver of life history differences among freshwater fish populations. During 1 year, we collected bimonthly and fortnightly samples from four populations of Iberian barbel, inhabiting permanent and temporary Mediterranean rivers with non-regulated and regulated flow regimes. We analysed data for fish age, growth and reproduction to (i) compare barbels' life cycles between permanent and temporary non-regulated rivers; (ii) assess the effect of two types of flow alteration in these traits; and (iii) identify flow variables significantly related with growth and reproductive cycles. Regional differences were related with the age of first maturation, growth rate and timing and duration of the reproductive season. Flow regulation promoted a decrease of fish growth rates, condition and gonad activity and an increase of maximum length and longevity. Seasonal variation of growth and gonad maturation were related with temperature and streamflow components. This study offers a multi-regional perspective of the relationship between fish biological cycles and streamflow variability, providing water resource managers with needed perspective about the effect of anthropogenic alteration of streamflow magnitudes.