Stream Populations Research Articles

Potential loss and rehabilitation of stream longitudinal connectivity: fish populations in urban streams with culverts

Riverine connectivity is important to the persistence of fish communities, but culverts may impede fish movements to varying degrees and in both directions. Baffles can be installed in culverts to mitigate upstream connectivity loss; however, evaluation of their effectiveness is limited. To examine the potential impacts of culverts and their potential rehabilitation with baffles, we sampled fish populations in 26 streams that contained either (i) nonbaffled culverts or (ii) baffled culverts or (iii) lacked culverts (reference streams) in Metro Vancouver, British Columbia, Canada. Using mixed effects models, we compared fish responses across these three stream types to infer effects at the whole-stream scale (i.e., over both upstream and downstream positions equally), the within-stream scale (i.e., upstream versus downstream of culverts), and the interaction of scales. Densities (n·m−2) of coastrange sculpin (Cottus aleuticus) and prickly sculpin (Cottus asper) were significantly lower in nonbaffled and baffled stream types than in reference stream types, while densities of cutthroat trout (Oncorhynchus clarkii) and rainbow trout (Oncorhynchus mykiss) were significantly lower in reference stream types, indicating whole-stream differences. Using multivariate statistics, we similarly found that fish community compositions were significantly different across stream types. For our various fish responses, we found no interaction between stream type and upstream or downstream position. Further, we found reaches directly downstream of baffled culverts had greater fish biomass and that overall species richness increased with age of baffles. These data suggest that culverts may drive changes in fish populations at whole-stream scales, and restoration of these effects with baffles may take decades.

Distributional ecology of a rare, endemic stonefly

AbstractRare species are difficult to study or conserve. Beloneuria jamesae Stark and Szczytko (Cheaha Stone) (Plecoptera∶Perlidae) is endemic to the Talladega Mountains, Alabama, USA, rarely collected, and considered imperiled. We collected stonefly larvae at 181 locations and found Cheaha Stone at 33% of these. Species distribution modeling by classification tree analysis identified elevation, stream size, and permanence as key habitat variables. Cheaha Stone was most prevalent in small permanent streams at higher elevation but extended into larger streams with sources at high elevation. Populations occurred infrequently in small streams at lower elevations. The known distribution of Cheaha Stone is protected within public lands, but climate warming and possible increases in drought frequency and severity could restrict the species to fragmented populations in small streams draining the highest summits of this low mountain range. Our georeferenced data and explicit classification tree are foundations fo...

Egg Cannibalism inPomacea canaliculata(Caenogastropoda: Ampullariidae) from the Southern Pampas: An Alternative Trophic Strategy?

Pomacea canaliculata is a freshwater gastropod native to southern South America and is listed among the world's 100 worst invaders. Diverse food sources can be exploited by this apple snail, including snails with gelatinous and subaquatic egg masses. Records of ingestion of their own egg masses (egg cannibalism), which are aerial and calcareous, have only been anecdotal in P. canaliculata. Our aims were to study egg cannibalism in a natural population and also under laboratory conditions. In a stream population from the southern Pampas, we recorded P. canaliculata attacking their own fresh egg masses, which had been naturally submerged by an increase in water level. In addition, when we artificially submerged fresh and old egg masses in a field experiment, we observed several snails readily attacking both. In the laboratory, we also observed the capture by pedal surface collecting of floating remains of egg masses. In laboratory trials, juveniles fed on eggs reached larger sizes than starved snails but smaller than those fed on lettuce; adult snails also eat eggs, but their growth rates were not affected by the food regime. Pomacea canaliculata eggs present defensive and anti-nutritive compounds that apparently dissuade almost all potential predators, but this snail did not appear to be negatively affected when feeds on its own eggs. The ingestion of egg remains and submerged egg masses is probably more frequent than previously considered in P. canaliculata, which may take advantage of using these alternative food resources when others are scarce.

Impact of deforestation on pearl mussel habitats in the Russian section of the Baltic Sea basin

Changes in the vegetation cover associated with intensive forest extermination may have a strong effect on the riverine environment, including the chances of survival for bivalve mollusc populations in small streams and rivers. In order to check this hypothesis, drainage area properties of the rivers with extinct and existing pearl mussel populations in the Russian section of the Baltic Sea basin were compared. Preservation of forest vegetation along the river banks of the studied rivers was correlated with the presence of pearl mussel populations. Traditional agriculture turned out to be, in some cases, more harmful for river ecosystems than urbanization and industrialization.

Adaptive divergence between lake and stream populations of an East African cichlid fish.

Divergent natural selection acting in different habitats may build up barriers to gene flow and initiate speciation. This speciation continuum can range from weak or no divergence to strong genetic differentiation between populations. Here, we focus on the early phases of adaptive divergence in the East African cichlid fish Astatotilapia burtoni, which occurs in both Lake Tanganyika (LT) and inflowing rivers. We first assessed the population structure and morphological differences in A.burtoni from southern LT. We then focused on four lake-stream systems and quantified body shape, ecologically relevant traits (gill raker and lower pharyngeal jaw) as well as stomach contents. Our study revealed the presence of several divergent lake-stream populations that rest at different stages of the speciation continuum, but show the same morphological and ecological trajectories along the lake-stream gradient. Lake fish have higher bodies, a more superior mouth position, longer gill rakers and more slender pharyngeal jaws, and they show a plant/algae and zooplankton-biased diet, whereas stream fish feed more on snails, insects and plant seeds. A test for reproductive isolation between closely related lake and stream populations did not detect population-assortative mating. Analyses of F1 offspring reared under common garden conditions indicate that the detected differences in body shape and gill raker length do not constitute pure plastic responses to different environmental conditions, but also have a genetic basis. Taken together, the A.burtoni lake-stream system constitutes a new model to study the factors that enhance and constrain progress towards speciation in cichlid fishes.

Quick divergence but slow convergence during ecotype formation in lake and stream stickleback pairs of variable age.

When genetic constraints restrict phenotypic evolution, diversification can be predicted to evolve along so-called lines of least resistance. To address the importance of such constraints and their resolution, studies of parallel phenotypic divergence that differ in their age are valuable. Here, we investigate the parapatric evolution of six lake and stream threespine stickleback systems from Iceland and Switzerland, ranging in age from a few decades to several millennia. Using phenotypic data, we test for parallelism in ecotypic divergence between parapatric lake and stream populations and compare the observed patterns to an ancestral-like marine population. We find strong and consistent phenotypic divergence, both among lake and stream populations and between our freshwater populations and the marine population. Interestingly, ecotypic divergence in low-dimensional phenotype space (i.e. single traits) is rapid and seems to be often completed within 100 years. Yet, the dimensionality of ecotypic divergence was highest in our oldest systems and only there parallel evolution of unrelated ecotypes was strong enough to overwrite phylogenetic contingency. Moreover, the dimensionality of divergence in different systems varies between trait complexes, suggesting different constraints and evolutionary pathways to their resolution among freshwater systems.

Predatory impact of non-native rainbow trout on endemic fish populations in headwater streams in the Cape Floristic Region of South Africa

Non-native rainbow trout Oncorhynchus mykiss have been widely introduced in the Cape Floristic Region (CFR) at the south-western tip of Africa and may pose a serious threat to endemic freshwater fishes in the region. Quantitative information about trout impacts in the CFR is scarce but is urgently needed to guide legislation and management efforts. We used a combination of comparative and experimental approaches to evaluate impacts of introduced trout on native fish populations in headwater streams draining the upper Breede River catchment in the CFR. Fish populations were surveyed, and 19 environmental variables measured, in 24 minimally-disturbed streams, half of which had been invaded by trout. The mean densities of native Breede River redfin Pseudobarbus burchelli, Cape kurper Sandelia capensis and Cape galaxias Galaxias zebratus, were 89–97 % lower in invaded streams than in streams without trout. Furthermore, while native fish were present at all 12 sites without trout, they were not recorded at seven of the 12 invaded sites. None of the measured environmental variables differed significantly between sites with and without trout, and distance-based linear models identified trout density as the best predictor of redfin and kurper density, while galaxias density was best predicted by other environmental variables (riparian vegetation, canopy cover, substrate length, site slope). Native fish ≤40 mm in length were largely absent from invaded streams, but generally abundant in streams without trout, and a field experiment confirmed that trout selectively consume small redfin. Taken together, these findings constitute evidence that trout have depleted the abundance of CFR-endemic fishes through size-selective predation. It is recommended that managers aim to prevent new trout introductions and consider eradicating trout populations where they pose a threat to highly threatened native species.

Genetic diversity among the Eurytemora affinis species complex in the Scheldt estuary and its tributaries using ISSR-PCR marker assay

As an estuary being restored, the Scheldt (Belgium/The Netherlands) offers an interesting setting to study the response of organisms and ecosystems to changing conditions. This study specifically deals with this with regard to the spatio-temporal distribution and possible genetic differentiation among the species complex Eurytemora affinis (copepoda, calanoida). Until the 1990s, E. affinis typically occurred downstream the Scheldt estuary (Belgium/The Netherlands). In parallel to water quality improvement, E.affinis has recently also occurred upstream the estuary and in some of the tributaries. This paper aims to assess the origin of the copepod sibling species complex E. affinis occurring upstream the Scheldt estuary through genetic characterization. Using the Inter Simple Sequence Repeat (ISSR) technique, we explored genetic pools of the E. affinis complex in three Scheldt localities (downstream, middle-estuary and upstream) and two of its tributaries. Four ISSR primers produced 75 polymorphic loci. Bayesian and hierarchical analysis revealed different but close genetic entities in both down and upstream localities. The middle-estuary individuals were genetically a composite mix of downstream and upstream populations (84% from downstream and 16% from upstream). A distinctive separation of the tributaries and the main Scheldt stream populations suggests that two fully independent genetic pools are present. It is of note that the tributaries showed a lack of genetic subdivision, that upstream and downstream E. affinis populations are closely related, and that the downstream population is most likely at the origin of the upstream one, which implies the necessity to guarantee sufficient oxygen concentration levels throughout the estuarine continuum to guarantee the presence of this species upstream. The results of the ISSR technique are discussed in comparison with genetic studies on E. affinis using COI barcoding.

Effects of timber harvest within streamside management zones on salamander populations in ephemeral streams of southeastern Kentucky

Timber harvest is an important extractive, economic activity to many human economies, but it can be detrimental to ecosystem function and species viability therein by degrading and fragmenting forest habitat. Salamanders comprise a significant amount of forest community biomass, and given their sensitivity to environmental stressors, including those caused by timber harvest, they often serve as important indicators of declines in forest ecosystem function. Several studies have focused on the impacts of timber harvest on salamanders inhabiting perennial and intermittent streams, the findings of which have helped inform best management practices for timber harvest in the U.S. Ephemeral headwater streams and associated riparia account for a small fraction of the total landscape, yet these features are critical to the functioning of forested ecosystems; however, few studies have examined how timber harvest impacts salamanders in or near these areas. Our objective was to investigate the effects of three different silvicultural treatments, each involving different streamside management zone (SMZ) characteristics, on salamander communities in southeastern Kentucky hardwood forest ephemeral streams. Data were collected by regular checks of pitfall traps, coverboards, and transect searches. Using both pre- and post-harvest data, abundance estimates were acquired using binomial mixture models. Declines in some species of terrestrial and stream-breeding salamanders were detected, and were shown to be likely related to characteristics of the corresponding silvicultural treatment. We suggest that application of modest SMZ regulations to ephemeral streams would likely reduce or alleviate salamander declines in these important headwater areas.

Importance of Understanding Landscape Biases in USGS Gage Locations: Implications and Solutions for Managers

ABSTRACTFlow and water temperature are fundamental properties of stream ecosystems upon which many freshwater resource management decisions are based. U.S. Geological Survey (USGS) gages are the most important source of streamflow and water temperature data available nationwide, but the degree to which gages represent landscape attributes of the larger population of streams has not been thoroughly evaluated. We identified substantial biases for seven landscape attributes in one or more regions across the conterminous United States. Streams with small watersheds (<10 km2) and at high elevations were often underrepresented, and biases were greater for water temperature gages and in arid regions. Biases can fundamentally alter management decisions and at a minimum this potential for error must be acknowledged accurately and transparently. We highlight three strategies that seek to reduce bias or limit errors arising from bias and illustrate how one strategy, supplementing USGS data, can greatly reduce bias.

Susceptibility to Myxobolus cerebralis among Tubifex tubifex Populations from Ten Major Drainage Basins in Colorado Where Cutthroat Trout Are Endemic

Establishment of Myxobolus cerebralis (Mc) resulted in declines of wild Rainbow Trout Oncorhynchus mykiss populations in streams across Colorado during the 1990s. However, the risk for establishment and spread of this parasite into high-elevation habitats occupied by native Cutthroat Trout O. clarkii was unknown. Beginning in 2003, tubificid worms were collected from all major drainages where Cutthroat Trout were endemic and were assayed by quantitative PCR to determine the occurrence and distribution of the various lineages of Tubifex tubifex (Tt) oligochaetes. Over a 5-year period, 40 groups of Tt oligochaetes collected from 27 streams, 3 natural lakes, 2 private ponds, and a reservoir were evaluated for their relative susceptibility to Mc. Exposure groups were drawn from populations of pure lineage III Tt, mixed-lineage populations where one or more of the highly resistant (lineage I) or nonsusceptible lineages (V or VI) were the dominant oligochaete and susceptible lineage III worms were the subdominant worm, or pure lineage VI Tt. Experimental replicates of 250 oligochaetes were exposed to 50 Mc myxospores per worm. The parasite amplification ratio (total triactinomyxons [TAMs] produced / total myxospore exposure) was very high among all pure lineage III Colorado exposure groups, averaging 363 compared with 8.24 among the mixed-lineage exposure groups. Lineage III oligochaetes from Mt. Whitney Hatchery in California, which served as the laboratory standard for comparative purposes, had an average parasite amplification ratio of 933 among 10 exposed replicates over a 5-year period. Lineage I oligochaetes were highly resistant to infection and did not produce any TAMs. Lineages V and VI Tt did not become infected and did not produce any TAMs. These results suggest that the risk of establishment of Mc is high for aquatic habitats in Colorado where Cutthroat Trout and lineage III Tt are sympatric.

The neural crest cell cycle is related to phases of migration in the head

Embryonic cells that migrate long distances must critically balance cell division in order to maintain stream dynamics and population of peripheral targets. Yet details of individual cell division events and how cell cycle is related to phases of migration remain unclear. Here, we examined these questions using the chick cranial neural crest (NC). In vivo time-lapse imaging revealed that a typical migrating NC cell division event lasted ∼1 hour and included four stereotypical steps. Cell tracking showed that dividing NC cells maintained position relative to non-dividing neighbors. NC cell division orientation and the time and distance to first division after neural tube exit were stochastic. To address how cell cycle is related to phases of migration, we used FACs analysis to identify significant spatiotemporal differences in NC cell cycle profiles. Two-photon photoconversion of single and small numbers of mKikGR-labeled NC cells confirmed that lead NC cells exhibited a nearly fourfold faster doubling time after populating the branchial arches. By contrast, Ki-67 staining showed that one out of every five later emerging NC cells exited the cell cycle after reaching proximal head targets. The relatively quiescent mitotic activity during NC cell migration to the branchial arches was altered when premigratory cells were reduced in number by tissue ablation. Together, our results provide the first comprehensive details of the pattern and dynamics of cell division events during cranial NC cell migration.

The neural crest cell cycle is related to phases of migration in the head

Embryonic cells that migrate long distances must critically balance cell division in order to maintain stream dynamics and population of peripheral targets. Yet details of individual cell division events and how cell cycle is related to phases of migration remain unclear. Here, we examined these questions using the chick cranial neural crest (NC). In vivo time-lapse imaging revealed that a typical migrating NC cell division event lasted ~1 hour and included four stereotypical steps. Cell tracking showed that dividing NC cells maintained position relative to non-dividing neighbors. NC cell division orientation and the time and distance to first division after neural tube exit were stochastic. To address how cell cycle is related to phases of migration, we used FACs analysis to identify significant spatiotemporal differences in NC cell cycle profiles. Two-photon photoconversion of single and small numbers of mKikGR-labeled NC cells confirmed that lead NC cells exhibited a nearly fourfold faster doubling time after populating the branchial arches. By contrast, Ki-67 staining showed that one out of every five later emerging NC cells exited the cell cycle after reaching proximal head targets. The relatively quiescent mitotic activity during NC cell migration to the branchial arches was altered when premigratory cells were reduced in number by tissue ablation. Together, our results provide the first comprehensive details of the pattern and dynamics of cell division events during cranial NC cell migration.

Prey size, prey abundance, and temperature as correlates of growth in stream populations of cutthroat trout

Growth and maximum size of stream fishes can be highly variable across populations. For salmonid fishes in streams, individuals from populations confined to headwater streams often exhibit small size at maturity in comparison to populations with access to main-stem rivers. Differences in prey size, prey availability, and metabolic constraints based on temperature may explain patterns of maximum size and growth. In this study, cutthroat trout from headwater stream populations that were isolated above a waterfall were compared to individuals from populations in similar sized streams without a movement barrier and from large main-stem rivers. Cutthroat trout from smaller streams with or without a movement barrier were significantly smaller at a given age than fish from main-stem rivers, where individuals were able to achieve a much larger maximum size. Comparisons of invertebrate drift abundance and size in the three types of streams revealed that drift size did not differ between stream categories, but was highest per volume of water in large main-stem rivers. Across all stream types, prey abundance declined from summer to fall. Temperature declined over the course of the season in a similar manner across all stream types, but remained relatively high later in the season in main-stem river habitats. Prey availability and temperature conditions in main-stem rivers may provide more optimal growing conditions for fish as individuals increase in size and become constrained by prey availability and temperature conditions in small streams. Maintaining connectivity between small spawning and rearing tributary streams and main-stem river habitats may be critical in maintaining large-bodied populations of stream salmonids.

Growth and reproduction of a stream population of Cobitis turcica in central Anatolia (Turkey)

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Age estimates for an adaptive lake fish radiation, its mitochondrial introgression, and an unexpected sister group: Sailfin silversides of the Malili Lakes system in Sulawesi.

BackgroundThe Malili Lakes system in central Sulawesi (Indonesia) is a hotspot of freshwater biodiversity in the Wallacea, characterized by endemic species flocks like the sailfin silversides (Teleostei: Atherinomorpha: Telmatherinidae) radiation. Phylogenetic reconstructions of these freshwater fishes have previously revealed two Lake Matano Telmatherina lineages (sharpfins and roundfins) forming an ancient monophyletic group, which is however masked by introgressive hybridization of sharpfins with riverine populations. The present study uses mitochondrial data, newly included taxa, and different external calibration points, to estimate the age of speciation and hybridization processes, and to test for phylogeographic relationships between Kalyptatherina from ancient islands off New Guinea, Marosatherina from SW Sulawesi, and the Malili Lakes flock.ResultsContrary to previous expectations, Kalyptatherina is the closest relative to the Malili Lakes Telmatherinidae, and Marosatherina is the sister to this clade. Palaeogeographic reconstructions of Sulawesi suggest that the closer relationship of the Malili Lakes radiation to Kalyptatherina might be explained by a 'terrane-rafting’ scenario, while proto-Marosatherina might have colonized Sulawesi by marine dispersal. The most plausible analysis conducted here implies an age of c. 1.9 My for the onset of divergence between the two major clades endemic to Lake Matano. Diversification within both lineages is apparently considerably more recent (c. 1.0 My); stream haplotypes present in the sharpfins are of even more recent origin (c. 0.4 My).ConclusionsSulawesi’s Telmatherinidae have most likely originated in the Sahul Shelf area, have possibly reached the island by both, marine dispersal and island/terrane-rafting, and have colonized the Malili Lakes system from rivers. Estimates for the split between the epibenthic sharpfins and the predominantly pelagic to benthopelagic roundfins in Lake Matano widely coincide with geological age estimates of this rift lake. Diversification within both clades clearly predates hybridization events with stream populations. For Lake Matano, these results support a scenario of initial benthic-pelagic divergence after colonization of the lake by riverine populations, followed by rapid radiation within both clades within the last 1 My. Secondary hybridization of stream populations with the sharpfins occurred more recently, and has thus most likely not contributed to the initial divergence of this benthic species flock.

Sea-trout populations in small coastal streams

Sea-trout populations in small coastal streams

Sea-trout populations in small coastal streams

In recent years there has been increasing interest in the conservation and management of small streams. They are essential to the health of the wider aquatic ecosystem and of fish populations throughout river catchments. Because of their size, small streams are particularly at risk from the predicted changes in temperature and flow regimes resulting from climate change. This paper deals with small coastal streams, which to date have received little if any attention from researchers, local authorities or fisheries management bodies. It seeks to summarise the information currently available on small coastal streams, to outline the potential importance of such streams from both an ecological and biodiversity perspective and suggest research topics that could help to conserve these sensitive biotopes and underpin the requirement to assess and categorise their role as producers of juvenile seatrout (Salmo trutta L.). It is argued that recruitment from such streams may be of critical importance to the abundance of sea-trout in the neighbouring coastal margins.

Genetic Variation in &amp;lt;i&amp;gt;Salamandra&amp;lt;/i&amp;gt; &amp;lt;i&amp;gt;infraimmaculata&amp;lt;/i&amp;gt; from Different Habitats Using Amplified Fragment Length Polymorphism

The purpose of the present study was to examine the genetic variation in Salamandra infraimmaculata from different breeding site habitats using the Amplified Fragment Length Polymorphism (AFLP) method. The results of the dendogram from a hierarchical cluster analysis show that the grouping of S. infraimmaculata as cluster 5 differs from all the other clusters, including the St1 (Tel-Dan stream) population, which was the most predictable. Five Haplogroups (Hg) were characterized. The mean number of alleles per locus in each population (Ne) ranged from 10.566 (Sp1) to 2.720 (Po6). An average estimated heterozygosity (He) by population ranged from 0.100 (Po6) to 0.186 (St1). Population St1, a permanent breeding site where water was available all year round, exhibited the highest level of polymorphism, while population Po6, from the ephemeral breeding site, exhibited the lowest level of polymorphism. Gene flow between clusters showed that clusters 3 and 4 are sources of migrants and also receive gene flow, while clusters 1 and 2 may be a source of migrants but may not receive much gene flow. A phylogenetic analysis, based on clustering using Nei’s genetic distance, demonstrated that the Tel-Dan population is located on a separate branch within its sub-population. The conclusion of the present study shows that the genetic divergence among isolated populations is not correlated to distance but is affected by the variation of habitats.

Population genetic structure of the freshwater anomuran Aegla uruguayana Schmitt, 1942 (Decapoda, Aeglidae) in the central region of Argentina

Aeglidae is the only freshwater family in the infraorder Anomura.Aegla uruguayanaSchmitt, 1942 is one of the most widely distributed species in southern South America and is found in different environments, which makes it an interesting object for population genetic studies. The main objective of this work was to analyse the genetic population structure ofA. uruguayanaalong a sea distance gradient for four populations that were studied in the La Plata Basin with an 1100-km range in relation to an east-west transect. The populations studied were the Río Tercero Reservoir, the Setúbal Lagoon, the Doll Stream and the Urquiza Stream. Aeglid DNA was extracted using a commercial kit that was amplified with ISSR markers. Of the 10 primers tested, we selected four that showed the best resolution and reproducible results. Our studies revealed a of 0.3479 ± 0.1383 (mean ± SD) and a global of 0.3583 (), demonstrating genetic differentiation among populations with low gene flow. The Urquiza Stream population showed a genetic structure clearly different from that of the other populations. However, the Río Tercero, Setúbal and Doll populations were well grouped with one effective connection among them. The geomorphologic history of the basin provides evidence for the isolation hypothesis. These data demonstrate the importance of geoclimatic history in the study region and the importance of using complete population distribution data where the species live. These data permit us to interpret that different populations have independent histories that are delineated by the geomorphological events that occurred on earth.