Larry Brown

Larry Brown
United States Geological Survey | USGS · California Water Science Center

PhD

About

120
Publications
21,932
Reads
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4,420
Citations
Introduction
I have over 40 years of experience working in California aquatic systems studying ecology of California fishes, benthic macroinvertebrates and benthic algae. I am currently studying relations between tidal wetlands and fishes in the San Francisco Estuary, effects of climate change on fishes in the San Francisco Estuary and watershed, effects of altered flow regimes on California stream systems, and changes in trophic dynamics in the Sacramento-San Joaquin Delta.
Additional affiliations
January 1991 - January 2016
United States Geological Survey
Position
  • Research Biologist
September 1980 - August 1991
University of California, Davis
Position
  • Graduate student assistant to Post-graduate Researcher
Description
  • I had my graduate career and a post-doc at UC Davis before joining USGS.
Education
January 1983 - June 1988
University of California, Davis
Field of study
  • Ecology
September 1980 - December 1982
University of California, Davis
Field of study
  • Ecology
March 1979 - June 1980
University of California, Davis
Field of study
  • Wildlife and Fisheries Biology

Publications

Publications (120)
Article
Accurate estimates of abundance are a cornerstone for resource managers to make effective decisions for fish conservation. However, multiple sampling methods often are required to sample fish communities and ignoring the detection process can create substantial bias in latent state parameter estimation (e.g., abundance, survival). We developed a jo...
Article
Full-text available
Estuaries represent critical aquatic habitat that connects surface water distributed between Earth’s landmasses and oceans. They are dynamic transitional ecosystems, which provide important habitat for fishes and other aquatic organisms. Effective conservation of species inhabiting estuaries requires knowledge of the habitat features that drive the...
Article
Full-text available
Hydrodynamic processes can lead to the accumulation and/or dispersal of water column constituents, including sediment, phytoplankton, and particulate detritus. Using a combination of field observations and stable isotope tracing tools, we identified how hydrodynamic processes influenced physical habitat, pelagic communities, and food web structure...
Article
Full-text available
Many estuarine ecosystems and the fish communities that inhabit them have undergone substantial changes in the past several decades, largely due to multiple interacting stressors that are often of anthropogenic origin. Few are more impactful than droughts, which are predicted to increase in both frequency and severity with climate change. In this s...
Article
Full-text available
The Biological Condition Gradient (BCG) is a conceptual model that describes changes in aquatic communities under increasing levels of anthropogenic stress. The BCG helps decision-makers connect narrative water quality goals (e.g., maintenance of natural structure and function) to quantitative measures of ecological condition by linking index thres...
Preprint
Full-text available
Many estuarine ecosystems and the fish communities that inhabit them have undergone substantial changes in the past several decades, largely due to multiple interacting stressors that are often of anthropogenic origin. Few are more impactful than droughts, which are predicted to increase in both frequency and severity with climate change. In this s...
Preprint
Full-text available
Many estuarine ecosystems and the fish communities that inhabit them have undergone significant changes in the past several decades, largely due to multiple interacting stressors that are often of anthropogenic origin. Few are more impactful than droughts, which are predicted to increase in both frequency and severity with climate change. In this s...
Article
Full-text available
Quantifying the natural flow regime is essential for management of water resources and conservation of aquatic ecosystems. Understanding the degree to which anthropogenic activities have altered flows is critical for developing effective conservation strategies. Assessing flow alteration requires estimates of flows expected in the absence of human...
Article
Knowledge of the habitats occupied by species is fundamental for the development of effective conservation and management actions. The collapse of pelagic fish species in the Sacramento–San Joaquin Delta, California, has triggered a need to better understand factors that drive their distribution and abundance. A study was conducted in summer–fall 2...
Article
Full-text available
This paper reviews and highlights recent research findings on food web processes since an earlier review by Kimmerer et al. (2008). We conduct this review within a conceptual framework of the Delta– Suisun food web, which includes both temporal and spatial components. The temporal component of our framework is based on knowledge that the landscape...
Article
Full-text available
Anthropogenic climate change amounts to a rapidly approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated. Climate change is projected to cha...
Article
Full-text available
This paper reviews what has been learned about Delta Smelt and its status since the publication of The State of Bay-Delta Science, 2008 (Healey et al. 2008). The Delta Smelt is endemic to the upper San Francisco Estuary. Much of its historic habitat is no longer available and remaining habitat is increasingly unable to sustain the population. As a...
Article
Full-text available
Long-term fish sampling data from the San Francisco Estuary were combined with detailed threedimensional hydrodynamic modeling to investigate the relationship between historical fish catch and hydrodynamic complexity. Delta Smelt catch data at 45 stations from the Fall Midwater Trawl (FMWT) survey in the vicinity of Suisun Bay were used to develop...
Article
Many advances in the field of bioassessment have focused on approaches for objectively selecting the pool of reference sites used to establish expectations for healthy waterbodies, but little emphasis has been placed on ways to evaluate the suitability of the reference-site pool for its intended applications (e.g., compliance assessment vs ambient...
Article
Full-text available
Climate change is driving rapid changes in environmental conditions and affecting population and species’ persistence across spatial and temporal scales. Integrating climate change assessments into biological resource management, such as conserving endangered species, is a substantial challenge, partly due to a mismatch between global climate forec...
Data
Calculated water temperatures for the GFDL-B1 climate change scenario. (XLSX)
Data
Median, minimum, and maximum values for the number of days each year when mean daily water temperature is ≥CLTmax, during each decade from 2010–2099, for the juvenile life stage of Delta Smelt (June-December) for the least-warming (PCM-B1), most-warming (GFDL-A2) and two intermediate (PCM-A2 and GFDL-B1) climate change scenarios. (PDF)
Data
Methods and results for measurements of north Delta water temperature. (PDF)
Data
Calculated water temperatures for the PCM-A2 climate change scenario. (XLSX)
Data
Calculated water temperatures for the GFDL-A2 climate change scenario. (XLSX)
Data
Median, minimum, and maximum values for the number of days per year when mean daily water temperature is ≥24°C, during each decade from 2010–2099, for the juvenile life stage of Delta Smelt (June-December) for the least-warming (PCM-B1), most-warming (GFDL-A2) and two intermediate (PCM-A2 and GFDL-B1) climate change scenarios. (PDF)
Data
Median, minimum, and maximum values for the number of days per year for the duration of the maturation window (last day of 24°C to beginning of the spawning window) during each decade from 2010–2099, for the adult life stage of Delta Smelt for the least-warming (PCM-B1), most-warming (GFDL-A2) and two intermediate (PCM-A2 and GFDL-B1) climate chang...
Data
Calculated water temperatures for the PCM-B1 climate change scenario. (XLSX)
Data
Median, minimum, and maximum values for the number of days per year for the duration of the spawning window (15–20°C), during each decade from 2010–2099, for the adult life stage of Delta Smelt for the least-warming (PCM-B1), most-warming (GFDL-A2) and two intermediate (PCM-A2 and GFDL-B1) climate change scenarios. (PDF)
Data
Median, minimum, and maximum values for the julian date of the beginning of the maturation window (last day of 24°C to beginning of the spawning window) each year during each decade from 2010–2099, for the adult life stage of Delta Smelt for the least-warming (PCM-B1), most-warming (GFDL-A2) and two intermediate (PCM-A2 and GFDL-B1) climate change...
Data
Median, minimum, and maximum values for the julian date of the beginning of the spawning window (15–20°C) each year, during each decade from 2010–2099, for the adult life stage of Delta Smelt for the least-warming (PCM-B1), most-warming (GFDL-A2) and two intermediate (PCM-A2 and GFDL-B1) climate change scenarios. (PDF)
Article
Full-text available
Estuaries are dynamic environments at the land-sea interface that are strongly affected by inter-annual climate variability. Ocean-atmosphere processes propagate into estuaries from the sea and atmospheric processes over land propagate into estuaries from watersheds. We examined the effects of these two separate climate-driven processes on pelagic...
Article
Full-text available
We used boosted regression trees (BRT) to model stream biological condition as measured by benthic macroinvertebrate taxonomic completeness, the ratio of observed to expected (O/E) taxa. Models were developed with and without exclusion of rare taxa at a site. BRT models are robust, requiring few assumptions compared with traditional modeling techni...
Technical Report
Full-text available
Executive Summary The main purpose of this report is to provide an up-to-date assessment and conceptual model of factors affecting Delta Smelt (Hypomesus transpacificus) throughout its primarily annual life cycle and to demonstrate how this conceptual model can be used for scientific and management purposes. The Delta Smelt is a small estuarine fi...
Article
Full-text available
We developed independent predictive disturbance models for a full regional data set and four individual ecoregions (Full Region vs. Individual Ecoregion models) to evaluate effects of spatial scale on the assessment of human landscape modification, on predicted response of stream biota, and the effect of other possible confounding factors, such as...
Article
Full-text available
Tidal marsh restoration is an important management issue in the San Francisco Estuary (estuary). Restoration of large areas of tidal marsh is ongoing or planned in the lower estuary (up to 6,000 ha, Callaway et al. 2011). Large areas are proposed for restoration in the upper estuary under the Endangered Species Act biological opinions (3,237 ha) an...
Article
Full-text available
Predictive models have been used to determine fish species that occur less frequently than expected (decreasers) and those that occur more frequently than expected (increasers) in streams in the eastern U.S. Coupling life history traits with 51 decreaser and 38 increaser fish species provided the opportunity to examine potential mechanisms associat...
Article
Full-text available
The authors developed a simple screening-level model of exposure of aquatic species to pyrethroid insecticides for the lower American River watershed (California, USA). The model incorporated both empirically derived washoff functions based on existing, small-scale precipitation simulations and empirical data on pyrethroid insecticide use and water...
Article
Full-text available
Benthic macroinvertebrates are integral components of stream ecosystems and are often used to assess the ecological integrity of streams. We sampled streams in the upper Clear Creek drainage in the Klamath–Siskiyou Ecoregion of northwestern California in fall 2004 (17 sites) and 2005 (original 17 plus 4 new sites) with the objectives of documenting...
Technical Report
Full-text available
Urban development is an important agent of environmental change in the United States. The urban footprint on the American landscape has expanded during a century and a half of almost continuous development. Eighty percent of Americans now live in metropolitan areas, and the advantages and challenges of living in these developed areas—convenience, c...
Data
Full-text available
The U.S. Geological Survey, in cooperation with the National Park Service and Whiskeytown National Recreation Area, performed a comprehensive aquatic biota survey of the upper Clear Creek watershed, Shasta County, California, during 2004-5. Data collected in this study can provide resource managers with information regarding aquatic resources, wate...
Article
Full-text available
As understanding of the complex relations among environmental stressors and biological responses improves, a logical next step is predictive modeling of biological condition at unsampled sites. We developed a boosted regression tree (BRT) model of biological condition, as measured by a benthic macroinvertebrate index of biotic integrity (BIBI), for...
Conference Paper
In Fall 2011, a number of studies were implemented by the Bureau of Reclamation (Reclamation) in cooperation with the Interagency Ecological Program to explore hypotheses about the importance of low salinity habitat (LSH) and its distribution to the ecology of the Sacramento-San Joaquin Delta (Delta), and specifically the biology of delta smelt Hyp...
Article
Full-text available
We aggregated invertebrate data from various sources to assemble data for modeling in two ecore-gions in Oregon and one in California. Our goal was to compare the performance of models developed using mul-tiple linear regression (MLR) techniques with models developed using three relatively new techniques: classification and regression trees (CART),...
Article
Full-text available
Pesticides applied on land are commonly transported by runoff or spray drift to aquatic ecosystems, where they are potentially toxic to fishes and other nontarget organisms. Pesticides add to and interact with other stressors of ecosystem processes, including surface-water diversions, losses of spawning and rearing habitats, nonnative species, and...
Article
Full-text available
Human effects on estuaries are often associated with major decreases in abundance of aquatic species. However, remediation priorities are difficult to identify when declines result from multiple stressors with interacting sublethal effects. The San Francisco Estuary offers a useful case study of the potential role of contaminants in declines of org...
Data
Sediment rating curve for the Sacramento River at Rio Vista, 1998–2002. (TIF)
Data
GFDL and PCM scenarios for suspended sediment concentration (SSC) in the Sacramento River at Rio Vista for constant and decreasing sediment supply. Each band represents the interquartile range of SSC. (TIF)
Data
Effects of high river flows on errors in modeled annual average Delta water temperatures. Difference between modeled and observed yearly average water temperature is compared to the annually averaged Sacramento River flow; model-observation deviations occur in years with high river flow. (TIF)
Data
Mean annual turbidity, declining throughout the Sacramento-San Joaquin Delta from 1975–2008. From monthly data provided by California Department of Water Resources, Environmental Monitoring Program. (TIF)
Data
Expanded description of methods with supporting references. (RTF)
Article
Full-text available
Accumulating evidence shows that the planet is warming as a response to human emissions of greenhouse gases. Strategies of adaptation to climate change will require quantitative projections of how altered regional patterns of temperature, precipitation and sea level could cascade to provoke local impacts such as modified water supplies, increasing...
Conference Paper
The San Francisco Estuary is the largest estuary on the west coast of the United States. As with many other estuaries, it has been highly altered by human activity. Over the past several decades, the ecosystems of the San Francisco estuary and watershed have undergone a substantial series of changes that have been associated with marked declines in...
Conference Paper
Like other estuaries on the Pacific Coast, the fish community of the San Francisco represents a rich and diverse combination of freshwater, marine and brackish water species. However, heavy urbanization in the surrounding watershed, water diversions, habitat degradation, and a remarkable number of invasive species has had severe effects on many fis...
Conference Paper
Abundance indices for four pelagic fishes (native delta smelt and longfin smelt and introduced threadfin shad and age-0 striped bass) in the upper San Francisco Estuary declined rapidly and unexpectedly to record low levels starting in 2002. In 2005, the Interagency Ecological Program (IEP) formed an interagency team to evaluate the potential cause...
Conference Paper
The San Joaquin Restoration Program (SJRRP) was established to restore 153 miles of the San Joaquin River, one of California’s largest rivers. Following completion of Friant Dam and subsequent diversions of water, sections of this reach of the river have been dry during much of the past 60 years. The legal settlement establishing SJRRP requires res...
Article
Full-text available
Changes in water temperatures caused by climate change in California’s Sacramento–San Joaquin Delta will affect the ecosystem through physiological rates of fishes and invertebrates. This study presents statistical models that can be used to forecast water temperature within the Delta as a response to atmospheric conditions. The daily average model...
Article
Full-text available
We studied the effects of predatory Sacramento squawfish (Ptychocheilus grandis) on habitat choice of juvenile California roach (Lavinia symmetricus), adult roach, and juvenile rainbow trout (Oncorhynchus mykiss) in artificial streams. In single-prey trials, the proportion of fish found in pool habitat declined in the presence of squawfish for juve...
Article
Full-text available
The Sacramento squawfish (Ptychocheilus grandis), a piscivorous cyprinid, was recently (ca. 1979) introduced into the Eel River, California, USA. We compared habitat and microhabitat use of resident fishes between areas where squawfish were present and absent at one location and between years before and after invasion by squawfish at a second locat...
Article
Full-text available
Changes in the position of the low salinity zone, a habitat suitability index, turbidity, and water temperature modeled from four 100-year scenarios of climate change were evaluated for possible effects on delta smelt Hypomesus transpacificus, which is endemic to the Sacramento–San Joaquin Delta. The persistence of delta smelt in much of its curren...
Article
Full-text available
The successful use of macroinvertebrates as indicators of stream condition in bioassessments has led to heightened interest throughout the scientific community in the prediction of stream condition. For example, predictive models are increasingly being developed that use measures of watershed disturbance, including urban and agricultural land-use,...
Conference Paper
We evaluated the possible effects on fishes of changes in water temperatures generated by four 100-year scenarios of climate change for the San Francisco estuary and watershed. Input data used to model water temperatures were from two regional climate models at two levels of greenhouse gas emissions. There were significant increasing trends for wat...
Article
Four species of pelagic fish of particular management concern in the upper San Francisco Estuary, California, USA, have declined precipitously since ca. 2002: delta smelt (Hypomesus transpacificus), longfin smelt (Spirinchus thaleichthys), striped bass (Morone saxatilis), and threadfin shad (Dorosoma petenense). The estuary has been monitored since...
Article
We examined trends in abundance of four pelagic fish species (delta smelt, longfin smelt, striped bass, and threadfin shad) in the upper San Francisco Estuary, California, USA, over 40 years using Bayesian change point models. Change point models identify times of abrupt or unusual changes in absolute abundance (step changes) or in rates of change...
Article
Full-text available
We examined associations of fish assemblages and fish traits with urbanization and selected environmental variables in nine major United States metropolitan areas. The strongest relations between fishes and urbanization occurred in the metropolitan areas of Atlanta, Georgia; Birmingham, Alabama; Boston, Massachusetts; and Portland, Oregon. In these...
Article
Full-text available
Studies of the effects of urbanization on stream ecosystems have usually focused on single metropolitan areas. Synthesis of the results of such studies have been useful in developing general conceptual models of the effects of urbanization, but the strength of such generalizations is enhanced by applying consistent study designs and methods to mult...
Article
Full-text available
Corbicula fluminea is well known as an invasive filter-feeding freshwater bivalve with a variety of effects on ecosystem processes. However, C. fluminea has been relatively unstudied in the rivers of the western United States. In June 2003, we sampled C. fluminea at 16 sites in the San Joaquin River watershed of California, which was invaded by C....