Geology topics

Barbara A. Martin

Publications and source records attributed to Barbara A. Martin.

At least 19 recordsLinked to original sources

USGS2024

Growth, survival, and cohort formation of juvenile Lost River (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) in Upper Klamath Lake, Oregon, and Clear Lake Reservoir, California—2021–22 monitoring report

Executive Summary The work reported in this publication provides updated data and interpretation for sampling years 2015 and 2022 of the juvenile monitoring project. The study objectives, background, study area, species description, and methods remained the same or similar throughout the years, while the executive summary, results, and discussion were updated each year. Therefore much of this paper was originally presented in previous reports (Bart and others 2020a, b; Bart and others, 2021; Burdick and others, 2016; Burdick and others, 2018; Martin and others, 2022) and is repeated here for the reader’s convenience. Populations of federally endangered Lost River ( Deltistes luxatus ) and shortnose suckers ( Chasmistes brevirostris ) in Upper Klamath Lake, Oregon, and Clear Lake Reservoir (hereinafter, Clear Lake), California, are experiencing long-term decreases in abundance. Upper Klamath Lake populations are decreasing not only because of adult mortality, which is relatively low, but also because they are not being balanced by recruitment of young adult suckers into adult spawning aggregations. Long-term monitoring of juvenile sucker populations is conducted to (1) determine if there are annual and species-specific differences in production, survival, and growth; (2) better understand when juvenile sucker mortality is greatest; and (3) identify potential causes of high juvenile sucker mortality particularly in Upper Klamath Lake. The U.S. Geological Survey (USGS) monitoring program, begun in 2015, tracks cohorts through summer months and among years in Upper Klamath and Clear Lakes. Data on juvenile suckers captured in trap nets are used to provide information on annual variability in age-0 sucker production, juvenile sucker apparent survival, growth, species composition, and health. Upper Klamath Lake indices of year-class strength suggest that the 2022 age-0 cohort is the lowest since standardized monitoring began. The 2021 cohort, like most cohorts, had moderately low catch rates their first year of life, with a steep drop off during the second year. Although the 2020 cohort persisted through the September 2022 sampling, this cohort was sparsely represented after the first year with no representatives from this cohort captured from July 2021 through July 2022. Despite apparently low fall through spring apparent survival, the relatively large 2019 cohort persisted in our 2020–21 samples, but has not been detected since June 2021. Klamath largescale ( Catostomus snyderi ) and shortnose suckers were only differentiated from each other starting in 2020. Shortnose suckers dominated the age-1 catch in 2020 and 2022, whereas age-1 Klamath largescale suckers were slightly more prevalent in 2021. Although there were occasionally age-2 and older suckers captured, none of these fish were Lost River suckers. Except for 2015, 2017, and 2021, there were more age-0 Lost River suckers than presumed shortnose suckers in Upper Klamath Lake. However, in all years sampled, there were more age-1 presumed shortnose suckers than Lost River suckers. Age distribution of suckers captured in Clear Lake indicates greater juvenile survival than in Upper Klamath Lake. Most juvenile suckers captured throughout the years were from the 2016 and 2017 cohorts; however, by 2022 most of these fish were no longer susceptible to standard trap nets and were not as prevalent in 2022 juvenile catches, and these suckers presumedly recruited to the adult population. As the 2016 and 2017 cohorts catches declined, so did the catch in overall numbers of suckers. Excluding age-0 catches, the 2016 cohort catches peaked at age-3 and the 2017 catches peaked at age-2. In 2022, the majority of the catch was composed of age-3 to age-5 suckers. The majority of suckers captured in Clear Lake during this multiyear project were classified as the combination of Klamath largescale suckers and shortnose suckers from the Lost River Basin, from the 2016 and 2017 cohorts. The few suckers identified as Lost River or definitive shortnose suckers were from the 2016 and 2017 cohorts. A lack of age-0 suckers captured in Clear Lake during years with low spawning tributary inflow or lake levels suggested that low water prevented spawning and year class formation. However, recent data indicate that some cohorts with Klamath largescale and shortnose sucker genetics that were not captured as age-0 suckers were detected in later years at age-1 or age-2. This finding indicates that juvenile suckers in Clear Lake may spend one or more years in the tributaries and that these cohorts may primarily be represented by Klamath largescale suckers. The first 7 years of this monitoring program indicated different patterns in recruitment and survival of juvenile suckers between Upper Klamath and Clear Lakes. Since the monitoring program began in 2015, age-0 sucker catch rates, interpreted as indices of year-class strength, were greatest in Upper Klamath Lake in 2016 and 2019. In those years, Lost River suckers made up the majority of age-0 sucker catches. However, in 2017 and 2020, the age-1 sucker catches from these cohorts were mainly composed of shortnose suckers or suckers with genetic markers of both Klamath largescale and shortnose suckers, indicating a low first year survival for Lost River suckers even when age-0 catches were high. Age-0 suckers do not fully recruit to our sampling gear in Upper Klamath Lake until August, experience high mortality by September, and are almost undetectable in subsequent years. In Clear Lake, suckers are often not captured until age-1 or age-2 and juvenile annual survival appears much greater; however, there does appear to be a drop-off in catch rates as the suckers age and become less susceptible to the fishing gear.

California, Oregon↗

USGS2023

Validating a non-lethal method of aging endangered juvenile Lost River and Shortnose Suckers

Populations of imperiled Lost River Deltistes luxatus and Shortnose Chasmistes brevirostris suckers in Upper Klamath Lake, Oregon, are experiencing long-term decreases in abundance due to limited recruitment of juvenile suckers into the adult populations. Researchers use estimated ages based on fin rays to study environmental factors affecting year-class formation, generate annual juvenile sucker survival indices, and study variations in early life history. Biased or imprecise age estimates can lead to erroneous conclusions and have implications for age-based survival estimates, indications of recruitment, and growth estimators. We examined fin rays collected from individual suckers captured on multiple occasions and determined that juvenile suckers deposit a translucent increment on fin rays annually. Size-at-age data for suckers first captured as young as age 0 corroborated our finding of annual increment formation and indicate that the first increments are formed at age 1. We used edge and marginal increment analysis conducted on fin rays to determine the timing of annual increment formation. Our results indicate that increment formation occurs on fin rays of juvenile suckers from October to May and peaks between February and April.

Oregon↗

USGS2022

Growth, survival, and cohort formation of juvenile Lost River (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) in Upper Klamath Lake, Oregon, and Clear Lake Reservoir, California—2020 monitoring report

Executive Summary Populations of federally endangered Lost River ( Deltistes luxatus ) and shortnose suckers ( Chasmistes brevirostris ) in Upper Klamath Lake, Oregon, and Clear Lake Reservoir (hereinafter, Clear Lake), California, are experiencing long-term decreases in abundance. Upper Klamath Lake populations are decreasing not only because of adult mortality, which is relatively low, but also because they are not being balanced by recruitment of young adult suckers into known adult spawning aggregations. Long-term monitoring of juvenile sucker populations is conducted to (1) determine if there are annual and species-specific differences in production, survival, and growth, (2) better understand when juvenile sucker mortality is greatest, and (3) help identify potential causes of high juvenile sucker mortality particularly in Upper Klamath Lake. The U.S. Geological Survey (USGS) monitoring program, begun in 2015, tracks cohorts through summer months and among years in Upper Klamath and Clear Lakes. Data on juvenile suckers captured in trap nets are used to provide information on annual variability in age-0 sucker apparent production, juvenile sucker apparent survival, apparent growth, species composition, and health. Upper Klamath Lake indices of year-class strength suggest that the 2020 age-0 cohort is one of the lowest since standardized monitoring began. Despite apparently low over-winter survival, the relatively large 2019 cohort persisted in our 2020 samples and continues to contribute to the populations. Although the 2019 cohort age-0 suckers were composed mainly of Lost River suckers, the age-1 suckers from the 2019 cohort were mainly shortnose suckers. Lost River suckers comprised the largest proportion of the 2020 year-class and were only captured in July and August. Shortnose suckers were mainly captured in August and September and comprised a smaller proportion of the 2020 year-class. Age distribution of suckers captured in Clear Lake indicates greater juvenile survival than in Upper Klamath Lake. Most juvenile suckers captured were age-3 and age-4 suckers classified as the combination of Klamath largescale suckers ( Catostomus snyderi ) and shortnose suckers from the Lost River Basin, from the 2016 and 2017 cohorts. A lack of age-0 suckers captured in Clear Lake during years with the low inflow or lake levels initially lead us to believe that low water prevented spawning and year class formation. However, recent data indicate that some cohorts that were not captured as age-0 suckers were detected in later years at age-1 or age-2. This finding indicates that juvenile suckers in Clear Lake may spend one or more years in the tributaries or that sampling efficacy for age-0 suckers varies among years because of water depth. The first 5 years of this monitoring program indicated different patterns in recruitment and survival of juvenile suckers between Upper Klamath and Clear Lakes. Since the monitoring program began in 2015, age-0 sucker catch rates, interpreted as indices of year-class strength, were greatest in Upper Klamath Lake in 2016 and 2019. In those years Lost River suckers made up the majority of age-0 sucker catches; however, in 2017 and 2020 the age-1 sucker catches from these cohorts were mainly composed of shortnose suckers or suckers with genetic markers of both Klamath largescale and shortnose suckers, indicating a low overwinter survival for Lost River suckers even when the age-0 catches were high. Age-0 suckers do not fully recruit to our sampling gear in Upper Klamath Lake until August, experience high mortality by September, and are almost undetectable by the following July or August in most years. In Clear Lake, suckers frequently are not captured until age-1 or age-2 and annual survival appears much greater.

California, Oregon↗

USGS2022

Distribution of bull trout (Salvelinus confluentus) in conjunction with habitat and trout assemblages in creeks within the Klamath Basin, Oregon 2010–16

Bull trout ( Salvelinus confluentus ) in the Klamath Basin are on the southernmost border of the range of the species, where threats are most severe and where bull trout are most imperiled. In their recovery plan the U.S. Fish and Wildlife Service (2015, https://ecos.fws.gov/ecp/report/species-with-recovery-plans ) suggested that Klamath Basin bull trout are at increased risk of extirpation due to habitat fragmentation, degradation of habitat complexity, and introduction of non-native trout species that often outcompete bull trout. The goals of this study were to determine if there was a lack of connectivity between habitat areas impeding migration, habitat differences, or interference by non-native species affecting bull trout distribution in the Klamath Basin. This study examined three populations of bull trout in conjunction with a concurrent native species (redband trout [ Oncorhynchus mykiss gairdnerii ]), and a concurrent non-native species (brown trout [ Salmo trutta ]) in tributaries of the upper Sprague River within the Klamath Basin. Culverts present at the beginning of the study may have impeded migration of bull trout, but culvert upgrades made during the study appeared to eliminate the impediments to migration. The presence of non-native brown trout appeared to cause bull trout to use a smaller portion of Leonard Creek, whereas the low numbers of brown trout in the studied portion of Brownsworth Creek did not appear to interfere with the local distribution of bull trout. Downstream migration of bull trout may have been impeded if there were increased numbers of brown trout or increased temperatures in the lower portions of the creeks outside of the study area. Although habitat complexity was not examined in detail during this study, there was an attempt to enhance the habitat for bull trout by introducing large woody debris into treatment sections of the creeks. We compared bull trout numbers between the treatment sections and nearby control sections prior to and after introduction of the large woody debris. The introduction of large woody debris did not appear to enhance the use of those areas by bull trout, but the large woody debris may not have been of suitable size to enhance the habitat for bull trout.

Oregon↗

USGS2021

Water quality, instream habitat, and the distribution of suckers in the upper Lost River watershed of Oregon and California, summer 2018

Executive Summary Endangered Lost River ( Deltistes luxatus) and shortnose ( Chasmistes brevirostris ) suckers primarily use lotic habitats during the spring spawning season in the Upper Klamath Lake watershed. However, summer-time surveys of the upper Lost River watershed in 1972, 1975 and 1989–90 indicated that adults of both endangered species use tributaries of Clear Lake Reservoir (hereafter: Clear Lake) year-round. Adult shortnose suckers have also been documented to use tributaries of Gerber Reservoir year-round. We surveyed the tributaries of Clear Lake and Gerber Reservoir to provide up-to-date information on the timing, distribution, and habitat use within the upper Lost River drainage by these two endangered sucker species. Contrary to previous studies, this study did not capture any Lost River suckers in the Clear Lake tributaries. Genetics samples from suckers collected during this study were used to verify that no Lost River suckers were captured. At the time of this study, genetics could not identify the differences between shortnose and the non-endangered Klamath largescale suckers ( Catostomus snyderi ), therefore, morphology was used to separate these two species. Furthermore, the shortnose suckers and the Klamath largescale suckers documented in the upper Lost River drainage are more similar to Klamath largescale suckers than shortnose suckers that exist in the Upper Klamath Lake recovery unit. Therefore, the suckers we documented during our surveys were most likely Klamath largescale suckers. We captured suckers, age-0 to age-9, in the Clear Lake tributaries within stream pools and flooded meadows behind water retention structures. However, no suckers were collected in small reservoirs sampled upstream of Clear Lake. Suckers were found in habitats with mud and fine substrate at depths of 0.5–3.0 meters, with most captured at 1.0 meter or less. Suckers co-occurred with nonnative species, which were more abundant in our survey than in previous surveys in the tributaries to Clear Lake. Gerber Reservoir tributaries yielded more suckers per unit effort than Clear Lake tributaries. All suckers captured in the tributaries of Gerber Reservoir were identified as Klamath Largescale suckers. The suckers in tributaries to Gerber Reservoir were collected in similar habitat as those in Clear Lake tributaries and were age-0 to age-6.

California, Oregon↗

USGS2021

Effect of temperature on survival of Lost River Suckers with a natural infection of Ichthyobodo spp.

To compensate for low natural survival of endangered Lost River Suckers Deltistes luxatus , the U.S. Fish and Wildlife Service and the Klamath Tribes have initiated captive rearing programs. We conducted laboratory experiments intended to determine the temperature for optimum growth of juvenile Lost River Suckers; however, due to an unanticipated infection with Ichthyobodo spp., we instead estimated survival in conjunction with temperature and parasite loads. Ichthyobodo spp. are common parasites that infest fish skin and gills; they are known to be present in Upper Klamath Lake and have been found in fish at both the federal and tribal fish-rearing facilities. All fish held at mean temperatures of 16°C and 19°C survived the entire 65-d experiment, whereas the median time to death was 27 d at 22°C, 8 d at 24°C, and 7 d at 26°C. Gill samples from all Lost River Suckers tested positive for Ichthyobodo spp. DNA, with a trend toward higher copy numbers in suckers that were held at a mean temperature of 22°C or warmer compared to those held at 19°C or cooler. Fish kept at all temperatures grew slowly. These results suggest that survival of Lost River Suckers with a natural infection of Ichthyobodo spp. was significantly impacted by temperature.

North American Journal of Aquaculture↗

USGS2020

Mortality of endangered juvenile Lost River Suckers associated with cyanobacteria blooms in mesocosms in Upper Klamath Lake, Oregon

Unsustainably high mortality within the first 2 years of life prevents endangered Lost River Suckers Deltistes luxatus in Upper Klamath Lake, Oregon, from recruiting to spawning populations. Massive blooms of the cyanobacterium Aphanizomenon flos‐aquae and their subsequent death and decay in the lake (bloom‐crashes) are associated with high pH, low percent oxygen saturation, high total ammonia concentrations, and spikes in the cyanotoxin microcystin. Poor water quality within the lake is considered the most likely cause of juvenile sucker mortality, but mechanisms causing the high mortality are not known. We introduced PIT‐tagged age‐1 Lost River suckers into three continuously monitored mesocosms in Upper Klamath Lake to determine the timing of juvenile sucker mortality relative to pH, temperature, and dissolved oxygen. Mortality was inferred from a lack of movement detected on remote PIT tag detection equipment within each mesocosm. Mortality was compared among mesocosms and an indoor tank‐held control group. We fitted time‐varying Cox hazard models to test hypotheses about short‐term and chronic effects of single and co‐occurring water quality parameters on the daily hazard rate. Presumed healthy or moribund fish that were collected pre‐season, mid‐season, or at the end of the study were examined macroscopically and histologically to generate inferences about the causes of mortality. Models did not indicate a plausible association between water quality variables and mortality. Hypoxia preceded periods of higher mortality at two of three sites but did not co‐occur with mortality. Hatchery‐reared Lost River Suckers confined to mesocosms may not represent the behavior of wild fish, and it is unclear whether the same factors affect the mortality of wild age‐0 suckers.

Oregon↗

USGS2020

Effects of harmful algal blooms and associated water-quality on endangered Lost River and shortnose suckers

Anthropogenic eutrophication contributes to harmful blooms of cyanobacteria in freshwater ecosystems worldwide. In Upper Klamath Lake, Oregon, massive blooms of Aphanizomenon flos-aquae and smaller blooms of other cyanobacteria are associated with cyanotoxins, hypoxia, high pH, high concentrations of ammonia, and potentially hypercapnia. Recovery of the endangered Lost River sucker Deltistes luxatus and shortnose sucker Chasmistes brevirostris in Upper Klamath Lake is obstructed by low survival in the juvenile life stage. Water quality associated with the harmful algal blooms and their decomposition (crashes) is often singled out as the primary cause of juvenile sucker mortality. We investigated this general hypothesis with a review of relevant literature and data from decades of monitoring in Upper Klamath Lake. Microcystins, hepatotoxins produced by some cyanobacteria, are unlikely to be directly lethal to suckers; potential effects of other cyanotoxins that are present in the lake warrant investigation. Dissolved-oxygen saturation declined following bloom crashes, but was infrequently low enough for long enough in Upper Klamath Lake to cause direct sucker mortality. Hypercapnia could potentially reach lethal concentrations in the fall and winter, but did not appear to be associated with the summer algal blooms. pH was highest during peaks in cyanobacteria growth, but infrequently reached directly lethal levels (> 10.3). However, pH frequently reached an observed sub-lethal effect level for juvenile suckers (10.0). Un-ionized ammonia rarely exceeded even the lowest effect level measured for suckers. Rather than act as a direct cause of large-scale mortality, the available evidence suggests that water quality associated with massive blooms of cyanobacteria in Upper Klamath Lake contributes to chronic stress for juvenile suckers and may increase mortality due to other factors.

Oregon↗

USGS2019

Effects of microcystin-LR on juvenile Lost River suckers (Deltistes luxatus) during feeding trials, Upper Klamath Lake, Oregon, 2014−16

Executive Summary Historically, populations of Lost River suckers ( Deltistes luxatus ) of the Upper Klamath Basin were so numerous that they were commercially harvested; however, declining numbers throughout the 20th century led to the listing of the species under the United States Endangered Species Act in 1988. Habitat destruction, poor water quality, competition with (and predation by) nonnative species, especially fathead minnows ( Pimephales promelas ) and yellow perch ( Perca flavescens ), are hypothesized as primary causes of population decline (U.S. Fish and Wildlife Service, 2013). Age data indicate that almost all adult suckers presently in Upper Klamath Lake spawning populations were hatched in the early 1990s. While entrainment of young fish (especially larvae) may contribute, catch-at-length and age data suggest consistently high mortality during the first year of life may be preventing the recruitment of young adults. The specific causes of juvenile sucker mortality are unknown; however, the absence of juvenile suckers in trap net catches coincides with degraded water quality associated with the decay of cyanobacteria blooms and exposure to toxic microcystin produced by Microcystis cyanobacteria. Water-quality data collected in Upper Klamath Lake from 2011 to 2016 suggest that microcystin concentrations in Upper Klamath Lake reached potentially lethal levels based on literature findings from studies on a variety of fish species. We conducted a laboratory feeding trial to determine if microcystin toxicity could potentially be a direct cause of juvenile Lost River sucker mortality. We examined the effects of environmentally relevant doses of microcystin on the survival and health of hatchery-reared juvenile Lost River suckers. Results from this laboratory study suggest that Lost River suckers are very tolerant of the microcystin-LR toxin. Histopathological analysis revealed no evidence of tissue changes associated with microcystin-LR exposure. Although no direct effects of microcystin-LR exposure were detected, suckers could potentially be negatively affected through added energy expenditures and stress associated with excretion of microcystin. Furthermore, microcystin may adversely affect other organisms in Upper Klamath Lake that could alter food availability or habitat of the suckers.

Oregon↗

USGS2019

Examination of movements and survival of Pahranagat roundtail chub (Gila robusta jordani) in the Pahranagat River and adjacent waters, Nevada, 2014–18

Executive Summary The Pahranagat roundtail chub ( Gila robusta jordani ; hereinafter “chub”) was federally listed as endangered in 1970 (U.S. Fish and Wildlife Service, 1970). In the decades following the listing, the chub has declined to extremely low numbers (Tuttle and others, 1990; Guadalupe, 2014). Loss of available habitat appears to be one of the main reasons for the decline of this species. Historically, the chub are assumed to have had approximately 30 kilometers (km) of habitat available to them, whereas currently they appear to primarily occupy 3.5 km of the Pahranagat River, up to 2.5 km of the Pahranagat Ditch, and a small portion of the Pahranagat Drain. Each year in mid-March, a gate at the top of the fish passage structure is closed to divert water down the Pahranagat Ditch, almost completely eliminating any flow into the Pahranagat Drain. The gate is usually removed in mid-October, allowing for flow to reoccur in the Pahranagat Drain. Due to the intermittent nature of the Pahranagat Drain, it is considered a sink for the species, and yearly salvage operations are conducted to remove chub from the Pahranagat Drain. The lower portion of the Pahranagat Ditch is also thought to be a sink for the species, due to high flows and limited structure potentially pushing the chub out of the system. Movements of passive-integrated-transponder (PIT) tagged chub indicate that adults and larger juveniles are not likely to be swept downstream to the point of exiting the system; however, the smaller juveniles and larvae are likely to be entrained in the Pahranagat Drain and possibly the lower portion of the Pahranagat Ditch. Only 2 of 64 PIT-tagged chub (3 percent) were observed to exit the system through the Pahranagat Ditch as they were last recorded on the Lower Ditch antenna. No PIT-tagged chub was observed exiting the system through the Pahranagat Drain. Although capture location was a good predictor of where PIT tagged fish were primarily detected, fish were observed to meander throughout the available habitat. Chub captured and released in the Pahranagat River were detected more often in the upper portion of the Pahranagat River, whereas chub captured and released in the Pahranagat Ditch were more often detected in and near the Pahranagat Ditch. This suggests some degree of site fidelity. However, the two chub that were captured in the Pahranagat Drain and relocated into the middle portion of the Pahranagat River near the Between Bridges antenna were not able to get back to the closed off Pahranagat Drain (closed to fish passage from mid-March through mid-October), but were primarily detected in and near the Pahranagat Ditch. Movements from one end of the system to the other end of the system (3.5 km) could occur within a day and there were no observed seasonal location preferences for the chubs. However, there was more activity in the uppermost sites during fall and winter, presumedly associated with spawning. Furthermore, chub were found to be more active during the daylight hours in fall and winter verses spring and summer. During summer, chubs were the least active, especially during daylight hours. Most of the fish tagged were estimated to be adults based on size; 84 percent of fish tagged in this study were greater than 100 millimeters (mm) total length (TL). One chub monitored during this study (139 mm TL when tagged) was observed for a total of 714 days following capture, indicating that chub can survive at least 3 years. Furthermore, two fish greater than 200 mm TL when tagged were detected for another 7 months after tagging, which supports life history descriptions in the Recovery Plan that states Pahranagat roundtail chub can reach 250 mm TL (U.S. Fish and Wildlife Service, 1998). In addition to natural mortality events, fish may die from extreme temperatures or other environmental stressors. None of the fish tagged in 2014 or 2015 were detected past August 31, 2016, which suggests that there may have been some external influence causing mortality of the few remaining fish from May 1, 2016, to August 31, 2016. Although habitat for chub has been limited for decades to a very small section of the Pahranagat River and the Pahranagat Ditch (U.S. Fish and Wildlife Service, 1998), this study suggests that recent declining numbers of chub are most likely due to mortality events and not due to the fish emigrating from the system through the Pahranagat Ditch or the Pahranagat Drain.

Nevada↗

USGS2017

Inter-annual variability in apparent relative production, survival, and growth of juvenile Lost River and shortnose suckers in Upper Klamath Lake, Oregon, 2001–15

Executive Summary Populations of the once abundant Lost River ( Deltistes luxatus ) and shortnose suckers ( Chasmistes brevirostris ) of the Upper Klamath Basin, decreased so substantially throughout the 20th century that they were listed under the Endangered Species Act in 1988. Major landscape alterations, deterioration of water quality, and competition with and predation by exotic species are listed as primary causes of the decreases in populations. Upper Klamath Lake populations are decreasing because fish lost due to adult mortality, which is relatively low for adult Lost River suckers and variable for adult shortnose suckers, are not replaced by new young adult suckers recruiting into known adult spawning aggregations. Catch-at-age and size data indicate that most adult suckers presently in Upper Klamath Lake spawning populations were hatched around 1991. While, a lack of egg production and emigration of young fish (especially larvae) may contribute, catch-at-length and age data indicate high mortality during the first summer or winter of life may be the primary limitation to the recruitment of young adults. The causes of juvenile sucker mortality are unknown. We compiled and analyzed catch, length, age, and species data on juvenile suckers from Upper Klamath Lake from eight prior studies conducted from 2001 to 2015 to examine annual variation in apparent production, survival, and growth of young suckers. We used a combination of qualitative assessments, general linear models, and linear regression to make inferences about annual differences in juvenile sucker dynamics. The intent of this exercise is to provide information that can be compared to annual variability in environmental conditions with the hopes of understanding what drives juvenile sucker population dynamics. Age-0 Lost River suckers generally grew faster than age-0 shortnose suckers, but the difference in growth rates between the two species varied among years. This unsynchronized annual variation in daily growth may be an indication that environmental conditions are affecting growth rates of these species in different ways. The combined evidence outlined in this report and in Simon and others (2012) indicates that years of relatively high age-0 sucker production occurred in the late 1990s through at least 2000, in 2006, and in 2011. Our analysis of annual age-0 sucker catch per unit effort (CPUE), which accounted for zero inflated data and annual variation in sampling gears and locations, indicated that 2006 had the greatest apparent relative production of age-0 suckers ≥ 45 mm standard length (SL) during the time period examined. Midsummer trap net effort by the U.S. Geological Survey (USGS) was too sparse to examine age-0 sucker CPUE from 2011 to 2013. Relatively frequent catches of age-1 suckers in 2001, 2007, and 2012 corroborated relatively high CPUE for age-0 suckers during 1999–2000, 2006, and 2011, as reported by USGS or Simon and others (2012). There were several indications in the data that juvenile sucker survival is low from at least midsummer of the first year of life through mid-September of the second year of life. Our estimated index of relative apparent age-0 sucker late-summer survival, which accounted for zero inflated data and variations in sampling gears and locations, was higher in 2009 than in 2004. Our index of apparent age-0 sucker mortality for all other years from 2001 to 2015 was similar among years. Seventy-five percent of age-1 suckers were captured prior to July 17 each year. In 2007, the one year with substantial age-1 sucker summertime catches, the proportion of nets to capture age-1 suckers decreased from July to mid-September. Maximum annual age-2+ sucker CPUE was 0.02 fish per net, 10,000 times less than the maximum annual age-0 sucker CPUE. Analysis of species data indicated that juvenile Lost River suckers may have greater apparent mortality than shortnose suckers. Lost River suckers made up a smaller proportion of age-0 suckers captured in July each year than would be expected, based on the abundance of adult Lost River suckers relative to shortnose suckers, and higher Lost River than shortnose sucker fecundity. The proportion of age-0 suckers captured that were Lost River suckers decreased from July to September in several years. Only 14 percent of age-1 or older juvenile suckers identified to species over the 15-year time period were Lost River suckers.

Oregon↗

USGS2013

Effects of Chiloquin Dam on spawning distribution and larval emigration of Lost River, shortnose, and Klamath largescale suckers in the Williamson and Sprague Rivers, Oregon

Chiloquin Dam was constructed in 1914 on the Sprague River near the town of Chiloquin, Oregon. The dam was identified as a barrier that potentially inhibited or prevented the upstream spawning migrations and other movements of endangered Lost River ( Deltistes luxatus Chasmistes brevirostris ) suckers, as well as other fish species. In 2002, the Bureau of Reclamation led a working group that examined several alternatives to improve fish passage at Chiloquin Dam. Ultimately it was decided that dam removal was the best alternative and the dam was removed in the summer of 2008. The U.S. Geological Survey conducted a long-term study on the spawning ecology of Lost River, shortnose, and Klamath largescale suckers ( Catostomus snyderi ) in the Sprague and lower Williamson Rivers from 2004 to 2010. The objective of this study was to evaluate shifts in spawning distribution following the removal of Chiloquin Dam. Radio telemetry was used in conjunction with larval production data and detections of fish tagged with passive integrated transponders (PIT tags) to evaluate whether dam removal resulted in increased utilization of spawning habitat farther upstream in the Sprague River. Increased densities of drifting larvae were observed at a site in the lower Williamson River after the dam was removed, but no substantial changes occurred upstream of the former dam site. Adult spawning migrations primarily were influenced by water temperature and did not change with the removal of the dam. Emigration of larvae consistently occurred about 3-4 weeks after adults migrated into a section of river. Detections of PIT-tagged fish showed increases in the numbers of all three suckers that migrated upstream of the dam site following removal, but the increases for Lost River and shortnose suckers were relatively small compared to the total number of fish that made a spawning migration in a given season. Increases for Klamath largescale suckers were more substantial. Post-dam removal monitoring only included 2 years with below average river discharge during the spawning season; data from years with higher flows may provide a different perspective on the effects of dam removal on the spawning migrations of the two endangered sucker species.

Oregon↗

USGS2012

Patterns of larval sucker emigration from the Sprague and lower Williamson Rivers of the Upper Klamath Basin, Oregon, after the removal of Chiloquin Dam - 2009-10 Annual Report

Executive Summary In 2009 and 2010, drift samples were collected from six sites on the lower Sprague and Williamson Rivers to assess drift patterns of larval Lost River suckers ( Deltistes luxatus ) (LRS) and shortnose suckers ( Chasmistes brevirostris ) (SNS). The objective of this study was to characterize the drift timing, relative abundance, and growth stage frequencies of larval suckers emigrating from the Sprague River watershed. These data were used to evaluate changes in spawning distribution of LRS and SNS in the Sprague River after the 2008 removal of Chiloquin Dam. Drift samples were collected at four sites on the Sprague River and one site each on the Williamson and Sycan Rivers. Data presented in this report is a continuation of a research project that began in 2004. Larval drift parameters measured in 2009 and 2010 were similar to those measured from 2004 to 2008. Most larvae and eggs were collected at the two drift sites downstream of the former Chiloquin Dam (river kilometer 0.7 on the Sprague River and river kilometer 7.4 on the Williamson River). Mean and peak sample densities increased with proximity to Upper Klamath Lake. Peak larval densities continued to be collected between 1 and 3 hours after sunset at Chiloquin, which is the drift site nearest a known spawning area. Catch distribution of larvae and eggs in the lower Sprague and Williamson Rivers suggests that most SNS and LRS spawning continues to occur downstream of the site of the former Chiloquin Dam. The sizes and growth stages indicate that larval emigration from spawning areas resulting from drift occurs within a few days after swim-up. Larval suckers appear to move downstream quickly until they reach suitable rearing habitat.

Oregon↗

USGS2011

Assessment of two nonnative poeciliid fishes for monitoring selenium exposure in the endangered desert pupfish

We assessed the suitability of two nonnative poeciliid fishes—western mosquitofish ( Gambusia affinis ) and sailfin mollies ( Poecilia latipinna )—for monitoring selenium exposure in desert pupfish ( Cyprinodon macularius ). Our investigation was prompted by a need to avoid lethal take of an endangered species (pupfish) when sampling fish for chemical analysis. Total selenium (SeTot) concentrations in both poeciliids were highly correlated with SeTot concentrations in pupfish. However, mean SeTot concentrations varied among fish species, with higher concentrations measured in mosquitofish than in mollies and pupfish from one of three sampled agricultural drains. Moreover, regression equations describing the relationship of selenomethionine to SeTot differed between mosquitofish and pupfish, but not between mollies and pupfish. Because selenium accumulates in animals primarily through dietary exposure, we examined fish trophic relationships by measuring stable isotopes ( δ 13 C and δ 15 N) and gut contents. According to δ 13 C measurements, the trophic pathway leading to mosquitofish was more carbon-depleted than trophic pathways leading to mollies and pupfish, suggesting that energy flow to mosquitofish originated from allochthonous sources (terrestrial vegetation, emergent macrophytes, or both), whereas energy flow to mollies and pupfish originated from autochthonous sources (filamentous algae, submerged macrophytes, or both). The δ 15 N measurements indicated that mosquitofish and mollies occupied similar trophic levels, whereas pupfish occupied a slightly higher trophic level. Analysis of gut contents showed that mosquitofish consumed mostly winged insects (an indication of terrestrial taxa), whereas mollies and pupfish consumed mostly organic detritus. Judging from our results, only mollies (not mosquitofish) are suitable for monitoring selenium exposure in pupfish.

Water, Air, & Soil Pollution↗

USGS2011

Selenium in aquatic biota inhabiting agricultural drains in the Salton Sea Basin, California

Resource managers are concerned that water conservation practices in irrigated farmlands along the southern border of the Salton Sea, Imperial County, California, could increase selenium concentrations in agricultural drainwater and harm the desert pupfish ( Cyprinodon macularius ), a federally protected endangered species. As part of a broader attempt to address this concern, we conducted a 3-year investigation to collect baseline information on selenium concentrations in seven agricultural drains inhabited by pupfish. We collected water, sediment, selected aquatic food-chain taxa (particulate organic detritus, filamentous algae, net plankton, and midge [Chironomidae] larvae), and two poeciliid fishes (western mosquitofish Gambusia affinis and sailfin molly Poecilia latipinna ) for selenium determinations. The two fish species served as ecological surrogates for pupfish, which we were not permitted to sacrifice. Dissolved selenium ranged from 0.70 to 32.8 μg/L, with selenate as the major constituent. Total selenium concentrations in other environmental matrices varied widely among drains, with one drain (Trifolium 18) exhibiting especially high concentrations in detritus, 5.98–58.0 μg Se/g; midge larvae, 12.7–50.6 μg Se/g; mosquitofish, 13.2–20.2 μg Se/g; and mollies, 12.8–30.4 μg Se/g (all tissue concentrations are based on dry weights). Although toxic thresholds for selenium in fishes from the Salton Sea are still poorly understood, available evidence suggests that ambient concentrations of this element may not be sufficiently elevated to adversely affect reproductive success and survival in selenium-tolerant poeciliids and pupfish.

Environmental Monitoring and Assessment↗

USGS2011

Unusual dominance by desert pupfish (Cyprinodon macularius) in experimental ponds within the Salton Sea Basin

In October 2006, months after shallow experimental ponds in the Salton Sea Basin were filled with water from the Alamo River and Salton Sea, fish were observed in several ponds, although inlets had been screened to exclude fish. During October 2007–November 2009, nine surveys were conducted using baited minnow traps to document species and relative abundance of fish. Surveys yielded 3,620 fish representing five species. Desert pupfish ( Cyprinodon macularius ), the only native species encountered, was the most numerous and comprised >93% of the catch. Nonnative species included western mosquitofish ( Gambusia affinis , 4.1%), sailfin molly ( Poecilia latipinna , 2.8%), and tilapia (a mixture of hybrid Mozambique tilapia Oreochromis mossambicus × O. urolepis and redbelly tilapia Tilapia zillii , <0.1%). Dominance by desert pupfish, which persisted over our 2 years of study, was unusual because surveys conducted in nearby agricultural drains yielded relatively few desert pupfish.

California↗

USGS2010

Final report: Baseline selenium monitoring of agricultural drains operated by the Imperial Irrigation District in the Salton Sea Basin

This report summarizes comprehensive findings from a 4-year-long field investigation to document baseline environmental conditions in 29 agricultural drains and ponds operated by the Imperial Irrigation District along the southern border of the Salton Sea. Routine water-quality collections and fish community assessments were conducted on as many as 16 sampling dates at roughly quarterly intervals from July 2005 to April 2009. The water-quality measurements included total suspended solids and total (particulate plus dissolved) selenium. With one exception, fish were surveyed with baited minnow traps at quarterly intervals during the same time period. However, in July 2007, fish surveys were not conducted because we lacked permission from the California Department of Fish and Game for incidental take of desert pupfish ( Cyprinodon macularius ), an endangered species. During April and October 2006–08, water samples also were collected from seven intensively monitored drains (which were selected from the 29 total drains) for measurement of particulate and dissolved selenium, including inorganic and organic fractions. In addition, sediment, aquatic food chain matrices [particulate organic detritus, filamentous algae, net plankton, and midge (chironomid) larvae], and two fish species (western mosquitofish, Gambusia affinis ; and sailfin molly, Poecilia latipinna ) were sampled from the seven drains for measurement of total selenium concentrations. The mosquitofish and mollies were intended to serve as surrogates for pupfish, which we were not permitted to sacrifice for selenium determinations. Water quality (temperature, dissolved oxygen, pH, specific conductance, and turbidity) values were typical of surface waters in a hot, arid climate. A few drains exhibited brackish, near-anoxic conditions, especially during summer and fall when water temperatures occasionally exceeded 30 degrees Celsius. Total selenium concentrations in water were directly correlated with salinity and inversely correlated with total suspended-solids concentrations. Although pupfish were found in several drains, sometimes in relatively high numbers, the fish faunas of most drains and ponds were dominated by nonnative species, especially mosquitofish, mollies, and red shiner ( Cyprinella lutrensis ). Dissolved selenium in water samples from the seven intensively monitored drains ranged from 0.700 to 32.8 micrograms per liter (?g/L), with selenate as the major constituent. Selenium concentrations in other matrices varied widely among drains and ponds, with one drain (Trifolium 18) exhibiting especially high concentrations in food chain matrices [particulate organic detritus, 5.98–58.0 micrograms of selenium per gram (?g Se/g); midge larvae, 12.7–50.6 ?g Se/g] and in fish (mosquitofish, 13.2–20.2 ?g Se/g; sailfin mollies, 12.8–30.4 ?g Se/g; all concentrations are based on dry weights). Although selenium was accumulated by all trophic levels, biomagnification (defined as a progressive increase in selenium concentration from one trophic level to the next higher level) in midge larvae and fish occurred only at lower exposure concentrations. Judging mostly from circumstantial evidence, the health and wellbeing of poeciliids and pupfish are not believed to be threatened by ambient exposure to selenium in the drains and ponds.

California↗

USGS2009

Mercury concentrations in fish from a Sierra Nevada foothill reservoir located downstream from historic gold-mining operations

This study examined mercury concentrations in whole fish from Camp Far West Reservoir, an 830-ha reservoir in northern California, USA, located downstream from lands mined for gold during and following the Gold Rush of 1848–1864. Total mercury (reported as dry weight concentrations) was highest in spotted bass (mean, 0.93 μg/g; range, 0.16–4.41 μg/g) and lower in bluegill (mean, 0.45 μg/g; range, 0.22–1.96 μg/g) and threadfin shad (0.44 μg/g; range, 0.21–1.34 μg/g). Spatial patterns for mercury in fish indicated high concentrations upstream in the Bear River arm and generally lower concentrations elsewhere, including downstream near the dam. These findings coincided with patterns exhibited by methylmercury in water and sediment, and suggested that mercury-laden inflows from the Bear River were largely responsible for contaminating the reservoir ecosystem. Maximum concentrations of mercury in all three fish species, but especially bass, were high enough to warrant concern about toxic effects in fish and consumers of fish.

California↗