Effects of biodiversity on ecosystem processes: Implications for ecosystem management
No abstract available.
ESA Positions↗
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Accurate mass analysis of ethanesulfonic acid degradates of acetochlor and alachlor using high-performance liquid chromatography and time-of-flight mass spectrometry
Degradates of acetochlor and alachlor (ethanesulfonic acids, ESAs) were analyzed in both standards and in a groundwater sample using high-performance liquid chromatography–time-of-flight mass spectrometry with electrospray ionization. The negative pseudomolecular ion of the secondary amide of acetochlor ESA and alachlor ESA gave average masses of 256.0750±0.0049 amu and 270.0786±0.0064 amu respectively. Acetochlor and alachlor ESA gave similar masses of 314.1098±0.0061 amu and 314.1153±0.0048 amu; however, they could not be distinguished by accurate mass because they have the same empirical formula. On the other hand, they may be distinguished using positive-ion electrospray because of different fragmentation spectra, which did not occur using negative-ion electrospray.
Journal of Chromatography A↗
Applying mark-resight, count, and telemetry data to estimate effective sampling area and fish density with stationary underwater cameras
Accurate estimates of abundance and density for geographically open populations must account for the effective sampling area (ESA) of sampling gears. We describe a Marked N-Mixture model to estimate ESA and density (number of individuals/unit area) from repeated counts of unmarked and marked individuals, integrating mark-resight, camera counts, and telemetry data of red snapper ( Lutjanus campechanus ) at a 1.6 km 2 reef off North Carolina, USA. Cameras recorded observations of unmarked and marked individuals, whereas telemetry data indicated the number of tagged fish present on the reef. We estimated density (95 individuals/km 2 , 95%CI: 58–149), ESA (which was lower when current direction was towards the camera), detection probability (0.06, 95%CI: 0.03–0.09), and covariate relationships. Simulation studies under different scenarios of data quality and space use identified positive bias in density estimates from N-mixture models due to fish movement. In contrast, the Marked N-Mixture model returned unbiased estimates of density, ESA, and detection parameters, and appears to be a more robust method for modeling density given the data available for this analysis. This approach can be applied to other populations where count and telemetry data overlap in space and time.
North Carolina↗
Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York. Part 3. Responses of Stream Base-Flow Chemistry to Hydrogeologic Factors and Nonpoint-Sources of Contamination
Base-flow samples were collected seasonally from 20 small streams in the 372-square-mile Pepacton Reservoir watershed to evaluate the effects of hydrogeologic factors and nonpoint sources of contamination on the chemical composition of ground-water discharge. The reservoir provides part of New York City?s water supply. The subbasins represented one of three general types of land use, each with at least 45 percent forested area (mostly on the hillsides): farmed (dairy) land, formerly farmed land with low-density residential development, or forested land with little or no development. The subbasin areas ranged from 0.38 to 10.23 square miles. All streams were sampled in December 2000 and in May, July, and October 2001. Three of the sites were designated as landuse- index sites and were sampled as many as five additional times during the study. No samples exceeded state or federal drinking-water standards for chloride, sodium, nitrate, orthophosphate, herbicides, or herbicide degradates. The chemical composition of base-flow samples was classified into major-ion water types, which were broadly defined as naturally occurring and road-salt-affected water types. About one-third of the base-flow samples were roadsalt- affected types. Natural water types were differentiated as dilute or evolved. Dilute waters have bicarbonate and sulfate as dominant anions and evolved waters have only bicarbonate as a dominant anion. Dilute water types indicate relatively short ground-water residence times or contact with unreactive aquifer material. Evolved waters have either longer ground-water residence time or contact with more reactive aquifer material than dilute ground waters. The larger subbasins with wider valley-bottom areas were more likely to have evolved water types than small subbasins with little floodplain development. Positive correlations between selected constituents and the intensity of nonpoint sources emphasize the connection between land use, shallow ground-water quality, and stream base-flow water quality. Chloride and sodium, which are relatively conservative constituents, showed strong linear relations with annual estimates of road-salt application during all four sampling periods. Nonconservative constituents, such as the nutrients nitrate and orthophosphate, showed linear relations with manure production rate among farmed basins, but only at specific times of the year because of losses through biologic activity. Nitrate showed the strongest relation in winter because losses to biological activity were at a minimum. Orthophosphate showed the strongest relation in early summer, when hydrologic and chemical conditions appear to favor release from sediments. Atmospheric nitrogen deposition is an additional source of nitrogen that can be released from mature or stressed forested basins. Detections of herbicides (atrazine, metolachlor, simazine) and herbicide degradates ( Metolachlor ESA, alachlor ESA, deethylatrazine) in base flow were closely correlated with subbasins in which corn was grown during the study. Atrazine was detected at the farmed index site only in early summer, after application and two rain storms. This detection corresponded to the peak orthophosphate concentration. In contrast, metolachlor ESA was detected in nearly all farmedindex- subbasin samples and peaked in late summer, when percent base-flow contributions from farmed valley-bottom areas were likely highest. The implications of this study are that seasonal and more frequent base-flow surveys of water chemistry from small stream basins can help refine the understanding of local hydrogeologic systems and define the effects of nonpointsource contamination on base-flow water quality. The concentration of most nonpoint sources in valley-bottom or lower-hillside areas helped indicate the relative contributions of water from hillside and valley-bottom areas at different times of year. The positive correlations between the intensity of nonpoint-source activities and nonpoint-source constituents in base flow underscores the link between land use (nonpoint sources), ground-water quality, and surface-water quality.
Scientific Investigations Report↗
Streambed scour of salmon (Oncorhynchus spp.) redds in the Sauk River, Northwestern Washington
The autumn and winter flood season of western Washington coincides with the incubation period of many Pacific salmon ( Onchorhynchus spp.) populations. During this period, salmon embryos incubating within gravel nests called “redds” are vulnerable to mobilization of surrounding sediment during floods. As overlying sediment is transported downstream, the vertical position of the streambed can be lowered, a process termed streambed scour; thus developing salmon embryos may be destroyed resulting in decreasing egg-to-fry survival rates. The Sauk River, which drains a 1,900 km 2 (733.5 mi 2 ) area of the central Cascade Range of Washington State, provides spawning and rearing habitat for several species of Pacific salmon including Chinook salmon ( O. tshawytscha ), which were listed as threatened under the Endangered Species Act (ESA) in 1999. In order to assess the hydrologic conditions when streambed scour and concomitant geomorphic changes occur, accelerometer scour monitors (ASMs), which record the time when streambed scour lowers the streambed to the level of salmon egg pockets, were deployed in two geomorphically different reaches of the Sauk River to monitor scour during water year 2018. Nineteen ASMs were deployed in an upstream reach, which was largely confined by valley walls with vegetated, stable banks and low channel-migration rates near the confluence of the Sauk and White Chuck Rivers. Twelve additional ASMs were deployed in a downstream reach within an unconfined valley with unvegetated, unstable banks and high channel-migration rates between the town of Darrington and the confluence of the Sauk and Suiattle Rivers. During the ASM deployment, discharge measured at the U.S. Geological Survey (USGS) streamgage Sauk River above White Chuck River, near Darrington, Washington (12186000), peaked at 479 m 3 /s (16,900 ft 3 /s) with an estimated 0.18 probability of annual exceedance (5.7-year recurrence interval). During the flood season, large-scale geomorphic changes, including channel migration and bar deposition, were measured at the downstream reach, but only minimal geomorphic changes were measured at the upstream reach. ASMs deployed at the downstream reach were not recovered after the flood season and total scour depth was presumed to have exceeded ASM anchor depth. At the upstream reach, 7 of the 19 deployed ASMs were recovered after the flood season and all recovered ASMs recorded scour at discharges that equaled or exceeded 204 m 3 /s (7,210 ft 3 /s). The remaining 12 ASMs deployed at the upstream reach were not recovered and total scour depth was presumed to have exceeded ASM anchor depth. Collectively, this analysis enhances the ability of fisheries managers to forecast egg-to-fry survival rates of salmonids by determining the hydrologic conditions at which scour at the level of salmon redds initiates.
Washington↗
Fire effects on wildlife in Central Hardwoods and Appalachian regions
Fire is being prescribed and used increasingly to promote ecosystem restoration (e.g., oak woodlands and savannas) and to manage wildlife habitat in the Central Hardwoods and Appalachian regions, USA. However, questions persist as to how fire affects hardwood forest communities and associated wildlife, and how fire should be used to achieve management goals. We provide an up-to-date review of fire effects on various wildlife species and their habitat in the Central Hardwoods and Appalachians. Documented direct effects (i.e., mortality) on wildlife are rare. Indirect effects (i.e., changes in habitat quality) are influenced greatly by light availability, fire frequency, and fire intensity. Unless fire intensity is great enough to kill a portion of the overstory, burning in closed-canopy forests has provided little benefit for most wildlife species in the region because it doesn’t result in enough sunlight penetration to elicit understory response. Canopy reduction through silvicultural treatment has enabled managers to use fire more effectively. Fire intensity must be kept low in hardwoods to limit damage to many species of overstory trees. However, wounding or killing trees with fire benefits many wildlife species by allowing increased sunlight to stimulate understory response, snag and subsequent cavity creation, and additions of large coarse woody debris. In general, a fire-return interval of 2 yr to 7 yr benefits a wide variety of wildlife species by providing a diverse structure in the understory; increasing browse, forage, and soft mast; and creating snags and cavities. Historically, dormant-season fire was most prevalent in these regions, and it still is when most prescribed fire is implemented in hardwood systems as burn-days are relatively few in the growing season of May through August because of shading from leaf cover and high fuel moisture. Late growing-season burning increases the window for burning, and better control on woody composition is possible. Early growing-season fire may pose increased risk for some species, especially herpetofauna recently emerged from winter hibernacula (April) or forest songbirds that nest in the understory (May to June). However, negative population-level effects are unlikely unless the burned area is relatively large and early growing-season fire is used continually. We did not find evidence that fire is leading to population declines for any species, including Endangered Species Act (ESA)-listed species (e.g., Indiana bat [ Myotis sodalis Mill. Allen] or northern long-eared bat [ M. septentrionalis Trouess.]). Instead, data indicate that fire can enhance habitat for bats by increasing suitability of foraging and day-roost sites. Similarly, concern over burning and displacement of woodland salamanders (Plethodontidae), another taxa of heightened conservation concern, is alleviated when fire is prescribed along ecologically appropriate aspect and slope gradients and not forced into mesic, high site index environments where salamanders are most common. Because topography across the Central Hardwoods and Appalachians is diverse, we contend that applying fire on positions best suited for burning is an effective approach to increase regional landscape heterogeneity and biological diversity. Herein, we offer prescriptive concepts for burning for various wildlife species and guilds in the Central Hardwoods and Appalachians.
Appalachian region, Central Hardwoods region↗
Ecology in the information age: Patterns of use and attrition rates of internet-based citations in ESA journals, 1997–2005
As the amount of information available on the internet has increased, so too has the number of citations to network-accessible information in scholarly research. We searched all papers in four Ecological Society of America journals from 1997 to 2005 for articles containing a citation to material on the internet. We then tested the links to determine whether the information cited in the paper was still accessible. We identified 877 articles that contained at least one link to information on the internet and a total of 2100 unique links. The majority of these citations were based on an object's location (Uniform Resource Locator; 77%), whereas the rest were based on an object's identity (eg Digital Object Identifier, GenBank Accession number). We found that 19–30% of the location-based links were unavailable and that there was a positive relationship between the age of an article and the probability of the link being inactive. Using an internet search engine, we recovered 72–84% of the lost information, leaving a total of 6.2% of the total citations unavailable. Our results highlight the problem of persistence of information stored on the world wide web and we include recommendations for minimizing this problem.
Frontiers in Ecology and the Environment↗
Monitoring and research on the Bi-State Distinct Population Segment of greater sage-grouse ( Centrocercus urophasianus ) in the Pine Nut Mountains, California and Nevada—Study progress report, 2011–15
The Bi-State distinct population segment (DPS) of greater sage-grouse ( Centrocercus urophasianus ) that occurs along the Nevada–California border was proposed for listing as threatened under the Endangered Species Act (ESA) by the U.S. Fish and Wildlife Service (FWS) in October 2013. However, in April 2015, the FWS determined that the Bi-State DPS no longer required protection under the ESA and withdrew the proposed rule to list the Bi-State DPS (U.S. Fish and Wildlife Service, 2015). The Bi-State DPS occupies portions of Alpine, Mono, and Inyo Counties in California, and Douglas, Esmeralda, Lyon, Carson City, and Mineral Counties in Nevada. Unique threats facing this population include geographic isolation, expansion of single-leaf pinyon ( Pinus monophylla ) and Utah juniper ( Juniperus osteosperma ), anthropogenic activities, and recent changes in predator communities. Estimating population vital rates, identifying seasonal habitat, quantifying threats, and identifying movement patterns are important first steps in developing effective sage-grouse management and conservation plans. During 2011–15, we radio- and Global Positioning System (GPS)-marked (2012–14 only) 44, 47, 17, 9, and 3 sage-grouse, respectively, for a total of 120, in the Pine Nut Mountains Population Management Unit (PMU). No change in lek attendance was detected at Mill Canyon (maximum=18 males) between 2011 and 2012; however, 1 male was observed in 2014 and no males were observed in 2013 and 2015. Males were observed near Bald Mountain in 2013, making it the first year this lek was observed to be active during the study period. Males were observed at a new site in the Buckskin Range in 2014 during trapping efforts and again observed during surveys in 2015. Findings indicate that pinyon-juniper is avoided by sage-grouse during every life stage. Nesting females selected increased sagebrush cover, sagebrush height, and understory horizontal cover, and brood-rearing females selected similar areas, but also preferred increased perennial forb abundance. Using maximum likelihood estimation, nest survival for the Pine Nut Mountains PMU during 2011–14 was 23.8 percent (95-percent confidence interval [CI]=0.3–40.6 percent) and appeared lower in comparison to the average 42 percent nest success for sage-grouse range-wide. Brood survival for 50-day brood-rearing phase in the Pine Nut Mountains PMU during 2011–14 was 53.8 percent (95-percent CI=30.0–73.4 percent). Adult survival during 2011–15 was 67.4 percent (95-percent CI=56.1–76.5 percent). During 2011–14, 696 raptor/raven surveys were completed and results indicate a greater number of raven detections ( n =464) in the Pine Nut Mountains PMU than at other study areas in Nevada. These data will be used to develop a predator index. We conducted a more minimal monitoring effort of sage-grouse populations during the 2015 field season, which included trapping efforts, general telemetry, brood monitoring, and GPS monitoring. Nest monitoring, microhabitat sampling, and raptor/raven surveys were not conducted in the 2015 season. Deployment of GPS transmitters has expanded our knowledge of movement corridors and fine-scale movement patterns by sage-grouse in the Pine Nut Mountains PMU. Movement corridors between seasonal habitats were identified with one sage-grouse traveling greater than 100 kilometers south to the Bodie Mountains in California for the winter season. The use of GPS technology to monitor movements in conjunction with intensive field efforts will be important in developing habitat models and maps for the Pine Nut Mountains PMU.
California, Nevada↗
Review of ESA SYMP 7: A dynamic perspective on ecosystem restoration–establishing temporal connectivity at the intersection between paleoecology and restoration ecology
Landscape connectivity is vital not only spatially, but also temporally; as ecosystems change, it is important to be aware of past, present, and future variables that may impact ecosystem function and biodiversity. As climate and environments continue to change, choosing appropriate restoration targets is becoming more challenging. By considering the paleoecological and paleoenvironmental record for a given region, restoration practitioners are not only able to bear witness to that region’s dynamic history, but also potentially identify multiple, alternative natural ecosystem states. Indeed, one of the deliverables of conservation paleobiology, a field that applies paleontological data and methods to present-day conservation, is to inform restoration targets. Consideration of future change is equally important, and paleoecological and paleoclimatological data are essential for informing models that can help us understand how climate change is affecting species and ecosystems at different temporal scales. The symposium “A dynamic perspective on ecosystem restoration: Establishing temporal connectivity at the intersection between paleoecology and restoration ecology” gathered representatives from macroecology, paleoecology, and restoration ecology to share their perspectives on temporal connectivity and how consideration of an ecosystem’s past, present, and future can positively impact restoration and conservation. Some speakers approached the topic theoretically, while others considered it from a more practical and applied standpoint. The goals of the symposium were to build a stronger relationship among the subdisciplines, stimulate new ideas, and identify data and/or products that would be useful to share across subdisciplines.
Bulletin Ecological Society of America↗
Biotic and abiotic influences on abundance and distribution of nonnative Chinook salmon and native ESA-listed steelhead in the Wind River, Washington
Biotic and abiotic factors influence fish populations and distributions. Concerns have been raised about the influence of hatchery fish on wild populations. Carson National Fish Hatchery produces spring Chinook salmon Oncorhynchus tshawytscha in the Wind River, Washington, and some spawn in the river. Managers were concerned that Chinook salmon could negatively affect wild steelhead O. mykiss and that a self-sustaining population of Chinook salmon may develop. Our objectives were to assess: 1) the distribution and populations of juvenile spring Chinook salmon and juvenile steelhead in the upper Wind River; 2) the influence of stream flow and of each population on the other; and 3) if Chinook salmon populations were self-sustaining. We snorkeled to determine distribution and abundance. Flow in the fall influenced upstream distribution and abundance of juvenile Chinook salmon. Juvenile Chinook salmon densities were consistently low (range 0.0 to 5.7 fish 100 m -2 ) and not influenced by number of spawners, winter flow magnitude, or steelhead abundance. Juvenile steelhead were distributed through the study section each year. Age-0 and age-1 steelhead densities (age-0 range: 0.04 to 37.0 fish 100 m -2 ; age-1 range: 0.02 to 6.21 fish 100 m -2 ) were consistently higher than for juvenile Chinook salmon. Steelhead spawner abundance positively influenced juvenile steelhead abundance. During this study, Chinook salmon in the Wind River appear to have had little effect on steelhead. Low juvenile Chinook salmon abundance and a lack of a spawner-to-juvenile relationship suggest Chinook salmon are not self-sustaining and potential for such a population is low under current conditions.
Northwest Science↗
Dissolved oxygen controls summer habitat of Clear Lake Hitch (Lavinia exilicauda chi), an imperilled potamodromous cyprinid
The Clear Lake Hitch is an imperiled minnow endemic to Clear Lake, Lake County, California, USA that is listed as threatened under the California Endangered Species Act (ESA) and is a candidate for listing under the United States ESA. It exhibits a potamodromous life cycle whereby adults, which reach up to 6+ years in age and over 350 mm in length, migrate into Clear Lake’s ephemeral tributaries briefly during spring to spawn. Conservation and management of Clear Lake Hitch is inhibited, in part, by a lack of information on the lacustrine distribution and habitat of non-breeding individuals within Clear Lake. To address this problem, we sampled Clear Lake Hitch with gill nets in a stratified random sampling design to determine the distribution and habitat associations in early summer 2017 and 2018. We identified abundance-habitat relationships for juvenile and adult Clear Lake Hitch using Bayesian zero-inflated negative binomial generalized linear mixed modeling. The results indicated that dissolved oxygen concentration was the most important habitat feature among those measured; both juvenile and adult Clear Lake Hitch were substantially more abundant in normoxic (> 2 mg l-1) than in hypoxic (< 2 mg l-1) habitat. Both life stages also exhibited weak positive relationships with chlorophyll fluorescence, suggesting that relatively productive habitats may support higher numbers of Clear Lake Hitch. Spatially, juveniles were most abundant in nearshore habitats while adults were ubiquitous, indicating an ontogentic habitat expansion that may be associated with a resource availability-predation risk tradeoff. Management actions undertaken to improve or alleviate water quality and hypoxia problems in Clear Lake would also improve Clear Lake Hitch habitat.
California↗
Snake River Fall Chinook Salmon life history investigations
Predation by nonnative fishes is one factor that has been implicated in the decline of juvenile salmonids in the Pacific Northwest. Impoundment of much of the Snake and Columbia rivers has altered food webs and created habitat favorable for species such as Smallmouth Bass Micropterus dolomieu . Smallmouth Bass are common throughout the Columbia River basin and have become the most abundant predator in lower Snake River reservoirs (Zimmerman and Parker 1995). This is a concern for Snake River Fall Chinook Salmon Oncorhynchus tshawytscha (hereafter, subyearlings) that may be particularly vulnerable due to their relatively small size and because their main-stem rearing habitats often overlap or are in close proximity to habitats used by Smallmouth Bass (Curet 1993; Tabor et al. 1993). Concern over juvenile salmon predation spawned a number of large-scale studies to quantify its effect in the late 1980s, 1990s, and early 2000s (Poe et al. 1991; Rieman et al. 1991; Vigg et al. 1991; Fritts and Pearsons 2004; Naughton et al. 2004). Smallmouth Bass predation represented 9% of total salmon consumption by predatory fishes in John Day Reservoir, Columbia River, from 1983 through 1986 (Rieman et al. 1991). In transitional habitat between the Hanford Reach of the Columbia River and McNary Reservoir, juvenile salmon (presumably subyearlings) were found in 65% of Smallmouth Bass (>200 mm) stomachs and comprised 59% of the diet by weight (Tabor et al. 1993). Within Lower Granite Reservoir on the Snake River, Naughton et al. (2004) showed that monthly consumption (based on weight) ranged from 5% in the upper reaches of the reservoir to 11% in the forebay. However, studies in the Snake River were conducted soon after Endangered Species Act (ESA) listing of Snake River Fall Chinook Salmon (NMFS 1992). During this time, Fall Chinook Salmon abundance was at an historic low, which may explain why consumption rates were relatively low compared to those from studies conducted in the Columbia and Yakima rivers where abundance was higher (e.g., Tabor et al. 1993; Fritts and Pearsons 2004). We speculate that predation on subyearlings by Smallmouth Bass in the Snake River may have increased in recent years for several reasons. Since their ESA listing, recovery measures implemented for Snake River Fall Chinook salmon have resulted in a large increase in the juvenile population (Connor et al. 2013). Considering that subyearlings probably now make up a larger portion of the forage fish population, it is plausible they should make up a large portion of Smallmouth Bass diets. Second, migrating subyearlings delay downstream movement in the transition zones of the Clearwater River and Snake River for varying lengths of time (Tiffan et al. 2010), which increases their exposure and vulnerability to predators. Spatial overlap in locations of Smallmouth Bass and subyearlings that died during migration provides support for this (Tiffan et al. 2010). Finally, the later outmigration of subyearlings from the Clearwater River results in their presence in Lower Granite Reservoir during the warmest summer months when predation rates of Smallmouth Bass should be highest. In 2016, we focused our efforts on Smallmouth Bass predation in Lower Granite Reservoir downstream of the transition zones and the confluence area where we worked during 2012–2015. Similar to past years, our first objective was to quantify Smallmouth Bass consumption rates of subyearlings, determine relative bass abundance, and describe bass diets. In addition, Tiffan et al. (2016a) posited that predation risk to subyearlings may be higher in shoreline habitats that are more suitable for Smallmouth Bass and lower in shoreline habitats that are more suitable for subyearlings. To test this hypothesis, our second objective examines the relationship between Smallmouth Bass predation of subyearlings and habitat suitability.
Idaho, Washington↗
Smallmouth bass predation on subyearling fall Chinook salmon in Lower Granite Reservoir, 2016–2017
Predation by nonnative fishes is one factor that has been implicated in the decline of juvenile salmonids in the Pacific Northwest. Impoundment of much of the Snake and Columbia Rivers has altered food webs and created habitat favorable for species such as smallmouth bass Micropterus dolomieu. Smallmouth bass are common throughout the Columbia River basin and have become the most abundant predator in lower Snake River reservoirs (Zimmerman and Parker 1995). This is a concern for Snake River fall Chinook salmon Oncorhynchus tshawytscha (hereafter, subyearlings) that may be particularly vulnerable due to their relatively small size and because their main-stem rearing habitats often overlap or are in close proximity to habitats used by smallmouth bass (Curet 1993; Tabor et al. 1993). Concern over juvenile salmon predation spawned a number of large-scale studies to quantify its effect in the late 1980s, 1990s, and early 2000s (Poe et al. 1991; Rieman et al. 1991; Vigg et al. 1991; Fritts and Pearsons 2004; Naughton et al. 2004). Smallmouth bass predation represented 9% of total salmon consumption by predatory fishes in John Day Reservoir, Columbia River, from 1983 through 1986 (Rieman et al. 1991). In transitional habitat between the Hanford Reach of the Columbia River and McNary Reservoir, juvenile salmon (presumably subyearlings) were found in 65% of smallmouth bass (>200 mm) stomachs and comprised 59% of the diet by weight (Tabor et al. 1993). Within Lower Granite Reservoir on the Snake River, Naughton et al. (2004) showed that monthly consumption (based on weight) ranged from 5% in the upper reaches of the reservoir to 11% in the forebay. However, studies in the Snake River were conducted soon after Endangered Species Act (ESA) listing of Snake River fall Chinook salmon (NMFS 1992). During this time, fall Chinook salmon abundance was at an historic low, which may explain why consumption rates were relatively low compared to those from studies conducted in the Columbia and Yakima Rivers where abundance was higher (e.g., Tabor et al. 1993; Fritts and Pearsons 2004). We speculate that predation on subyearlings by smallmouth bass in the Snake River may have increased in recent years for several reasons. Since their ESA listing, recovery measures implemented for Snake River fall Chinook salmon have resulted in a large increase in the juvenile population (Connor et al. 2013). Considering that subyearlings probably now make up a larger portion of the forage fish population, it is plausible they should make up a larger portion of smallmouth bass diets. Second, migrating subyearlings delay downstream movement in the transition zones of the Clearwater River and Snake River for varying lengths of time (Tiffan et al. 2010), which increases their exposure and vulnerability to predators. Spatial overlap in locations of smallmouth bass and subyearlings that died during migration provides support for this (Tiffan et al. 2010). Finally, the later outmigration of subyearlings from the Clearwater River results in their presence in Lower Granite Reservoir during the warmest summer months when predation rates of smallmouth bass should be highest. In 2016 and 2017, we focused our smallmouth bass predation efforts in Lower Granite Reservoir downstream of the transition zones and the confluence area where we worked during 2012–2015. This report primarily covers results from 2017 but some results from 2016 are also included for comparison. Similar to past years, our first objective was to quantify smallmouth bass consumption rates of subyearlings, determine bass abundance, and describe bass diets. In addition, Tiffan et al. (2016a) posited that predation risk to subyearlings may be higher in shoreline habitats that are more suitable for smallmouth bass and lower in shoreline habitats that are more suitable for subyearlings. To test this hypothesis, our second objective was to examine the relationship between smallmouth bass predation and subyearling habitat suitability. Our final objective was to combine estimates of consumption with smallmouth bass abundance to derive estimates of total Chinook salmon losses to smallmouth bass for 2016 and 2017.
Idaho, Washington↗
Crims Island-Restoration and monitoring of juvenile salmon rearing habitat in the Columbia River Estuary, Oregon, 2004-10
Under the 2004 Biological Opinion for operation of the Federal Columbia River Power System released by the National Marine Fisheries Service, the U.S. Army Corps of Engineers (USACE), the Bonneville Power Administration (BPA), and the Bureau of Reclamation (Reclamation) were directed to restore more than 4,047 hectares (10,000 acres) of tidal marsh in the Columbia River estuary by 2010. Restoration of Crims Island near Longview, Washington, restored 38.1 hectares of marsh and swamp in the tidal freshwater portion of the lower Columbia River. The goal of the restoration was to improve habitat for juveniles of Endangered Species Act (ESA)-listed salmon stocks and ESA-listed Columbian white-tailed deer. The U.S. Geological Survey (USGS) monitored and evaluated the fisheries and aquatic resources at Crims Island in 2004 prior to restoration (pre-restoration), which began in August 2004, and then post-restoration from 2006 to 2009. This report summarizes pre- and post-restoration monitoring data used by the USGS to evaluate project success. We evaluated project success by examining the interaction between juvenile salmon and a suite of broader ecological measures including sediments, plants, and invertebrates and their response to large-scale habitat alteration. The restoration action at Crims Island from August 2004 to September 2005 was to excavate a 0.6-meter layer of soil and dig channels in the interior of the island to remove reed canary grass and increase habitat area and tidal exchange. The excavation created 34.4 hectares of tidal emergent marsh where none previously existed and 3.7 hectares of intertidal and subtidal channels. Cattle that had grazed the island for more than 50 years were relocated. Soil excavated from the site was deposited in upland areas next to the tidal marsh to establish an upland forest. Excavation deepened and widened an existing T-shaped channel to increase tidal flow to the interior of the island. The western arm of the existing 'T-channel' was extended westward and connected to Bradbury Slough to create a second outlet to the main river. New intertidal channels were constructed from the existing 'T-channel' and tidal mudflats became inundated at high tide to increase rearing habitat for juvenile salmonids. The restoration action resulted in a 95-percent increase in available juvenile salmon rearing habitat. We collected juvenile salmon and other fishes at Crims Island and a nearby reference site using beach seines and fyke nets annually from March through August during all years. Benthic invertebrates were collected with sediment corers and drift invertebrates were collected with neuston nets. Juvenile salmon stomach contents were sampled using lavage. Vegetation and sediments characteristics were surveyed and we conducted a topographic/bathymetric survey using a RTK (real time kinematic) GPS (global positioning system). The fish assemblage at Crims Island, composed primarily of threespine stickleback (Gasterosteus aculeatus), non-native banded killifish (Fundulus diaphanus), peamouth chub (Mylocheilus caurinus), subyearling Chinook salmon (Oncorhynchus tshawytscha) (hereinafter referred to as subyearlings), and small numbers of juvenile chum salmon (Oncorhynchus keta), did not differ appreciably pre- and post-restoration. Subyearlings were the primary salmonid collected and were seasonally abundant from April through May during all years. The abundance of juvenile salmon declined seasonally as water temperature exceeded 20 degrees C in the Reference site by mid-June; however, subyearlings persisted at the Mainstem site and in subtidal channels of the Restoration site through the summer in water temperatures exceeding 22 degrees C. Residence times of subyearlings in Crims Island backwaters generally were short consisting of one or two tidal cycles. Median residence time was longer in the Restoration site than in the Reference site pre- and post-restoration. Small (mean = 55.7 millimeters) subyea
Scientific Investigations Report↗