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San Francisco Bay, California is considered a mercury-impaired watershed. Elevated concentrations of mercury are found in water and sediment as well as fish and estuarine birds. Sources of mercury to the watershed since 1845 include sediment-associated mercury from mercury mining, mercury losses from gold amalgamation activities in mines of the Sierra Nevada, aerial deposition of mercury from global and regional emissions to air, and the direct discharge of mercury to Bay waters associated with the urbanization and industrialization of the estuary. We assessed historical trends in mercury bioaccumulation by measuring mercury concentrations in feathers of the endangered California Ridgway’s rail (formerly California...
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Tracklines and associated observations were mapped and analyzed using ArcMap (ESRI, Redlands, CA). GPS data were recorded in NAD27 map datum and projected to an USGS Albers Equal Area Conic map projection for presentation and subsequent density analyses. Concatenated GPS and observation data were then used to generate point and line coverages in ArcMap (ESRI, Redlands, CA). We designed a custom analytic tool using ArcMap Model Builder that allows for the construction and export of user-specified and effort-adjusted spatial binning of species observations along continuous trackines. For the purposes of this report, we calculated seabird density estimates and marine mammal counts along continuous 3.0-kilometer and...
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The GIS shapefile "Census summary of southern sea otter 2016" provides a standardized tool for examining spatial patterns in abundance and demographic trends of the southern sea otter (Enhydra lutris nereis), based on data collected during the spring 2016 range-wide census. The USGS range-wide sea otter census has been undertaken twice a year since 1982, once in May and once in October, using consistent methodology involving both ground-based and aerial-based counts. The spring census is considered more accurate than the fall count, and provides the primary basis for gauging population trends by State and Federal management agencies. This Shape file includes a series of summary statistics derived from the raw census...
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The spring 2016 mainland sea otter count began on 1 May and was completed on 11 May. Overall viewing conditions this year were very good, being more favorable than those during the 2015 spring census (3.1 vs. 2.6, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent) and contributed to the relatively short duration of the count. The surface canopies of kelp (Macrocystis sp.) were considered by most participants to be below normal for this time of year in the northern half of the range and about normal in the southern half. Sea otters along the mainland were surveyed (using a combination of ground-based and aerial-based surveys) from Pillar Point in San Mateo County in the north, to Rincon Point in the south...
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Background - Interest in developing alternative sources of renewable energy to reduce dependence on oil has increased in recent years. Some sources of renewable energy being considered will include power generation infrastructure and support activities located within continental shelf waters, and potentially within deeper waters off the U.S. Pacific coast and beyond state waters (i.e., outside three nautical miles). Currently, the Bureau of Ocean Energy Management (BOEM) is considering renewable energy proposals off the coast of Oregon, California, and Hawaii. From 1999–2002, the U.S. Geological Survey (USGS) and Humboldt State University (HSU) worked with BOEM (formely known as the Minerals Management Service,...
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The GIS shapfile "Range extent of southern sea otter 2016" is a simple polyline representing the geographic distribution of the southern sea otter (Enhydra lutris nereis) in mainland California, based on data collected during the spring 2016 range-wide census. The USGS range-wide sea otter census has been undertaken twice a year since 1982, once in May and once in October, using consistent methodology involving both ground-based and aerial-based counts. The spring census is considered more accurate than the fall count, and provides the primary basis for gauging population trends by State and Federal management agencies. Sea otter distribution in California (the mainland range) is considered to comprise a band of...
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The GIS layer "Census_sum_15" provides a standardized tool for examining spatial patterns in abundance and demographic trends of the southern sea otter (Enhydra lutris nereis), based on data collected during the spring 2015 range-wide census. The USGS range-wide sea otter census has been undertaken twice a year since 1982, once in May and once in October, using consistent methodology involving both ground-based and aerial-based counts. The spring census is considered more accurate than the fall count, and provides the primary basis for gauging population trends by State and Federal management agencies. This Shape file includes a series of summary statistics derived from the raw census data, including sea otter density...
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Sea otters are well-known tool users, employing objects such as rocks or shells to break open invertebrate prey. We used a series of generalized linear mixed effect models (GLMEs) to examine observational data on prey capture and tool use from 211 tagged individuals from five geographically defined study areas throughout the sea otter’s range in California. Our best supported model was able to explain 75% of the variation in the frequency of tool-use by individual sea otters with only ecological and demographic variables. In one study area, where sea otter food resources were abundant, all individuals had similar diets focusing on preferred prey items and used tools at low to moderate frequencies (4-38% of prey...
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The spring 2015 mainland sea otter count began on 2 May and wasn’t completed until 2 July. The delay in finishing the census was due primarily to limited availability of the survey plane (because of the need for the plane during the oil spill in the Refugio State Beach area). Overall viewing conditions this year were more favorable than those during the 2014 spring census (View Score = 2.6 vs. 2.3, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent). The surface canopies of kelp (Macrocystis sp.) were considered by most participants to be about normal for this time of year. Sea otters along the mainland were surveyed (using a combination of ground-based and aerial-based surveys) from Pillar Point...
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The GIS layer "Range_extent_15" is a simple polyline representing the geographic distribution of the southern sea otter (Enhydra lutris nereis) in mainland California, based on data collected during the spring 2015 range-wide census. The USGS range-wide sea otter census has been undertaken twice a year since 1982, once in May and once in October, using consistent methodology involving both ground-based and aerial-based counts. The spring census is considered more accurate than the fall count, and provides the primary basis for gauging population trends by State and Federal management agencies. Sea otter distribution in California (the mainland range) is considered to comprise a band of potential habitat stretching...
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Tracklines and associated observations were mapped and analyzed using ArcMap (ESRI, Redlands, CA). GPS data were recorded in NAD27 map datum and projected to an USGS Albers Equal Area Conic map projection for presentation and subsequent density analyses. Concatenated GPS and observation data were then used to generate point and line coverages in ArcMap (ESRI, Redlands, CA). We designed a custom analytic tool using ArcMap Model Builder that allows for the construction and export of user-specified and effort-adjusted spatial binning of species observations along continuous trackines. For the purposes of this report, we calculated seabird density estimates and marine mammal counts along continuous 3.0-kilometer and...
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The GIS shapefile "Extra limit observations 2016" is a point layer representing the locations of sea otter sightings that fall outside the officially recognized range of the southern sea otter (Enhydra lutris nereis) in mainland California. These data were collected during the spring 2016 range-wide census. The USGS range-wide sea otter census has been undertaken twice a year since 1982, once in May and once in October, using consistent methodology involving both ground-based and aerial-based counts. The spring census is considered more accurate than the fall count, and provides the primary basis for gauging population trends by State and Federal management agencies. Sea otter distribution in California (the mainland...
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This file contains the flight trackline Global Positioning System (GPS) point data from the aerial surveys. Surveys were flown at 60 meters (200 feet) above sea level at 160 kilometers per hour (90 knots) ground speed. The surveys were flown in a high-winged, twin engine Partenavia PN 68 Observer aircraft following methods developed for seabirds by Briggs et al. (1987). GPS points were recorded every five seconds to allow adequate spatial coverage of the trackline (222 meters is traversed every five seconds at the survey speed of 160 kilometers per hour) and to limit the size of the resulting data files. Data was collected using a laptop computer running the program dLOG (R.G. Ford Consulting, Inc.) that allowed...
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The goal of this project was to primarily assess east-west connectivity across Route 67 and secondarily, north-south connectivity across Scripps Poway Parkway and Poway Road, two highly trafficked roads to the west of Route 67. We collected deer scat piles from both sides of these crossings in spring between March and June of 2015, and again in fall throughout October 2015. Collected pellets were extracted and amplified using protocols and loci developed by Bohonak and Mitelberg (2014). DNA fingerprinting results were used to investigate mule deer movement in the region directly by identifying individuals which had been captured multiple times throughout the study period. We also assessed movement indirectly through...
    map background search result map search result map Historical methyl mercury in San Francisco Bay Annual California Sea Otter Census - 2015 Spring Census Summary 2015 Census Summary Shapefile 2015 Range Extent Shapefile DNA fingerprinting of Southern Mule Deer (Odocoileus hemionus fuliginatus) to determine movement across California State Route 67 Annual California Sea Otter Census - 2016 Spring Census Summary Annual California Sea Otter Census: 2016 Census Summary Shapefile Annual California Sea Otter Census: 2016 Extra limit observations shapefile Annual California Sea Otter Census: 2016 Range Extent Shapefile Bird Density and Marine Mammal Counts Based on 3000 Meter Bins in Southern California, 1999-2002 Bird Density and Marine Mammal Counts Based on 7700 Meter Bins in Southern California, 1999-2002 At-Sea Aerial Survey GPS Points in Southern California, 1999-2002 Tool-use frequency by individual sea otters in California DNA fingerprinting of Southern Mule Deer (Odocoileus hemionus fuliginatus) to determine movement across California State Route 67 2015 Range Extent Shapefile Annual California Sea Otter Census: 2016 Range Extent Shapefile Annual California Sea Otter Census - 2015 Spring Census Summary 2015 Census Summary Shapefile Annual California Sea Otter Census - 2016 Spring Census Summary Annual California Sea Otter Census: 2016 Census Summary Shapefile Tool-use frequency by individual sea otters in California At-Sea Aerial Survey GPS Points in Southern California, 1999-2002 Bird Density and Marine Mammal Counts Based on 7700 Meter Bins in Southern California, 1999-2002 Bird Density and Marine Mammal Counts Based on 3000 Meter Bins in Southern California, 1999-2002 Historical methyl mercury in San Francisco Bay