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At least 1,585 records · Page 88Linked to original sources
USGS2021

Migration strategies supporting salmonids in Arctic Rivers: A case study of Arctic Cisco and Dolly Varden

Amphidromous fish such as Dolly Varden (Salvelinus malma) and Arctic Cisco (Coregonus autumnalis) have distinct life histories that facilitate their success in Arctic environments. Both species spawn in freshwater and make annual migrations between marine, brackish, or freshwater environments. Dolly Varden rear for one or more years in freshwater before migrating to sea whereas Arctic Cisco migrate to sea during their first summer. By contrast, Pacific salmon (Oncorhynchus spp.) spawn in freshwater, but once they smolt and go to sea they remain there until they mature and return to spawn. Salmon migrate at variable ages depending on species. Arctic marine environments offer productive food resources during summer, but during winter they are too cold for salmonids that lack antifreeze proteins. To avoid the cold sea during winter, Dolly Varden return to freshwater while Arctic Cisco overwinter in brackish estuaries. The lack of migration back to freshwater for overwintering helps explain why Pacific salmon success is limited in Arctic waters and suggests major increases in success will not be realized until Arctic seas provide suitable overwinter conditions. In this paper we contrast these migration strategies, discuss potential changes in a warming Arctic, and highlight information needs especially for juvenile fish.

Alaska↗
USGS2018

Sewage loading and microbial risk in urban waters of the Great Lakes

Despite modern sewer system infrastructure, the release of sewage from deteriorating pipes and sewer overflows is a major water pollution problem in US cities, particularly in coastal watersheds that are highly developed with large human populations. We quantified fecal pollution sources and loads entering Lake Michigan from a large watershed of mixed land use using host-associated indicators. Wastewater treatment plant influent had stable concentrations of human Bacteroides and human Lachnospiraceae with geometric mean concentrations of 2.77 × 10 7 and 5.94 × 10 7 copy number (by quantitative PCR) per 100 ml, respectively. Human-associated indicator levels were four orders of magnitude higher than norovirus concentrations, suggesting that these human-associated bacteria could be sensitive indicators of pathogen risk. Norovirus concentrations in these same samples were used in calculations for quantitative microbial risk assessment. Assuming a typical recreational exposure to untreated sewage in water, concentrations of 7,800 copy number of human Bacteroides per 100 mL or 14,000 copy number of human Lachnospiraceae per 100 mL corresponded to an illness risk of 0.03. These levels were exceeded in estuarine waters during storm events with greater than 5 cm of rainfall. Following overflows from combined sewer systems (which must accommodate both sewage and stormwater), concentrations were 10-fold higher than under rainfall conditions. Automated high frequency sampling allowed for loads of human-associated markers to be determined, which could then be related back to equivalent volumes of untreated sewage that were released. Evidence of sewage contamination decreased as ruminant-associated indicators increased approximately one day post-storm, demonstrating the delayed impact of upstream agricultural sources on the estuary. These results demonstrate that urban areas are a diffuse source of sewage contamination to urban waters and that storm-driven release of sewage, particularly when sewage overflows occur, creates a serious though transient human health risk.

Wisconsin↗
USGS2001

California's Yolo Bypass: Evidence that flood control can be compatible with fisheries, wetlands, wildlife, and agriculture

Unlike conventional flood control systems that frequently isolate rivers from ecologically-essential floodplain habitat, California's Yolo Bypass has been engineered to allow Sacramento Valley floodwaters to inundate a broad floodplain. From a flood control standpoint, the 24,000 ha leveed floodplain has been exceptionally successful based on its ability to convey up to 80% of the flow of the Sacramento River basin during high water events. Agricultural lands and seasonal and permanent wetlands within the bypass provide key habitat for waterfowl migrating through the Pacific Flyway. Our field studies demonstrate that the bypass seasonally supports 42 fish species, 15 of which are native. The floodplain appears to be particularly valuable spawning and rearing habitat for the splittail (Pogonichthys macrolepidotus), a federally-listed cyprinid, and for young chinook salmon (Oncorhynchus tshawytscha), which use the Yolo Bypass as a nursery area. The system may also be an important source to the downstream food web of the San Francisco Estuary as a result of enhanced production of phytoplankton and detrital material. These results suggest that alternative flood control systems can be designed without eliminating floodplain function and processes, key goals of the 1996 Draft AFS Floodplain Management Position Statement.

California↗
USGS1968

An electric beam trawl for the capture of larval lampreys

The chemicals used to control the sea lamprey, Petromyzon marinus , in the Great Lakes have drastically reduced populations of larval lampreys in tributary streams. These larvicides are too costly and difficult to apply, however, in inland lakes, estuaries, and bays. Populations of sea lampreys in these areas constitute a threat to the refinement of the control. The gear available to locate, ample, and evaluate larval populations in deep water are inefficient. Electric shockers, satisfactory for collecting ammocoetes in streams, are limited to shallow water. The use of mechanical devices such as the Petersen dredge, anchor dredge, and the orange-peel dredge is time consuming, inefficient, and relatively ineffective in providing reliable quantitative evaluation of population size and composition over large areas of bottom. A device was required to sample adequately many areas in a short period of time, regardless of the depth of water. Mobility also was essential to permit operation of the unit in the various Great Lakes and in inland waters. An electrified beam trawl has been developed that most nearly meets these requirements. It has been used successfully to collect larvae of the sea lamprey, American brook lamprey ( Lampetra lamottei ), northern brook lamprey ( Ichthyomyzon fossor ), and silver lamprey ( I. unicuspis ). Effectiveness of the trawl did not appear to differ with species.

Transactions of the American Fisheries Society↗
USGS1998

Effects of a delayed onset of piscivory on the size of age-0 bluefish

Variation in advection or other physical forces may accelerate or delay arrival of young marine fishes into productive nearshore habitats, thereby affecting the length of the available growing season. The bluefish Pomatomus saltatrix is an oceanic spawner whose juvenile stages, upon entry into estuarine waters, become piscivorous and thereby experience greatly increased growth. Size attained during the growing season may therefore be determined by time of arrival into estuarine habitats. We exposed bluefish recently recruited to an estuary to three diet shift treatments in which test fish were fed adult brine shrimp Artemia sp. for 0 , 10, or 20 d before they were switched to piscine prey. Bluefish that had a delayed onset of piscivory were smaller after 40 d of growth, indicating that they did not fully compensate for prior periods of slow growth. These bluefish did exhibit immediate moderate growth compensation (about 6% over 10 d) resulting from increased consumption rates, but relatively low growth efficiencies prevented full recovery of their growth losses. Low growth efficiencies may have resulted from an induced developmental handicap or an energetic penalty for prolonged feeding on an Artemia diet. The timing of age - 0 bluefish recruitment into estuarine environments can have a lasting influence on size attained during the first growing season.

Transactions of the American Fisheries Society↗
USGS2002

Induction of skin ulcers in Atlantic menhaden by injection and aqueous exposure to the zoospores of Aphanomyces invadans

The infectivity and role of Aphanomyces invadans in the etiology of skin ulcers in Atlantic menhaden Brevoortia tyrannus were investigated with two laboratory challenges. In the first experiment, Atlantic menhaden received subcutaneous injections with secondary zoospores from one of three cultures of Aphanomyces : WIC (an endemic isolate of A. invadans in Atlantic menhaden from the Wicomico River, Maryland), PA7 (an isolate of A. invadans from striped snakehead Channa striata (also known as chevron snakehead), infected with epizootic ulcerative syndrome from Thailand), and ATCC-62427 (an isolate from Atlantic menhaden from North Carolina). Fish were injected with 1.9 × 10 2 (WIC-low), 1.9 × 10 3 (WIC-high), 5.2 × 10 2 (PA7), or 6.0 × 10 2 (ATCC-62427) zoospores and held in static water at 23.5°C (6‰ salinity) for 21 d. Both low and high doses of WIC caused incipient, granulomatous lesions after 5 d. Fish injected with the high-dose WIC died within 7 d. All fish injected with the low-dose WIC were dead after 10 d. Fish injected with zoospores of PA7 developed lesions after 9 d. Fish injected with the ATCC-62427 isolate or those that received subcutaneous injections of sterile water (controls) did not develop lesions. In the second experiment, fish were bath-exposed with zoospores of the WIC isolate after various trauma-inducing treatments. These treatments consisted of handling fish with a net (net stress, exposed for 2 h to either 70 or 700 zoospores/mL), physically removing a few scales (trauma, exposed for 1 h to 700 zoospores/mL), or acclimating fish with less handling (acclimated, untraumatized, exposed for 5.5 h to 110 zoospores/mL). Unexposed fish served as controls. Mortality ranged from 94% to 100% for net-handled and traumatized fish, with the prevalence of ulcerous lesions ranging from 70% to 79% in net-handled fish. However, mortality was 24% for the “untraumatized” fish and the prevalence of lesions was 32%. Fish injected with or exposed to bath challenges of zoospores developed lesions that were grossly and histologically identical to those observed in naturally infected Atlantic menhaden from several estuaries and rivers along the mid-Atlantic coast of the USA. The deeply penetrating ulcers were characterized by dermatitis, myofibrillar degeneration, and deep, necrotizing granulomatous myositis. Experimentally induced lesions, however, exhibited invasiveness, often involving the kidney. Injected or bath-exposed fish developed incipient granulomas after 5 d, which progressed to overt lesions over 7–9 d. We have here demonstrated that ulcerative skin lesions can be experimentally induced in Atlantic menhaden after exposure to oomycete zoospores of an endemic strain of A. invadans .

Journal of Aquatic Animal Health↗
USGS1998

A collapsible trap for capturing ruffe

A modified version of the Windermere trap was designed, constructed, and tested for its effectiveness in capturing ruffe Gymnocephalus cernuus . The inexpensive, lightweight, collapsible trap was easily deployed and retrieved from a small boat. Field tests conducted at the St. Louis River estuary in western Lake Superior in spring 1995 and 1996 indicated that the trap was effective in capturing ruffe. Proportions of the ruffe in trap and bottom trawl catches were similar in 1995 and 1996. This trap could be a useful tool in surveillance, monitoring, or control programs for ruffe or similar species, either to augment existing sampling programs or especially in situations where gillnetting or bottom trawling are not feasible.

North American Journal of Fisheries Management↗
USGS2010

Salinity tolerance of the African Jewelfish Hemichromis letourneuxi , a non-native cichlid in South Florida (USA)

The African Jewelfish (Cichlidae: Hemichromis letourneuxi ) is a predatory, non-native fish that has recently (since 2000) begun to expand its geographic range across south Florida. The salinity tolerance of H. letourneuxi was unknown, and thus it was unclear whether the species could use estuarine or coastal environments. The response of H. letourneuxi to chronic change in salinity was evaluated here by exposing fish to progressively increasing salinities (0–80 ppt). Fish were held at target salinities for a minimum of 30 days. The species showed excellent survival from 0–50 ppt. At 60 ppt, only 25% of the fish survived, and mean estimated survival time was 12 days. Above 60 ppt, mortality was 100%. Fish grew equally well from 0–50 ppt. In another experiment, fish were transferred directly from freshwater to various salinities from 5–35 ppt (seawater) and held for seven days, after which survivors were returned to freshwater. All fish transferred directly from freshwater to salinities up to 20 ppt survived; only 56% survived when transferred from freshwater to 25 ppt, and none survived transfer above 25 ppt. Experimental results indicated that H. letourneuxi can persist easily in salinities prevalent in coastal environments, even during periods of hypersalinity common in south Florida estuaries. Salinity will not restrict its dispersal by coastal pathways.

Florida↗
USGS2009

Small estuarine fishes feed on large trematode cercariae: Lab and field investigations

In aquatic ecosystems, dense populations of snails can shed millions of digenean trematode cercariae every day. These short-lived, free-living larvae are rich in energy and present a potential resource for consumers. We investigated whether estuarine fishes eat cercariae shed by trematodes of the estuarine snail Cerithidea californica. In aquaria we presented cercariae from 10 native trematode species to 6 species of native estuarine fishes. Many of these fishes readily engorged on cercariae. To determine if fishes ate cercariae in the field, we collected the most common fish species, Fundulus parvipinnis (California killifish), from shallow water on rising tides when snails shed cercariae. Of 61 killifish, 3 had recognizable cercariae in their gut. Because cercariae are common in this estuary, they could be frequent sources of energy for small fishes. In turn, predation on cercariae by fishes (and other predators) could also reduce the transmission success of trematodes. ?? 2009 American Society of Parasitologists.

Journal of Parasitology↗
USGS2002

Clam density and scaup feeding behavior in San Pablo Bay, California

San Pablo Bay, in northern San Francisco Bay, California, is an important wintering area for Greater ( Aythya marila ) and Lesser Scaup ( A. affinis ). We investigated variation in foraging behavior of scaup among five sites in San Pablo Bay, and whether such variation was related to densities of their main potential prey, the clams Potamocorbula amurensis and Macoma balthica . Time-activity budgets showed that scaup spent most of their time sleeping at some sites, and both sleeping and feeding at other sites, with females feeding more than males. In the first half of the observation period (12 January–5 February 2000), percent time spent feeding increased with increasing density of P. amurensis , but decreased with increasing density of M. balthica (diet studies have shown that scaup ate mostly P. amurensis and little or no M. balthica ). Densities of M. balthica stayed about the same between fall and spring benthic samples, while densities of P. amurensis declined dramatically at most sites. In the second half of the observation period (7 February–3 March 2000), percent time feeding was no longer strongly related to P. amurensis densities, and dive durations increased by 14%. These changes probably reflected declines of P. amurensis , perhaps as affected by scaup predation. The large area of potential feeding habitat, and alternative prey elsewhere in the estuary, might have resulted in the low correlations between scaup behavior and prey densities in San Pablo Bay. These low correlations made it difficult to identify specific areas of prey concentrations important to scaup.

Condor↗
USGS2004

Redistribution and growth of the Caspian Tern population in the Pacific Coast region of North America, 1981-2000

We examined nesting distribution and demography of the Pacific Coast population of Caspian Terns ( Sterna caspia ) using breeding records and band recoveries spanning two decades since the first population assessment. Since 1980, population size has more than doubled to about 12 900 pairs, yet the proportion of the population nesting at inland (18%) versus coastal sites (82%) has remained constant. Although the breeding range of the Pacific Coast population has expanded northward into Alaska and farther south in Mexico, there was no net latitudinal shift in the distribution of breeding pairs or new colonies. The distribution of breeding birds among areas changed dramatically, however, with 69% of breeding terns now nesting in Oregon (primarily in the Columbia River estuary) versus 4% during the late 1970s. During the past 20 years, there has continued to be a greater proportion of Caspian Terns breeding at anthropogenic sites compared to natural sites. Estimated annual survival rates for hatch-year and after-third-year birds during 1981-1998 were greater than during 1955-1980, consistent with the higher rate of population increase in recent decades. Fecundity required to maintain a stable population ( λ = 1 ) was estimated at 0.32–0.74 fledglings pair −1 , depending on band recovery probabilities for sub-adults. Caspian Terns readily moved among breeding sites and rapidly colonized new areas; however, a greater concentration of breeding Caspian Terns among fewer colonies in response to anthropogenic factors is an important conservation concern for this species.

Condor↗
USGS2005

Further evidence for the invasion and establishment of Pterois volitans (Teleostei: Scorpaenidae) along the Atlantic Coast of the United States

We document the continued population expansion of red lionfish, Pterois volitans, the first documented successful introduction of an invasive marine fish species from the western Pacific to Atlantic coastal waters of the United States. Red lionfish are indigenous to the Indo-Pacific and have apparently established one or more breeding populations on reefs off the southeastern United States. Fifty-nine specimens, most presumably adult red lionfish, were documented or collected on live-bottom reefs off North Carolina, South Carolina, and Florida, and on a manmade structure off Georgia. Observation/collection depths and bottom water temperatures for these fish ranged from 40-99 m and 13.8-24.4??C, respectively. Eleven juvenile lionfish, believed to be expatriated from southeastern waters, were collected in estuaries along the coast of Long Island, NY, at depths of 0-5 m and water temperatures ranging from 13.8-16.5??C. Twelve of the total 70 specimens collected or observed were positively identified as red lionfish. Based on histological assessment of gonad tissue, two reproductively-active males and one immature female were collected. The life history of red lionfish, especially their reproductive biology and food habits, should be investigated along the east coast of the US to determine the potential impacts of this species on ecosystems they have invaded.

Southeastern Naturalist↗
USGS2008

Primary production and carrying capacity of former salt ponds after reconnection to San Francisco Bay

Over 6,110 ha of the commercial production salt ponds surrounding South San Francisco Bay, CA, have been decommissioned and reconnected to the bay, most as part of the largest wetlands restoration program in the western United States. These open water ponds are critical habitat for millions of birds annually and restoration program managers must determine the appropriate balance between retention of ponds versus re-conversion to tidal salt marsh, knowing that both are essential ecosystems for endangered bird species. Our study describes the ecological value of the new open water pond ecosystems as feeding habitats for birds. We used the oxygen rate of change method to determine ecosystem metabolic parameters from high resolution time-series of dissolved oxygen concentration. Areal gross primary production (8.17 g O 2 m −2 d −1 ) was roughly double the world’s most productive estuaries. High rates of phytoplankton photosynthesis were balanced by equally high rates of community respiration (8.25 g O 2 m −2 d −1 ). Metabolic equilibrium was delicately poised: sharp irradiance and temperature shifts triggered short term photosynthesis reduction resulting in oxygen depletion. We converted net primary production (NPP) into potential carrying capacity of the forage biota that support targeted pond waterbirds. NPP was processed through both a pelagic food web, resulting in forage biota for piscivorous birds and a benthic food web, resulting in forage biota for shorebirds and diving benthivores. Both food webs included efficient algal-based and inefficient detrital trophic pathways. The result of all primary production being routed through simple food webs was high potential forage production and energy supply to waterbirds, equivalent to 11–163 million planktivorous fish or 19–78 billion small estuarine clams within the 330-ha pond between May and October. Food quantity does not necessarily equal quality and these systems have the potential to produce toxic or inedible algae. Our study provides the first measurement of primary production in the open water ponds of San Francisco Bay and presents a novel approach for transforming primary production into forage production as a metric of an ecosystem’s energetic carrying capacity.

California↗
USGS2008

Sensitivity of wetland saturated hydraulic heads and water budgets to evapotranspiration

The sensitivity of wetland saturated hydraulic heads and water budgets to evapotranspiration (ET) was examined using a simplified hydrologic model and eight representations of ET. Estimates of ET that created the most reliable wetland saturated hydraulic heads and water budgets employed vegetation coefficients to correct potential ET, calculated by the Priestley-Taylor equation, to actual ET. The accuracy of simulated hydraulic heads generally improved by < 1 cm, however, when using the most reliable ET estimates based on vegetation coefficients. An ET estimate that used a regression-defined extinction depth created substantial errors in simulated water budgets. Specifically, the extinction-depth ET overestimated the annual actual ET by about 40 (400 mm). An ET approximation that overestimates actual ET by 400 mm annually applied in a regional hydrologic model over the 5400 km 2 area of Everglades National Park would underestimate the annual volume of water available for ground-water recharge and surface-water runoff to coastal estuaries by 2.3 billion m 3 . For comparison, this underestimation is about two thirds of the mean volume of water in Lake Okeechobee (3.8 billion m 3 ), the largest lake in Florida, and clearly demonstrates unbiased estimates of ET are necessary for reliably simulating wetland water budgets. ?? 2008 The Society of Wetland Scientists.

Wetlands↗
USGS2005

Albino mutation rates in red mangroves (Rhizophora mangle L.) as a bioassay of contamination history in Tampa Bay, Florida, USA

We assessed the sensitivity of a viviparous estuarine tree species, Rhizophora mangle, to historic sublethal mutagenic stress across a fine spatial scale by comparing the frequency of trees producing albino propagules in historically contaminated (n=4) and uncontaminated (n=11) forests in Tampa Bay, Florida, USA. Data from uncontaminated forests were used to provide estimates of background mutation rates. We also determined whether other fitness parameters were negatively correlated with mutagenic stress (e.g., degree of outcrossing and numbers of reproducing trees km-1). Contaminated sites in Tampa Bay had significantly higher frequencies of trees that were heterozygous for albinism per 1000 total reproducing trees (FHT) than uncontaminated forests (mean ?? SE: 11.4 ?? 4.3 vs 4.3 ?? 0.73, P<0.022). Two sites that were contaminated by oil failed to show elevated FHT, although in the first instance, the mutagenic effects of the oil may have been reduced by several weeks of weathering in open water before coming ashore, and in the second > 25 yrs of subsequent recruitment and tree replacement may have allowed an initial elevation in the FHT to decay. Patterns of FHT were not explained by distance from the bay mouth or the degree of urbanization. However, there was a significant positive relationship between tree size and FHT (r=0.83, P<0.018), which suggests that forests with older or larger trees provide a more lasting record of cumulative mutagenic stress. No other fitness parameters correlated with FHT. There was a difference in FHT between two latitudes, as determined by comparing Tampa Bay with literature values for Puerto Rico. The sensitivity of this bioassay for the effects of mutagens will facilitate future monitoring of contamination events and comparisons of bay-wide recovery in future decades. Development of a database of FHT values for a range of subtropical and tropical estuaries is underway that will provide a baseline against which to compare mutational consequences of global change. ?? 2005, The Society of Wetland Scientists.

Wetlands↗
USGS2017

Standardization and application of an index of community integrity for waterbirds in the Chesapeake Bay, USA

In recent decades, there has been increasing interest in the application of ecological indices to assess ecosystem condition in response to anthropogenic activities. An Index of Waterbird Community Integrity was previously developed for the Chesapeake Bay, USA. However, the scoring criteria were not defined well enough to generate scores for new species that were not observed in the original study. The goal of this study was to explicitly define the scoring criteria for the existing index and to develop index scores for all waterbirds of the Chesapeake Bay. The standardized index then was applied to a case study investigating the relationship between waterbird community integrity and shoreline development during late summer and late fall (2012–2014) using an alternative approach to survey methodology, which allowed for greater area coverage compared to the approach used in the original study. Index scores for both seasons were negatively related to percentage of developed shorelines. Providing these updated tools using the detailed scoring system will facilitate future application to new species or development of the index in other estuaries worldwide. This methodology allows for consistent cross-study comparisons and can be combined with other community integrity indices, allowing for more effective estuarine management.

Chesapeake Bay↗
USGS2018

California gull (Larus californicus) space use and timing of movements in relation to landfills and breeding colonies

Expanding gull (Laridae) populations throughout the world have been attributed to the availability of anthropogenic food subsidies. The influence of landfills on California Gull ( Larus californicus ) space use and the timing of their movements was evaluated in San Francisco Bay, California, USA. Using radio telemetry, 108 California Gulls were tracked, > 7,000 locations were recorded, and > 1 million detections were obtained at automated logger systems placed at the two main landfills and three major breeding colonies. Population home range (31-35 km 2 ) and core use areas (2-3 km 2 ) overlapped landfills and colonies, and expanded after breeding. California Gull attendance at landfills (1.6-19.0 km from colonies) increased throughout breeding and post-breeding, whereas attendance at colonies was low during pre-breeding (20%-40% per day), increased during breeding (60%-80% per day), and declined into and during post-breeding (< 20% per day). California Gull attendance at landfills was greatest when garbage was delivered from 06:00 hr in the morning until 18:00 hr at night. In contrast, California Gull attendance at colonies during breeding was greater at night from 20:00 hr to 05:00 hr (50%-70% per hr) than during the day from 06:00 hr to 18:00 hr (30%-40% per hr). Landfills played a predominant role in California Gull space use and the timing of their movements in this highly urbanized estuary.

California↗
USGS2006

Sexing Forster's Terns using morphometric measurements

Forester's Terns (Sterna forsteri), like most seabirds, are monomorphic and are difficult to sex without extensive behavioral observations or genetic sexing. We conducted the first morphological study and discriminant function analysis on Forster's Terns to develop a method to accurately identify their sex in the field. A sample of 84 terns from the San Francisco Bay estuary were captured or collected, measured, and the sex of 40 female and 44 male terns was confirmed by genetic analyses or via necropsy. Male Forster's Terns were larger than females for 7 of 9 morphological measurements, with head-bill length showing the least amount of overlap between the sexes, followed by culmen length and culmen depth at the gonys. Sexual size dimorphism was greatest with retrix R6 length, followed by culmen width, and culmen depth. A discriminant function including only head-bill length accurately sexed 82% of Forster's Terns, whereas a second discriminant function incorporating both head-bill length and culmen depth at the gonys increased sexing accuracy to 87%. When we used a 75% posterior probability or greater of accurately sexing Forster's Terns, we excluded only 18% of the sample that overlapped and accurately sexed 94% of the remaining individuals. Our results indicate that Forster's Terns can be accurately sexed in the field using only 2 morphological measurements.

Waterbirds↗