Robert A. Leidy

• PhD
• Ecologist at University of California, Berkeley

Intermittent streams that cease to flow during dry periods represent more than half of the global river network, and are particularly common in arid and semi‐arid regions. They are characterised by high spatial and temporal variability in aquatic habitat, forming a shifting habitat mosaic that supports diverse assemblages of native and endemic spec...

Since 1970, there has been an overall decline in wildlife populations in the order of 52%. Freshwater species populations have declined by 76%; species populations in Central and South America have declined by 83%; and in the Indo-Pacific by 67%. These are often not complete extinctions, but large declines in the numbers of animals in each species,...

Chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), has contributed to amphibian declines globally, but drivers of outbreaks vary locally. Here we explore the role of drought in population and host-disease dynamics of the endangered stream-breeding foothill yellow-legged frog (Rana boylii). In central California (...

Streamflow duration information underpins many management decisions. However, hydrologic data are rarely available where needed. Rapid streamflow duration assessment methods (SDAMs) classify reaches based on indicators that are measured in a single brief visit. We evaluated a proposed framework for developing SDAMs to develop an SDAM for the Arid W...

The third in a series of Streamflow Duration Assessment Methods being developed cooperatively by the U.S. Environmental Protection Agency and the U.S. Army Corps of Engineers for nationwide coverage.

During the spring of 2006, we observed predation by California whiptail (Aspidoscelis tigris munda) on the endemic coastal roach (Hesperoleucus venustus) from an isolated pool along an intermittent reach of Coyote Creek, Santa Clara County, California, USA. Our observation is the first published record, to the best of our knowledge, of a whiptail i...

Freshwater biodiversity loss exceeds that in terrestrial systems; fishes are a predominant indicator of this catastrophe. Current worldwide estimates of freshwater fish species threatened with extinction are about 30%. We discuss why standard monitoring of the status of most fishes is inadequate to keep up with declines. Rapid population declines a...

Caddisflies within the genus Gumaga are generally considered shredders (i.e., consumers of leaf litter) or grazers (i.e., consumers of algae). We report on observations of Gumaga nigricula scavenging animal carcasses within and adjacent to isolated pools along intermittent reaches of Coyote Creek, Santa Clara County, California, USA. In particular,...

.—During the summers of 2015 and 2018, we observed predation on Foothill Yellow-legged Frogs (Rana boylii) by a giant water bug (Abedus indentatus), a California Red-legged Frog (Rana draytonii), and a Diablo Range Gartersnake (Thamnophis atratus zaxanthus) adjacent to 3 separate isolated pools along intermittent reaches of Coyote Creek, Santa Clar...

During late summer and fall 2014, we documented western pond turtle (Actinemys marmorata) mortality, as indicated by the presence of turtle shells, along a 3.7-km reach of Coyote Creek in the Diablo Range of central California. In total, we observed 39 western pond turtle shells scattered irregularly along our study reach. Shells were found in dry...

Urbanization is one of the leading threats to freshwater biodiversity, and urban regions continue to expand globally. Here we examined the relationship between recent urbanization and shifts in stream fish communities. We sampled fishes at 32 sites in the Alameda Creek Watershed, near San Francisco, California, in 1993-1994 and again in 2009, and w...

Background/Question/Methods The Alameda Creek Watershed is the largest watershed draining directly into San Francisco Bay and supports a diverse fish assemblage. This watershed has experienced considerable human population growth in recent years, leading us to ask how land change has influenced the fish community. In 2009, we resampled 70 sites a...

Download full text at https://www.sfei.org/documents/alameda-creek-watershed-historical-ecology-study

Background/Question/Methods There are approximately 70 small streams that flow directly into the San Francisco Bay (Bay), that vary in their surrounding landscape. Bay watersheds include high-density urban areas to rural agricultural landscapes. Broad scale spatial analyses utilizing GIS watershed tools can be useful in elucidating correlations b...

Many factors contribute to the nonrandom processes of extinctions and invasions that are changing the structure of ecological communities worldwide. These factors include the attributes of the species, their abiotic environment, and the interactions and feedbacks between them. The relative importance of these factors has been difficult to quantify....

There are approximately 70 small streams that flow directly into the San Francisco Bay (Bay), many of which are surrounded by highly urbanized landscapes. Urban development often leads to altered hydrographs and stream channel morphology, and high concentrations of contaminants. These physical changes can have ecological consequences. Broad scale s...

There are approximately 70 small streams that flow directly into the San Francisco Bay (Bay), many of which are surrounded by highly urbanized landscapes. Urban development often leads to altered hydrographs and stream channel morphology, as well as high concentrations of contaminants. These physical changes can have ecological consequences. Previo...

Urbanization is known to have pernicious consequences for native stream fishes globally. The San Francisco Estuary (SFE), California, is one of the largest, most urbanized estuaries in North America and non‐native freshwater fishes are widespread in many of its catchments. Nevertheless, a diverse native and endemic freshwater fish species assemblag...

Prepared for Contra Costa County and the Contra Costa Watershed

Background/Question/Methods The San Francisco Bay is the largest estuary on the West Coast of the United States, and is heavily invaded and urbanized. We studied the largest watershed draining into San Francisco Bay, Alameda Creek, which encompasses over 1554 km2 and a wide range of habitats from highly urbanized lowland reaches to relatively prist...

Reportamos una agregación no subterránea del sapo Rana boylii que ocurrió durante la última parte del verano en la sierra del Diablo, condado de Santa Clara, California. Nuestra observación provee el primer registro publicado de agregación en esta especie.

Background/Question/Methods The San Francisco Bay (Bay) is the largest estuary on the West Coast of the United States, and considered one of the most heavily invaded systems in the world. There are approximately 70 streams that flow into the Bay, many of which are surrounded by highly urbanized landscapes. Although these systems are heavily invaded...

California’s deserts are characterized by meager rainfall and, consequently, scattered sources of permanent surface water, extreme seasonal and diurnal fluctuations in temperature, diverse landforms, tortured geologic complexity, and myriad biogeochemical interactions. Together these factors support an often unappreciated, yet astonishingly singula...

Duffy and Kraus (2008) provide a broadly relevant and generally insightful overview of what plagues implementation of effective conservation science. That their overview is true is largely because many, if not all, of their insights and proffered solutions to remedy the ineffectiveness of conservation science apply globally. That is, one could repl...

Kaczynski and Alvarado (2006) have challenged the established southern boundary of coho salmon (Oncorhynchus kisutch) at the San Lorenzo River. They conclude that it is improbable coho salmon maintained self-sustaining populations south of San Francisco Bay, based primarily on evidence from early museum collections and literature, the archaeologica...

Thesis (Ph. D.)--University of California, Davis, 2004. Includes bibliographical references. Photocopy.

The historical status of coho salmon, Oncorhynchus kisutch, was assessed in 65 watersheds surrounding the San Francisco Estuary, California. We reviewed published literature, unpublished reports, field notes, and specimens housed at museum and university collections and public agency files. In watersheds for which we found historical information fo...

In the five years since we first reviewed the status of the world’s fishes (Moyle and Leidy 1992), there has been an explosion of new information on the conservation of aquatic organisms and their ecosystems. Notwithstanding this surge of interest, many aquatic ecosystems remain poorly understood because conservation biology remains primarily focus...

A brief precis of ecology is discussed, emphasizing the central theme of succession in the classical paradigm. This is followed by mention of the nonequilibrium paradigm and its central theme of patch dynamics. Conservation implications of this paradigm shift in ecology include (1) the replacement of a model in which some species are better adapted...

Thecontemporary paradigm in ecol- ogy,patch dynamicsanditslogicalcom- panions, ecosystemandlandscapeecol- ogy, quite recently has received signifi- cant attention in the ecological and con- servation literature (e.g., Botkin 1990, Gosselink et al. 1990,Keiter and Boyce 1991, Pulliarn and Danielson 1991, Salwasser 1991, Walker 1992, among many other...

This article describes the need to base environmental policy concerning wetlands on current understanding of natural systems. The authors highlight patterns of wildlife use within wetland habitats in the San Francisco Estuary. As a clear mandate of the Clean Water Act, federal protection should be given wetlands with highly variable seasonal hydrol...

Fishes are appropriate indicators of trends in aquatic biodiversity because their enormous variety reflects a wide range of environmental conditions. Fish also have a major impact on the distribution and abundance of other organisms in waters they inhabit. Examination of trends in freshwater fish faunas from different parts of the world indicate th...

Microhabitat selection by the johnny darter (Etheostoma nigrum) was examined in the North Laramie River, Platte County, Wyoming, where it does not occur with other darter species in the same stream reach. Electivity indices based on microhabitat observations indicate that E. nigrum avoids riffles and selects certain microhabitats characterized by i...

In order to receive a Department of Army permit to discharge dredged or fill material into “waters of the United States,” including wetlands, a permit applicant may have to clearly demonstrate that the proposed discharge is unavoidable and the least environmentally-damaging practicable alternative. Failure to do so as required under EPA’s 404(b)(1)...

One hundred and seventy-five streams within the basin of San Francisco Bay were sampled in summer 1981 to determine patterns of fish distribution and abundance. The species pool contains a small number of native species (11), many endemic, complemented by a larger number of exotic fishes (20), introduced primarily from the large riverine systems of...

Thesis (M.S. in Wildland Resource Science)--University of California, Berkeley, Dec. 1984. Includes bibliographical references (leaves 160-167).

Current federal regulatory limitations in protecting vernal pools can be attributed to incomplete data on the status of vernal pools statewide, lack of a methodology for assessing the functions of vernal pool ecosystems, failure to incorpo-rate contemporary ecological principles into the development of compensatory mitigation strategies, and a piec...