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USGS2006

Nest fate and productivity of American Oystercatchers, Cumberland Island National Seashore, Georgia

The American Oystercatcher (Haematopus palliatus) is listed as a species of high priority by the U.S. Shorebird Conservation Plan and is state-listed as rare in Georgia; however, biologists have not focused on identifying the causes of egg and hatchling losses. In 2003 and 2004, continuous video monitoring was used to document reproductive success of American Oystercatchers and identify causes of nest failure at Cumberland Island National Seashore, Georgia. The modified Mayfield method and program CONTRAST were used to determine and compare survival of eggs and nestlings. Eleven pairs made 32 nest attempts during two seasons. Nine attempts were successful, fledging 15 chicks. Daily survival of clutches was 0.973 (95% CI = 0.960-0.987) for 2003, 0.985 (95% CI = 0.974-0.995) for 2004, and 0.979 (95% CI = 0.970-0.987) for combined years. Daily survival was greater on the North End, than on the South End of the island (X21 = 7.211, P = 0.007). Eighteen of 20 nest failures during the egg stage and one of eight chick losses were documented. Egg predators included raccoon (Procyon lotor, N = 9), bobcat (Lynx rufus, N = 3), and American Crow (Corvus brachyrhynchos, N = 1). A ghost crab (Ocypode quadata) preyed on one chick. Other causes of nest failure were tidal overwash (N = 1), horse trampling (N = 1), abandonment (N = 2), and human destruction (N = 1). The North End of the island has one of the highest reproductive rates reported along the Atlantic coast. Predator control may be an effective means of increasing reproductive success on the South End of the island.

Waterbirds↗

USGS2008

Importance of sampling design and analysis in animal population studies: a comment on Sergio et al

1. The use of predators as indicators and umbrellas in conservation has been criticized. In the Trentino region, Sergio et al. (2006; hereafter SEA) counted almost twice as many bird species in quadrats located in raptor territories than in controls. However, SEA detected astonishingly few species. We used contemporary Swiss Breeding Bird Survey data from an adjacent region and a novel statistical model that corrects for overlooked species to estimate the expected number of bird species per quadrat in that region. 2. There are two anomalies in SEA which render their results ambiguous. First, SEA detected on average only 6.8 species, whereas a value of 32 might be expected. Hence, they probably overlooked almost 80% of all species. Secondly, the precision of their mean species counts was greater in two-thirds of cases than in the unlikely case that all quadrats harboured exactly the same number of equally detectable species. This suggests that they detected consistently only a biased, unrepresentative subset of species. 3. Conceptually, expected species counts are the product of true species number and species detectability p. Plenty of factors may affect p, including date, hour, observer, previous knowledge of a site and mobbing behaviour of passerines in the presence of predators. Such differences in p between raptor and control quadrats could have easily created the observed effects. Without a method that corrects for such biases, or without quantitative evidence that species detectability was indeed similar between raptor and control quadrats, the meaning of SEA's counts is hard to evaluate. Therefore, the evidence presented by SEA in favour of raptors as indicator species for enhanced levels of biodiversity remains inconclusive. 4. Synthesis and application. Ecologists should pay greater attention to sampling design and analysis in animal population estimation. Species richness estimation means sampling a community. Samples should be representative for the community studied and the sampling fraction among communities compared should be the same on average, otherwise formal estimation approaches must be applied to avoid misleading inference.

Journal of Applied Ecology↗

USGS2010

Mechanical suppression of northern pike (Esox lucius) populations in small Arizona reservoirs

Introduced populations of northern pike Esox lucius have provided angling opportunities in the western United States (McMahon and Bennett 1996). However, the northern pike is a voracious piscivore and its large size, high fecundity, and broad physiological tolerance make it capable of drastically altering ecosystems it invades (Marchetti et al. 2004). Indeed, predation by northern pike has been shown to significantly alter fish community structure and put native fishes at a higher extinction risk (He and Kitchell 1990, Findlay et al. 2000). Predation by northern pike is viewed as a significant threat to native stocks of salmonids in Washington, British Columbia, and California (McMahon and Bennett 1996, California Department of Fish and Game [CDFG] 2003).

Arizona↗

USGS2011

Ecological influence and pathways of land use in sagebrush

Land use in sagebrush (Artemisia spp.) landscapes influences all sage-grouse (Centrocer-cus spp.) populations in western North America. Croplands and the network of irrigation canals cover 230,000 km2 and indirectly influence up to 77% of the Sage-Grouse Conservation Area and 73% of sagebrush land cover by subsidizing synanthropic predators on sage-grouse. Urbanization and the demands of human population growth have created an extensive network of con-necting infrastructure that is expanding its influence on sagebrush landscapes. Over 2,500 km 2 are now covered by interstate highways and paved roads; when secondary roads are included, 15% of the Sage-Grouse Conservation Area and 5% of existing sagebrush habitats are 2.5 km from roads. Density of secondary roads often exceeds 5 km/km 2 , resulting in widespread motorized access for recreation, creating extensive travel corridors for management actions and resource development, subsidizing predators adapted to human presence, and facilitating spread of exotic or invasive plants. Sagebrush lands also are being used for their wilderness and recreation values, including off highway vehicle use. Approximately 12,000,000 animal use months (AUM amount of forage to support one livestock unit per month) are permitted for grazing livestock on public lands in the western states. Direct effects of grazing on sage-grouse populations or sagebrush landscapes are not possible to assess from current data. However, management of lands grazed by livestock has influenced sagebrush ecosystems by vegetation treatments to increase forage and reduce sagebrush and other plant species unpalatable to livestock. Fences (2 km/km 2 in some regions), roads, and water developments to manage livestock movements further modify the landscape. Oil and gas development influences 8% of the sagebrush habitats with the highest intensities occurring in the eastern range of sage-grouse; 20% of the sagebrush distribution is indirectly influenced in the Great Plains, Wyoming Basin, and Colorado Plateau SMZs. Energy development physically removes habitat to construct well pads, roads, power lines, and pipelines; indirect effects include habitat fragmentation, soil disturbance, and facilitation of exotic plant and animal spread. More recent development of alternative energy, such as wind and geothermal, creates infrastructure in new regions of the sage-grouse distribution. Land use will continue to be a dominant stressor on sage-brush systems; its individual and cumulative effects will challenge long-term conservation of sage-grouse populations.

Book chapter↗

USGS2011

Status and limiting factors of three rare plant species in the coastal lowlands and mid-elevation woodlands of Hawai`i Volcanoes National Park

Two endangered plant species ( Portulaca sclerocarpa , `ihi mākole, and Sesbania tomentosa , `ōhai) and a species of concern ( Bobea timonioides , `ahakea) native to the coastal lowlands and dry mid-elevation woodlands of Hawai`i Volcanoes National Park were studied for more than two years to determine their stand structure, short-term mortality rates, patterns of reproductive phenology, success of fruit production, seed germination rates in the greenhouse, presence of soil seed bank, and survival of both natural and planted seedlings. The role of rodents as fruit and seed predators was evaluated using exclosures and seed offerings in open and closed stations or cages. Rodents were excluded from randomly selected plants of P. sclerocarpa and from branches of S. tomentosa, and flower and fruit production were compared to that of adjacent unprotected plants. Tagged S. tomentosa fruit were also monitored monthly to detect rodent predation.

Hawai'i↗

USGS1995

Northern Pintail ( Anas acuta )

The Northern Pintail is a medium-sized dabbling duck of slender, elegant lines and conservative plumage coloration. It is circumpolar in distribution and abundant in North America, with core nesting habitat in Alaska and the Prairie Pothole Region of southern Canada and the northern Great Plains. Breeders favor shallow wetlands interspersed throughout prairie grasslands or arctic tundra. An early fall migrant, the species arrives on wintering areas beginning in August, after wing molt, often forming large roosting and feeding flocks on open, shallow wetlands and flooded agricultural fields. The birds consume grains, marsh plant seeds, and aquatic invertebrates throughout the fall and winter. Northern Pintails are among the earliest nesting ducks in North America, beginning shortly after ice-out in many northern areas. Individuals form new pair bonds each winter but are highly promiscuous during the nesting season, with mated and unmated males often involved in vigorous, acrobatic Pursuit Flights. Annual nest success and productivity vary with water conditions, predation, and weather. Females build nests on the ground, often long distances from water. Only the female incubates; her mate leaves shortly after incubation begins. Ducklings hatch together in one day, follow the female to water after a day in the nest, and fledge by July or August. Adults and ducklings consume mainly aquatic invertebrates during the breeding season. Predators and farming operations destroy many thousands of Northern Pintail nests annually; farming has also greatly reduced the amount of quality nesting cover available. Winter habitats are threatened by water shortages, agricultural development, contamination, and urbanization. Periods of extended drought in prairie nesting regions have caused dramatic population declines, usually followed by periods of recovery. Over the long term, however, the continental population of Northern Pintails has declined significantly from 6 million birds in the early 1970s to less than 3 million in the late 1980s and early 1990s. However, new conservation measures, such as habitat restoration and enhancement of agricultural lands, as well as prudent harvest restrictions, suggest that Northern Pintails should have a secure future in North America.

Book chapter↗

USGS1998

Health evaluation of pronghorns (Antilocapra americana) on Hart Mountain National Antelope Refuge in southeastern Oregon, 1996-1997.

One hundred four neonatal (fawns) and 40 adult female (does) pronghorn antelope (pronghorns) ( Antilocapra americana ) were captured on the Hart Mountain National Antelope Refuge (HMNAR) in Lake County, southeastern Oregon, between 13 May 1996 and 26 May 1997. Blood and fecal samples were taken for an investigation of low fawn survival that may be due to disease and/or poor nutrition. No abnormalities were found in hematological parameters of adult does (n = 40) or fawns (n = 44 to 67). In general, there were lower serum total proteins (TP) and Blood Urea Nitrogen (BUN) concentrations in this population than in other populations from Alberta, Canada; Idaho; and Baker City, Oregon. Mean BUN values in does were significantly lower (p < 0.001) in December than March. The duration of this apparently low protein content of the December diet may affect the weight of the newborn and consequent survivability if it should continue into late gestation (March-May). Serum copper (Cu) levels in does (range 0.39 to 0.74 ppm) were considered marginal when compared to domestic animals and some wild ungulates. Fawns had low but apparently normal Cu levels at birth and reached the does' marginal values in about three days. Whole blood and serum Selenium (Se) levels (<100 ng/ml) were considered to be marginal to low in most segments of the pronghorn population in this study. However, serum levels of vitamin E (range 1.98 - 3.27 pg/ml), as determined from the does captured in March, are apparently sufficient to offset any signs of deficiency due to low Se levels. No clinical signs of Cu or Se deficiency were observed. Does captured in December 1996 were tested for neutralizing antibodies to Brucella spp. (n = 20, neg.), Leptospira spp. (n = 20, neg.), bluetongue virus (n = 20, 35% pos.), epizootic hemorrhagic disease virus (n = 20, 30% pos.), respiratory syncytial virus (n = 18, neg.), parainfluenza virus type 3 (n = 18, 67% pos.), infectious bovine rhinotracheitis (n = 18, neg.), and bovine viral diarrhea (n = 18, neg.). Seventeen fawns (9F,8M), nine in 1996 and eight in 1997, survived until at least mid-July each year. Fifty-five of 87 dead fawns were necropsied. Predation by coyotes (Canis latrans) accounted for the majority of fawn mortality (62%), as determined by necropsy, during the two combined summer periods. Other causes of mortality for the combined years included predation by eagle (4%), dystocia (2%), septicemic pasteurellosis (5%), starvation/weak fawn syndrome

Oregon↗

USGS1998

History and status of introduced mammals and impacts to breeding seabirds on the California channel and Northwestern Baja California Islands

The California Channel Islands, U.S.A., and Northwestern Baja California Islands, Mexico, host important breeding populations of several seabird species, including the endemic Black-vented Shearwater (Puffinus opisthomelas) and Xantus' Murrelet (Synthliboramphus hypoleucus). Mammals introduced to nearly all of the islands beginning in the late 1800s to early 1900s include: cats (Felis catus), dogs (Canis familiaris), Black Rats (Rattus rattus), rabbits and hares (Leporidae), goats (Capra hirca), sheep (Ovis ones), and other grazers. Cats, dogs and rats are seabird predators, grazers such as goats and sheep cause habitat degredation, and rabbits destroy habitat and compete with hole-nesting seabirds. Cats, which were introduced to at least 19 islands and currently occur on ten islands, have had the greatest impacts on seabirds, including the extinction of the endemic Guadalupe Storm-Petrel (Oceanodroma macrodactyla). Cats are known to have eliminated or severely reduced colonies of Black-vented Shearwaters, Cassin's Auklets (Ptychoramphus aleuticus) and Xantus' Murrelets. Black Rats have occurred on a minimum of seven islands and have reduced numbers of small, hole-nesting alcids on at least one island. At many islands, defoliation and erosion caused by rabbits and large grazing mammals has been severe. Their effects on seabirds are not well documented but potentially are serious. Impacts from introduced mammals have been most severe on islands with no native mammalian predators. On the Northwestern Baja California Islands, temporary and permanent human settlements have led to a greater diversity and source of introductions. Programs to remove introduced mammals and to reduce the possibility of future introductions are needed to restore seabird populations and to preserve the biodiversity of the region. Surveys are needed particularly on the Northwestern Baja California Islands to update the status and distribution of seabirds and to further assess impacts from introduced mammals.

Waterbirds↗

USGS1999

Health evaluation of a pronghorn antelope population in Oregon

During 1996 and 1997, the U.S. Fish and Wildlife Service conducted a study to determine the cause(s) of population decline and low survival of pronghorn antelope (Antilocapra americana) fawns on Hart Mountain National Antelope Refuge (HMNAR) located in southeastern Oregon (USA). As part of that study, blood, fecal, and tissue samples from 104 neonatal fawns, 40 adult does, and nine adult male pronghorns were collected to conduct a health evaluation of the population. Physiological parameters related to nutrition and/or disease were studied. No abnormalities were found in the complete blood cell counts of adults (n = 40) or fawns (n = 44 to 67). Serum total protein and blood urea nitrogen (BUN) levels were lower compared to other pronghorn populations. Does had mean BUN values significantly lower (P < 0.001) in December 1996 than March 1997. Serum copper (Cu) levels in does (range 0.39 to 0.74 ppm) were considered marginal when compared to domestic animals and other wild ungulates. Fawns had low (0.28 ppm) Cu levels at birth and reached the does' marginal values in about 3 days Whole blood, serum and liver selenium (Se) levels were considered marginal to low in most segments of the pronghorn population. However, serum levels of vitamin E (range 1.98 to 3.27 ??g/ml), as determined from the does captured in March, were apparently sufficient to offset any signs of Se deficiency. No clinical signs of Cu or Se deficiency were observed. Fifty-five of 87 dead fawns were necropsied. Trauma, due to predation by coyotes (Canis latrans), accounted for 62% of the mortality during mid-May to mid-July of each year. Other causes included predation by golden eagles (Aquila chrysaetos) (4%), dystocia (2%), septicemic pasteurellosis (4%), starvation (5%), and unknown (23%). Adult females were tested for serum neutralizing antibodies to Brucella spp. (n = 20, negative), Leptospira interrogans (n = 20, negative), bluetongue virus (n = 20, 35% positive), epizootic hemorrhagic disease virus (n = 20, 30% positive), respiratory syncytial virus (n = 18, negative), parainfluenza virus type 3 (n = 18, 67% positive), infectious bovine rhinotracheitis (n = 18, negative), and bovine viral diarrhea (n = 18, negative). Considering the parameters examined, we found no apparent predisposing factors to mortality including those killed by coyotes, but some nutritional parameters suggest that pronghorns on HMNAR exist on a diet low in protein and Se and marginal in Cu. The effect these factors have on the population is not known.

Journal of Wildlife Diseases↗

USGS2002

Effects of habitat fragmentation on passerine birds breeding in Intermountain shrubsteppe

Habitat fragmentation and loss strongly influence the distribution and abundance of passerine birds breeding in Intermountain shrubsteppe. Wildfires, human activities, and change in vegetation communities often are synergistic in these systems and can result in radical conversion from shrubland to grasslands dominated by exotic annuals at large temporal and spatial scales from which recovery to native conditions is unlikely. As a result, populations of 5 of the 12 species in our review of Intermountain shrubsteppe birds are undergoing significant declines; 5 species are listed as at-risk or as candidates for protection in at least one state. The process by which fragmentation affects bird distributions in these habitats remains unknown because most research has emphasized the detection of population trends and patterns of habitat associations at relatively large spatial scales. Our research indicates that the distribution of shrubland-obligate species, such as Brewer's Sparrows (Spizella breweri), Sage Sparrows (Amphispiza belli), and Sage Thrashers (Oreoscoptes montanus), was highly sensitive to fragmentation of shrublands at spatial scales larger than individual home ranges. In contrast, the underlying mechanisms for both habitat change and bird population dynamics may operate independently of habitat boundaries. We propose alternative, but not necessarily exclusive, mechanisms to explain the relationship between habitat fragmentation and bird distribution and abundance. Fragmentation might influence productivity through differences in breeding density, nesting success, or predation. However, local and landscape variables were not significant determinants either of success, number fledged, or probability of predation or parasitism (although our tests had relatively low statistical power). Alternatively, relative absence of natal philopatry and redistribution by individuals among habitats following fledging or post-migration could account for the pattern of distribution and abundance. Thus, boundary dynamics may be important in determining the distribution of shrubland-obligate species but insignificant relative to the mechanisms causing the pattern of habitat and bird distribution. Because of the dichotomy in responses, Intermountain shrubsteppe systems present a unique challenge in understanding how landscape composition, configuration, and change influence bird population dynamics.

Conference Paper↗

USGS2003

Assessing recovery feasibility for piping plovers using optimization and simulation

Optimization and simulation modeling can be used to account for demographic and economic factors simultaneously in a comprehensive analysis of endangered-species population recovery. This is a powerful approach that is broadly applicable but underutilized in conservation biology. We applied the approach to a population recovery analysis of threatened and endangered piping plovers (Charadrius melodus) in the Great Plains of North America. Predator exclusion increases the reproductive success of piping plovers, but the most cost-efficient strategy of applying predator exclusion and the number of protected breeding pairs necessary to prevent further population declines were unknown. We developed a linear programming model to define strategies that would either maximize fledging rates or minimize financial costs by allocating plover pairs to 1 of 6 types of protection. We evaluated the optimal strategies using a stochastic population simulation model. The minimum cost to achieve a 20% chance of stabilizing simulated populations was approximately $1-11 million over 50 years. Increasing reproductive success to 1.24 fledglings/pair at minimal cost in any given area required fencing 85% of pairs at managed sites but cost 23% less than the current approach. Maximum fledging rates resulted in >20% of simulated populations reaching recovery goals in 30-50 years at cumulative costs of <$16 million. Protecting plover pairs within 50 km of natural resource agency field offices was sufficient to increase simulated populations to established recovery goals. A range-wide management plan needs to be developed and implemented to foster the involvement and cooperation among managers that will be necessary for recovery efforts to be successful. We also discuss how our approach can be applied to a variety of wildlife management issues.

Wildlife Society Bulletin↗

USGS2003

Late Neoproterozoic felsite (602.3 +/- 2 Ma) and associated metadiabase dikes in the Reading Prong, Pennsylvania, and rifting of Laurentia

Felsite dikes in the Rittenhouse Gap iron mine district of the Reading Prong, eastern Pennsylvania, have a close geochemical affinity with the peralkaline Battle Mountain Member of the Robertson River Igneous Suite (RRIS), northern Virginia. These newly recognized Rittenhouse Gap Felsite dikes of the Swabia Creek Igneous Suite (SCIS) of eastern Pennsylvania plot as within-plate, A-type, A1 granites on various discriminant diagrams, but are quite distinct from late Neoproterozoic Catoctin Metarhyolite of Pennsylvania which has lower Ga/Al and Nb, but higher Eu. Newly recognized metadiabase dikes, also found in the Rittenhouse Gap district and proposed as Tunnel Mine Metadiabase of the SCIS, classify as alkali within-plate or continental initial rifting alkali tholeiites. They are quite distinct chemically and mineralogically from Catoctin Metabasalt flows and equivalent metadiabase dikes in Pennsylvania, which have lower Nb. Sr and Nd isotopic data indicate that the Tunnel Mine Metadiabase and Rittenhouse Gap Felsite are of mantle origin, but that the latter also includes a crustal component. The SCIS bimodal volcanics in Pennsylvania suggest a previously unrecognized rift environment in Pennsylvania at 602 Ma, somewhat predating the recognized, latest Neoproterozoic Catoctin event in Pennsylvania. As such, they fill in both temporal and geographic gaps for the rifting of Laurentia in Pennsylvania. It is proposed that the SCIS melt developed from a remnant ember of the northeastward trace of the older Mount Rogers-RRIS hotspot as Laurentia rotated clockwise. However, release and intrusion of the SCIS may have been related to younger Catoctin event crustal thinning that slightly predated the mafic dike phase of the Catoctin as Laurentia later migrated northward over a second hotspot. Eventually, the mafic phase associated with this second hotspot sufficiently attenuated the crust to allow introduction of Catoctin volcanics.

Northeastern Geology and Environmental Sciences↗

USGS2004

Persistence of identifiable remains of white sturgeon juveniles in digestive tracts of northern pikeminnow

Juvenile white sturgeon, Acipenser transmontanus, have not been commonly identified as prey items in digestive tracts of fishes collected in the wild. In particular, the diet of northern pikeminnow, Ptychocheilus oregonensis, an abundant Pacific Northwest freshwater predator which has been widely studied, has not included juvenile white sturgeon. To aid in interpreting these results and help in planning future feeding studies, we determined the persistence of identifiable remains of white sturgeon juveniles in this predator's digestive tract. Northern pikeminnow (mean total length = 476 mm), were force-fed meals of 2 or 3 juvenile white sturgeon (mean total length = 91 mm). After digestive periods of 4, 8, 16, 24, 28, and 32h at a water temperature of about 17 ??C, fish were sacrificed, digestive tracts removed, and contents examined. Our results indicate that juvenile white sturgeon would be readily discernable in digestive tracts of northern pikeminnow at least a day after feeding, with scutes remaining undigested and identifiable for 28 h.

California Fish and Game↗

USGS2006

Trophic transfer of trace metals from the polychaete worm Nereis diversicolor to the polychaete N. virens and the decapod crustacean Palaemonetes varians

Diet is an important exposure route for the uptake of trace metals by aquatic invertebrates, with trace metal trophic transfer depending on 2 stages - assimilation and subsequent accumulation by the predator. This study investigated the trophic transfer of trace metals from the sediment-dwelling polychaete worm Nereis diversicolor from metal-rich estuarine sediments in southwestern UK to 2 predators - another polychaete N. virens (Cu, Zn, Pb, Cd, Fe) and the decapod crustacean Palaemonetes varians (Cu, Zn, Pb, Cd, Fe, Ag, As, Mn). N. virens showed net accumulation of Cu, Zn, Pb and Cd from the prey; accumulation increased with increasing prey concentration, but a coefficient of trophic transfer decreased with increasing prey concentration, probably because a higher proportion of accumulated metal in the prey is bound in less trophically available (insoluble) detoxified forms. The trace metal accumulation patterns of P. varians apparently restricted significant net accumulation of metals from the diet of N. diversicolor to just Cd. There was significant mortality of the decapods fed on the diets of metal-rich worms. Metal-rich invertebrates that have accumulated metals from the rich historical store in the sediments of particular SW England estuaries can potentially pass these metals along food chains, with accumulation and total food chain transfer depending on the metal assimilation efficiencies and accumulation patterns of the animal at each trophic level. This trophic transfer may be significant enough to have ecotoxicological effects. ?? Inter-Research 2006.

Marine Ecology Progress Series↗

USGS2006

Albatross species demonstrate regional differences in North Pacific marine contamination

Recent concern about negative effects on human health from elevated organochlorine and mercury concentrations in marine foods has highlighted the need to understand temporal and spatial patterns of marine pollution. Seabirds, long-lived pelagic predators with wide foraging ranges, can be used as indicators of regional contaminant patterns across large temporal and spatial scales. Here we evaluate contaminant levels, carbon and nitrogen stable isotope ratios, and satellite telemetry data from two sympatrically breeding North Pacific albatross species to demonstrate that (1) organochlorine and mercury contaminant levels are significantly higher in the California Current compared to levels in the high-latitude North Pacific and (2) levels of organochlorine contaminants in the North Paci.c are increasing over time. Black-footed Albatrosses (Phoebastria nigripes) had 370-460% higher organochlorine (polychlorinated biphenyls [PCBs], dichlorodiphenyltrichloroethanes [DDTs]) and mercury body burdens than a closely related species, the Laysan Albatross (P. immutabilis), primarily due to regional segregation of their North Pacific foraging areas. PCBs (the sum of the individual PCB congeners analyzed) and DDE concentrations in both albatross species were 130-360% higher than concentrations measured a decade ago. Our results demonstrate dramatically high and increasing contaminant concentrations in the eastern North Pacific Ocean, a finding relevant to other marine predators, including humans. ?? 2006 by the Ecological Society of America.

Ecological Applications↗

USGS2010

Influence of a low intensity electric sea lion deterrence system on the migratory behavior of fishes in the upstream migrant tunnel (UMT) at Bonneville Dam.

Predation by pinnipeds, such as California sea lions (Zalophus alifornianus), Pacific harbor seals (Phoca vitulina), and Stellar sea lions (Eumetopias jubatus) on returning adult Pacific salmon (Oncorhynchus spp.) in the Columbia River basin has become an increasing concern for fishery managers trying to conserve and restore threatened and endangered runs of salmonids. As a result, Smith-Root Incorporated (SRI; Vancouver, Washington) proposed a demonstration project to evaluate the potential of an electrical array to deter marine mammals (SRI 2007). The objective of their work was to develop, deploy, and evaluate a passive, integrated electric and sonar array that selectively inhibits upstream marine mammal movements and predation, without injuring pinnipeds or affecting anadromous fish migrations. However, before such a device could be placed in the field, concerns by regional fishery managers about the potential effects of such a device on the migratory behavior of or injury to Pacific salmon, steelhead (O. mykiss), Pacific lampreys (Entoshpenus tridentata), and white sturgeon (Acipenser transmontanus) needed to be addressed.

Oregon, Washington↗

USGS2010

Snake River Fall Chinook Salmon life history investigations annual report, 2009

In 2009, we used radio and acoustic telemetry to evaluate the migratory behavior, survival, mortality, and delay of subyearling fall Chinook salmon in the Clearwater River and Lower Granite Reservoir. We released a total of 1,000 tagged hatchery subyearlings at Cherry Lane on the Clearwater River in mid August and we monitored them as they passed downstream through various river and reservoir reaches. Survival through the free-flowing river was high (>0.85) for both radio- and acoustic-tagged fish, but dropped substantially as fish delayed in the Transition Zone and Confluence areas. Estimates of the joint probability of migration and survival through the Transition Zone and Confluence reaches combined were similar for both radio- and acoustic-tagged fish, and ranged from about 0.30 to 0.35. Estimates of the joint probability of delaying and surviving in the combined Transition Zone and Confluence peaked at the beginning of the study, ranging from 0.323 (SE =NA; radio-telemetry data) to 0.466 (SE =0.024; acoustic-telemetry data), and then steadily declined throughout the remainder of the study. By the end of October, no live tagged juvenile salmon were detected in either the Transition Zone or the Confluence. As estimates of the probability of delay decreased throughout the study, estimates of the probability of mortality increased, as evidenced by the survival estimate of 0.650 (SE =0.025) at the end of October (acoustic-telemetry data). Few fish were detected at Lower Granite Dam during our study and even fewer fish passed the dam before PIT-tag monitoring ended at the end of October. Five acoustic-tagged fish passed Lower Granite Dam in October and 12 passed the dam in November based on detections in the dam tailrace; however, too few detections were available to calculate the joint probabilities of migrating and surviving or delaying and surviving. Estimates of the joint probability of migrating and surviving through the reservoir was less than 0.2 based on acoustic-tagged fish. Migration rates of tagged fish were highest in the free-flowing river (median range = 36 to 43 km/d) but were generally less than 6 km/d in the reservoir reaches. In particular, median migration rates of radio-tagged fish through the Transition Zone and Confluence were 3.4 and 5.2 km/d, respectively. Median migration rate for acoustic-tagged fish though the Transition Zone and Confluence combined was 1 km/d. We radio tagged 84 smallmouth bass and six channel catfish in the Confluence reach and later detected 48 bass and 1 catfish during mobile tracking. Predators were primarily located along shorelines in the Confluence, but a couple of smallmouth bass did swim into the Clearwater River. Most radio-tagged subyearlings that we determined to be dead were also located in shoreline areas suggesting that predation could account for some of the mortality we observed. Our total dissolved gas (TDG) monitoring in the lower Clearwater River showed a cyclic pattern of low (~102%) TDG in the morning and higher (~110%) TDG in the late afternoon. Using a compensation depth of 1 m, we found that 15.4% (3.9 ha) of the lower 13 km of the Clearwater River would not provide fish with an opportunity for depth compensation in a low flow year. Water temperatures in the Clearwater River showed diel variations of about 2°C, and generally ranged from 10-12°C during summer flow augmentation. The Clearwater River generally showed little thermal variation while our tagged fish were at large, whereas the Snake River at the downstream boundary of the Confluence was thermally heterogeneous until mid-September. In the unimpounded Clearwater River, simulated water velocities ranged from about 1.3 to 1.5 m/s before flow augmentation ended, and were about 0.6 m/s thereafter. By comparison, velocities at the Clearwater River mouth were about 0.3 m/s during flow augmentation, and about 0.1 m/s thereafter. From October 2008 to February 2009 and from July 2009 to March 2010 we used monthly mobile hydroacoustic surveys to estimate the number of juvenile Chinook salmon in Little Goose and Lower Granite reservoirs, the first two reservoirs encountered on the lower Snake River by downstream migrants. Concurrent lampara seining was used to verify acoustic targets, calculate condition factors, and to examine spatial and temporal density patterns. Our data indicated that holdovers are larger in warmer water temperature years and smaller in colder water temperature years. Lampara catch data indicated that holdovers were seasonally the most abundant and in the best condition in November and December, whereas the hydroacoustic data showed population peaks in October in Lower Granite Reservoir and in January in Little Goose Reservoir. Maximum population estimates in Lower Granite Reservoir were 6,929 in October 2008 and 7,218 in October 2009. In Little Goose Reservoir, maximum population estimates were 9,645 in January 2009 and 10,419 in January 2010. By February, abundances and relative condition factors decreased as most holdovers had probably moved past Lower Granite and Little Goose dams. Spatial differences were primarily longitudinal with greater holdover abundances in the lower reaches of both reservoirs.

Report↗

USGS2012

Snake River fall Chinook salmon life history investigations: Annual report 2010

This report summarizes three research activities conducted in 2010-2011. The first was a radiotelemetry study conducted in the lower Clearwater River. The second was a hydroacoustic study conducted in Lower Granite and Little Goose reservoirs. The third was an analysis of covariates affecting juvenile fall Chinook salmon survival and behavior. In 2010, we used radiotelemetry to evaluate the migratory behavior, delay, and relative mortality of subyearling fall Chinook salmon in the Clearwater River and Lower Granite Reservoir. We captured, tagged, and released a total of 100 run-at-large subyearlings in the Transition Zone of the lower Clearwater River in late July and monitored their downstream movement past fixed detection sites and by mobile tracking through the end of August. The Transition Zone is that portion of the river where it transitions from free-flowing to impounded habitat. Median residence time of fish that passed through the Transition Zone, Confluence, and Upper Reservoir reaches was relatively short (8.8-25.6 h). However, for fish that remained in the Transition Zone that were detected by mobile tracking, median residence time was over 30 d (N=6). Median migration rates through the study reaches were variable but slow (range 2.9-17.2 km/d) compared to that of more active migrants indicating that subyearlings from the Clearwater River were not actively migrating during July and August. The fate of radio-tagged subyearlings was determined from mobile tracking records. A total of 37 of the 71 fish detected during tracking were deemed to be dead, 22 were determined to be alive, and the fate of 16 was unknown. We also radio tagged 66 smallmouth bass in the Confluence reach and later detected 59 bass during mobile tracking. Predators were primarily located along shorelines in the Confluence reach, but a few fish did swim downstream into the Upper Reservoir reach. Most radio-tagged subyearlings that we determined to be dead were also located in shoreline areas suggesting that predation could account for some of the mortality we observed.

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