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At least 1,549 records · Page 86Linked to original sources
USGS2016

Sediment budgets, transport, and depositional trends in a large tidal delta

The Sacramento-San Joaquin Delta is the largest delta on the west coast of the United States. It is formed where the confluence of California’s two largest rivers (the Sacramento and San Joaquin) meet the ocean tides and has a significant physical gradient from fluvial to tidal. It is a semidiurnal system (two high and two low tides per day). Today, the Delta is one of the most manipulated in the United States. Once composed of many shallow, meandering and braided dendritic channels and dead-end sloughs and wetlands, it is now a network of leveed canals moving clear water around subsided islands. It historically has supported a biologically diverse tidal wetland complex, of which only 3% remains today (Whipple et al., 2012). It has also witnessed a collapse in the native fish populations. The Delta provides critical habitat for native species, however the hydrology and water quality are complicated by manipulations and diversions to satisfy multiple statewide objectives. Today water managers face co-equal goals of water supply to Californians and maintenance of ecosystem health and function. The Delta is a hub for both a multi-hundred-million dollar agricultural industry and a massive north-to-south water delivery system, supplying the primary source of freshwater to Central Valley farmers and drinking water for two-thirds of California’s population. Large pump facilities support the water demand and draw water from the Delta, further altering circulation patterns and redirecting the net flow toward the export facilities (Monsen et al., 2007). Fluvial sedimentation, along with organic accumulation, creates and sustains the Delta landscape. Hydraulic mining for gold in the watershed during the late 1800s delivered an especially large sediment pulse to the Delta. More recently, from 1955 to the present, a significant sediment decline has been observed that is thought to have been caused mostly by the construction of water storage reservoirs that trap the upstream sediment supply (Wright and Schoellhamer, 2004). Today, one concern is whether the volume of sediment supplied from the upper watershed is sufficient to support ecological function and sustain the Delta landscape and ecosystem in the face of climate change, sea level rise, and proposed restoration associated with the Bay Delta Conservation Plan (http://baydeltaconservationplan.com). Ecosystem health is a management focus and 150,000 acres of restoration is currently proposed, therefore it is of increasingly important to understand the quantity of sediment available for marsh and wetland restoration throughout the Bay Delta Estuary. It is also important to understand the pathways for sediment transport and the sediment budget into each of three Delta regions (figure 1) to guide restoration planning, modeling, and management.

California↗
USGS2002

Water withdrawals and trends in ground-water levels and stream discharge in Louisiana

In 2000, approximately 10,400 mgal/ d (million gallons per day) of water was withdrawn from ground - and surface- water sources in Louisiana , an increase of 10 percent from 1990. In 2000, about 16 percent (1,600 Mgal/ d ) of the water withdrawn was ground water . Approximately 93 percent of the ground water withdrawn was from four aquifers or aquifer systems: the Chicot aquifer system (49 percent), the Mississippi River alluvial aquifer (22 percent), the Sparta aquifer (4 percent), and the Southern Hills aquifer system (18 percent). Three of these, the Chicot aquifer system, the Sparta aquifer, and the Southern Hills aquifer system, contain areas where declines in ground - water levels from 1990-2000 are 1 ft/yr (foot per year) or greater. The Chicot aquifer system in southwestern Louisiana is the most heavily pumped aquifer or aquifer system in the State. By 2000, water levels in areas of Calcasieu, Jefferson Davis, and Acadia Parishes had declined to 50 feet or more below sea level. Water levels in areas of largest withdrawals declined as much as 1.7 ft/yr during the period 1990-2000. The Sparta aquifer in north-central Louisiana is the fourth most heavily pumped aquifer in the State. Approximately 68.2 Mgal/d was withdrawn in 2000. Water levels in the aquifer declined to more than 200 feet below sea level in the Monroe area by 1997. During 1990-2000, water level declines ranged from 0.1 to 5.2 ft/yr at monitor wells screened in the aquifer. The Southern Hills aquifer system of southeastern Louisiana is composed of numerous freshwater aquifers. This aquifer system is the third most heavily pumped aquifer or aquifer system in the State (291 Mgal/d in 2000). By the 1970's saltwater encroachment had been documented in major aquifers in the Baton Rouge area. Water levels in deep aquifers having largest withdrawals declined about 0.2 to 3.5 ft/yr or more during the period 1990-2000. In 2000, about 84 percent (8,700 Mgal/d) of the water withdrawn in Louisiana was surface water. Stream discharge data were analyzed for 59 continuous discharge stations. Eleven stations on nine streams had decreasing mean annual discharge during the period 1990-2000.

Louisiana↗
USGS1993

Population trends of Alaskan seabirds

Ornithology in Alaska formally began with the observations of Georg Wilhelm Steller during Vitus Bering's voyage of discovery in 1741. Steller's journal makes brief mention of various seabird species he encountered during his travels in the Gulf of Alaska and Aleutian Islands (Frost and Engel 1988). For more than 100 years following Steller, the Russian-American Company was active in commercial fur harvesting throughout southern coastal Alaska, but this period saw little contribution to a scientific understanding of the region's avifauna. With the purchase of Alaska by the United States in 1867, a period of American exploration began that included significant work by pioneering naturalists such as Dall (1873, 1874), Elliot (1881), Nelson (1883), and Turner (1885, 1886). While this activity established a comprehensive list and general knowledge of the distribution of seabird species occurring in Alaska, early observers provided no quantitative estimates of abundance for any colony or region. The observations of Heath (1915) and Willett (1912, 1915, 1917) at two locations in southeastern Alaska are notable for including the first numerical estimates of any seabird populations for comparison with recent data. Willett's (1912, 1915) estimates of 13 species are given in Table 1 with results from a 1976 Survey at Forrester Island (DeGange et al. 1977) and a 1981 survey at St. Lazaria Island (Nelson et al 1982). In the aggregate, seabird numbers appeared to increase dramatically at both sites, but the differences may be largely artificial. Because Willett (1915) did not employ rigorous sampling methods, DeGange et al. (1977) surmised that he grossly underestimated the populations of burrowing species such as storm-petrels, Cassin's Auklets. and Rhinoceros Aulkets. Nelson et al. (1982) offered a similar interpretation of total storm-petrel numbers at St. Lazaria, but felt that a shift in the species ratio of Leach's and Fork-tailed Storm-Petrels had likely occurred. It seems reasonably certain that real changes in some of the open-nesters like Common Murres (down at Forrester Island, up at St. Lazaria) and Glaucous-winged and Herring Gulls (absent or down at both sites) have occurred since Willet's time.

Alaska↗
USGS2017

The growth of sport shooting participation: What does this trend mean for conservation revenue?

Enacted in 1937, the Federal Aid in Wildlife Restoration Act – more commonly known as the Pittman-Robertson Act – is one of the oldest and most reliable sources of funding for wildlife conservation in the United States. The result of organized support form sportsmen, fish and wildlife agencies, firearms manufacturers, conservation organizations, and even garden clubs, the PR Act created an excise tax on so-called “long guns” and ammunition used by hunters, thereby establishing the first sustainable source of revenue dedicated to conservation and land management efforts throughout the country. Later, legislators amended the PR Act to include an excise tax on pistols, revolvers, bows, arrows, and other archery equipment.

The Wildlife Professional↗
USGS2015

Sampling to estimate population size and detect trends in Tricolored Blackbirds

The Tricolored Blackbird ( Agelaius tricolor ) is a medium-sized passerine that nests in the largest colonies of any North American landbird since the extinction of the passenger pigeon ( Ectopistes migratorius ) over 100 years ago (Beedy and Hamilton 1999). The species has a restricted range that occurs almost exclusively within California, with only a few hundred birds scattered in small groups in Oregon, Washington, Nevada, and northwestern Baja California, Mexico (Beedy and Hamilton 1999). Tricolored Blackbirds are itinerant breeders (i.e., breed more than once per year in different locations) and use a wide variety of nesting substrates (Hamilton 1998), many of which are ephemeral. They are also insect dependent during the breeding season, and reproductive success is strongly correlated with relative insect abundance (Meese 2013). Researchers have noted for decades that Tricolored Blackbird’s insect prey are highly variable in space and time; Payne (1969), for example, described the species as a grasshopper follower because they are preferred food items, and high grasshopper abundance is often associated with high reproductive success (Payne 1969, Meese 2013). Thus, the species’ basic reproductive strategy is tied to rather infrequent periods of relatively high insect abundance in some locations followed by much longer periods of range -wide relatively low insect abundance and poor reproductive success. Of course, anthropogenic factors such as habitat loss and insecticide use may be at least partly responsible for these patterns (Hallman et al. 2014, Airola et al. 2014).

Central Valley Bird Club Bulletin↗
USGS2017

Status and trends in the Lake Superior fish community, 2016

In 2016, the Lake Superior fish community was sampled with daytime bottom trawls at 76 nearshore and 35 offshore stations. Spring and summer water temperatures in 2016 were warmer than average and considerably warmer than observed in 2014 and 2015. In the nearshore zone, a total of 17,449 individuals from 20 species or morphotypes were collected. Nearshore lakewide mean biomass was 2.2 kg/ha, which was near the lowest biomass on record for this survey since it began in 1978. In the offshore zone, a total 8,487 individuals from 16 species or morphotypes were collected lakewide. Offshore lakewide mean biomass was 4.5 kg/ha, which was the lowest biomass recorded since the offshore survey began in 2011. The density of age-1 Cisco was 5.0 fish/ha, which was 35% of that measured in 2015. Larval Coregonus were collected in surface trawls at 144 locations lakewide from May to July. The average nearshore lakewide larval Coregonus density estimate was 1,630 fish/ha, which was similar to that estimated in 2015.

Lake Superior↗
USGS1982

Recent trends in the west Greenland salmon fishery, and implications for Thick-billed Murres

In the late 1960s and early 1970s, a high net-mortality of seabirds, particularly Thick-billed Murres ( Uria lomvia ), was associated with the west Greenland salmon fishery. Since 1972, the domestic fishery has been controlled by quotas and fishery opening dates and non-Greenlandic offshore drift-net fishery was phased out in 1975. These restrictions probably resulted in a substantial decrease in murre net-mortality. However, the Greenlandic fishery has changed considerably since 1972 when seabird bycatch was last examined in detail. Fishing vessels now use monofilament nylon nets almost exclusively; fishing effort has redistributed closer to murre breeding colonies and intensive drift-netting occurs offshore on the continental shelf. These factors, combined with a change in 1981 to a later fishing season have probably resulted in a renewal of significant murre net-morality at west Greenland.

Conference Paper↗
USGS1957

Water problems in the present trend towards greater aridity

In the past few days we have heard a number of scientists, gathered here at Scripps Institution of Oceanography, discuss research work which, in one manner or another, bears on problems related to water resources. They have been discussing, particularly, problems in the field of climatology, and have speculated on the meaning of the results of this research. One of the problems under discussion was the nature, and possible cause, of the climatic fluctuation which we have experienced in recent decades, and its relation to climatic changes in recent geologic time since the last glaciation. These discussions have given me the courage, or perhaps the recklessness, to indulge in some speculation relative to various aspects of water resource problems in the United States.

Conference Paper↗
USGS2018

A global audit of the status and trends of Arctic and Northern Hemisphere goose populations

This report attempts to review the abundance, status and distribution of natural wild goose populations in the northern hemisphere. The report comprises three parts that 1) summarise key findings from the study and the methodology and analysis applied; 2) contain the individual accounts for each of the 68 populations included in this report; and 3) provide the datasets compiled for this study which will be made accessible on the Arctic Biodiversity Data Service.

Report↗
USGS2018

Status and trends of pelagic prey fish in Lake Huron, 2017

Scientists from the U.S. Geological Survey’s Great Lakes Science Center conducted integrated acoustic and mid-water trawl surveys of Lake Huron in 1997 and annually from 2004-2017. The 2017 survey was conducted during September and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Mean lake-wide pelagic fish density was 1582 fish/ha and mean pelagic fish biomass was 10.5 kg/ha in 2017, which represents 96% and 93% of the long-term mean respectively. Mean lake-wide biomass was 23% higher in 2017 as compared to 2016. The total estimated lake-wide standing stock biomass of pelagic fish species, excluding cisco, was ~49 kt (± 10.4 kt), consisting almost entirely of bloater (26.8 kt; 55%) and rainbow smelt (22 kt; 45%), with small contributions from sticklebacks (0.13 kt; 0.26 %), emerald shiner (0.09 kt; 0.18%), and alewife (0.004kt; <0.005%). Age-0 rainbow smelt abundance increased from 155 fish/ha in 2016 to 598 fish/ha in 2017. Biomass of age-1+ rainbow smelt increased from 2.5 kg/ha in 2016 to 4.1 kg/ha in 2017. Age-0 bloater abundance increased from 94 fish/ha in 2016 to 342 fish/ha in 2017. Biomass of age-1+ bloater in 2017 (5.0 kg/ha) remained at levels similar to 2016 (5.2 kg/ha). Emerald shiner density decreased from 38.6 fish/ha in 2016 to 19.5 fish/ha in 2017. Emerald shiner biomass remained at 0.02 kg/ha between 2016-2017 which represented 19% of the long-term mean. Cisco lake-wide mean biomass was estimated at 2.2 kg/ha and mean density was estimated at 5.1 fish/ha in 2017. Bloater and rainbow smelt will likely continue to be the primary pelagic species available to offshore predators in coming years.

Michigan, Ontario↗
USGS2018

Barataria and Terrebonne Bays: Chapter F in Emergent wetlands status and trends in the northern Gulf of Mexico: 1950-2010

The study area included in the Barataria and Terrebonne Bays vignette of southeastern Louisiana spans eastward from Terrebonne Bay to Barataria Bay (Figure 1) and includes portions of Terrebonne, Lafourche, St. Charles, Jefferson, Orleans, Plaquemines, and St. Bernard Parishes. This area falls between the Mississippi River on the east and northeast, extends down through the western shore of Lake Salvador and the Dixie Delta Canal, then runs west to Houma and follows Louisiana Route 315 to the coast; Barataria and Terrebonne Bays are separated from each other by Bayou Lafourche.

Louisiana↗
USGS2018

Mississippi Delta: Chapter G in Emergent wetlands status and trends in the northern Gulf of Mexico: 1950-2010

The Mississippi River Delta, the tip of the longest river in North America, is located in the coastal plains of southeastern Louisiana. The study area included in the Mississippi River Delta vignette of southeastern Louisiana follows the Mississippi River southward from Port Sulphur within the modern Plaquemines-Balize Delta lobe (Figure 1). It extends eastward through Long Bay into California Bay and then encapsulates most of the land to the east of the river; it extends south into Lake Washington and Lake Robinson, then to the Gulf of Mexico, and includes the land to the west of the river. All of this area is within Plaquemines Parish. The mouth of the Mississippi includes four subdeltas (West Bay, Cubit’s Gap, Baptiste Collette, and Garden Island Bay) which began formation between 1839 and 1891 (Coleman and others, 1998). As of 2010, the total land area from Venice, LA to the gulf was 357.50 square km (138.03 square miles) and had ranged from 208.08 square km (80.34 square miles) to 393.70 square km (152.01 square miles) since 1973 (Couvillion and others, 2011).

Louisiana↗