Ecology of Freshwater Fish最新文献

Rocio is a small genus of Neotropical freshwater fishes that is distributed in Atlantic drainages of northern Middle America. Two species of Rocio, R. spinosissima and R. octofasciata, exhibit sympatry in the Río Dulce basin in eastern Guatemala. Rocio spinosissima is endemic to the Río Dulce basin, while R. octofasciata has a larger geographic range that includes this area. Our goal was to explore the ecological and morphological variation shown by these two closely related species and determine their differences. A combination of field work, analysis of museum specimens, and ecological niche modelling helped to better understand the differences in habitat and environmental characteristics, along with the body shape variation. Local-scale environmental data suggest that both species inhabit lentic environments, with R. spinosissima using narrower and low canopy-covered habitats and R. octofasciata inhabiting areas with a larger range of environmental characteristics. Ecological Niche Models indicated that land cover, soil, precipitation, and temperature largely define the distribution of both species. Body shape differs between species, with R. spinosissima exhibiting a rounder and deeper body while R. octofasciata is more elongated. Specimens of R. octofasciata across its distribution also show variation in head shape, mouth position, fin, and caudal peduncle characteristics, possibly as a response to trophic strategies that reduce competition. Similarities in their environments and morphologies allow us to identify broadly overlapping niches in the two species of Rocio, while the fine scale differences documented between species will have conservation implications for the endemic R. spinosissima.

Salmonids are well known for their natal homing behaviour, meaning they return to breed in the same area where they originated. However, not all individuals return to their natal breeding grounds—a behavioural trait known as straying. The prevalence of straying is difficult to explore and therefore quantitative estimates for straying are seldom reported. In this study, otolith microchemistry and genetics were combined to investigate patterns of straying over ecological and evolutionary time, respectively, between neighbouring rivers flowing into Mariager fjord, Denmark. Otolith microchemistry was used to determine the river of origin for sea trout (Salmo trutta) upon their return to freshwater and 288 SNP markers were used to determine genetic structure among the rivers in the fjord. In this system, where the distance between rivers is short, otolith microchemistry achieved 80% accuracy in assigning juvenile brown trout to their natal river, thus allowing us to determine that approximately 43% of the adult sea trout had returned to non-natal rivers to spawn, with a similar proportion of strayers and natal homers in all of the rivers. Genetic analysis further supported that there was substantial gene flow among individuals originating from different rivers, indicating that sea trout in Mariager fjord make up one population. The findings obtained from otolith microchemistry and genetics complement each other and provide further evidence that sea trout in this system migrate to non-natal rivers and spawn there, which consequently affects the genetic structure of the population.

Connectivity is a foundational concept in ecology and conservation and was the organising theme for the 2022 Annual Meeting of the Southeastern Fishes Council, a professional organisation dedicated to the study and conservation of freshwater fishes native to the southeast region of the United States (US). We introduce a Special Contribution of five papers selected from presentations at that meeting that illustrate perspectives on connections created by fish migration and dispersal, evolved life histories and habitat affinities and interspecific facilitation. Although focused on streams of the southeast US, each of these topics is broadly relevant to freshwater fish conservation, particularly with respect to causes and consequences of migratory fish depletion, population fragmentation and species declines. Many other connections relevant to the ecology and conservation of freshwater fishes remain relatively unexplored but could substantively advance conservation. We highlight the potential that species evolutionary histories, that is connections through time, reconstructed using species distributions and phylogenies may improve predictions of species responses to environmental change. Identifying species interdependencies, including undiscovered interactions that support survival or reproduction, could provide insights into how species losses may cascade as aquatic communities unravel. Finally, efforts to elucidate diverse connections between people and freshwater biodiversity, particularly where fisheries are historic and streams mostly go unnoticed, may prove essential to building public support for conservation measures. A research agenda anchored on ‘biodiversity connections’ has the potential to advance ecological understanding and public engagement, elements essential to conserving freshwater fishes.

After serving as Senior Editor of EFF for 6 years (2017–2023), Phaedra Budy has decided to step away from the editorship to focus on her research laboratory. She previously served as a member of the Editorial Board of EFF from 2010 to 2017. All those associated with the journal, both fellow editors and Wiley staff, thank Phaedra for her commitment to the journal. Phaedra will continue her contributions to the journal, however, as she will serve as Guest Editor of the forthcoming special issue devoted to proceedings of the symposium Advances in the Population Ecology of Stream-Dwelling Salmonids VI.

In turn, we welcome Keith Gido, University of Kansas, as Senior Editor beginning January 2024. His research specialisations include the effects of invasive species and fish assemblage structure, focusing on the conservation of aquatic systems in the western and central United States. The research focuses on the impact of global change on diversity-ecosystem function relationships in streams, patterns and processes regulating species diversity and habitat associations of fishes in streams and reservoirs, and dynamics of non-coevolved fish assemblages.

EFF publishes papers devoted to basic ecology of freshwater fishes, and EFF is strongly committed to conservation. We seek to publish important research revealing or supporting knowledge of phenomena without consideration given to applications of that knowledge. As a journal publishing pure, fundamental science, EFF is not a fisheries or management journal. Nonetheless, authors may wish to include a brief, concise statement about the implications of their research for ecological or environmental management aimed at the conservation of fishes or their habitats without regard to human use, which can be done in concluding the discussion.

Where feasible authors are strongly encouraged to focus the title, abstract and introduction of their reports on the phenomena studied by deemphasizing or excluding the locality or taxon involved and detailing them in the methods. We understand, however, that there may be cases where including the region or taxon is appropriate.

EFF offers authors the option of Free Format submission for a simplified and streamlined submission process. Free format submission eases the process of preparing a manuscript and allows the author to complete the process faster. Authors may submit their manuscripts in the format of their choosing. EFF's publisher, Wiley, updates the formatting into the journal's style when a manuscript is accepted for publication.

Table 2 shows the papers cited most often in the 2-year period (2020–2021) covered by Clarivate's Journal Citation Report for June 2023. We thank the authors for their contributions to the journal and congratulate them on their achievements.

EFF publishes special issues or contributions (special sections) drawn from proceedings of conferenc

Australia has a highly endemic freshwater fish fauna, but basic biological knowledge for most is lacking. This includes an understanding, and description, of their parasite fauna. Additionally, the impacts of introduced fish species, and their parasites which have transferred across to native species, are also mostly unknown. This review provides the current level of knowledge of parasitic infection of the freshwater fish in Australia, both introduced and native. Only about a third of the native freshwater fish, but almost two-thirds of introduced fish, have been reported as a host for a parasite. The majority of records occur along the eastern coastline of Australia and throughout the Murray Darling Basin; two drainage regions were yet to record any parasite infections. Of the 124 fish species, across 43 families, found as hosts in Australia, only 11 species had more than 10 reports of infection, with 31% of fish species only having single reports. A total of 13 different types of parasites were reported, with digeneans, protozoans, nematodes and monogeneans the most commonly reported. Significant gaps in the knowledge of parasites, and their potential impacts, of Australian freshwater fish still exist, and the need for fish biologists and fish parasitologists to work together is highlighted to ensure that as much information about each group can be obtained.

It is well established that non-native fish can become invasive and outcompete and displace native fish populations. However, little research has explored the potential benefits that non-native fish may provide to native fish populations. To address this information gap, we examined how the availability of non-native perch (Perca fluviatilis) as prey could benefit populations of the endemic longfin eel (Anguilla dieffenbachii) and the native shortfin eel (Anguilla australis) in two neighbouring open-water wetlands in the Rakatu-Redcliff wetland complex in the Southland region of Aotearoa New Zealand. The Redcliff wetland fish community comprised native fish only, while the Rakatu wetland comprised native fish and non-native perch. We compared the size, condition, population density, population size structure and diet of eels in these wetlands. While eels were not necessarily larger or better conditioned in Rakatu wetland, their population density was three times higher than the Redcliff wetland, with young-of-the-year perch comprising ca. 40% of their diet. Furthermore, juvenile eel density was four times lower in Redcliff wetland, suggesting that cannibalism may occur at this site to support the existing eel population. Based on our findings, we suggest that freshwater managers consider the predator–prey dynamics of both native and non-native fish before removing non-native species, to avoid unintended negative consequences for native predatory fish species.

Conflicts can arise in developmental pathways that prevent an individual entering different developmental life stages that result in the expression of different phenotypes within a specific time period. In salmonids, theory suggests that sexual maturation may inhibit subsequent smolting within the same 12-month period and that this is partly the result of the time and the apparently conflicting physiological changes for these processes to occur, and partly because of the energy requirements for these physiologically taxing processes. This study tested whether sexually mature male Atlantic salmon (Salmo salar L.) parr, caught in the autumn, would subsequently smolt the following spring. Through individual identification using PIT telemetry, minimum estimates of 3.0% (n = 6/203) and 5.9% (n = 1/17) of Atlantic salmon parr that were sexually mature in two river catchments during the autumn were subsequently identified as smolts in the following spring. We therefore suggest that, in line with previous studies on domesticated Atlantic salmon and laboratory-based experiments, there is no developmental conflict but that life-history expression is mediated by environmental and genetic processes.

Russian olive (Elaeagnus angustifolia) is an invasive, fruit-bearing riparian tree that dominates riparian zones of the San Juan River in the southwestern United States. Previous research in this river suggests olive fruit is common in diets of invasive channel catfish (Ictalurus punctatus), but its energetic importance is unknown (i.e. critical for catfish fitness vs. incidental consumption). We assessed Russian olive consumption in channel catfish diets bimonthly for 1 year, hypothesizing that olive consumption would be greatest during periods of high olive availability and low benthic aquatic invertebrate availability. We found that catfish consumed olive fruit throughout the year and that olive comprised up to 44% of total stomach contents by mass, with peaks in spring and fall. Regression models revealed the presence and mass of olive fruit in catfish stomachs were positively associated with catfish total length, with a significant interaction between water temperature and river discharge. Catfish were more likely to consume olive fruit during higher flows, regardless of temperature and at low discharge with higher temperature. Contrary to our hypothesis, neither olive nor benthic invertebrate availability were associated with olive presence in channel catfish diets. Nutrition analysis indicated that olive alone was a low-quality diet item but has the potential to provide a reliable energy source. We used seasonal data to estimate the energetic contribution of olive fruit to catfish populations using a bioenergetic model, which estimated that olive fruit accounted for 35.6% of energy (Joules) consumed by catfish populations and satisfied 38% of their metabolic demand. Our results suggest that Russian olive fruit is a significant subsidy to channel catfish in the San Juan River. However, more research is needed to determine the indirect effects of this interaction on native fishes and ecosystem function.

Ecosystem engineers facilitate beneficiary species by ameliorating physical habitat. The stress-gradient hypothesis (SGH) predicts the importance of facilitation in communities should increase with physical stress but has rarely been tested in freshwater. Bluehead Chubs (Nocomis leptocephalus) build gravel nests for spawning, which can reduce negative effects of sedimentation for lithophilic species including invertebrates and other taxa. Our goal was to test the SGH using chubs and benthic assemblages as a model system. We surveyed assemblages in chub nests, paired unmodified substrate and reach-wide samples in 10 Piedmont streams in South Carolina, USA, placed across a gradient of sedimentation. Based on the SGH, we predicted benthic assemblage diversity in chub nests would show no relationship to increasing embeddedness but that diversity in unmodified substrate should decrease with embeddedness. We found that taxa counts, richness and Shannon diversity were higher in chub nests than unmodified substrate but were lower than reach-wide samples. Canonical correspondence analyses indicated benthic assemblages differed between nests and unmodified substrate, but assemblages in both microhabitats were nested subsets of the more diverse reach-wide assemblage. Contrary to our hypotheses, diversity in both microhabitats decreased significantly with substrate embeddedness but was consistently higher in nests. While substrate modification by chubs clearly facilitated benthic diversity at the microhabitat scale, it was not sufficient to overcome the worst effects of sedimentation. This study provides mixed evidence for SGH in streams; chub nesting appears to be facilitative at the microhabitat scale but may not have reach-wide effects on benthic assemblages in this system.

Adult Pacific lamprey (Entosphenus tridentatus) were counted using consistent methodology since 2005 with a video monitoring system as they passed Leaburg Dam (McKenzie River, Oregon, USA) en route to upstream spawning areas. In this study we evaluated the detection efficiency of the video system and upstream distribution of Pacific lamprey using the video counts of lamprey passage (herein, “dam counts”), passive integrated transponder (PIT) tags, and radio telemetry. In 2019–2020 we collected, tagged and tracked 32 adult lamprey (4 from the McKenzie River and 28 that were translocated from Willamette Falls). All fish were tagged and released into the tailrace of Leaburg Dam in June 2019. Oregon Department of Fish and Wildlife employees and volunteers from the local community conducted mobile radiotracking above and below the dam in drift boats (114 mainstem river kilometers) and on foot (several tributaries). The estimated detection efficiency for dam counts was 92% (95% confidence interval: 67%–99%). Fifty percent (16 of 32) of the tagged lamprey passed the dam, including 13 of 28 that were translocated. Thirty-seven percent (6 of 16) of lamprey that passed Leaburg Dam were detected in a restored reach of the South Fork McKenzie, 32.6 river kilometers upstream of the dam.