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At least 811 records · Page 45Linked to original sources

USGS2006

Reassessing a troublesome fact of mountain life: Avalanches in Glacier National Park

For the past decade, our U.S. Geological Survey (USGS) research team has rummaged through Glacier National Park’s archives looking for records of snow avalanches. Our searches have paid off. We have found photographs that show snow avalanches blocking progress during the annual spring opening of the famed Going-to-the-Sun Road, ranger logs that describe cabins and telephone lines destroyed by avalanches, and superintendents’ reports that recount avalanche accidents that killed employees or visitors. Recently, we have combined these historical sources with field studies to investigate whether snow avalanches in the park may be more cyclical than random and as much an ecological process as a natural hazard. Our ongoing research in Montana has yielded relevant information for park managers elsewhere who deal with avalanche threats to park infrastructure and for ecologists seeking a better understanding of how mountain ecosystems function. Our research has focused on two transportation corridors: the Going-to-the-Sun Road that bisects the center of the park, and John F. Stevens Canyon, at the park’s southwest corner ( fig. 1 ). The Going-to-the-Sun Road is the park’s most visited attraction; deep snow and avalanches force the road’s closure each winter, and in spring, park crews dig it out using bulldozers and other heavy equipment ( fig. 2 ). Springtime avalanches can bury workers or push equipment off the road and over cliffs ( figs. 3a and 3b ), as happened in 1953, when two workers died. Our research started with a study of how interannual variations in snowfall and avalanches affect the road opening. The initial study helped park managers predict and plan for the road opening in spring and respond to the many topical questions from park visitors and locals. More recent studies have focused on determining the conditions that create springtime avalanches, which are a poorly understood aspect of the avalanche phenomenon.

Wyoming↗

USGS2016

Tolerance to multiple climate stressors: A case study of Douglas-fir drought and cold hardiness

Drought and freeze events are two of the most common forms of climate extremes which result in tree damage or death, and the frequency and intensity of both stressors may increase with climate change. Few studies have examined natural covariation in stress tolerance traits to cope with multiple stressors among wild plant populations. We assessed the capacity of coastal Douglas‐fir ( Pseudotsuga menziesii var. menziesii ), an ecologically and economically important species in the northwestern USA, to tolerate both drought and cold stress on 35 populations grown in common gardens. We used principal components analysis to combine drought and cold hardiness trait data into generalized stress hardiness traits to model geographic variation in hardiness as a function of climate across the Douglas‐fir range. Drought and cold hardiness converged among populations along winter temperature gradients and diverged along summer precipitation gradients. Populations originating in regions with cold winters had relatively high tolerance to both drought and cold stress, which is likely due to overlapping adaptations for coping with winter desiccation. Populations from regions with dry summers had increased drought hardiness but reduced cold hardiness, suggesting a trade‐off in tolerance mechanisms. Our findings highlight the necessity to look beyond bivariate trait–climate relationships and instead consider multiple traits and climate variables to effectively model and manage for the impacts of climate change on widespread species.

California, Oregon, Washington↗

USGS2026

Quality and quantity of terrestrial landscape connectivity in the US Great Lakes Coastal Zone

Context The Great Lakes Coastal Zone (GLCZ), the world’s longest continuous freshwater coastline, consists of interspersed natural and developed landcover and is inhabited by millions of people. Anthropogenic change fragments the GLCZ, decreasing landscape connectivity. Objectives We evaluated functional landscape connectivity of the U.S. GLCZ, assessing regional connectivity, protected areas’ effects on connectivity, and identified pinchpoints where connectivity is most vulnerable. Methods We modeled landscape connectivity to describe corridors and redundant pathways for two scenarios: (1) continuous terrestrial habitat patches and (2) protected areas. We compared these two scenarios by total corridor area and quality at two spatial scales (coastal zone and ecoregion). We used random forest analyses to examine how ecological factors influenced the connectivity rank and pinchpoint values. A principal components analysis identified how land cover influenced connectivity among ecoregions. Results The GLCZ was 69% connected. Although 91% of the GLCZ’s high-quality habitat was within corridors, less than 50% of the corridor area was high-quality (low resistance to movement). While the northernmost region retained high-quality connectivity, connectivity loss and degradation increased with development further south. Corridors between protected areas provided less connectivity, of worse quality, in areas of development and agriculture. Lower connectivity was associated with higher impervious surface cover. Conclusions Protected area placement affected both the quantity and quality of connectivity. Improving and maintaining functional connectivity could be accomplished by strategically restoring and protecting habitats most vulnerable to connectivity loss, predominantly in urban and agricultural regions. Our connectivity improvement index is a useful tool to identify areas where connectivity may be improved.

Illinois, Indiana, Michigan, Minnesota, New York, ↗

USGS2017

Fuel-reduction management alters plant composition, carbon and nitrogen pools, and soil thaw in Alaskan boreal forest

Increasing wildfire activity in Alaska's boreal forests has led to greater fuel-reduction management. Management has been implemented to reduce wildfire spread, but the ecological impacts of these practices are poorly known. We quantified the effects of hand-thinning and shearblading on above- and belowground stand characteristics, plant species composition, carbon (C) and nitrogen (N) pools, and soil thaw across 19 black spruce ( Picea mariana ) dominated sites in interior Alaska treated 2-12 years prior to sampling. The density of deciduous tree seedlings was significantly higher in shearbladed areas compared to unmanaged forest (6.4 vs. 0.1 stems m −2 ), and unmanaged stands exhibited the highest mean density of conifer seedlings and layers (1.4 stems m −2 ). Understory plant community composition was most similar between unmanaged and thinned stands. Shearblading resulted in a near complete loss of aboveground tree biomass C pools while thinning approximately halved the C pool size (1.2 kg C m −2 compared to 3.1 kg C m −2 in unmanaged forest). Significantly smaller soil organic layer (SOL) C and N pools were observed in shearbladed stands (3.2 kg C m −2 and 116.8 g N m −2 ) relative to thinned (6.0 kg C m −2 and 192.2 g N m −2 ) and unmanaged (5.9 kg C m −2 and 178.7 g N m −2 ) stands. No difference in C and N pool sizes in the uppermost 10 cm of mineral soil was observed among stand types. Total C stocks for measured pools was 2.6 kg C m −2 smaller in thinned stands and 5.8 kg C m −2 smaller in shearbladed stands when compared to unmanaged forest. Soil thaw depth averaged 13 cm deeper in thinned areas and 46 cm deeper in shearbladed areas relative to adjacent unmanaged stands, although variability was high across sites. Deeper soil thaw was linked to shallower SOL depth for unmanaged stands and both management types, however for any given SOL depth, thaw tended to be deeper in shearbladed areas compared to unmanaged forest. These findings indicate that fuel-reduction management alters plant community composition, C and N pools, and soil thaw depth, with consequences for ecosystem structure and function beyond those intended for fire management.

Alaska↗

USGS2006

History of the Fort Collins Science Center, U.S. Geological Survey

The U.S. Geological Survey’s Fort Collins Science Center ("the Center") has been a nucleus of research, technology development, and associated scientific activities within the Department of the Interior for more than 30 years. The Center’s historical activities are deeply rooted in federal biological resources research and its supporting disciplines, particularly as they relate to the needs of the U.S. Department of the Interior and its resource management agencies. The organizational framework and activities of the Center have changed and adapted over the years in response to shifts in the scientific issues and challenges facing the U.S. Department of the Interior and with the development of new strategies to meet these challenges. Thus, the history of the Center has been dynamic. The Center has been nested within the U.S. Geological Survey since 1996. From 1993 to 1996 the Center was a major unit of the National Biological Service (named the National Biological Survey at its inception). This was a period of great organizational flux. During that time the Center comprised multiple field stations and science functions that prior to 1993 had been scattered among the U.S. Bureau of Land Management, the U.S. Bureau of Reclamation, the National Park Service, and the U.S. Fish and Wildlife Service. In 1993, certain biological research components of these agencies were assigned to join with the National Ecology Research Center, formerly one of the major research and development hubs of the U.S. Fish and Wildlife Service. This was the year when biological resources research in the U.S. Department of the Interior was consolidated by the Secretary of the Interior, who in an April 1993 memo explaining his intentions wrote, "Our Department has, without doubt, the best biologists in the world." Soon after formation of the new agency, the Center was re-named the Midcontinent Ecological Science Center, reflecting its geographic location within the new Midcontinent administrative region of the National Biological Service (the other three original administrative regions were the eastern, western, and southern). The change in name to the Fort Collins Science Center took place in 2002, soon after the center moved to new facilities on the Colorado State University Natural Resources Research Campus. At various times during the period when it was part of the National Biological Service (1993–96), the Center served as the administrative and programmatic home base for a wide number of science activities in numerous Western states (table 1). This reflected the previous fragmentation of biological and related science efforts across resource management agencies in the U.S. Department of the Interior. The organization of the 2 Center within the National Biological Service was a manifestation of the desire of the Secretary of the Interior to consolidate its biological science activities in administratively independent entities that would ensure that the science retained its objectivity. Congress later recognized the need to maintain a hierarchical independence between biological science and resource management in the Department. However, Congress also saw that the U.S. Geological Survey, with its long history of objective science support to the nation in geology, water resources, geography, and remote sensing, was a suitable alternative home for these biological science functions. Thus, in 1996 Congress transferred the biological resources functions of the National Biological Service to the U.S. Geological Survey. Detailed overviews and opinions about the history and policy issues surrounding the formation and subsequent fate of the National Biological Service can be found elsewhere (for example Cohn, 1993, 2005; Kaufman, 1993; Kreeger, 1994; Pulliam, 1995, 1998a,b; Reichhardt, 1994; Wagner, 1999)

Open-File Report↗

USGS2011

The interactions between vegetation and erosion: new directions for research at the interface of ecology and geomorphology

Vegetation and processes of erosion and deposition are interactive. An objective of this paper is to review selected studies that emphasize the interdependencies. The reviews suggest new directions for research uniting ecology and geomorphology – the sub‐discipline of biogeomorphology. The research, which recently has become vigorous, includes the sources, movement, and fates of fluvial loads of sediment, organic carbon, nutrients, contaminants, and woody debris to low‐energy storage sites; the function of biota in causing soil evolution, stability, and sequestration of carbon; the development of new methods to characterize watersheds based on edaphic conditions; and the refinement of current empirical and conceptual models and dendrochronological techniques to measure landscape change. These well acknowledged topics and others less well anticipated ensure that biogeomorphology will remain vibrant.

Earth Surface Processes and Landforms↗

USGS2014

Landscape effects on mallard habitat selection at multiple spatial scales during the non-breeding period

Previous studies that evaluated effects of landscape-scale habitat heterogeneity on migratory waterbird distributions were spatially limited and temporally restricted to one major life-history phase. However, effects of landscape-scale habitat heterogeneity on long-distance migratory waterbirds can be studied across the annual cycle using new technologies, including global positioning system satellite transmitters. We used Bayesian discrete choice models to examine the influence of local habitats and landscape composition on habitat selection by a generalist dabbling duck, the mallard (Anas platyrhynchos), in the midcontinent of North America during the non-breeding period. Using a previously published empirical movement metric, we separated the non-breeding period into three seasons, including autumn migration, winter, and spring migration. We defined spatial scales based on movement patterns such that movements >0.25 and <30.00 km were classified as local scale and movements >30.00 km were classified as relocation scale. Habitat selection at the local scale was generally influenced by local and landscape-level variables across all seasons. Variables in top models at the local scale included proximities to cropland, emergent wetland, open water, and woody wetland. Similarly, variables associated with area of cropland, emergent wetland, open water, and woody wetland were also included at the local scale. At the relocation scale, mallards selected resource units based on more generalized variables, including proximity to wetlands and total wetland area. Our results emphasize the role of landscape composition in waterbird habitat selection and provide further support for local wetland landscapes to be considered functional units of waterbird conservation and management.

Landscape Ecology↗

USGS2006

Nest survival in dusky Canada geese ( Branta canadensis occidentalis ): Use of discrete-time models

The Dusky Canada Goose ( Branta canadensis occidentalis ) population that breeds in the Copper River Delta, Alaska, has declined substantially since the late 1970s. Persistent low numbers have been attributed to low productivity in recent years. We examined patterns in survival rates of 1,852 nests to better understand ecological processes that influenced productivity during 1997-2000. We compared 10 nonparametric models of daily survival rate of nests (DSR) that included variation among years, calendar dates, nest initiation dates, and nest ages with equivalent models based on parametric functions. The unequivocal best model included patterns of DSR that varied among discrete periods of years, calendar dates, and nest ages. Generally, DSR was low early in the nesting season and higher midseason. Across years, patterns in DSR were most variable early and late in the nesting season. Daily survival rates of nests declined between the first and second week after initiation, increased until the fourth week, and then declined during the last week before hatch. Nest survival probability estimates ranged from 0.07 to 0.71 across years and nest initiation dates. Mean rates of nest survival ranged between 0.21 and 0.31 each year. We suggest (1) considering models that do not limit estimates of daily nest survival to parametric forms; (2) placing greater emphasis on sample size when nests are rare, to obtain accurate estimates of nest survival; and (3) developing new techniques to estimate the number of nests initiated.

The Auk↗

USGS2026

Evaluation and synthesis of the Yolo Bypass fish monitoring program

The Yolo Bypass is the largest functional remnant floodplain of the Sacramento River, providing benefits to aquatic taxa of the San Francisco Bay and Sacramento–San Joaquin Delta (hereafter, Bay-Delta). Because of the Yolo Bypass’s vital role in flood control and its ecological effects, the California Department of Water Resources started the Yolo Bypass Fish Monitoring Program (YBFMP) to monitor the aquatic ecology of the floodplain. Here, we present a scientific evaluation of the monitoring program to assess the efficacy and efficiency of the program in meeting its objective of collecting biological data to understand the ecological role the Yolo Bypass plays in the larger Bay-Delta. We used a multivariate assessment of floodplain flow to classify flood events (no flood, intense, early, late) and water years (low, average, high). To assess efficacy, we used a null hypothesis approach to determine if the YBFMP could distinguish variability in measured constituents (water quality and nutrient concentrations; phytoplankton, zooplankton, drift invertebrates, and fish communities; and densities of Chinook salmon [ Oncorhynchus tshawytscha ], Sacramento splittail [ Pogonichthys macrolepidotus ], and prickly sculpin [ Cottus asper ]) across different flood regime classifications. To assess efficiency, we used a data subsampling approach to quantify the amount of data needed to reach similar conclusions to analyses that used the entire dataset. Regarding efficacy, we concluded that the YBFMP is generally effective at identifying variability across various spatial and temporal scales (including flood regimes). Regarding efficiency, we concluded that reduced sampling effort would likely result in similar conclusions, enabling program managers to identify sites or periods that do not provide data essential to meeting program objectives. Our evaluation of the YBFMP indicated where data variability might limit mechanistic inference (particularly for phytoplankton and zooplankton), thus indicating that a series of targeted studies may be a prerequisite for further analysis. This evaluation has also identified areas where existing sampling may not be providing additional informational value, allowing for reallocation of effort to address management concerns.

California↗

USGS2018

Flood effects on soil thermal regimes in contrasting cold‐desert river floodplains (Yampa and Green rivers, Colorado)

Heat transfer theory suggests that floodplain soils in dryland riverine ecosystems can be cooled by hyporheic flows generated during spring floods. I compared soil temperature cycles and associated hydrologic factors on a free‐flowing river to those on a river where flows and surface water temperatures are now regulated. Spring surface water temperatures were comparable on the 2 rivers, as was apparent diffusivity of the soil under mature Populus fremontii in a year when severe drought produced similar soil moisture regimes. Over 9 years of monitoring, mean annual maximum soil temperature was higher on the regulated river than on the free‐flowing river (10 cm depth: 33 vs. 23 °C; 40 cm depth: 30 vs. 20°C, respectively), and sinusoidal models of the annual temperature cycle at each depth indicated higher means and greater amplitudes on the regulated river. The annual maximum soil temperature was inversely related to peak flood discharge on the free‐flowing river but not on the regulated river. Temporal shifts in the lag between diel cycles at 40 and 10 cm depths—an index of soil thermal diffusivity—suggested that the capillary fringe is strongly involved in heat exchange. An increase in the lag during some water table declines suggested that shallow soils may undergo flood‐induced evaporative cooling. Hyporheic recharge can be an ecologically important determinant of growing‐season soil temperatures at plant rooting depth in dryland river floodplains. Reductions in spring flood magnitude due to river regulation, water abstraction, or climate change can increase these temperatures and thereby alter ecosystem structure and functioning.

Colorado↗

USGS2024

Temporal habitat use of mule deer in the Pueblo of Santa Ana, New Mexico

Mule deer ( Odocoileus hemionus ) are important economically, culturally, and recreationally to the Pueblo of Santa Ana in central New Mexico, USA. Studies of habitat selection improve our understanding of mule deer ecology in central New Mexico and provide the Tribe with valuable information for management of mule deer. We used global positioning system telemetry-collar data collected on mule deer around the Pueblo of Santa Ana to create resource selection functions from proximity-based habitat predictors using a generalized linear mixed model. We created separate resource selection functions for females and males during summer and winter at different times of the day. Season generally had a greater effect on mule deer habitat use than the time of day. Female and male mule deer selected for similar habitats but were sexually segregated in their summer distributions. These findings are consistent with results from other locations where mule deer partitioned habitat similarly between seasons and sexes. Supported models reaffirm accepted patterns of habitat selection for mule deer to the Pueblo of Santa Ana where local results were lacking. Our results can help managers identify locations in and around the Pueblo of Santa Ana where future development such as highway expansion are likely to conflict with mule deer activity and locations where habitat enhancement projects such as adding water sources can have the greatest effect for the deer population.

New Mexico↗

USGS2015

Broadening the regulated-river management paradigm: A case study of the forgotten dead zone hindering Pallid Sturgeon recovery

The global proliferation of dams within the last half century has prompted ecologists to understand the effects of regulated rivers on large-river fishes. Currently, much of the effort to mitigate the influence of dams on large-river fishes has been focused on downriver effects, and little attention has been given to upriver effects. Through a combination of field observations and laboratory experiments, we tested the hypothesis that abiotic conditions upriver of the dam are the mechanism for the lack of recruitment in Pallid Sturgeon ( Scaphirhynchus albus ), an iconic large-river endangered species. Here we show for the first time that anoxic upriver habitat in reservoirs (i.e., the transition zone between the river and reservoir) is responsible for the lack of recruitment in Pallid Sturgeon. The anoxic condition in the transition zone is a function of reduced river velocities and the concentration of fine particulate organic material with high microbial respiration. As predicted, the river upstream of the transition zone was oxic at all sampling locations. Our results indicate that transition zones are an ecological sink for Pallid Sturgeon. We argue that ecologists, engineers, and policy makers need to broaden the regulated-river paradigm to consider upriver and downriver effects of dams equally to comprehensively mitigate altered ecosystems for the benefit of large-river fishes, especially for the Pallid Sturgeon.

Fisheries↗

USGS2019

Projected urban growth in the Southeastern USA puts small streams at risk

Future land-use development has the potential to profoundly affect the health of aquatic ecosystems in the coming decades. We developed regression models predicting the loss of sensitive fish (R2=0.39) and macroinvertebrate (R2=0.64) taxa as a function of urban and agricultural land uses and applied them to projected urbanization of the rapidly urbanizing Piedmont ecoregion of the southeastern USA for 2030 and 2060. The regression models are based on a 2014 investigation of water quality and ecology of 75 wadeable streams across the region. Based on these projections, stream kilometers experiencing >50% loss of sensitive fish and invertebrate taxa will nearly quadruple to 19,500 and 38,950 km by 2060 (16 and 32% of small stream kilometers in the region), respectively. Uncertainty was assessed using the 20 and 80% probability of urbanization for the land-use projection model and using the 95% confidence intervals for the regression models. Adverse effects on stream health were linked to elevated concentrations of contaminants and nutrients, low dissolved oxygen, and streamflow alteration, all associated with urbanization. The results of this analysis provide a warning of potential risks from future urbanization and perhaps some guidance on how those risks might be mitigated.

PLoS ONE↗

USGS2022

Regularizing priors for Bayesian VAR applications to large ecological datasets

Using multi-species time series data has long been of interest for estimating inter-specific interactions with vector autoregressive models (VAR) and state space VAR models (VARSS); these methods are also described in the ecological literature as multivariate autoregressive models (MAR, MARSS). To date, most studies have used these approaches on relatively small food webs where the total number of interactions to be estimated is relatively small. However, as the number of species or functional groups increases, the length of the time series must also increase to provide enough degrees of freedom with which to estimate the pairwise interactions. To address this issue, we use Bayesian methods to explore the potential benefits of using regularized priors, such as Laplace and regularized horseshoe, on estimating interspecific interactions with VAR and VARSS models. We first perform a large-scale simulation study, examining the performance of alternative priors across various levels of observation error. Results from these simulations show that for sparse matrices, the regularized horseshoe prior minimizes the bias and variance across all inter-specific interactions. We then apply the Bayesian VAR model with regularized priors to a output from a large marine food web model (37 species) from the west coast of the USA. Results from this analysis indicate that regularization improves predictive performance of the VAR model, while still identifying important inter-specific interactions.

PeerJ↗

USGS2019

Genetically-informed seed transfer zones for Pleuraphis jamesii, Sphaeralcea parvifolia, and Sporobolus cryptandrus across the Colorado Plateau and adjacent regions

(Massatti) Introduction: The majority of native plant materials (NPMs) utilized for restoration purposes are developed for widely distributed species that provide a variety of ecosystem services (Wood et al. 2015; Butterfield et al. 2017). Disturbed ecosystems benefit from the use of appropriate NPMs, which are those that display ecological fitness at the restoration site, are compatible with conspecifics and other members of the plant community, and that do not demonstrate invasive tendencies (Jones 2013). Furthermore, the use of appropriate NPMs can help address specific environmental challenges, rejuvenate ecosystem function, and improve the delivery of ecosystem services (Hughes 2008). While many NPMs have been developed for restoration (e.g., Aubry et al. 2005), there is interest in broadening the diversity of species available and the geographic representation of sources to provide appropriate choices in relation to the characteristics of any restoration site. In addition, researchers are providing guidance to managers and practitioners regarding how best to transfer NPMs across the landscape. For example, guidance on seed transfer has been derived from genecological studies, which utilize common gardens to correlate phenotypic variation to environmental gradients (summarized in Kilkenny 2015), molecular studies, which identify putative adaptive genetic loci and infer environmental drivers of variation (Shryock et al. 2017), and climate modeling studies, which can provide guidance when species-specific data are unavailable (Bower et al. 2014; Doherty et al. 2017). All of these approaches intend to improve the long-term viability of NPMs at restoration sites, thereby improving outcomes and stretching limiting restoration resources (e.g., time and money).

Colorado Plateau↗

USGS2012

Use of alligator hole abundance and occupancy rate as indicators for restoration of a human-altered wetland

Use of indicator species as a measure of ecosystem conditions is an established science application in environmental management. Because of its role in shaping wetland systems, the American alligator (Alligator mississippiensis) is one of the ecological indicators for wetland restoration in south Florida, USA. We conducted landscape-level aerial surveys of alligator holes in two different habitats in a wetland where anthropogenic modification of surface hydrology has altered the natural system. Alligator holes were scarcer in an area where modified hydrology caused draining and frequent dry-downs compared to another area that maintains a functional wetland system. Lower abundance of alligator holes indicates lack of alligator activities, lower overall species diversity, and lack of dry-season aquatic refugia for other organisms. The occupancy rate of alligator holes was lower than the current restoration target for the Everglades, and was variable by size class with large size-class alligators predominantly occupying alligator holes. This may indicate unequal size-class distribution, different habitat selection by size classes, or possibly a lack of recruitment. Our study provides pre-restoration baseline information about one indicator species for the Everglades. Success of the restoration can be assessed via effective synthesis of information derived by collective research efforts on the entire suite of selected ecological indicators.

Florida↗

USGS2017

QFASAR: Quantitative fatty acid signature analysis with R

Knowledge of predator diets provides essential insights into their ecology, yet diet estimation is challenging and remains an active area of research. Quantitative fatty acid signature analysis (QFASA) is a popular method of estimating diet composition that continues to be investigated and extended. However, software to implement QFASA has only recently become publicly available. I summarize a new R package, qfasar , for diet estimation using QFASA methods. The package also provides functionality to evaluate and potentially improve the performance of a library of prey signature data, compute goodness-of-fit diagnostics, and support simulation-based research. Several procedures in the package have not previously been published. qfasar makes traditional and recently published QFASA diet estimation methods accessible to ecologists for the first time. Use of the package is illustrated with signature data from Chukchi Sea polar bears and potential prey species.

Methods in Ecology and Evolution↗

USGS2023

Accounting for spatiotemporal sampling variation in joint species distribution models

Estimating relative abundance is critical for informing conservation and management efforts and for making inferences about the effects of environmental change on populations. Freshwater fisheries span large geographic regions, occupy diverse habitats and consist of varying species assemblages. Monitoring schemes used to sample these diverse populations often result in populations being sampled at different times and under different environmental conditions. Varying sampling conditions can bias estimates of abundance when compared across time, location and species, and properly accounting for these biases is critical for making inferences. We develop a joint species distribution model (JSDM) that accounts for varying sampling conditions due to the environment and time of sampling when estimating relative abundance. The novelty of our JSDM is that we explicitly model sampling effort as the product of known quantities based on time and gear type and an unknown functional relationship to capture seasonal variation in species life history. We use the model to study relative abundance of six freshwater fish species across the state of Minnesota, USA. Our model enables estimates of relative abundance to be compared both within and across species and lakes, and captures the inconsistent sampling present in the data. We discuss how gear type, water temperature and day of the year impact catchability for each species at the lake level and throughout a year. We compare our estimates of relative abundance to those obtained from a model that assumes constant catchability to highlight important differences within and across lakes and species. Synthesis and applications : Our method illustrates that assumptions relating indices of abundance to observed catch data can greatly impact model inferences derived from JSDMs. Specifically, not accounting for varying sampling conditions can bias inference of relative abundance, restricting our ability to detect responses to management interventions and environmental change. While our focus is on freshwater fisheries, this model architecture can be adopted to other systems where catchability may vary as a function of space, time and species.

Journal of Applied Ecology↗