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Learning and resolving uncertainty should be important components of management decisions, but not every type of uncertainty is equally important to resolve. For rare, threatened, and endangered species, information may be limited and there is often great urgency to halt potential population declines. Therefore, the most important uncertainties are those that would lead to different decisions intended to improve outcomes for species of interest. The New England cottontail (Sylvilagus transitionalis) is an endemic species to the northeastern United States and is listed as a species of special concern, threatened, or endangered in all states in its current range. States within the historical New England cottontail range have made substantial investments in habitat management, captive breeding, and research, but considerable demographic, management, and monitoring uncertainties remain. Connecticut is the geographic core of the current range of the species and therefore has been the focus of many management efforts, including improving habitat, creating new habitat patches, removing eastern cottontails (Sylvilagus floridanus), and releasing captive‐bred New England cottontails. We used a value of information analysis to identify the optimal management decision given current uncertainty and to evaluate how sources of uncertainty might lead to changes in management decisions. Given the current understanding of the New England cottontail in Connecticut, we identified the optimal management decision as improving existing habitat patches without monitoring for the species and managers could expect a 3.4% increase in populations if decision‐making uncertainty could be fully resolved. Multiple sources of uncertainty influenced results, but variation in New England cottontail density and the response of the species to the removal of eastern cottontails were most likely to result in changes to management decisions. At lower New England cottontail densities, releasing captive‐bred individuals competed with improving habitat as the optimal management action. Accounting for the value of information benefits New England cottontail management by guiding research efforts toward information that is most beneficial for decision‐makers and providing insights into parameter thresholds that would lead to changes in management decisions. [ABSTRACT FROM AUTHOR]

Thermal refuges provide critical habitat for cold‐water‐dependent salmonids in marginal riverscapes during extreme heat events globally. Studies of thermal refuge use by salmonids are complicated by short‐term changes in weather conditions during heat waves, intermittent fish use, and the use of different analytical endpoints. We passively surveyed cold‐water‐dependent brown, rainbow, and brook trout (hereafter "trout") thermoregulating in several thermal refuges along the Housatonic River, Connecticut, USA, during a two‐week heatwave using underwater action cameras (UACs). Using these data, we assessed the influence of various short‐term riverscape conditions on the abundance of trout within thermal refuges using a zero‐inflated Poisson, time‐stratified N‐mixture model in a Bayesian framework that accounts for imperfect detection. We detected at least one trout per sampling occasion, and estimated abundances summed across all thermal refuges ranged from 63.99 (95% credible interval [CRI] = 55.0–79.0) to 182.04 (167.0–199.0). We estimated higher trout abundances in larger thermal refuges located in low‐gradient river sections, and refuges that were deeper and cooler than the Housatonic River during the sampling occasion (all β estimates >0.0 and did not overlap zero). We also found evidence that less variable and cooler temperature regimes in the nearby Housatonic River led to higher estimated trout abundances within thermal refuges (all β estimates <0.0 and did not overlap zero). Last, we found that trout detection probabilities within thermal refuges were moderate (range = 0.521–0.634) when using UAC surveys and that the video image brightness negatively influenced detection (αbright = −0.193, 95% CRI = −0.330 to −0.058). To aid in trout population persistence in dynamic, marginal riverscapes as the climate changes, focusing on modifiable refuge attributes (e.g., depth, cold‐water plume area), and strategically targeting refuges in riverscape segments beneficial to trout may be tactics that could enhance conservation strategies globally. [ABSTRACT FROM AUTHOR]

Perceived predation risks by terrestrial predators are major ecological forces in aquatic systems, particularly for aggregating fish. Riverscape thermal refuges are discrete, localized cold‐water patches where fish temporarily aggregate to buffer against heat events. Predation pressures by terrestrial predators at thermal refuges may decrease the thermoregulatory benefits of refuge use, but quantifying such effects can be challenging and controversial when sampling can impose additional stress on fish. We passively monitored terrestrial predator visitation patterns and predation at four thermal refuges in the Housatonic River, Connecticut, USA, between May 18th and September 29th, 2022, with camera traps, a common wildlife monitoring method. Specifically, we (1) assessed diel visitation patterns by different categories of terrestrial predators at thermal refuges and determined if patterns varied among predator categories or with prevailing environmental conditions, and (2) estimated the probability of predation by hour of the day combined across all predator categories, quantifying general predation pressures at refuges. We detected at least one terrestrial predator at a thermal refuge each day, and mean hourly visitation rates (count/h) were highly variable across predator categories and sampling dates. The most supported generalized additive mixed model indicated that terrestrial predator visitation rates (count/h/day) varied with mean daily river discharge and water temperature differential, and relationships differed across categories of terrestrial predators. We observed 22 separate predation attempts on thermoregulating salmonids and predicted that the probability of predation by any terrestrial predator increased from 0.002 to 0.017 throughout a 24 h day (p =.004). Camera traps provided novel evidence that terrestrial predators are pervasive at riverine thermal refuges, which is relevant for refuge conservation and management globally. We recommend the implementation of a coordinated monitoring network across riverine thermal refuges using camera traps, further enriching our ecological understanding of cumulative predator effects in refuges across complex riverscapes. [ABSTRACT FROM AUTHOR]

We evaluated spatiotemporal changes in the mean and variation in largemouth bass (Micropterus salmoides) mercury concentrations over three discrete time periods (1995, 2005–2006, and 2019–2021) across 56 Connecticut waterbodies. We detected largemouth bass raw mercury concentrations that exceeded the US Environmental Protection Agency (USEPA) Fish Tissue Residue Criterion (≥ 0.30 µg g−1 ww) in 75.1%, 63.3%, and 47.7% of all fish sampled during 1995, 2005–2006, and 2019–2021, respectively. Total length (TL)-adjusted largemouth bass mercury concentrations declined across all ecoregions in Connecticut between subsequent sampling periods but increased between 2005–2006 and 2019–2021 in the Northwest Hills/Uplands ecoregion. The coefficient of variation (CV) of largemouth bass TL-adjusted mercury concentrations increased through time, increasing from 25.78% during 1995 to 36.47% during 2019–2021. The probability of a largemouth bass having a raw mercury concentration > 0.30 µg g−1 ww increased with total length (TL), but the TL with a 50% probability varied across ecoregions and periods. The variation in largemouth bass mercury concentrations highlights the roles that changes to individual behaviors, food web structure, lake properties, and legacy mercury may play in shaping broad patterns and trends in mercury consumption risks. [ABSTRACT FROM AUTHOR]

Thermal refuges are thermally distinct riverscape features used by aquatic organisms during unfavourable thermal events, facilitating resilience in marginal environments. However, the thermal refuge concept is nebulous, and the often interchangeable use of the term 'thermal refugia' creates additional ambiguity. We argue that lexical differences resulting from divergent scholarly trainings hinder holistic understanding of thermal refuges; thus, existing studies would benefit from a structured framework for thermal refuge conceptualization. Herein, we articulate an ecohydrological typology for defining and characterizing thermal refuges in streams and rivers by identifying key hydrological and thermal characteristics and variations in ecological function described in the literature. We use concepts that are easily definable, measurable and transferable across disciplines, riverscapes and species to discriminate among thermal refuge types. Future work can use our typology as a basis for more informed interdisciplinary discussion and interpretation of thermal refuges' role in riverscapes through more hypothesis‐driven research and conservation‐focused management. [ABSTRACT FROM AUTHOR]

Local extirpation events are often poorly documented and the causes are not well understood. A case in point is the bridle shiner (Notropis bifrenatus), a cyprinid that is declining and carries various conservation listings over most of its range.Recent research suggested that the apparent decline of the bridle shiner in the state of Connecticut may be in part an artefact of changes in survey methods: seining has been replaced by electrofishing, which is less efficient in bridle shiner habitat. The present study included a re‐evaluation of the distribution of the species in light of this recent finding.Historical sites in Connecticut were seined, and it was found that nine populations once thought to be extirpated were in fact extant. Nonetheless, bridle shiner occurrences have declined by 60% over 50 years. Potential correlates of extirpation, such as landscape and habitat fragmentation metrics, were identified using geospatial tools. Through an information‐theoretic approach, models were constructed to investigate the relative contribution of land use and habitat fragmentation to the extirpation of the bridle shiner.Land use had greater support as a correlate of the decline, and the current bridle shiner distribution in Connecticut could be explained by areas of high forest cover and low impervious cover. It is hypothesized that the adverse impacts of land use on the bridle shiner are attributable to its ecological specialization on submerged vegetation, notwithstanding its otherwise broad physiochemical tolerance.These results provide needed context on the decline of this species and provide potential avenues for conservation actions. This research emphasizes the impacts that land alterations can have on freshwater species and the importance of accurately characterizing extirpation events. [ABSTRACT FROM AUTHOR]

Stream connectivity promotes resilience and population viability of aquatic organisms. Landscape genetic approaches, traditionally applied to terrestrial systems, may reveal important watershed‐level dynamics that influence connectivity. Additional validation would improve understanding of how the models perform when gene flow is constrained to dendritic networks. The objectives of this study were to use simulations to assess the utility of landscape genetics analyses in dendritic stream networks and investigate riverscape variables influencing gene flow among brook trout Salvelinus fontinalis populations in headwater streams.We used an individual‐based simulation program to simulate different dispersal scenarios and used combinations of landscape genetic models, model selection methods, and genetic metrics to determine the best combination for riverscape systems. We also sampled brook trout from 76 headwater streams in two watersheds (c. 1,000 km2) in Connecticut, U.S.A. to assess connectivity and riverscape influences on genetic structuring.Gravity models with Bayesian information criterion (BIC) selection were the most accurate (>85%) landscape genetic models that consistently identified the correct simulated gene flow barrier. However, all models performed poorly when unidirectional barriers were simulated without a distance‐based dispersal limitation. Excluding this scenario, model accuracy for the gravity models using BIC selection was >90% across multiple genetic metrics, validating the application of landscape genetic models to riverscape systems.We found highly variable levels of brook trout genetic connectivity (FST range 0.01–0.19) at the watershed level (5–15 river km). Gravity models identified increases in upstream impervious surfaces and decreases in riparian tree canopy cover as riverscape variables associated with increases in genetic differentiation in one watershed, while the other watershed was consistent with an isolation by distance pattern.In this study we used demogenetic (i.e. combined demographic and genetic) simulations to demonstrate the utility of landscape genetics techniques in dendritic river networks. Our empirical genetic study documented gene flow among headwater populations of brook trout at the watershed level and also suggested connectivity can be limited by watershed development. Incorporating the heterogeneity of riverscapes into connectivity‐focused conservation planning is essential to the development of effective restoration actions, and landscape genetics approaches can be useful tools to identify watershed‐level connectivity in stream systems. [ABSTRACT FROM AUTHOR]

Context: Conservation planning increasingly needs to be effective in areas that are influenced by anthropogenic land uses, yet many planning tools do not give equal consideration to ecological, social, and economic objectives, nor do they enable identification or comparison of tradeoffs among objectives. We explore outcomes and tradeoffs for the proposed expansion of a US wildlife refuge in a region characterized by strong town character and high human population density, development, and property values. Objectives: Our objectives were to: (1) determine whether acquisition targets could be achieved given competing objectives; (2) evaluate tradeoffs between social, economic, and ecological objectives; and (3) evaluate how landscape development influences tradeoffs. Methods: We used genetic algorithms to generate and evaluate outcomes for refuge expansion that could systematically navigate multi-objective tradeoffs. Ecological objectives included maximizing total protected habitat, priority habitats, and connectivity between protected properties. Economic and social objectives included minimizing acquisition cost, loss of areas under high development pressure, and town character conflict. Results: Land acquisition targets could be met, though not without economic and social tradeoffs. Positive outcomes for area protected and connectivity resulted in poor outcomes for the other four objectives. Win–win refuge expansion solutions were available for some objectives, but there were also consistent tradeoff relationships, which were exacerbated in areas with high development pressure. Conclusion: This multi-objective approach allows decision makers to account for tradeoffs and hard choices between social-ecological objectives. Explicit consideration of multiple, competing objectives and their benefits, losses, and costs increases transparency and improves decision making. [ABSTRACT FROM AUTHOR]

Camera trapping is a standard tool in ecological research and wildlife conservation. Study designs, particularly for small-bodied or cryptic wildlife species often attempt to boost low detection probabilities by using non-random camera placement or baited cameras, which may bias data, or incorrectly estimate detection and occupancy. We investigated the ability of non-baited, multi-camera arrays to increase detection probabilities of wildlife. Study design components were evaluated for their influence on wildlife detectability by iteratively parsing an empirical dataset (1) by different sizes of camera arrays deployed (1–10 cameras), and (2) by total season length (1–365 days). Four species from our dataset that represented a range of body sizes and differing degrees of presumed detectability based on life history traits were investigated: white-tailed deer (Odocoileus virginianus), bobcat (Lynx rufus), raccoon (Procyon lotor), and Virginia opossum (Didelphis virginiana). For all species, increasing from a single camera to a multi-camera array significantly improved detection probability across the range of season lengths and number of study sites evaluated. The use of a two camera array increased survey detection an average of 80% (range 40–128%) from the detection probability of a single camera across the four species. Species that were detected infrequently benefited most from a multiple-camera array, where the addition of up to eight cameras produced significant increases in detectability. However, for species detected at high frequencies, single cameras produced a season-long (i.e, the length of time over which cameras are deployed and actively monitored) detectability greater than 0.75. These results highlight the need for researchers to be critical about camera trap study designs based on their intended target species, as detectability for each focal species responded differently to array size and season length. We suggest that researchers a priori identify target species for which inference will be made, and then design camera trapping studies around the most difficult to detect of those species. [ABSTRACT FROM AUTHOR]

Adaptive management (AM) is a systematic process for improving environmental management policies and practices in a way that incorporates uncertainty and learning. In the realm of natural resources, AM is increasingly being used by management agencies in the United States (e.g., U.S. Fish and Wildlife Service and the National Park Service) and non‐governmental organizations (e.g., The Nature Conservancy and World Wildlife Fund). As such, it is important that students in natural resources, conservation, and environmental management majors become familiar with the concepts of AM. This case study uses the real‐world example of the Herring River estuary restoration project (Cape Cod, MA) to demonstrate the theoretical processes involved in adaptively managing an ecosystem governed by ecological uncertainties and a wide range of stakeholders. Through the incorporation of role‐play, students gain experience with the AM framework while actively learning about the role of uncertainty and stakeholder perspectives in decision‐making. The case was tested with a group of students from an introductory course on environmental conservation to gauge student interest and verify proof of concept. Following the case study, students felt that they would be able to define adaptive management and explain the concept to their classmates, despite no prior exposure to AM. [ABSTRACT FROM AUTHOR]

Non-random mortality associated with commercial and recreational fisheries have the potential to cause evolutionary changes in fish populations. Inland recreational fisheries offer unique opportunities for the study of fisheries induced evolution due to the ability to replicate study systems, limited gene flow among populations, and the existence of unexploited reference populations. Experimental research has demonstrated that angling vulnerability is heritable in Largemouth Bass Micropterus salmoides, and is correlated with elevated resting metabolic rates (RMR) and higher fitness. However, whether such differences are present in wild populations is unclear. This study sought to quantify differences in RMR among replicated exploited and unexploited populations of Largemouth Bass. We collected age-0 Largemouth Bass from two Connecticut drinking water reservoirs unexploited by anglers for almost a century, and two exploited lakes, then transported and reared them in the same pond. Field RMR of individuals from each population was quantified using intermittent-flow respirometry. Individuals from unexploited reservoirs had a significantly higher mean RMR (6%) than individuals from exploited populations. These findings are consistent with expectations derived from artificial selection by angling on Largemouth Bass, suggesting that recreational angling may act as an evolutionary force influencing the metabolic rates of fishes in the wild. Reduced RMR as a result of fisheries induced evolution may have ecosystem level effects on energy demand, and be common in exploited recreational populations globally. [ABSTRACT FROM AUTHOR]

This research described coastal habitat characteristics at a landscape scale and followed a geospatial modelling approach to predict the probability of habitat use by the population of Atlantic horseshoe crabs ( Limulus polyphemus) in Long Island Sound (LIS, USA). This approach was developed to aid in decision-making regarding management of horseshoe crab spawning locations., Geospatial data layers were created within which beach slope, wave exposure, surface substrate type, and distance from offshore aggregations of crabs (i.e. hotspots) were summarized for beaches in the western, central, and eastern regions of the Connecticut coast of LIS., Spawning abundances derived from field surveys conducted in May and June of 2009 and 2010 were used with remotely-sensed habitat characteristics to develop a resource selection function from a candidate model set based on polytomous logistic regression., A single best model (Akaike weight = 0.97) for predicting the probability of habitat use by spawning horseshoe crabs was selected using an information-theoretic approach. The parameter estimates predicted a greater probability of habitat use with increasing slope, decreasing wave exposure, and decreasing distance from offshore hotspots., Small 'pocket' beaches surrounded by rocky headlands, marshes, and developed areas are the typical habitat available to support horseshoe crab spawning in LIS. As spawning densities in LIS are relatively small and suitable spawning habitat is fragmented, geospatial methods are especially useful for identifying high-use sites and maximizing the conservation value of management actions., Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Bridle ShinerNotropis bifrenatusis a small, rare minnow species native to northeastern streams and lakes. It is declining over most of its range and currently is listed as a species of concern in Connecticut. Surveys conducted with seine nets in the 1960s found Bridle Shiners at 56 locations statewide. In contrast, surveys conducted in the 1990s using electrofishing detected Bridle Shiners at 8 locations. Different sampling techniques made it difficult to assess what portion of the observed decline might be a sampling artifact, confounding efforts to assess the actual conservation status. We sampled 18 habitat patches in three Connecticut watersheds in 2012 to determine if seining for Bridle Shiners yielded a higher detection probability than backpack electrofishing. A multimethod occupancy estimation modeling approach, using the program PRESENCE, quantified the probability of correctly detecting Bridle Shiners by gear and as detection covaried with habitat features. Backpack electrofishing detection probability was lower and approximately half that of seining. The abundance of Bridle Shiners in the sample patch was the most supported covariate to detection and particularly aided detection for electrofishing. High mean water velocity improved the detection probability of backpack electrofishing and reduced that of seining. It is possible that the 1990s sampling underestimated the number of populations of Bridle Shiners, and a repeat survey of all historic locations using a seine is recommended. Received April 3, 2014; accepted September 15, 2014 [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

- We examined habitat factors related to reach-scale brook trout Salvelinus fontinalis counts of four size classes in two headwater stream networks within two contrasting summers in Connecticut, USA. Two study stream networks (7.7 and 4.4 km) were surveyed in a spatially continuous manner in their entirety, and a set of Bayesian generalised linear mixed models was compared. Trout abundance was best described by a zero-inflated overdispersed Poisson model. The effect of habitat covariates was not always consistent among size classes and years. There were nonlinear relationships between trout counts and stream temperature in both years. Colder reaches harboured higher trout counts in the warmer summer of 2008, but this pattern was not observed in the cooler and very wet summer of 2009. Amount of pool habitat was nearly consistently important across size classes and years, and counts of the largest size class were correlated positively with maximum depth and negatively with stream gradient. Spatial mapping of trout distributions showed that reaches with high trout counts may differ among size classes, particularly between the smallest and largest size classes, suggesting that movement may allow the largest trout to exploit spatially patchy habitats in these small headwaters. [ABSTRACT FROM AUTHOR]

Linear and heterogeneous habitat makes headwater stream networks an ideal ecosystem in which to test the influence of environmental factors on spatial genetic patterns of obligatory aquatic species. We investigated fine-scale population structure and influence of stream habitat on individual-level genetic differentiation in brook trout ( Salvelinus fontinalis) by genotyping eight microsatellite loci in 740 individuals in two headwater channel networks (7.7 and 4.4 km) in Connecticut, USA. A weak but statistically significant isolation-by-distance pattern was common in both sites. In the field, many tagged individuals were recaptured in the same 50-m reaches within a single field season (summer to fall). One study site was characterized with a hierarchical population structure, where seasonal barriers (natural falls of 1.5-2.5 m in height during summer base-flow condition) greatly reduced gene flow and perceptible spatial patterns emerged because of the presence of tributaries, each with a group of genetically distinguishable individuals. Genetic differentiation increased when pairs of individuals were separated by high stream gradient (steep channel slope) or warm stream temperature in this site, although the evidence of their influence was equivocal. In a second site, evidence for genetic clusters was weak at best, but genetic differentiation between individuals was positively correlated with number of tributary confluences. We concluded that the population-level movement of brook trout was limited in the study headwater stream networks, resulting in the fine-scale population structure (genetic clusters and clines) even at distances of a few kilometres, and gene flow was mitigated by 'riverscape' variables, particularly by physical barriers, waterway distance (i.e. isolation-by-distance) and the presence of tributaries. [ABSTRACT FROM AUTHOR]

Brook trout Salvelinus fontinalis populations have declined in much of the native range in eastern North America and populations are typically relegated to small headwater streams in Connecticut, USA. We used sibship reconstruction to infer mating systems, dispersal and effective population size of resident (non-anadromous) brook trout in two headwater stream channel networks in Connecticut. Brook trout were captured via backpack electrofishing using spatially continuous sampling in the two headwaters (channel network lengths of 4.4 and 7.7 km). Eight microsatellite loci were genotyped in a total of 740 individuals (80-140 mm) subsampled in a stratified random design from all 50 m-reaches in which trout were captured. Sibship reconstruction indicated that males and females were both mostly polygamous although single pair matings were also inferred. Breeder sex ratio was inferred to be nearly 1:1. Few large-sized fullsib families (>3 individuals) were inferred and the majority of individuals were inferred to have no fullsibs among those fish genotyped (family size = 1). The median stream channel distance between pairs of individuals belonging to the same large-sized fullsib families (>3 individuals) was 100 m (range: 0-1,850 m) and 250 m (range: 0-2,350 m) in the two study sites, indicating limited dispersal at least for the size class of individuals analyzed. Using a sibship assignment method, the effective population size for the two streams was estimated at 91 (95%CI: 67-123) and 210 (95%CI: 172-259), corresponding to the ratio of effective-to-census population size of 0.06 and 0.12, respectively. Both-sex polygamy, low variation in reproductive success, and a balanced sex ratio may help maintain genetic diversity of brook trout populations with small breeder sizes persisting in headwater channel networks. [ABSTRACT FROM AUTHOR]

Seasonal temperature increases have been shown to correlate with changes in the migration timing of fish. We looked at existing temperature and fish count data for anadromous alewives Alosa pseudoharengus in several southern New England streams. Run initiation, defined as occurring when the first 5% of the total annual run migrated, was associated with 9°C. A weighted-mean migration temperature, considered an overall indicator of total run timing, revealed that 13°C was a consistent predictor of run timing for one historic and three recent alewife streams over several years. Because historical and recent daily water temperatures with concurrent fish counts were unavailable for any one site, we used the occurrence of 9°C and 13&degC stream temperatures to determine the magnitude of any detectable shift in the migration timing of alewives between the 1970s and recent years. Stream temperatures in the spring warmed to 13°C about 12 d earlier in recent years than they did in the 1970s. This implied that alewife runs occurred about 12 d earlier on average. Run initiations occurred about 13 d earlier. Management of the water supply to fish passage facilities may need to be adjusted to accommodate these shifts in migration timing. [ABSTRACT FROM AUTHOR]

The electrofishing distance needed to estimate fish species richness at the stream or river reach scale is an important question in fisheries science. This distance is governed by the shape of the species accumulation curve, which, in turn, is influenced by a combination of factors, including the number of species, their overall abundances, habitat associations, the efficiency of the sampling method, and the occurrence of rare species. In this study we document the influence of rare species on the species accumulation curves from stream and river sites in data sets from five dispersed regions of the USA. Spatial discontinuity (i.e., a noncontinuous distribution within reaches) was observed in four of the five data sets, and the four data sets contained numerically rare species represented by one or two individuals (termed singletons and doubletons, respectively). Numerically rare species were typically proportionately rare (i.e., <1% of the total number of individuals captured), but proportionately rare species were not always numerically rare and were dependent on the total number of fish captured. Species richness asymptotes were reached at shorter electrofishing distances when singletons and doubletons were removed. The number of singletons and doubletons in the samples remained relatively constant with increasing sampling effort (i.e., sampling distance and total abundance). Simulation modeling indicated that individual aggregation within species was not a plausible reason for spatially discontinuous species distributions. When accurately detecting the presence of species is a sampling goal, the presence and prevalence of numerically rare species may need to be considered in determining sampling protocols. [ABSTRACT FROM AUTHOR]

Flathead catfish from the main stems of the Grand River and Cuivre River were implanted with 400-d radio transmitters to determine an annual movement cycle. Substantial variation was observed within and between watersheds. Flathead catfish displayed annual movement that consisted of three main periods punctuated by brief migrations. The first, a period of overwintering was followed by migration from wintering areas in early spring, followed in turn by the prespawn/spawning period, which is characterized by increased activity, including longer movements (up to 187.6 km) during spates. After another short migration period came a third period of postspawn summer/fall restricted movement, which was followed by fall migration back to overwintering areas. Within this framework, individual fish displayed at least three variations of this annual pattern. Some individuals entered Grand River and Cuivre River watersheds during the prespawn/spawning period only, returning to the Missouri River or the Mississippi River during summer/fall, overwintering there, and reentering the tributary the following spring. Other individuals entered tributary watersheds for the prespawn/spawning period and remained there for the summer/fall period, returning to the big rivers to overwinter. In the Grand River, all individuals moved downstream (9-45 km) to the Missouri River and overwintered. Finally, some individuals in Cuivre River remained throughout the year, migrating short distances within the river to spawn, feed, and overwinter. The finding that fish were harvested at locations tens of kilometers from the areas where they spent considerable time suggests a larger scale for management than has previously been proposed. [ABSTRACT FROM AUTHOR]

Flathead catfish were radio-tracked in the Grand River and Cuivre River, Missouri, from late July until they moved to overwintering habitats in late October. Fish moved within a definable area, and although occasional long-distance movements occurred, the fish typically returned to the previously occupied area. Seasonal home range was calculated with the use of kernel density estimation, which can be interpreted as a probabilistic utilization distribution that documents the internal structure of the estimate by delineating portions of the range that was used a specified percentage of the time. A traditional linear range also was reported. Most flathead catfish (89%) had one 50% kernel-estimated core area, whereas 11% of the fish split their time between two core areas. Core areas were typically in the middle of the 90% kernel-estimated home range (58%), although several had core areas in upstream (26%) and downstream (16%) portions of the home range. Home-range size did not differ based on river, sex, or size and was highly variable among individuals. The median 95% kernel estimate was 1,085 m (range, 70- 69,090 m) for all fish. The median 50% kernel-estimated core area was 135 m (10-2,260 m). The median linear range was 3,510 m (150-50,400 m). Fish pairs with core areas in the same and neighboring pools had static joint space use values of up to 49% (area of intersection index), indicating substantial overlap and use of the same area. However, all fish pairs had low dynamic joint space use values (<0.07; coefficient of association), indicating that fish pairs were temporally segregated, rarely occurring in the same location at the same time. [ABSTRACT FROM AUTHOR]

The blue sucker (Cycleptus elongatus) was sampled as individuals arrived, spawned, and departed from a spawning riffle in the Grand River of northcentral Missouri, USA. The Grand River basin was not known to support blue sucker reproduction with few individuals ever recorded. The spawning site is unique in character for the lower river. Individuals began arriving in early April when water temperatures reached 10-12°C. Females with freely-flowing roe were sampled in late April after a large rise in river stage and concurrent lowering of the water temperature 4-5 degrees to 16.5°C. The spawning aggregation had a mean age of 15 y and ranged from 9 to 22 y based on scales that probably underestimated true ages. Males outnumbered females 5.5:1. Mean length was 659 mm for males and 721 mm for females. Females were longer at age than males and no significant age-length relationship was evident. [ABSTRACT FROM AUTHOR]

Fish assemblages were systematically sampled along the transition from channelized to unchannelized reaches in seven streams in northern Missouri, USA. Streams ranged in size from 4th to 8th order and were located in the Central Dissected Till Plains including the Grand, Chariton, Salt, and Fabius watersheds. Maximum species richness was reached 3-5 km downstream from the end of channelization. A limited core group of 10 species was present at most of the sites (channelized and unchannelized locations), and a diverse group of 45 species was present at relatively few sites (rarely channelized locations). The core group consisted largely of tolerant, omnivorous species and contained no top carnivores. The 45-species diverse group included a greater proportion of intolerant, benthic invertivorous, lithophilous, and carnivorous species. The effect of channelization extended well into unchannelized reaches and should be considered by conservation planners. [ABSTRACT FROM AUTHOR]

Presents kernel density estimates of linear home range for flathead catfish Pylodictis olivaris in the U.S. Basis of kernel home range estimates; Definition of linear home range; Key issues in the use of kernel density estimates.