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At least 1,081 records · Page 60Linked to original sources

USGS2007

Multibeam observations of mine burial near Clearwater, FL, including comparisons to predictions of wave-induced burial

A Kongsberg Simrad EM 3000 multibeam sonar (Kongsberg Simrad, Kongsberg, Norway) was used to conduct a set of six repeat high-resolution bathymetric surveys west of Indian Rocks Beach (IRB), just to the south of Clearwater, FL, between January and March 2003, to observe in situ scour and burial of instrumented inert mines and mine-like cylinders. Three closely located study sites were chosen: two fine-sand sites, a shallow one located in ??? 13 m of water depth and a deep site located in ???14 m of water depth; and a coarse-sand site in ???13 m. Results from these surveys indicate that mines deployed in fine sand are nearly buried within two months of deployment (i.e., they sunk 74.5% or more below the ambient seafloor depth). Mines deployed in coarse sand showed a lesser amount of scour, burying until they present roughly the same hydrodynamic roughness as the surrounding rippled bedforms. These data were also used to test the validity of the Virginia Institute of Marine Science (VIMS, Gloucester Point, VA) 2-D burial model. The model worked well in areas of fine sand, sufficiently predicting burial over the course of the experiment. In the area of coarse sand, the model greatly overpredicted the amount of burial. This is believed to be due to the presence of rippled bedforms around the mines, which affect local bottom morphodynamics and are not accounted for in the model, an issue currently being addressed by the modelers. This paper focuses specifically on two instrumented mines: an acoustic mine located in fine sand and an optical instrumented mine located in coarse sand. ?? 2007 IEEE.

IEEE Journal of Oceanic Engineering↗

USGS2007

In situ time-series measurements of subseafloor sediment properties

The capabilities and diversity of subsurface sediment sensors lags significantly from what is available for the water column, thereby limiting progress in understanding time-dependent seabed exchange and high-frequency acoustics. To help redress this imbalance, a new instrument, the autonomous sediment profiler (ASP), is described herein. ASP consists of a four-electrode, Wenner-type resistivity probe and a thermistor that log data at 0.1-cm vertical intervals over a 58-cm vertical profile. To avoid resampling the same spot on the seafloor, the probes are moved horizontally within a 20 times 100-cm -2 area in one of three preselected patterns. Memory and power capacities permit sampling at hourly intervals for up to 3-mo duration. The system was tested in a laboratory tank and shown to be able to resolve high-frequency sediment consolidation, as well as changes in sediment roughness. In a field test off the southern coast of France, the system collected resistivity and temperature data at hourly intervals for 16 d. Coupled with environmental data collected on waves, currents, and suspended sediment, the ASP is shown to be useful for understanding temporal evolution of subsurface sediment porosity, although no large depositional or erosional events occurred during the deployment. Following a rapid decrease in bottom-water temperature, the evolution of the subsurface temperature field was consistent with the 1-D thermal diffusion equation coupled with advection in the upper 3-4 cm. Collectively, the laboratory and field tests yielded promising results on time-dependent seabed change.

IEEE Journal of Oceanic Engineering↗

USGS2020

In situ measurements of compressional wave speed during gravity coring operations in the New England mud patch

This paper presents measurements of sediment sound-speed profiles measured in situ using the acoustic coring system (ACS). The reported measurements were obtained from seven gravity cores collected in the New England Mud Patch. The ACS uses two sets of transducers mounted below the penetrating tip of a sediment corer to make in situ measurements of geoacoustic properties as the corer penetrates the seabed. The in situ sound-speed profiles are interpreted in the context of stratigraphic layering measured by a seismic survey, and the measured sound-speed profiles are consistent with the geophysical description. The in situ sound-speed profiles measured by the ACS were compared to conventional measurements of sound speed on the recovered cores using the multisensor core logger (MSCL). The MSCL data displayed both random and systematic errors that were attributed to disturbance from the coring process and/or the handling of the sediments after collection. Finally, using porosity and grain size distributions measured from discrete samples of the cored sediments, the in situ sound-speed measurements were compared to empirical regressions based on independent data sets.

Atlantic Ocean, New England Mud Patch↗

USGS2012

Observations of ocean circulation and sediment transport experiment offshore of Fire Island, NY

Researchers from the U.S. Geological Survey (USGS) Woods Hole Coastal and Marine Science Center (WHCMSC), in collaboration with Coastal Carolina University (CCU) and University of South Carolina (USC), conducted a scientific field study to investigate the ocean circulation and sediment transport processes offshore of Fire Island, NY. Although the physical processes along the entire linear extent of Fire Island (~50 km) are of interest to the project, one particular region of focus is at the western end of the island where offshore sand ridges out to depths of 20 m extend across the inner shelf and connect to the near-shore bar system. The primary objective was to measure the physical processes around the sand ridges, including circulation patterns, wave parameters, bottom stress, and suspended sediment. Transects of instrumentation were positioned along and across the crests and troughs of the ridge field. A site at the top of a ridge and a site at the bottom of an adjacent trough were each populated with two tripods designed to provide high-resolution measurements near the sea-bed to record sediment re-suspension events. Measurements at these two sites include near bottom velocity profiles, acoustic Doppler velocimeters, pressure, optical transmission and backscatter at high sampling rates. Other measurements include upward looking velocity profiles, temperature, salinity, sonar images and profiles, and sediment size classes. Five smaller tripods were deployed to complete lines alongshore and across shore over a 5 km area to provide a regional picture. These tripods recorded upward looking velocity profiles and near bottom temperature, pressure and salinity. Surface buoys marked the position of the tripods and collected surface measurements at six of the sites. One buoy gathered meteorological measurements. The sites were occupied from January to April, 2012. This deployment was similar to previous efforts off Cape Hatteras, NC, in 2009, and is part of an ongoing effort to understand regional patterns in circulation and sediment transport and the interaction of inner shelf and near shore processes. New instrumentation for the USGS was introduced, including a variety of current and wave measurement equipment, acquisition and telemetry in near-realtime of the weather data, time series sonar imaging equipment, and anti-fouling wipers. Preliminary results suggest a complex and subtle relationship between wind and across shore current velocity in this region, and a more straightforward relationship between winds and alongshore currents. This paper also includes a preliminary report on the effectiveness of new measurement techniques used during this experiment.

New York↗

USGS2026

Development and field testing of a UAS-based software-defined radar for measuring freshwater bathymetry

We provide an overview of an uncrewed aircraft system (UAS)-based software-defined radar (SDRadar) system for high-resolution geophysical observations. The radar transceiver is implemented on a Radio Frequency System-on-Chip (RFSoC) platform, along with an ultra-wideband Vivaldi antenna that has a starting operating frequency of 150 MHz, enabling the system to be used across different applications, including measurements of freshwater bathymetry. In addition to system design and subsystem performance assessments, this paper presents the results of field testing conducted along the Sacramento River near Glenn, California, USA. The radar-derived river depth measurements are compared with ground truth data collected from a crewed boat using an acoustic Doppler current profiler (ADCP). The results show good agreement, with a root mean square error (RMSE) of 0.079 m.

California↗

USGS2019

Nest structure affects auditory and visual detectability, but not predation risk, in a tropical songbird community

Offspring mortality varies dramatically among species with critical demographic and evolutionary ramifications, yet the causes of this variation remain unclear. Nests are widely used for breeding across taxa and thought to influence offspring mortality risk. Traditionally, more complex, enclosed nest structures are thought to reduce offspring predation by reducing the visibility of nest contents and muffling offspring sounds compared to open nests. Direct tests of the functional bases for nest structure influence on predation risk are lacking. We used experiments and 10 years of observational data to examine how nest structure influences nest predation risk in a diverse community of tropical songbirds. First, we examined how nest size was related to nest structure and nest predation rates across species. Second, we assessed how nest structure influences the detectability of nestling begging calls both in field and in laboratory settings. Finally, we examined how the acoustic properties of different nest structures influence nest predation risk. Specifically, we experimentally broadcast begging calls from open and enclosed nests to determine how auditory cues and nest structure interact to affect predation on plasticine and quail eggs. We also tested whether nest structure was associated with differences in nest predation rates between the incubation (no begging cues) and nestling (begging cues) stages. We found that enclosed nests are larger than open nests after accounting for adult size, and larger nests had increased predation rates. Moreover, enclosed nests did not consistently alter nestling begging calls in ways that reduce the likelihood of predation compared to open nests. Indeed, begging cues increased predation rates for enclosed but not open‐cup nests in our playback experiment, and nest predation rates showed greater increases after hatching in enclosed than open‐cup nests. Ultimately, enclosed nests do not necessarily provide greater predation benefits than open nests in contrast to long‐standing theory.

Functional Ecology↗

USGS2022

NABat ML: Utilizing deep learning to enable crowdsourced development of automated, scalable solutions for documenting North American bat populations

Bats play crucial ecological roles and provide valuable ecosystem services, yet many populations face serious threats from various ecological disturbances. The North American Bat Monitoring Program (NABat) aims to use its technology infrastructure to assess status and trends of bat populations, while developing innovative and community-driven conservation solutions. Here, we present NABat ML , an automated machine-learning algorithm that improves the scalability and scientific transparency of NABat acoustic monitoring. This model combines signal processing techniques and convolutional neural networks (CNNs) to detect and classify recorded bat echolocation calls. We developed our CNN model with internet-based computing resources (‘cloud environment’), and trained it on >600,000 spectrogram images. We also incorporated species range maps to improve the robustness and accuracy of the model for future ‘unseen’ data. We evaluated model performance using a comprehensive, independent, holdout dataset. NABat ML successfully distinguished 31 classes (30 species and a noise class) with overall weighted-average accuracy and precision rates of 92%, and ≥90% classification accuracy for 19 of the bat species. Using a single cloud-environment computing instance, the entire model training process took <16 h. Synthesis and applications . Our convolutional neural network (CNN)-based model, NABat ML , classifies 30 North American bat species using their recorded echolocation calls with an overall accuracy of 92%. In addition to providing highly accurate species-level classification, NABat ML and its outputs are compatible with Bayesian and other statistical techniques for measuring uncertainty in classification. Our model is open-source and reproducible, enabling future implementations as software on end-user devices and cloud-based web applications. These qualities make NABat ML highly suitable for applications ranging from grassroots community science initiatives to big-data methods developed and implemented by researchers and professional practitioners. We believe the transparency and accessibility of NABat ML will encourage broad-scale participation in bat monitoring, and enable development of innovative solutions needed to conserve North American bat species.

Journal of Applied Ecology↗

USGS2016

Discharge and nutrient transport between lakes in a hydrologically complex area of Voyageurs National Park, Minnesota, 2010-2012

An acoustic Doppler velocity meter (ADVM) was deployed in the narrows between Namakan and Kabetogama Lakes in Voyageurs National Park, Minnesota, from November 3, 2010, through October 3, 2012. The ADVM can account for wind, seiche, and changing flow direction in hydrologically complex areas. The objectives were to (1) estimate discharge and document the direction of water flow, (2) assess whether specific conductance can be used to determine flow direction, and (3) document nutrient and chlorophyll a concentrations at the narrows. The discharge direction through the narrows was seasonal. Water generally flowed out of Kabetogama Lake and into Namakan Lake throughout the ice-covered season. During spring, water flow was generally from Namakan Lake to Kabetogama Lake. During the summer and fall, the water flowed in both directions, affected in part by wind. Water flowed into Namakan Lake 70% of water year 2011 and 56% of water year 2012. Nutrient and chlorophyll a concentrations were highest during the summer months when water-flow direction was unpredictable. The use of an ADVM was effective for assessing flow direction and provided flow direction under ice. The results indicated the eutrophic Kabetogama Lake may have a negative effect on the more pristine Namakan Lake. The results also provide data on the effects of the current water-level management plan and may help determine if adjustments are necessary to help protect the aquatic ecosystem of Voyageurs National Park.

Minnesota↗

USGS2022

Evaluation of select velocity measurement techniques for estimating discharge in small streams across the United States

Multiple instruments and methods exist for collecting discrete streamflow measurements in small streams with low flows, defined here as less than 5.7 m 3 /s (200 ft3/s). Included in the available methods are low-cost approaches that are infrequently used, in part, because their uncertainty is not well known. In this work, we evaluated the accuracy and suitability of three low-cost velocity measurement methods (surface float [SF], velocity head rod [VR], and rising body [RB]) and three conventional current meters (acoustic Doppler velocimeter, and mechanical Price type AA and Price Pygmy meters) relative to discharge calculated from stable artificial hydraulic controls. A total of 231 measurements were made by 20 individuals during 88 site visits to 24 sites in eight states. Accuracies were assessed for all methods and precision was evaluated for the low-cost methods. The median percent error was below 5% for conventional methods, and below 20% for the low-cost methods. The SF was the most accurate (median absolute percent error 14%) and precise (mean percent precision of 11%) low-cost method. The RB and VR, respectively, had 15% and 20% median absolute percent error and 29% and 12% mean percent precision. Results suggest that low-cost methods, when used appropriately, can be used to estimate discharge data under low flow conditions when measurements with conventional methods are not feasible and the associated accuracies meet end-user measurement objectives.

continental United States↗

USGS2022

Estimating occupancy from autonomous recording unit data in the presence of misclassifications and detection heterogeneity

1. Autonomous Recording Units (ARUs) are now widely used to survey communities of species. These surveys generate spatially and temporally replicated counts of unmarked animals, but such data typically include false negatives and misclassified detections, both of which may vary across sites in proportion to abundance. These data challenges can bias estimates of occupancy, and the typical approach of verifying individual detections is expensive. 2. We developed a Bayesian implementation of a two-species, false-positive N-mixture model for estimating occupancy from ARU data or other counts of unmarked animals that does not require manual verification. The model accounts for species misclassification and abundance-induced detection heterogeneity, as well as false negatives. To evaluate this model, we simulated 200 data sets for each of 29 scenarios, including scenarios in which misclassifications outnumbered correct classifications for rare species. We also applied the model to acoustic surveys of bats conducted on Fort Carson Army Post and Piñon Canyon Maneuver Site, Colorado, USA. 3. In the simulation study, bias, coverage, and root mean square error for occupancy estimates obtained from the two-species false-positive N-mixture model were superior to metrics obtained from two competing two-species false-positive occupancy models. Across 29 scenarios, absolute bias was consistently low (range: -0.03–0.07), while coverage averaged 93% (range: 74%–98%). For alternative occupancy models, absolute bias was often high (range: -0.36–0.39), and coverage averaged from 47%–65%. Although our model included an abundance parameter, abundance estimates were not reliable. For two species of Myotis bats, we estimated that 1%–5% of field-recorded detections were misclassified. Estimated occupancy (0.91 and 0.76) was lower than naïve estimates (1.00 and 0.94). Competing occupancy models implausibly estimated local occupancy of 0.00 at sites with numerous detections. 4. Our two-species, false-positive N-mixture model is significant because it accounts for detection heterogeneity and improves occupancy estimates without expensive manual verification of detections. Our field application indicated that misclassifications were not common, yet affected occupancy inferences. Given that ARUs are increasingly used to survey a broad range of taxa, such an occupancy model could be widely useful.

Methods in Ecology and Evolution↗

USGS2014

Disease and community structure: white-nose syndrome alters spatial and temporal niche partitioning in sympatric bat species

Aim Emerging infectious diseases present a major perturbation with apparent direct effects such as reduced population density, extirpation and/or extinction. Comparatively less is known about the potential indirect effects of disease that likely alter community structure and larger ecosystem function. Since 2006, white-nose syndrome (WNS) has resulted in the loss of over 6 million hibernating bats in eastern North America. Considerable evidence exists concerning niche partitioning in sympatric bat species in this region, and the unprecedented, rapid decline in multiple species following WNS may provide an opportunity to observe a dramatic restructuring of the bat community. Location We conducted our study at Fort Drum Army Installation in Jefferson and Lewis counties, New York, USA, where WNS first impacted extant bat species in winter 2007–2008. Methods Acoustical monitoring during 2003–2011 allowed us to test the hypothesis that spatial and temporal niche partitioning by bats was relaxed post-WNS. Results We detected nine bat species pre- and post-WNS. Activity for most bat species declined post-WNS. Dramatic post-WNS declines in activity of little brown bat ( Myotis lucifugus , MYLU), formerly the most abundant bat species in the region, were associated with complex, often species-specific responses by other species that generally favoured increased spatial and temporal overlap with MYLU. Main conclusions In addition to the obvious direct effects of disease on bat populations and activity levels, our results provide evidence that disease can have cascading indirect effects on community structure. Recent occurrence of WNS in North America, combined with multiple existing stressors, is resulting in dramatic shifts in temporal and spatial niche partitioning within bat communities. These changes might influence long-term population viability of some bat species as well as broader scale ecosystem structure and function.

New York↗

USGS2015

Establishing conservation baselines with dynamic distribution models for bat populations facing imminent decline

Aim Bat mortality rates from white-nose syndrome and wind power development are unprecedented. Cryptic and wide-ranging behaviours of bats make them difficult to survey, and population estimation is often intractable. We advance a model-based framework for making spatially explicit predictions about summertime distributions of bats from capture and acoustic surveys. Motivated by species-energy and life-history theory, our models describe hypotheses about spatio-temporal variation in bat distributions along environmental gradients and life-history attributes, providing a statistical basis for conservation decision-making. Location Oregon and Washington, USA. Methods We developed Bayesian hierarchical models for 14 bat species from an 8-year monitoring dataset across a ~430,000 km 2 study area. Models accounted for imperfect detection and were temporally dynamic. We mapped predicted occurrence probabilities and prediction uncertainties as baselines for assessing future declines. Results Forest cover, snag abundance and cliffs were important predictors for most species. Species occurrence patterns varied along elevation and precipitation gradients, suggesting a potential hump-shaped diversity–productivity relationship. Annual turnover in occurrence was generally low, and occurrence probabilities were stable among most species. We found modest evidence that turnover covaried with the relative riskiness of bat roosting and migration. The fringed myotis ( Myotis thysanodes ), canyon bat ( Parastrellus hesperus ) and pallid bat ( Antrozous pallidus ) were rare; fringed myotis occurrence probabilities declined over the study period. We simulated anticipated declines to demonstrate that mapped occurrence probabilities, updated over time, provide an intuitive way to assess bat conservation status for a broad audience. Main conclusions Landscape keystone structures associated with roosting habitat emerged as regionally important predictors of bat distributions. The challenges of bat monitoring have constrained previous species distribution modelling efforts to temporally static presence-only approaches. Our approach extends to broader spatial and temporal scales than has been possible in the past for bats, making a substantial increase in capacity for bat conservation.

Oregon, Washington↗

USGS2018

Phylogeny and species traits predict bird detectability

Avian acoustic communication has resulted from evolutionary pressures and ecological constraints. We therefore expect that auditory detectability in birds might be predictable by species traits and phylogenetic relatedness. We evaluated the relationship between phylogeny, species traits, and field‐based estimates of the two processes that determine species detectability (singing rate and detection distance) for 141 bird species breeding in boreal North America. We used phylogenetic mixed models and cross‐validation to compare the relative merits of using trait data only, phylogeny only, or the combination of both to predict detectability. We found a strong phylogenetic signal in both singing rates and detection distances; however the strength of phylogenetic effects was less than expected under Brownian motion evolution. The evolution of behavioural traits that determine singing rates was found to be more labile, leaving more room for species to evolve independently, whereas detection distance was mostly determined by anatomy (i.e. body size) and thus the laws of physics. Our findings can help in disentangling how complex ecological and evolutionary mechanisms have shaped different aspects of detectability in boreal birds. Such information can greatly inform single‐ and multi‐species models but more work is required to better understand how to best correct possible biases in phylogenetic diversity and other community metrics.

Ecography↗

USGS2025

Does habitat or climate change drive species range shifts?

A primary prediction of climate change ecology is that species will track their climate niche poleward and upslope. However, studies have shown species responding in surprising ways. In this study, we aim to understand the impact of global change on species ranges by considering both climate and habitat changes. Using occupancy analysis of acoustic survey data in the mountains of the northeastern United States, we tested specific predictions of range responses to warming (shifting upslope), precipitation change (shifting downslope), and forest composition change (shifting downslope). We found that American red squirrels Tamiasciurus hudsonicus , key nodes in northern North American food webs, are not tracking increasing temperatures upslope, despite substantial warming in recent decades. Structural equation modeling indicates that red squirrel abundance is primarily influenced by red-spruce forest cover, which has shifted downslope with recovery from historical logging and acid deposition. Accounting for the multiple dimensions of global change will enable better predictions and more effective conservation strategies.

Connecticut, Maine, Massachusetts, New Hampshire, ↗

USGS2015

Sex-biased survivorship and differences in migration of wild steelhead (Oncorhynchus mykiss) smolts from two coastal Oregon rivers

In salmonids with partial migration, females are more likely than males to undergo smoltification and migrate to the ocean (vs. maturing in freshwater). However, it is not known whether sex affects survivorship during smolt migration (from fresh water to entry into the ocean). We captured wild steelhead ( Oncorhynchus mykiss) smolts in two coastal Oregon rivers (USA) and collected fin tissue samples for genetic sex determination (2009; N = 70 in the Alsea and N = 69 in the Nehalem, 2010; N = 25 in the Alsea). We implanted acoustic tags and monitored downstream migration and survival until entry in to the Pacific Ocean. Survival was defined as detection at an estuary/ocean transition array. We found no effect of sex on smolt survivorship in the Nehalem River in 2009, or in the Alsea River in 2010. However, males exhibited significantly lower survival than females in the Alsea River during 2009. Residency did not influence this result as an equal proportion of males and females did not reach the estuary entrance (11% of males, 9% of females). The sexes did not differ in timing or duration of migration, so those variables seem unlikely to explain sex-biased survivorship. Larger males had higher odds of survival than smaller males in 2009, but the body size of females did not affect survivorship. The difference in survivorship between years in the Alsea River could be due to flow conditions, which were higher in 2010 than in 2009. Our findings suggest that sex may affect steelhead smolt survival during migration, but that the difference in survivorship may be weak and not a strong factor influencing adult sex ratios.

Oregon↗

USGS2016

Do intracoelomic telemetry transmitters alter the post-release behaviour of migratory fish?

Electronic tags have become a common tool in fish research, enhancing our understanding of how fish interact with their environment and move among different habitats, for estimating mortality and recording internal physiological states. An often-untested assumption of electronic tagging studies is that tagged fish are representative of untagged conspecifics and thus show ‘normal’ behaviour (e.g. movement rates, swimming activity, feeding). Here, we use a unique data set for potamadromous walleye (Sander vitreus) in Lake Huron and Lake Erie tributaries to assess whether the lack of appropriate controls in electronic tagging could seriously affect behavioural data. We used fish tagged in previous years and compared their migratory behaviour during the spawning season to fish tagged in a current year at the same location. The objective of the study was to determine whether intracoelomic acoustic tag implantation altered downstream movement of walleye after spawning. Fish tagged in a given season travelled slower downstream from two river spawning sites than fish tagged in previous years. Fish tagged one or two years earlier showed no differences between each other in downstream travel time, in contrast to fish tagged in a given year. Our results support notions that standard collection and intracoelomic tagging procedures can alter short-term behaviour (i.e. days, weeks, months), and as such, researchers should use caution when interpreting data collected over such time periods. Further, whenever possible, researchers should also explicitly evaluate post-tagging effects on behaviour as part of their experimental objectives.

Maumee Bay, Saginaw Bay↗

USGS2017

Spawning site fidelity and apparent annual survival of walleye (Sander vitreus) differ between a Lake Huron and Lake Erie tributary

Fidelity to spawning habitats can maximise reproductive success of fish by synchronising movements to sites of previous recruitment. To determine the role of reproductive fidelity in structuring walleye Sander vitreus populations in the Laurentian Great Lakes, we used acoustic telemetry combined with Cormack–Jolly–Seber capture–recapture models to estimate spawning site fidelity and apparent annual survival for the Tittabawassee River in Lake Huron and Maumee River in Lake Erie. Walleye in spawning condition were tagged from the Tittabawassee River in Lake Huron and Maumee River in Lake Erie in 2011–2012. Site fidelity and apparent annual survival were estimated from return of individuals to the stream where tagged. Site fidelity estimates were higher in the Tittabawassee River (95%) than the Maumee River (70%) and were not related to sex or fish length at tagging. Apparent annual survival of walleye tagged in the Tittabawassee did not differ among spawning seasons but was higher for female than male walleye and decreased linearly as fish length increased. Apparent annual survival of walleye tagged in the Maumee River did not differ among spawning seasons but was higher for female walleye than male walleye and increased linearly as fish length increased. Greater fidelity of walleye tagged in the Tittabawassee River than walleye tagged in the Maumee River may be related to the close proximity to the Maumee River of other spawning aggregations and multiple spawning sites in Lake Erie. As spawning site fidelity increases, management actions to conserve population structure require an increasing focus on individual stocks.

Lake Erie, Lake Huron↗

USGS2018

Multiple metrics provide context for the distribution of a highly mobile fish predator, the blue catfish

Data sets with increased spatial and temporal resolution can help researchers and resource managers quantify representative distributional patterns of mobile sportfish. In this research, first, we illustrate patterns of sportfish distribution using individual ( percent of population, residence time, number of movements ) and combined distributional metrics. Second, we apply these metrics to one highly mobile fish species, the blue catfish ( Ictalurus furcatus ), across a range of spatial (whole reservoir, region, site) and temporal (year, month, diel period) scales. Specifically, we tracked 123 acoustically tagged blue catfish with a 20-receiver array in Milford Reservoir, KS, USA. When we integrated metrics, four site-specific distributional patterns emerged: (a) a large, active multi-site fish aggregation, (b) localised site fidelity, (c) transitional sites and (d) rarely used locations. These patterns would not have been detected using a single metric as each measurement revealed a different piece of the distribution story. For example, if we had only quantified percent of population, we could identify fish location, but not whether individual fish spent time at a location or were just passing through. Our examination of multiple scales also provided a novel context for interpreting site-specific patterns. As an illustration of this insight, using conventional approaches, we would have observed heterogeneity, but we would not have detected fish aggregations, in which individual fish either remained or repeatedly returned to a site. In summary, our results show the advantage of setting the entire ecosystem as the study boundary to integrate multiple responses using a spatially and temporally extensive data set.

Kansas↗