The contribution of young-of-year fishes to aquatic food web dynamics in an arid-land river system (Rio Grande, New Mexico)

1. Larval fishes have a rich history in ichthyological research. However, relatively little attention has been given to the role of young-of-year (YOY) fishes in ecosystem processes. Despite difficulties of sampling and identifying these small fishes, YOY may serve an important role in the dynamics of some aquatic communities. The specific role of YOY fishes in aquatic, desert food webs remains largely uncharacterized. 2. We hypothesize that YOY fishes may control abundance and community composition of lower trophic levels (i.e., aquatic invertebrates) because they are numerically dominant predators during the growing season. The goal of this study is to determine the role of YOY fishes in aquatic food webs and the impact they have on trophic dynamics of dryland river food webs using the Rio Grande as an example. 3. A mesocosm experiment was designed to assess the effect of YOY fish predators on meio- and micro- faunal invertebrate prey density and diversity. We manipulated presence and absence of YOY fishes and leaf litter, and compared invertebrate diversity and abundance across an array of 24 stock tanks. 4. Data showed that YOY fishes significantly influence the composition of invertebrate communities, as does allochthonous carbon. Community composition varied among treatments both because fishes preferred some taxa over others and because of instances of avoidance by invertebrates. Stable isotope analyses (carbon and nitrogen) suggest important indirect effects on the behavior of invertebrates in fish-treated mesocosms. 5. Results suggest that YOY fishes play an important role in aquatic food web dynamics and that community composition of aquatic invertebrates is, in part, subject to direct and indirect changes induced by the presence of YOY fishes

Drivers And Impacts Of The Invasive Round Goby (neogobius Melanostomus) In Michigan Tributaries To The Great Lakes

The abundance and persistence of the invasive round goby (Neogobius melanostomus) has often resulted in antagonistic interactions between the invasive and its native competitors. In this study, I sought to quantify the consequences and environmental context of these interactions in Great Lakes tributaries. Specifically, I aimed to identify changes in feeding and reproductive behavior in a native competitor in response to round goby invasion, identify potential solutions to increase regular stream monitoring by tapping into citizen science programs, and quantify the environmental context associated with successful goby invasion. Surveys of fish communities were conducted over three years in seven Michigan tributaries to the Great Lakes. Each site was evaluated for fish assemblage composition, round goby abundance, and habitat quality. Individual round goby and a native competitor, the Johnny darter (Etheostoma nigrum), were dissected for a diet comparison and to identify investment in reproduction to illustrate changes in feeding and reproductive behavior by the native species. To inform better practices for stream management and invasion detection, a quality assessment of two citizen science programs in the area was completed. Citizen data was directly compared to traditional research focused sampling methods to verify the validity of the data and its potential inclusion in ecological research. Finally, a model was developed to identify the environmental context common to sites invaded by round goby. Results suggest that Johnny darter diet diversity decreases, trophic position increases, and reproductive timing changes when goby are present. Citizen science may provide a way to monitor stream degradation which can facilitate these negative interactions. Despite differences in sampling methodology, qualitative citizen data reached similar conclusions about site quality as quantitative research methods. As identified by the environmental context model, altered riparian land use and decreased native species diversity are common characteristics of sites invaded by round goby. Regular monitoring for these characteristics may help identify locations vulnerable to round goby invasion so prevention and mitigation resources can be efficiently allocated. This research provides background on round goby invasion that can be utilized to better manage native species and ecosystems to increase resistance to and reduce the impacts of invasion

Otolith microchemistry and diadromy in Patagonian river fishes

Coastal habitats in Chile are hypothesized to support a number of diadromous fish species. The objective of this study was to document migratory life histories of native galaxiids and introduced salmonids from a wide latitudinal range in Chilean Patagonia (39–48°S). Otolith microchemistry data were analysed using a recursive partitioning approach to test for diadromy. Based on annular analysis of Sr:Ca ratios, a diadromous life history was suggested for populations of native Aplochiton taeniatus, A. marinus, and Galaxias maculatus. Lifetime residency in freshwater was suggested for populations of A. zebra and G. platei. Among introduced salmonids, populations of Oncorhynchus tshawytscha and O. kisutch exhibited patterns consistent with anadromy, whereas the screened population of O. mykiss appeared restricted to freshwater. Salmo trutta exhibited variable patterns suggesting freshwater residency and possibly anadromy in one case. The capacity and geographic scope of hydropower development is increasing and may disrupt migratory routes of diadromous fishes. Identification of diadromous species is a critical first step for preventing their loss due to hydropower development

Evaluation of an Educational Campaign to Improve the Conscious Consumption of Recreationally Caught Fish

Consumption guidelines are a common way of improving conscious consumption behaviors in areas where game fish are known to contain contaminants. However, guideline information can be difficult to distribute, and effectiveness difficult to measure. To increase the distribution and effectiveness of guideline information for the Detroit River, an educational campaign was launched in 2010, which included distribution of pamphlets with consumption information, posting of permanent signs at popular fishing locations, and hiring River Walkers to personally communicate with anglers. In 2013 and 2015, we conducted in-person surveys of active shoreline anglers to determine the effectiveness of education and outreach efforts. Results from the survey indicated that 55% of anglers were aware of the guidelines in 2013, and by 2015 36% had communicated the information to family or friends. However, anglers were often unwilling to reduce consumption of popular game species, despite high contaminant levels. Encouragingly, black anglers were most likely to supplement their diet with species lower in contaminants. Our results suggest that utilizing multiple educational strategies including reaching out directly to individual anglers may improve conscious consumption behavior among the targeted population, providing a template for educational campaigns to successfully target vulnerable populations

Data from: Retrospective stable isotope analysis reveals ecosystem responses to river regulation over the last century

Disruption of natural flow regimes, nutrient pollution, and other consequences of human population growth and development have impacted most major rivers of the world. Alarming losses of aquatic biodiversity and biotic homogenization coincide with human-caused river alteration, but effects on aquatic ecosystem processes are not as well documented. This is because unaltered systems for comparison are scarce, and some ecosystem-wide effects may take decades to manifest. We evaluated aquatic ecosystem responses to extensive river-floodplain engineering and nutrient addition in the Rio Grande of southwestern North America as revealed by changes in trophic structure of, and resource availability to, the fish community. Stable Isotope Analysis (SIA) was conducted on museum-preserved fishes collected over a 70-year period of intensive river management and exponential human population growth. Trophic complexity and resource heterogeneity for fish consumers (measured as 'isotopic niche breadth') decreased following sediment deprivation and channelization, and these effects persist into the present. Increased nutrient inputs led to δ15N enrichment in the entire fish community at all affected sites, and a shift to autochthonous sources of carbon at the most proximal site downstream of wastewater release probably via 'bottom-up' transfer. Overall, retrospective SIA of apex consumers suggests radical change and functional impairment of a floodplain river ecosystem already marked by significant biodiversity loss

C, N Stable Isotope (delta) values for Rio Grande fishes from 1939-2002

Isotopic ratios for carbon and nitrogen reported in delta values (per mil) for fishes obtained from the Museum of Southwestern Biology (MSB) at the University of New Mexico for study of aquatic food web change over time. Sample No.= sequential number to track and count samples, Catalog No. = MSB catalog number, Field No. = number linking to field notes of Melanie S. Edwards, Species = taxonomic name, Date Range = years pooled for comparison, Location = sample site on the Rio Grande, New Mexico,delta 15N, delta 13C,Day,Month, Year. CORRECTED DATA: 1.0 per mil HAS BEEN ADDED TO CARBON, 0.5 SUBTRACTED FROM NITROGEN FOR SAMPLES WITH MSB CATALOG NUMBER. 2002 DATA ARE UNCORRECTED

What's in a Name? Patterns, Trends, and Suggestions for Defining Non-Perennial Rivers and Streams.

Rivers that cease to flow are globally prevalent. Although many epithets have been used for these rivers, a consensus on terminology has not yet been reached. Doing so would facilitate a marked increase in interdisciplinary interest as well as critical need for clear regulations. Here we reviewed literature from Web of Science database searches of 12 epithets to learn (Objective 1-O1) if epithet topics are consistent across Web of Science categories using latent Dirichlet allocation topic modeling. We also analyzed publication rates and topics over time to (O2) assess changes in epithet use. We compiled literature definitions to (O3) identify how epithets have been delineated and, lastly, suggest universal terms and definitions. We found a lack of consensus in epithet use between and among various fields. We also found that epithet usage has changed over time, as research focus has shifted from description to modeling. We conclude that multiple epithets are redundant. We offer specific definitions for three epithets (non-perennial, intermittent, and ephemeral) to guide consensus on epithet use. Limiting the number of epithets used in non-perennial river research can facilitate more effective communication among research fields and provide clear guidelines for writing regulatory documents

What's in a Name? Patterns, Trends, and Suggestions for Defining Non-Perennial Rivers and Streams.

Rivers that cease to flow are globally prevalent. Although many epithets have been used for these rivers, a consensus on terminology has not yet been reached. Doing so would facilitate a marked increase in interdisciplinary interest as well as critical need for clear regulations. Here we reviewed literature from Web of Science database searches of 12 epithets to learn (Objective 1-O1) if epithet topics are consistent across Web of Science categories using latent Dirichlet allocation topic modeling. We also analyzed publication rates and topics over time to (O2) assess changes in epithet use. We compiled literature definitions to (O3) identify how epithets have been delineated and, lastly, suggest universal terms and definitions. We found a lack of consensus in epithet use between and among various fields. We also found that epithet usage has changed over time, as research focus has shifted from description to modeling. We conclude that multiple epithets are redundant. We offer specific definitions for three epithets (non-perennial, intermittent, and ephemeral) to guide consensus on epithet use. Limiting the number of epithets used in non-perennial river research can facilitate more effective communication among research fields and provide clear guidelines for writing regulatory documents

Pervasive changes in stream intermittency across the United States

Non-perennial streams are widespread, critical to ecosystems and society, and the subject of ongoing policy debate. Prior large-scale research on stream intermittency has been based on long-term averages, generally using annually aggregated data to characterize a highly variable process. As a result, it is not well understood if, how, or why the hydrology of non-perennial streams is changing. Here, we investigate trends and drivers of three intermittency signatures that describe the duration, timing, and dry-down period of stream intermittency across the continental United States (CONUS). Half of gages exhibited a significant trend through time in at least one of the three intermittency signatures, and changes in no-flow duration were most pervasive (41% of gages). Changes in intermittency were substantial for many streams, and 7% of gages exhibited changes in annual no-flow duration exceeding 100 days during the study period. Distinct regional patterns of change were evident, with widespread drying in southern CONUS and wetting in northern CONUS. These patterns are correlated with changes in aridity, though drivers of spatiotemporal variability were diverse across the three intermittency signatures. While the no-flow timing and duration were strongly related to climate, dry-down period was most strongly related to watershed land use and physiography. Our results indicate that non-perennial conditions are increasing in prevalence over much of CONUS and binary classifications of ‘perennial’ and ‘non-perennial’ are not an accurate reflection of this change. Water management and policy should reflect the changing nature and diverse drivers of changing intermittency both today and in the future