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At least 307 records · Page 17Linked to original sources

USGS2018

Remaining populations of an upland stream fish persist in refugia defined by habitat features at multiple scales

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.

Virginia, West Virginia↗

USGS2022

Assessment of a habitat equivalency analysis for freshwater mussels in the upper Mississippi River

The upper Mississippi River (UMR) contains diverse, dense, and reproducing assemblages of native freshwater mussels. In the case of an injury to mussels and their habitats, such as a hazardous material spill, train derailment, or barge grounding, resource managers have few restoration strategies. Resource managers need a means to document, quantify, and mitigate adverse effects on mussels resulting from injury. Habitat equivalency analysis (HEA), developed for use with a wide variety of habitat types, is a restoration scaling technique that compares ecological services lost from injury to ecological services gained through restoration actions. The U.S. Fish and Wildlife Service and Iowa Department of Natural Resources modified the HEA for use with native mussels. The mussel HEA has been applied within the UMR to estimate the quantity of restoration needed to compensate the public for injuries to mussels due to contaminant spills and construction projects. Our objective was to describe the UMR HEA for a general audience and assess if the four biological input variables used in the mussel HEA were reasonable based on literature values. We also evaluated the performance of HEA under a range of input scenarios. Although the input estimates used in HEA were within ranges reported in the peer-reviewed literature or were supported by professional judgment in the absence of peer-reviewed literature, outcomes of the mussel HEA were highly variable and would benefit from additional research to reduce uncertainty in the biological inputs. The application of HEA to mussels provides resource managers with a tool to quantify mussel-related ecological services lost from injury and to guide restoration efforts in the UMR.

Freshwater Mollusk Biology and Conservation↗

USGS2016

Comparative use of side and main channels by small-bodied fish in a large, unimpounded river

Ecological theory and field studies suggest that lateral floodplain connectivity and habitat heterogeneity provided by side channels impart favourable habitat conditions for lotic fishes, especially fluvial fishes dependent on large patches of shallow, slow velocity habitats for some portion of their life cycle. However, anthropogenic modification of large, temperate floodplain rivers has led to extensive channel simplification and side-channel loss. Highly modified rivers consist of simplified channels in contracted, less dynamic floodplains. Most research examining the seasonal importance of side channels for fish assemblages in large rivers has been carried out in heavily modified rivers, where side-channel extents are substantially reduced from pre-settlement times, and has often overlooked small-bodied fishes. Inferences about the ecological importance of side channels for small-bodied fishes in large rivers can be ascertained only from investigations of large rivers with largely intact floodplains. The Yellowstone River, our study area, is a rare example of one such river. We targeted small-bodied fishes and compared their habitat use in side and main channels in two geomorphically distinct types of river bends during early and late snowmelt runoff, and autumn base flow. Species compositions of side and main channels differed throughout hydroperiods concurrent with the seasonal redistribution of the availability of shallow, slow current-velocity habitats. More species of fish used side channels than main channels during runoff. Additionally, catch rates of small fishes were generally greater in side channels than in main channels and quantitative assemblage compositions differed between channel types during runoff, but not during base flow. Presence of and access to diverse habitats facilitated the development and persistence of diverse fish assemblages in our study area. Physical dissimilarities between side and main channels may have differentially structured the side- and main-channel fish assemblages during runoff. Patches of shallow, slow current-velocity (SSCV) habitats in side channels were larger and had slightly slower water velocities than SSCV habitat patches in main channels during runoff, but not during base flow. Our findings establish a baseline importance of side channels to riverine fishes in a large, temperate river without heavy anthropogenic modification. Establishing this baseline contributes to basic fluvial ecology and provides empirical justification for restoration efforts that reconnect large rivers with their floodplains.

Montana↗

USGS2012

Ecological impacts of non-native species

Non-native species are considered one of the greatest threats to freshwater biodiversity worldwide (Drake et al. 1989; Allen and Flecker 1993; Dudgeon et al. 2005). Some of the first hypotheses proposed to explain global patterns of amphibian declines included the effects of non-native species (Barinaga 1990; Blaustein and Wake 1990; Wake and Morowitz 1991). Evidence for the impact of non-native species on amphibians stems (1) from correlative research that relates the distribution or abundance of a species to that of a putative non-native species, and (2) from experimental tests of the effects of a non-native species on survival, growth, development or behaviour of a target species (Kats and Ferrer 2003). Over the past two decades, research on the effects of non-native species on amphibians has mostly focused on introduced aquatic predators, particularly fish. Recent research has shifted to more complex ecological relationships such as influences of sub-lethal stressors (e.g. contaminants) on the effects of non-native species (Linder et al. 2003; Sih et al. 2004), non-native species as vectors of disease (Daszak et al. 2004; Garner et al. 2006), hybridization between non-natives and native congeners (Riley et al. 2003; Storfer et al. 2004), and the alteration of food-webs by non-native species (Nystrom et al. 2001). Other research has examined the interaction of non-native species in terms of facilitation (i.e. one non-native enabling another to become established or spread) or the synergistic effects of multiple non-native species on native amphibians, the so-called invasional meltdown hypothesis (Simerloff and Von Holle 1999). Although there is evidence that some non-native species may interact (Ricciardi 2001), there has yet to be convincing evidence that such interactions have led to an accelerated increase in the number of non-native species and cumulative impacts are still uncertain (Simberloff 2006). Applied research on the control, eradication, and management of non-native species has only just begun but some promising results have already emerged (see below), giving hope to a very difficult conservation issue. This chapter provides an overview of the role of non-native species in amphibian declines and summarizes the current state of knowledge of non-native species that are known, or considered to be, a threat to amphibian species and populations. The biological and socio-economic issues of non-native species control are examined and brief case studies of successful eradication programmes are provided.

Book chapter↗

USGS1980

Laboratory procedure for estimating residue dynamics of xenobiotic contaminants in a freshwater food chain

A laboratory method of measuring the accumulation, transfer, elimination, and degradation of xenobiotic contaminants is described for organisms in a freshwater food chain (microorganisms, filter-feeder, and fish). A flow-through diluter-system, 14 C-labeled contaminants, gas and thin-layer chromatography, autoradiography, and liquid scintillation spectrometry are used in making residue determinations. Accumulation factors and various index values are developed for measuring and estimating potential accumulation of xenobiotic contaminants by aquatic organisms. The laboratory procedure is economical, simple, reproducible, and ecologically relevant.

Technical Paper↗

USGS1998

Summary of findings about circulation and the estuarine turbidity maximum in Suisun Bay, California

Suisun Bay, California, is the most landward subembayment of San Francisco Bay (fig. 1) and is an important ecological habitat (Cloern and others, 1983; Jassby and others, 1995). During the 1960s and 1970s, data collected in Suisun Bay were analyzed to develop a conceptual model of how water, salt, and sediment move within and through the Bay. This conceptual model has been used to manage freshwater flows from the Sacramento-San Joaquin Delta to Suisun Bay to improve habitat for several threatened and endangered fish species. Instrumentation used to measure water velocity, salinity, and suspended-solids concentration (SSC) greatly improved during the 1980s and 1990s. The U.S. Geological Survey (USGS) has utilized these new instruments to collect one of the largest, high-quality hydrodynamic and sediment data sets available for any estuary. Analysis of these new data has led to the revision of the conceptual model of circulation and sediment transport in Suisun Bay.

Fact Sheet↗

USGS2020

Cryptic lives of conspicuous animals: Otolith chemistry chronicles life histories of coastal lagoon fishes

Bar-built coastal lagoons are dynamic ecosystems at the land-sea interface that are important habitats for a variety of species. This study examined the habitat ecology of two lagoon species, the endangered Tidewater Goby ( Eucyclogobius newberryi ) and the Prickly Sculpin ( Cottus asper ) by reconstructing individual life histories from patterns in the concentration of the element Sr (as ratioed to Ca; Sr:Ca) in otoliths. Specific objectives were to (1) elucidate any movements of individual fishes among three primary habitat components of typical bar-built lagoon systems: coastal ocean, brackish lagoon, and freshwater watershed streams, and (2) determine if either species exhibited a consistent life history as defined by a stereotypical otolith Sr:Ca chronology, which could be indicative of a consistent range of salinity or temperature occupied through ontogeny. Results suggested that Tidewater Goby was a lagoon resident and that Prickly Sculpin exhibited migrations between lagoon and watershed stream habitats. There was no strong evidence in either species of ocean occupancy or of a stereotypical Sr:Ca chronology, the latter suggesting the full range of available lagoon habitat in terms of salinity and temperature was likely utilized at all life stages. These findings add to the body of evidence that bar-built lagoons are not isolated habitats, and holistic management of these habitats with adjoining watershed and marine environments could increase habitat connectivity across the landscape, with potential benefits to fishes.

California↗

USGS2022

Microhabitat use of larval fish in a South Carolina Piedmont stream

Understanding habitat use and nursery areas of larval fish is a key component to managing and conserving riverine fishes. Yet, freshwater researchers often focus only on adult fishes, resulting in a limited understanding of the habitat requirements for the early life stages of freshwater fishes. The goal of this study was to quantify the larval fish microhabitat use of three fish families in Twelvemile Creek, a fifth-order tributary of Lake Hartwell (Savannah River basin) in the Piedmont ecoregion of South Carolina, USA. We used handheld dipnets to sample larval fishes along 20 equidistant transects spaced 10 m apart weekly from May to July 2021 along a 200 m stream reach. We also collected microhabitat data at each larval fish capture location. Most captured individuals were in the metalarval stage and were identified to the family level. A partial distance-based redundancy analysis indicated that water velocity contributed to changes in larval fish assemblage structure. Larval fishes occupied a subset of the available habitat that was characterized by low water velocity, non- Podostemum substrate, and shallow habitats close to the shore or bed rock structure. We also detected temporal patterns in larval fish counts, with peak Percidae and Leuciscidae counts in late July and the highest Catostomidae counts in late May–early June. Our results suggest that larval fishes select habitats with low water velocity and shallow habitats close to shore microhabitat characteristics, and that riffle-pool sequences may serve as a nursery habitat for Percidae, Catostomidae and Leuciscidae metalarvae.

South Carolina↗

USGS2023

Appendix D: Synthesis element 1 (revised): Water temperature effects on fisheries and stream health in nontidal waters

A limited review of relevant scientific literature related to temperature sensitivities of fish species, stream health indicators, and any related geospatial information was conducted. Based on this review, we provide a syntheses of information related to nontidal waters in the Chesapeake Bay Rising stream temperatures will have a range of impacts on nontidal aquatic ecosystems. Cold headwaters and associated species like brook trout and sculpin are especially vulnerable to higher stream temperatures. Efforts could be taken to identify and protect high quality resilient cold headwater brook trout (Salvelinus fontinalis) habitat. More information on groundwater impacts on stream temperatures and ecologically relevant temperature thresholds for species of concern could help resource managers identify temperature resilient habitats and populations. A vulnerability assessment could be valuable to better understand the drivers and stressors of rising stream temperatures, their effects on aquatic resources, and the risk to fish and other aquatic species. Further research could help in developing and fully vetting a complete list of cold/cool water benthic macroinvertebrate taxa and freshwater mussel taxa that are vulnerable to temperature change in the Chesapeake watershed.

Report↗

USGS1999

Freshwater discharge to Florida Bay

The South Florida Ecosystem Program is a collaborative effort by Federal agencies, working with State and local agencies, to help resolve land-use demands and water-supply issues in south Florida. The role of the U.S. Geological Survey in the program is to provide scientific insight into south Florida's hydrology and geology, which are an integral part of the fragile ecosystems of the Everglades, Florida Bay, and the Florida Keys. Historical changes in water-management practices to accommodate a large and rapidly growing urban population along the Atlantic coast, as well as intensive agricultural activities, have resulted in a highly managed hydrologic system with canals, levees, and pumping stations. These structures have altered the hydrology of the Everglades ecosystem, including Florida Bay. Currently, there are plans to change the quantity of water delivered to Everglades National Park and Florida Bay to restore the natural flow of the system. Florida Bay, home to several endangered species, is a valuable breeding ground for marine life and an important recreational and sport fishing area. Florida Bay encompasses about 850 square miles in total area with an average depth of less than 3.5 feet. It is bordered by the mainland portion of Everglades National Park to the north, the Florida Keys to the east and south, and is open to the Gulf of Mexico to the west. During the last decade, Florida Bay has experienced algal blooms and seagrass die-offs which are signals of ecological deterioration that has been attributed to an increase in salinity and nutrient content of bay waters. Salinity and nutrient content are directly related to the amount and quality of freshwater that enters the bay and to flow patterns within the bay. Restoration of the Florida Bay ecosystem requires a better understanding of the linkage between the amount of water and nutrients flowing into the bay and the salinity and quality of the bay environment.

Florida↗

USGS2023

A global ecological signal of extinction risk in marine ray-finned fishes (class Actinopterygii)

Many marine fish species are experiencing population declines, but their extinction risk profiles are largely understudied in comparison to their terrestrial vertebrate counterparts. Selective extinction of marine fish species may result in rapid alteration of the structure and function of ocean ecosystems. In this study, we compiled an ecological trait dataset for 8,185 species of marine ray-finned fishes (class Actinopterygii) from FishBase and used phylogenetic generalized linear models to examine which ecological traits are associated with increased extinction risk, based on the International Union for the Conservation of Nature Red List. We also assessed which threat types may be driving these species toward greater extinction risk and whether threatened species face a greater average number of threat types than non-threatened species. We found that larger body size and/or fishes with life histories involving movement between marine, brackish, and freshwater environments are associated with elevated extinction risk. Commercial harvesting threatens the greatest number of species, followed by pollution, development, and then climate change. We also found that threatened species, on average, face a significantly greater number of threat types than non-threatened species. These results can be used by resource managers to help address the heightened extinction risk patterns we found.

Cambridge Prisms: Extinction↗

USGS2002

Modeling fish community dynamics in Florida Everglades: Role of temperature variation

Temperature variation is an important factor in Everglade wetlands ecology. A temperature fluctuation from 17°C to 32°C recorded in the Everglades may have significant impact on fish dynamics. The short life cycles of some of Everglade fishes has rendered this temperature variation to have even more impacts on the ecosystem. Fish population dynamic models, which do not explicitly consider seasonal oscillations in temperature, may fail to describe the details of such a population. Hence, a model for fish in freshwater marshes of the Florida Everglades that explicitly incorporates seasonal temperature variations is developed. The model's main objective is to assess the temporal pattern of fish population and densities through time subject to temperature variations. Fish population is divided into 2 functional groups (FGs) consisting of small fishes; each group is subdivided into 5-day age classes during their life cycles. Many governing sub-modules are set directly or indirectly to be temperature dependent. Growth, fecundity, prey availability, consumption rates and mortality are examples. Several mortality sub-modules are introduced in the model, of which starvation mortality is set to be proportional to the ratio of prey needed to prey available at that particular time step. As part of the calibration process, the model is run for 50 years to ensure that fish densities do not go to extinction, while the simulation period is about 8 years. The model shows that the temperature dependent starvation mortality is an important factor that influences fish population densities. It also shows high fish population densities at some temperature ranges when this consumption need is minimum. Several sensitivity analyses involving variations in temperature terms, food resources and water levels are conducted to ascertain the relative importance of temperature dependence terms.

Water Science and Technology↗

USGS2021

Synthesis of data and studies relating to Delta Smelt biology in the San Francisco Estuary, emphasizing water year 2017

In the San Francisco Estuary (SFE), the effects of freshwater flow on the aquatic ecosystem have been studied extensively over the years and remains a contentious management issue. It is especially contentious with regards to the Delta Smelt (Hypomesus transpacificus), a species endemic to the SFE that has been listed as threatened under the Federal Endangered Species Act and endangered by the State of California. Early studies of Delta Smelt distribution within the SFE suggested that Delta Smelt habitat is determined largely by freshwater flow; however, the exact mechanisms and processes producing such benefits remained unclear. In the summer of 2017, the Flow Alteration Management, Analysis, and Synthesis Team (FLOAT-MAST) was established to analyze, synthesize, and summarize the data collected from the various flow-related monitoring and special studies occurring in 2017(see Table Intro 4). This report will focus on the 2017 summer-fall status of Delta Smelt and its habitat following a record wet year. There has been a long-term decline in the abundance of Delta Smelt associated with a decline in other pelagic fishes. Investigators concluded that the decline has likely been caused by the interactive effects of several causes, including changes in both physical and biotic habitats, many of which are tied to amount and timing of freshwater flow. For this report, we formulated a number of basic predictions about the likely effects of high flows in 2017 on Delta Smelt and their habitat (Table 3). We use a qualitative weight of evidence approach to evaluate whether these predictions were supported by available data. Data sources included a variety of long-term monitoring surveys conducted by Interagency Ecological Program (IEP) agencies, as well as model outputs. Delta Smelt population, health, and life history metrics rarely responded as predicted. Water temperature appears to have a stronger effect on Delta Smelt growth rate and some metrics of life history diversity than outflow or X2 position. Other life history diversity attributes varied but did not appear to be driven by outflow or temperature. Health status was difficult to interpret. Low prevalence of lesions and improved nutritional condition during the drought was contradicted by declining overall population levels. Because of the sparse catches of Delta Smelt in the post-POD years, we consider the data insufficient to reach firm conclusions about the predictions concerning range and distribution of Delta Smelt, especially in the fall. The prediction of high survival was not supported. The 2017 Delta Smelt year class began with poor recruitment in spring of 2017 and below average survival for spring to summer and summer to fall. Thus, low production and low survival led to low abundance of all life stages. During the fall to winter period survival improved, yet the resulting adults were low in number. Foraging success of the fish captured, as measured by stomach fullness, was high for juveniles and adults in 2017 relative to recent years associated with the higher densities of common zooplankton prey that occurred in 2017.

California↗

USGS2018

Chasing a changing climate: Reproductive and dispersal traits predict how sessile species respond to global warming

Aim Studies of species' range shifts have become increasingly relevant for understanding ecology and biogeography in the face of accelerated global change. The combination of limited mobility and imperilled status places some species at a potentially greater risk of range loss, extirpation or extinction due to climate change. To assess the ability of organisms with limited movement and dispersal capabilities to track shifts associated with climate change, we evaluated reproductive and dispersal traits of freshwater mussels (Unionida), sessile invertebrates that require species‐specific fish for larval dispersal. Location North American Atlantic Slope rivers. Methods To understand how unionid mussels may cope with and adapt to current and future warming trends, we identified mechanisms that facilitated their colonization of the northern Atlantic Slope river basins in North America after the Last Glacial Maximum. We compiled species occurrence and life history trait information for each of 55 species, and then selected life history traits for which ample data were available (larval brooding duration, host fish specificity, host infection strategy, and body size) and analysed whether the trait state for each was related to mussel distribution in Atlantic Slope rivers. Results Brooding duration ( p < .01) and host fish specificity ( p = .02) were significantly related to mussel species distribution. Long‐term brooders were more likely than short‐term brooders to colonize formerly glaciated rivers, as were host generalists compared to specialists. Body size and host infection strategy were not predictive of movement into formerly glaciated rivers ( p > .10). Main conclusions Our results are potentially applicable to many species for which life history traits have not been well‐documented, because reproductive and dispersal traits in unionid mussels typically follow phylogenetic relationships. These findings may help resource managers prioritize species according to climate change vulnerability and predict which species might become further imperilled with climate warming. Finally, we suggest that similar trait‐based decision support frameworks may be applicable for other movement limited taxa.

Diversity and Distributions↗

USGS2009

Evaluation of a gastric radio tag insertion technique for anadromous river herring

Anadromous river herring (alewives Alosa pseudoharengus and blueback herring A. aestivalis ), which constitute a historically and ecologically important component of coastal rivers, have declined precipitously throughout the Atlantic seaboard. Suggested causes of river herring decline include commercial fishing and predation by striped bass Morone saxatilis . Although the causes of this recent trend are poorly understood, river herring are especially vulnerable to adverse impacts during their spring spawning migration. Radiotelemetry is an especially useful method for addressing potential problems encountered during the movement of these fish from the ocean to freshwater. In spite of frequent calls for evaluation of telemetry methods, controlled tests of posttagging effects are rare for alosids and virtually nonexistent for anadromous river herring. We developed a protocol for gastric tagging of anadromous river herring, and we used hatchery and field studies to evaluate behavior, tag placement, stress response, and posttagging mortality. We also compared tagger effects and quantified posttagging upstream movements of fish in the field. In controlled hatchery trials, no fish died at 10 min, 1 h, or 14 d posttagging. No tags were rejected, and only 1 of 35 tags ruptured the gut. In field cages, mortality, plasma cortisol, glucose, and chloride measured at 24 h were similar between tagged and untagged fish. In the field, 12 of 14 fish moved upriver after tagging and spent 114 h on average at upriver sites. Using a variety of approaches, we found no evidence that our tagging protocol adversely affected river herring in comparison with untagged fish that were subjected only to handling and holding. Our protocol, evaluated by comparing responses of tagged and untagged fish under controlled conditions, may be useful in future studies that seek to understand causes of decline for anadromous river herring.

Massachuetts↗

USGS2019

Social equity shapes zone-selection: Balancing aquatic biodiversity conservation and ecosystem services delivery in the transboundary Danube River Basin

Freshwater biodiversity is declining, despite national and international efforts to manage and protect freshwater ecosystems. Ecosystem-based management (EBM) has been proposed as an approach that could more efficiently and adaptively balance ecological and societal needs. However, this raises the question of how social and ecological objectives can be included in an integrated management plan. Here, we present a generic model-coupling framework tailored to address this question for freshwater ecosystems, using three components: biodiversity, ecosystem services (ESS), and a spatial prioritisation that aims to balance the spatial representation of biodiversity and ESS supply and demand. We illustrate this model-coupling approach within the Danube River Basin using the spatially explicit, potential distribution of (i) 85 fish species as a surrogate for biodiversity as modelled using hierarchical Bayesian models, and (ii) four estimated ESS layers produced by the Artificial Intelligence for Ecosystem Services (ARIES) platform (with ESS supply defined as carbon storage and flood regulation, and demand specified as recreation and water use). These are then used for (iii) a joint spatial prioritisation of biodiversity and ESS employing Marxan with Zones, laying out the spatial representation of multiple management zones. Given the transboundary setting of the Danube River Basin, we also run comparative analyses including the country-level purchasing power parity (PPP)-adjusted gross domestic product (GDP) and each country's percent cover of the total basin area as potential cost factors, illustrating a scheme for balancing the share of establishing specific zones among countries. We demonstrate how emphasizing various biodiversity or ESS targets in an EBM model-coupling framework can be used to cost-effectively test various spatially explicit management options across a multi-national case study. We further discuss possible limitations, future developments, and requirements for effectively managing a balance between biodiversity and ESS supply and demand in freshwater ecosystems.

Science of the Total Environment↗

USGS2024

Climate vulnerability assessment of Oregon hatchery programs

The goal of this project was to assess the vulnerability to climate change impacts for a sample set of hatchery programs representing different geographic areas and primary anadromous species raised in state-managed Oregon hatcheries (Summary Figure 1). Freshwater and marine ecosystem processes can significantly influence salmon and steelhead survival, and understanding how these factors have affected historical returns can help managers evaluate the climate vulnerability of hatchery stocks. We examined stock-specific trends in smolt-to-adult returns (SARs), which represent the proportion of smolts released from the hatchery that are recovered in fisheries or as returning adult spawners. SARs are among the most consistent long term estimators of survival for hatchery-origin stocks. Depending on the stock, adult recoveries could occur in marine fisheries, freshwater fisheries, returns to the hatchery or another collection facility, and spawning ground surveys. We collected time series data on relevant ecological indicators and used generalized additive models (GAMs) to explore both univariate and multivariate relationships with SARs for each hatchery stock. An additional aspect of this assessment was to evaluate the climate vulnerability of resident trout stocking programs in the Department's East and West regions, incorporating insights from Oregon Department of Fish and Wildlife (ODFW) staff interviews and published data on the thermal tolerance of hatchery trout stocks. This assessment is provided in the ‘Climate vulnerability of trout stocking programs’ subsection below.

Oregon↗

USGS2010

Understanding behavioral responses of fish to pheromones in natural freshwater environments

There is an abundance of experimental studies and reviews that describe odorant-mediated behaviors of fish in laboratory microcosms, but research in natural field conditions has received considerably less attention. Fish pheromone studies in laboratory settings can be highly productive and allow for controlled experimental designs; however, laboratory tanks and flumes often cannot replicate all the physical, physiological and social contexts associated with natural environments. Field experiments can be a critical step in affirming and enhancing understanding of laboratory discoveries and often implicate the ecological significance of pheromones employed by fishes. When findings from laboratory experiments have been further tested in field environments, often different and sometimes contradictory conclusions are found. Examples include studies of sea lamprey (Petromyzon marinus) mating pheromones and fish alarm substances. Here, we review field research conducted on fish pheromones and alarm substances, highlighting the following topics: (1) contradictory results obtained in laboratory and field experiments, (2) how environmental context and physiological status influences behavior, (3) challenges and constraints of aquatic field research and (4) innovative techniques and experimental designs that advance understanding of fish chemical ecology through field research.

Journal of Comparative Physiology A↗