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Ecological communities are structured by combinations of biotic and abiotic factors acting at different spatial scales. However, the relative influence of the different scale‐related variables on assemblage composition is poorly understood, despite being key to the effective and efficient management of fluvial ecosystems. We took advantage of the relatively recent and well‐studied history of salmonid introductions in Patagonia to evaluate if non‐native species show different patterns of association with abiotic factors depending on the spatial scale of the environmental filter. We used a hierarchical approach to characterised environmental variables at the basin and reach scales to assess their influence on the presence, abundance and structure of the salmonid assemblages in breeding streams. We saw no evidence that presence/absence patterns of salmonid distribution were driven by landscape variables, except for those basins with physical environmental barriers to colonisation. However, we did find evidence for relative abundances being influenced by climatic and geomorphological variables (e.g., precipitation and relief). Our results do not support a scenario in which any of the salmonid species modulates the distribution of the other species, suggesting that interference has played only a minor role in determining current fish distribution in fluvial systems of the region. Instead, current patterns of presence and abundance of salmonids are best explained as the product of environmental filters. Our findings contribute to our understanding of the ecology of individual species and provide insight into the mechanisms structuring fish assemblages in Southern Hemisphere's lotic systems. [ABSTRACT FROM AUTHOR]

Aim: Conserving stream biota could require strategies that preserve habitats conveying resistance to ecological impacts of changing land use and climate. Retrospective analyses of species' responses to anthropogenic disturbances can inform such strategies. We developed a hierarchical framework to contrast environmental conditions underlying persistence versus extirpation of an imperilled stream fish, Candy Darter (Etheostoma osburni), over decades of changing land use. The decline of E. osburni may broadly represent the challenge of conserving sensitive freshwater species in intensively used upland environments. Location: New River drainage, Appalachian Mountains, USA. Methods: We surveyed fish and habitat in historically occupied sites to identify population refugia, and used multivariate and spatial analyses to address three questions: (a) what are the environmental correlates of refugia? (b) are the pathways by which land use impacts instream habitat constrained by catchment‐ and/or segment‐scale features? and (c) are E. osburni distributional dynamics spatially structured and explained by fine sediment and warm stream temperatures? Results: We confirmed a recently localized distribution similar to other upland species, marked by at least seven extirpations from streams throughout E. osburni's southern range. Catchment‐scale features primarily constrained land use and finer‐scale habitat, leading to either extirpations or population‐supporting refugia defined by features at multiple scales. Refugium habitats contained cooler temperatures and less fine sediment. Rare mismatches between persistence and habitat suitability were explained by network location, suggesting unmeasured environmental gradients and/or dispersal contributed to distributional dynamics. Main conclusions: We provided insight at multiple spatial scales into how aquatic species' distributions become fragmented and localized. Our results demonstrate that natural landscape heterogeneity imparts spatially variable resistance of sensitive species to intensive land uses. By recognizing the scale‐specific features that buffer populations from extirpation, conservation strategies could be tailored to protect naturally occurring refugium habitats and focus restoration in systems where such habitats are broadly lacking. [ABSTRACT FROM AUTHOR]

An understanding of the factors associated with the distribution of fishes is fundamental to stream ecology, and can be used to assess and prioritize conservation areas. Mountain sucker Catostomus platyrhynchus is generally stable across its range in Western North America, but recent studies have documented declines at finer spatial scales near the periphery of its range, including the Black Hills of South Dakota. Despite its wide-ranging distribution, little information exists on mountain sucker autecology or community dynamics. The objective of this study was to evaluate the hierarchical influence of physical and biological variables on the distribution and abundance of mountain sucker in streams of the Black Hills, South Dakota, USA. We evaluated the support for candidate models that incorporated multiple spatial scales and potential biotic interactions to model mountain sucker presence and abundance using an information theoretic approach. Mountain sucker presence was best explained by a combination of reach-scale habitat and fish assemblage variables, including a negative influence of trout abundance. Mountain sucker abundance increased with periphyton coverage, a food resource. These models increase understanding of mountain sucker ecology, can be used to assess and prioritize areas of conservation interest for this native fish in the Black Hills, and can identify management actions that will provide the most effective conservation strategies for this species. [ABSTRACT FROM AUTHOR]

Myxobolus cerebralis caused severe declines in rainbow trout populations across Colorado following its introduction in the 1980s. One promising approach for the recovery of Colorado’s rainbow trout populations has been the production of rainbow trout that are genetically resistant to the parasite. We introduced one of these resistant crosses, known as the GR×CRR (cross between the German Rainbow [GR] and Colorado River Rainbow [CRR] trout strains), to the upper Colorado River. The abundance, survival, and growth of the stocked GR×CRR population was examined to determine if GR×CRRs had contributed offspring to the age-0 population, and determine whether these offspring displayed increased resistance and survival characteristics compared to their wild CRR counterparts. Apparent survival of the introduced GR×CRR over the entire study period was estimated to be 0.007 (±0.001). Despite low survival of the GR×CRRs, age-0 progeny of the GR×CRR were encountered in years 2008 through 2011. Genetic assignments revealed a shift in the genetic composition of the rainbow trout fry population over time, with CRR fish comprising the entirety of the fry population in 2007, and GR-cross fish comprising nearly 80% of the fry population in 2011. A decrease in average infection severity (myxospores fish−1) was observed concurrent with the shift in the genetic composition of the rainbow trout fry population, decreasing from an average of 47,708 (±8,950) myxospores fish−1 in 2009 to 2,672 (±4,379) myxospores fish−1 in 2011. Results from this experiment suggest that the GR×CRR can survive and reproduce in rivers with a high prevalence of M. cerebralis. In addition, reduced myxospore burdens in age-0 fish indicated that stocking this cross may ultimately lead to an overall reduction in infection prevalence and severity in the salmonid populations of the upper Colorado River. [ABSTRACT FROM AUTHOR]

Intentional release of wild-caught individuals has been widely used to establish new populations of the commercially valuable but threatened reef gastropodTrochus niloticusin oceanic islands. Is this also a viable strategy to enhance depleted populations of this species and other marine invertebrates? We monitored growth and survival of 765 translocated individuals and 486 in their original habitat for 5–9 months. Individuals translocated to a severely overexploited reef (mainland Palawan) grew 2–3 times faster than those at Tubbataha Reefs Natural Park, Phillipines. Despite variations in growth between the three sites, survival probabilities were consistently high, ranging between 0.77 and 0.92. So translocation is feasible, and sites at which a species has previously been found are likely to be suitable for their growth and survival. If site management can control over-fishing, this approach is likely to be a valuable tool for enhancing field populations of a large invertebrates likeTrochusthat have a short lived planktonic larva. [ABSTRACT FROM PUBLISHER]

Translocations are frequently used to increase the abundance and range of endangered fishes. One factor likely to affect the outcome of translocations is fish movement. We introduced embryos from five Westslope Cutthroat TroutOncorhynchus clarkii lewisipopulations (both hatchery and wild) at five different locations within a fishless watershed. We then examined the movement of age-1 and age-2 fish and looked for differences in movement distance among source populations and among introduction sites; we also examined the interactions among age, population, and introduction site. At age 1, most individuals (90.9%) remained within 1,000 m their introduction sites. By age 2, the majority of individuals (58.3%) still remained within 1,000 m of their introduction site, but considerably more individuals had moved downstream, some more than 6,000 m from their introduction site. We observed a significant interaction between age and source population (F4, 1077 = 15.45,P< 0.0001) as well as between age and introduction site (F41, 1077= 11.39,P< 0.0008), so we presented results in the context of these interactions. Within age-groups, we observed differences in movement behavior among source populations and among donor populations of Westslope Cutthroat Trout. We discuss these findings in light of previous research on juvenile salmonid movement. Received April 20, 2012; accepted June 3, 2013 [ABSTRACT FROM PUBLISHER]

Impending changes in climate will interact with other stressors to threaten aquatic ecosystems and their biota. Native Colorado River cutthroat trout ( CRCT; Oncorhynchus clarkii pleuriticus) are now relegated to 309 isolated high-elevation (>1700 m) headwater stream fragments in the Upper Colorado River Basin, owing to past nonnative trout invasions and habitat loss. Predicted changes in climate (i.e., temperature and precipitation) and resulting changes in stochastic physical disturbances (i.e., wildfire, debris flow, and channel drying and freezing) could further threaten the remaining CRCT populations. We developed an empirical model to predict stream temperatures at the fragment scale from downscaled climate projections along with geomorphic and landscape variables. We coupled these spatially explicit predictions of stream temperature with a Bayesian Network ( BN) model that integrates stochastic risks from fragmentation to project persistence of CRCT populations across the upper Colorado River basin to 2040 and 2080. Overall, none of the populations are at risk from acute mortality resulting from high temperatures during the warmest summer period. In contrast, only 37% of populations have a ≥90% chance of persistence for 70 years (similar to the typical benchmark for conservation), primarily owing to fragmentation. Populations in short stream fragments <7 km long, and those at the lowest elevations, are at the highest risk of extirpation. Therefore, interactions of stochastic disturbances with fragmentation are projected to be greater threats than warming for CRCT populations. The reason for this paradox is that past nonnative trout invasions and habitat loss have restricted most CRCT populations to high-elevation stream fragments that are buffered from the potential consequences of warming, but at risk of extirpation from stochastic events. The greatest conservation need is for management to increase fragment lengths to forestall these risks. [ABSTRACT FROM AUTHOR]

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ABSTRACT Fisheries resource conservation is a national priority in the USA because of the high economic and social value of fish to society. Landscape spatial planning to identify focal areas for conservation of fishes is an important step to targeted site-level interventions to protect or restore fish habitats, because it can provide a strategic approach to guide conservation efforts. Computerized spatial planning algorithms that identify networks of sites that meet user-specified targets for species representation indicate locations with favourable conditions for fish protection., Here a commonly used systematic planning software, Marxan, was employed with previously published fish range and human disturbance predictions to define a network of conservation focal areas for rivers in Michigan. This network focused on large-bodied species, small-bodied species, species of greatest conservation need (SGCN), and all species together., Depending on the scenario, the networks identified comprised between 14 and 20% of Michigan stream length in over 1700 focal areas ranging from 6 to 8 km in average length. Mean focal area sizes were much larger for the Upper Peninsula than the Lower Peninsula. Approximately 35% of the focal areas defined flowed through already protected lands, but less than 5% had upstream catchments that were secure within protected areas. There was a 45% overlap in the focal areas selected for the large- and small-bodied fish and SGCN., The rivers defined may serve as appropriate core areas for fish conservation. Resultant maps show locations with a high natural potential to conserve all of Michigan's native fish species, and can serve as a reference point for regionalization of comprehensive state-wide planning efforts for fish conservation. It is recommended that this study is followed up with additional planning steps to define complementary conservation zones for protecting the functionality of ecosystems to support fishes, and to forward methods for incorporating spatial metapopulation dynamics into the planning process., Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of Fisheries is the property of Wiley-Blackwell 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.)

Management strategies that increase biological diversity and promote varied approaches to population protection are more likely to succeed during a future in which global warming drives rapid environmental change and increases uncertainty of future conditions. We describe how the concept of a diverse management portfolio can be applied to native trout conservation by increasing representation (protecting and restoring diversity), resilience (having sufficiently large populations and intact habitats to facilitate recovery from rapid environmental change), and redundancy (saving a sufficient number of populations so that some can be lost without jeopardizing the species). Saving diversity for native trout requires the conservation of genetically pure populations, the protection and restoration of life history diversity, and the protection of populations across the historical range. Protecting larger stronghold populations is important because such populations will have a better chance of surviving future disturbances, including those associated with climate change. The long-term persistence of populations is likely to require management for larger population sizes and larger habitat patches than currently exist for many native trout populations. Redundancy among these elements is important given that many populations are small and occupy reduced habitat in fragmented stream systems and therefore are increasingly vulnerable to extirpation. Application of the concept is further described in case studies of Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri and Rio Grande cutthroat trout O. clarkii virginalis, two subspecies that illustrate many of the challenges that are common to management of western native trout. Received May 16, 2011; accepted January 12, 2012 [ABSTRACT FROM AUTHOR]

Prior to installation of a fishway at a road crossing in 2001, a remnant population of endangered Macquarie perch (Macquaria australasica) was confined to a 6-km section of the Cotter River, Australian Capital Territory. The purpose of the fishway was to provide passage past a barrier and to increase the extent of spawning grounds for M. australasica to an additional 22 km of river. The aim of the current study was to quantify the extent of nursery grounds of M. australasica in the Cotter River catchment by developing and applying a rapid, non-destructive technique for surveying juvenile M. australasica. From October to January in 2006-07 and 2007-08, pools were surveyed by snorkelling in the lower Cotter River to detect juvenile and larval M. australasica. The 9-km study reach consisted of the four pools immediately upstream of Cotter Reservoir, seven pools further upstream but still downstream of the rockramp fishway and 14 pools upstream of the fishway. In 2006-07, juvenile M. australasica were detected at 22 of 25 pools, including 13 of 14 pools upstream of the fishway. In spring/summer 2007-08, low visibility conditions frequently occurred throughout the river preventing survey on several occasions. However, recruitment of M. australasica was again detected upstream of the fishway. The increased extent of the nursery grounds of this M. australasica population has proven to be timely as an enlargement of the Cotter Reservoir, due for completion in 2012, will inundate more than 90% of prefishway nursery grounds in the Cotter River. Our study has demonstrated the benefit of installing a fishway in expanding the nursery grounds and the number of recruits of a remnant population of the endangered M. australasica. We also demonstrate the benefits of employing a visual survey technique to quantify the extent of the riverine nursery grounds of a fish population. Snorkel based surveys for larvae and juveniles quantified the upstream expansion in nursery grounds of the endangered Macquarie perch Macquaria australasica. The successful expansion has arisen from installation of a fishway on the Cotter River, Australian Capital Territory. [ABSTRACT FROM AUTHOR]

Subspecies of inland cutthroat trout Oncorhynchus clarkii occupy a fraction of their historic ranges, and displacement by normative brook trout Salvelinus fontinalis is among the greatest threats to existing populations in small, headwater streams. Electrofishing is often used to suppress brook trout and enhance cutthroat trout populations, but these efforts are labor intensive and costly. To help managers more effectively plan and implement brook trout control programs, we used survival estimates from a field experiment to construct matrix population models for both species and linked the models by making the vital rates of young cutthroat trout a function of brook trout density to represent the effect of invasion. We then explored the response of cutthroat trout populations (growth rate [λ] and probability of persistence for 50 years) to brook trout suppression across various levels of electrofishing frequency, sampling intensity, capture efficiency, and brook trout immigration rate. Cutthroat trout (λ = 1.10) and brook trout (λ = 1.20) both had moderate to high values of λ when biotic interactions were weak or absent, but the cutthroat trout λ declined markedly (λ = 0.61) when biotic interactions with brook trout were strong. Model results supported the hypothesis that rapid displacement of cutthroat trout is facilitated by the brook trout's inherent demographic advantage and biotic effects on young cutthroat trout. Where annual brook trout suppression was not possible, the temporal distribution of suppression events within a systematic control design strongly influenced the response of cutthroat trout. The absolute response and cost effectiveness of suppression efforts were influenced particularly by the brook trout immigration rate and also by removal efficiency. Multiple consecutive years of suppression (≥3 years) benefited cutthroat trout, but to be effective such suppression should not be interrupted for more than two consecutive years once initiated. Eradication would be ideal, but the maintenance control of brook trout and the management of cutthroat trout in sympatry with brook trout will probably remain among the viable management options for the foreseeable future. [ABSTRACT FROM AUTHOR]

The article discusses a study on the estimation of required habitat size that is efficient for fish conservation in streams. It describes a procedure that would estimate viable population size and the area of habitat needed to support an endangered stream fish population. It evaluates the population fates with stochastic demography and random variation using Monte Carlo Simulations. It uses the data for Rio Grande Cutthroat trout or the Oncorhynchus clarkii virginalis. It mentions that there is an occurrence of minimum viable population size at the highest survival rate of young of year and no population-wide year class failures.

Habitat fragmentation edge effects on riverine fish could have implications for stream fish populations and their management. We examined effects of forest fragmentation on banded kokopu and longfin eels in New Zealand. Banded kokopu prefer small shaded streams with bouldery substrates and instream cover, whereas longfin eels are found in a variety of habitats. We hypothesized that the densities of banded kokopu would be higher in forested than grassland streams, and the densities would be lower around forest margins. We sampled pools in streams flowing from native podocarp/broad-leaf forests into grassland using Gee–Minnow traps. Pools were sampled longitudinally on each stream from >50 m into the forest to >50 m downstream from the forest margin in open grassland. Banded kokopu densities were higher in interior habitat ?50 m into forests than in grassland streams. Fish caught in grassland pools were smaller than in forested pools. Longfin eels were caught in all streams, but numbers and sizes were similar in habitats; thus not likely to generate the pattern observed for banded kokopu. We found that terrestrial habitat fragmentation can impact stream fish populations by decreasing their occupancy of habitats in the vicinity of the boundary between different terrestrial habitats. [ABSTRACT FROM AUTHOR]

We describe the historical and current distributions and genetic status of westslope cutthroat trout Oncorhynchus clarkii lewisii (WCT) throughout its range in the western United Stares using data and expert opinion provided by fish managers. Westslope cutthroat trout historically occupied 90,800 km and currently occupy 54,600 km; however, these are probably underestimates due to the large-scale (1:100,000) mapping we used. Genetic analyses found no evidence of genetic introgression in 768 samples (58% of samples tested), but the numbers of individuals tested per sample were variable and sample sites were not randomly selected. Approximately 42% of the stream length occupied by WCT is protected by stringent land use restrictions in national parks (2%), wilderness areas (19%), and roadless areas (21%). A total of 563 WCT populations (39,355 km) are being managed as "conservation populations," and while most (457, or 81%) conservation populations were relatively small, isolated populations, large and interconnected metapopulations occupied much more stream length (34,820 km, or 88%). While conservation populations were distributed throughout the historical range (occupying 67 of 70 historically occupied basins), they were much denser at the core than at the fringes. From the information provided we determined that conserving isolated populations (for their genetic integrity and isolation from nonnative competitors and disease) and metapopulations (for their diverse life histories and resistance to demographic extinction) is reasonable. We conclude that while the distribution of WCT has declined dramatically from historical levels, as a subspecies WCT are not currently at imminent risk of extinction because (1) they are still widely distributed, especially in areas protected by stringent land use restrictions; (2) many populations are isolated by physical barriers from invasion by nonnative fish and disease; and (3) the active conservation of many populations is occurring. [ABSTRACT FROM AUTHOR]

We investigated relationships between the absence of salmonids and low summer water temperatures across a 150-km² Rocky Mountain watershed. A model predicting maximum July water temperature (MJT) from measurements of perennial stream length, wetted width, and midrange basin elevation was developed from temperature data obtained at 20 sites across the watershed. The model was used to predict MJT in 75 reaches across the watershed where salmonids were sampled. The lowest predicted MJT in reaches where age-0 and juvenile-adult brook trout Salvelinus fontinalis were observed was 9°C. The lowest predicted MJT in reaches where age-0 progeny of the genus Oncorhynchus spp. (i.e., rainbow trout O. mykiss or cutthroat trout O. clarkii) were observed was 13°C and where Oncorhynchus spp. adults where observed was 12°C. The probability of occurrence of both age-0 and adult brook trout and Oncorhynchus spp. increased as MJT increased above these thresholds. Our results indicate that low MJT in some portions of a mountain watershed can be related to the absence of salmonids. Consequently, data on MJT may provide managers with a means of assessing where summer water temperatures are not suitable for establishment of naturalized salmonid populations. [ABSTRACT FROM AUTHOR]

Fishes listed under the U.S. Endangered Species Act receive intensive management, but evaluations of population characteristics are rare. We report population and habitat characteristics of federally threatened greenback cutthroat trout Oncorhynchus clarki stomias in 12 streams in north-central Colorado surveyed in 1998 and 1999. Our objectives were to assess population size, structure, and distribution, to evaluate a model developed by Harig and Fausch (2002) to assess translocation success, and to compare population characteristics to those reported in the recovery plan. Allopatric population sizes in l0 streams varied from 170 to 7,347 greenback cutthroat trout at least 75 mm long, whereas the 2 streams with brook trout throughout supported 0-142 greenback cutthroat trout. Populations displayed few upstream-downstream trends in fish abundance or mean length, and the coefficient of variation among sampled reaches within streams averaged 61%. As the density of fish at least 75 mm long increased, the percentage of juvenile (<75 mm) fish in a population increased, the percentage of adult (> 125 mm) fish longer than 200 mm decreased, and the average weight of a 200-mm fish declined. The abundance of juvenile fish was positively correlated with summer water temperature. Population estimates were highly correlated with the translocation model index values, suggesting that the translocation model may apply to other cutthroat trout taxa in similar environments. Of the 12 streams for which our extensive field data are available, 4 satisfied the recovery criteria we studied and other criteria in the recovery plan; 8 did not. We conclude that many populations of greenback cutthroat trout, including some that meet recovery criteria, are still at risk of extinction and that a reliable monitoring protocol needs to be established. [ABSTRACT FROM AUTHOR]

1. Endangered native populations of stream salmonids in Japan face three major threats: (i) negative interactions with introduced hatchery-reared fish, (ii) fragmentation of habitat by impassable dams and (iii) recreational angling. 2. To prevent imminent extinction of many local populations, we evaluated these threats and possible conservation actions for red-spotted masu salmon ( Oncorhynchus masou ishikawae) and white-spotted charr ( Salvelinus leucomaenis japonicus) in the Fuji River system in central Japan. 3. Red-spotted masu salmon and white-spotted charr occupied only 0.73 and 2.4% of suitable thermal habitats, respectively, with masu salmon typically occupying habitats closer to human population centres. 4. Population viability analysis resulted in a 100-year probability of extinction of 78.1% for masu salmon and 48.1% for charr. However, extinction risk of both species was predicted to be <5% if the carrying capacity increased from 141 to 303 for masu salmon and from 94 to 125 for charr, by allowing fish passage at the lower end of the habitat, and if annual adult survival rate increased by 0.04. Adult survival rate was the principal factor associated with population persistence. 5. To conserve isolated populations of stream-dwelling salmonids, we recommend (i) assessing the distribution of remnant native and non-native fish populations, (ii) that fishing regulations are modified to improve adult survival and population persistence and (iii) that fragmented reaches be reconnected to adjacent habitat, for example by removing or modifying artificial barriers to increase the carrying capacity of the isolated populations. Reconnection of fragmented reaches should, however, be avoided if it results in non-native fish invading isolated populations. [ABSTRACT FROM AUTHOR]