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At least 1,621 records · Page 90Linked to original sources

Use of mesocosm data to predict effects in aquatic ecosystems: Limits to interpretation: Chapter 16

Aquatic mesocosm studies are being used to refute a presumption of risk derived from laboratory toxicity tests conducted under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Mesocosm studies incorporate many biological, chemical and physical characteristics of natural ecosystems. Hence, they serve as realistic surrogates of natural ecosystems and allow tests of pesticide effect at the population, community, and ecosystem level. We discuss two factors, ecosystem trophic status and organism life history, which influence the results derived from aquatic mesocosm studies. Trophic status influences the fat and effects of chemicals which strongly sorb or biologically degrade, yet may not be as important in the fate and effects of more water soluble chemicals. Life history traits of organisms and the intensity, frequency, and duration of the pesticide disturbance also determine the mesocosm response pattern.

Book chapter↗

Columbia River Project water use plan: Mid Columbia River sturgeon incubation and rearing study (Year 1)

This report describes the results from the first year of a three-year investigation on the effects of different thermal regimes on incubation and rearing early life stages of white sturgeon. The Columbia River has been significantly altered by the construction of dams resulting in annual flows and water temperatures that differ from historical levels. White sturgeon have been demonstrated to spawn in two very distinct sections of the Columbia River in British Columbia, Canada, which are both located immediately downstream of hydropower facilities. The thermal regimes differ substantially between these two areas. The general approach of this study was to incubate and rear white sturgeon early life stages under two thermal regimes; one mimicking the current, cool water regime of the mid Columbia River downstream from Revelstoke Dam, and one mimicking a warmer regime similar to conditions found on the lower Columbia River at the international border. It describes the development of thermal profiles to be used in laboratory experiments from historic Columbia River temperature data. First-year results suggest that thermal regimes during incubation influence rate of egg development and size at hatch. Eggs incubated under the warm thermal regime hatched sooner than those incubated under the cool thermal regime. Mean length of free embryos at hatch was significantly different between thermal regimes with free embryos from the cool thermal regime being larger at hatch. However, free embryos from the warm thermal regime had a significantly higher mean weight at hatch. Mortality between hatch and initiation of feeding was extremely high in both treatments and virtually all fish reared under the warm thermal regime died prior to initiation of feeding. A proportion of the fish reared under the cool thermal regime did begin feeding; however, growth rates were extremely low as the onset of feeding corresponded with decreasing thermal regime temperatures. Chronic low levels of mortality resulted in few fish remaining when the growth trials were terminated at 154 days after egg fertilization. The starvation trials showed that the fish in the warm thermal regime exhausted their yolk reserves faster than fish in the cool thermal regime. The ability to resist starvation may be important in dispersal to downstream rearing areas.

British Columbia↗

Retrospective analysis of AYK Chinook salmon growth

Harvests of Yukon and Kuskokwim Chinook salmon declined significantly during 1998- 2002 in response to fewer returning salmon. Factors affecting the decline in Chinook salmon abundance are largely unknown. Growth of salmon in freshwater and the ocean is generally thought to influence salmon survival, therefore we examined historical Chinook salmon catch trends and developed growth indices of age-1.3 and age-1.4 Yukon and Kuskokwim Chinook salmon during each year and life stage in freshwater and the ocean, 1964-2004, using measurements of salmon scale growth. Availability of Yukon scales was greater than that of Kuskokwim scales during 1964-2004. Harvests of Yukon and Kuskokwim Chinook salmon rapidly increased in the mid-1970s, then rapidly declined in the late 1990s, apparently in response to the 1976/77 ocean regime shift and the 1997/98 El Nino event. Runs of Nushagak District Chinook salmon (Bristol Bay) also appeared to have been affected by these events in addition to the 1989 regime shift. The rapid responses of Chinook salmon abundance to climate change suggest late life stages were primarily affected, at least initially. Therefore, we searched for Chinook salmon growth patterns that might be related to changes in climate.

Alaska↗

Otters

The otters (Mustelidae; Lutrinae) provide a unique look into the evolution of marine living by mammals. This is because most extant marine mammals have been so highly modified by long periods of selection for life in the sea that they bare little resemblance to their terrestrial ancestors. Marine otters, by contrast, are recent expatriates from terrestrial and freshwater habitats, and some species still live in both environments. Contrasts within this group, and among the otters, terrestrial mammals, and the more highly adapted pinnipeds and cetaceans potentially offer deep insight into mammalian adaptations to life in the sea. Among the marine mammals, sea otters also provide the clearest understanding of predation and ocean ecosystem function. This is due in part to serendipitous opportunities provided by history and in part by the relative ease with which shallow coastal systems where sea otters live can be observed and studied. These two qualities of the otters are what make them interesting to marine mammalogy. Thus, our contribution to this volume on the marine mammals is built around these themes.

Book chapter↗

Otters, Marine

The otters (Mustelidae; Lutrinae) provide an exceptional perspective into the evolution of marine living by mammals. Most extant marine mammals (e.g. the cetaceans, pinnipeds, and sirenians) have been so highly modified by long periods of selection for life in the sea that they bear little resemblance to their terrestrial ancestors. Marine otters, in contrast, are more recent expatriates from freshwater habitats and some species still live in both environments. Contrasts among species within the otters, and among the otters, terrestrial mammals, and the more highly adapted pinnipeds and cetaceans provide powerful insights into mammalian adaptations to life in the sea (Estes, 1989). Among the marine mammals, sea otters ( Enhydra lutris , Fig. 1) provide the clearest understanding of consumer-induced effects on ecosystem function. This is due in part to opportunities provided by history and in part to the relative ease with which shallow coastal systems where sea otters live can be observed and studied. Although more difficult to study than sea otters, other otter species reveal the connectivity among the marine, freshwater, and terrestrial systems. These three qualities of the otters – their comparative biology, their role as predators, and their role as agents of ecosystem connectivity – are what make them interesting to marine mammalogy. The following account provides a broad overview of the comparative biology and ecology of the otters, with particular emphasis on those species or populations that live in the sea. Sea otters are features prominently, in part because they live exclusively in the sea whereas other otters have obligate associations with freshwater and terrestrial environments (Kenyon, 1969; Riedman and Estes, 1990).

Book chapter↗

Identity, reproductive potential, distribution, ecology and management of invasive Pomacea maculata in the southern United States

Established populations of introduced Pomacea maculata, a highly fecund, large species of apple snail native to South America, now occur throughout southeast Asia, in Spain and extensively across the southern United States. Substantial research on nonnative apple snails takes place in Southeast Asia and has frequently identified apple snails as P. canaliculata. That these Asian populations represent at least two Pomacea species, P. canaliculata and P. maculata, has been confirmed through anatomical and genetic evidence. However, the two species are often still confused because of their similar shell morphologies and life history traits. This contribution reviews the distribution, life history, ecology and management of P. maculata introduced to the southern USA. So far the agricultural impacts of P. maculata in the USA fail to match those of non-native applesnails elsewhere, but the invasion of wetlands by this species suggests the need for increased vigilance to prevent further spread and avoid the ecological impacts that have been associated elsewhere with P. canaliculata.

Book chapter↗

Factors affecting fat content in mottled ducks on the Upper Texas Gulf Coast

Body condition, or an individual's ability to address metabolic needs, is an important measure of organism health. For waterfowl, body condition, usually some measure of fat, provides a useful proxy for assessing energy budgets during different life history periods and potentially is a measure of response to ecosystem changes. The mottled duck (Anas fulvigula) is relatively poorly studied in respect to these dynamics and presents a unique case because its non-migratory life-history strategy releases it from metabolic costs experienced by many related migratory waterfowl species. Additionally, as a species in decline and of conservation concern in many parts of its range, traditional methods of fat content estimation that involve destructive sampling are less viable. The goal of this study was to produce an equation for estimating fat content in mottled ducks using birds (n = 24) donated at hunter-check stations or collected by law enforcement efforts on the Texas Chenier Plain National Wildlife Refuge Complex from 2005 - 2007. Morphometric measurements were taken, and ether extraction and fat removal was used to estimate percent body fat content and abdominal fat mass, respectively. A hierarchical simple linear regression modeling approach was used to determine external morphometrics that best predicted abdominal fat content. A ratio model based on body mass and a length metric (keel and wing chord length possessed equal model support) provided the best relationship with abdominal fat in sampled individuals. We then applied the regression equation to historical check station data to examine fluctuations in fat content over time; fat content or condition varied relatively little with the exception of years characterized by major disturbances. The mottled duck condition model created here can be used to better monitor population status and health without destructively sampling individuals.

Journal of the Southeastern Association of Fish an↗

Effects of a growth check on daily age estimates of age-0 alligator gar

Accurate age and growth information is essential for a complete knowledge of life history, growth rates, age at sexual maturity, and average life span in fishes. Alligator gar are becoming increasingly managed throughout their range and because this species spawns in backwater flooded areas, their offspring are prone to stranding in areas with limited prey, potentially affecting their growth. Because fish growth is tightly linked with otolith growth and annulus formation, the ability to discern marks not indicative of annuli (age checks) in alligator gar would give managers some insight when estimating ages. Previous studies have suggested that checks are often present prior to the first annulus in otoliths of alligator gar, affecting age estimates. We investigated check formation in otoliths of alligator gar in relation to growth and food availability. Sixteen age-0 alligator gar were marked with oxytetracycline (OTC) to give a reference point and divided equitably into two groups: a control group with abundant prey and an experimental group with limited prey. The experimental group was given 2 g of food per week for 20 days and then given the same prey availability as the control group for the next 20 days. After 40 days, the gar were measured, sacrificed, and their sagittae removed to determine if checks were present. Checks were visible on 14 of the 16 otoliths in the experimental group, associated with low growth during the first 20 days when prey was limited and accelerated growth after prey availability was increased. No checks were observed on otoliths of the control group, where growth and prey availability were consistent. Age estimates of fish in the control group were more accurate than those in the experimental group, showing that fish growth as a function of prey availability likely induced the checks by compressing daily ring formation.

Journal of the Southeastern Association of Fish an↗

Validation of daily increments periodicity in otoliths of spotted gar

Accurate age and growth information is essential in successful management of fish populations and for understanding early life history. We validated daily increment deposition, including the timing of first ring formation, for spotted gar (Lepisosteus oculatus) through 127 days post hatch. Fry were produced from hatchery-spawned specimens, and up to 10 individuals per week were sacrificed and their otoliths (sagitta, lapillus, and asteriscus) removed for daily age estimation. Daily age estimates for all three otolith pairs were significantly related to known age. The strongest relationships existed for measurements from the sagitta (r2 = 0.98) and the lapillus (r2 = 0.99) with asteriscus (r2 = 0.95) the lowest. All age prediction models resulted in a slope near unity, indicating that ring deposition occurred approximately daily. Initiation of ring formation varied among otolith types, with deposition beginning 3, 7, and 9 days for the sagitta, lapillus, and asteriscus, respectively. Results of this study suggested that otoliths are useful to estimate daily age of spotted gar juveniles; these data may be used to back calculate hatch dates, estimate early growth rates, and correlate with environmental factor that influence spawning in wild populations. is early life history information will be valuable in better understanding the ecology of this species.

Journal of the Southeastern Association of Fish an↗

A review of literature for gray and harbor seals

Climate change is impacting marine species, causing shifts in occurrence, distribution, and phenology, which can ultimately effect ecosystem structure and functioning (Parmesan & Yohe 2003; Burrows et al. 2011). The study of the timing of recurring biological events throughout an organism’s life is known as phenology (Parmesan & Yohe 2003). The way organisms respond to climate change through altered timing offers insight into their sensitivity and adaptability (Parmesan & Yohe 2003). To gain an understanding of pinniped vulnerability to climate change, specifically through changes in phenology, a comprehensive literature search was conducted using several online databases (e.g., Web of Science, Google Scholar and PubMed). Combinations of relevant terms were searched in order to find studies pertaining to the life history of two regionally important pinniped species: the gray seal (Halichoerus grypus) and the harbor seal (Phoca vitulina). Although special attention was given to studies conducted in the Northwestern Atlantic region, publications giving information on populations in other parts of the world provided important proxy information. Keyword searches were conducted in Web of Science and Google Scholar and represent the published literature through 2017. The remainder of the publications found were cited in the literature returned from the two searches. This document provides an annotated bibliography organized by species (gray and harbor seals) and region, with topical sections for important attributes (e.g. foraging). The focus of this search was for the Gulf of Maine region, but other relevant information yielded by the literature search is presented in order of approximate distance from the focal area.

Report↗

Reaffirmed occurrence of two vulnerable caddisfly species of conservation concern

Maramec Spring is home to two Ozark endemic caddisfly Species of Conservation Concern (SOCC). The Missouri Glyphospsyche Caddisfly, Glyphospsyche missouri , (Critically Imperiled; State Rank-S1; Global Rank-G1) is known from Maramec Spring and the receiving spring branch and nowhere else in the world. Similarly, the Artesian Agapetus Caddisfly, Agapetus artesus , (Vulnerable; State Rank-S3 and Global Rank-G3) is known to occur only at Maramec Spring, Greer Spring, and a single reach of the Eleven Point River. Both species are considered representative fauna of Caves/Karst (Springs) habitat systems described in the Missouri State Wildlife Action Plan. However, little is known about distribution, life history, environmental requirements, or tolerance to environmental stress of either species. Further, prior to this study, it had been 14 years since G. missouri was last recorded to occur at Maramec Spring or the receiving spring branch, and 29 years since A. artesus was last documented to occur at Maramec Spring. On 15 November 2017, a team conducted reconnaissance of Maramec Spring Branch and of the Meramec River immediately downstream from the confluence of the spring branch to document occurrence and characterize aquatic habitat of immature life-stages (larvae and/or pupae) of the species, if found. A second visit was made on 10, January 2018.

Report↗

Status of three-dimensional geological mapping and modeling activities in the U.S. Geological Survey

The U.S. Geological Survey (USGS), created in 1879, is the national geological survey for the United States and the sole science agency within its cabinet-level bureau, the Department of the Interior. The USGS has a broad mission, including: serving the Nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect quality of life. USGS scientific activities are organized around major topics, or Mission Areas, aligned with distinct science themes; three-dimensional (3-D) modelling typically supports research and project work within a specific Mission Area. The vastness, diversity, and complexity of the geological landscape of the United States has resulted in the creation of 3-D geological framework models that are local or regional in scale; a National-scale 3-D model is only beginning to evolve. This paper summarizes 3-D geological modeling at the USGS and does not discuss 3-D modeling that is conducted by other Federal agencies, state geological surveys, academia, or industry within the U.S. This paper updates and expands upon a similar status report of USGS 3-D modeling activities of Jacobsen et al. (2011).

Report↗

Survival and recruitment dynamics of Black-legged Kittiwakes Rissa tridactyla at an Alaskan colony

The majority of seabirds breed colonially and exhibit considerable site fidelity over the course of their long lifespans. Initial colony selection can therefore have substantial fitness consequences; however, factors contributing to recruitment into colonies and subsequent fidelity remain unclear. We used multi-state capture-recapture models to test several hypotheses related to apparent fledgling survival, the probability of recruitment to natal colonies, and apparent post-recruitment survival in Black-legged Kittiwakes with data from individuals banded as chicks and subsequently resighted at a colony in south-central Alaska over a twenty-year period. Competitive models suggested that apparent fledgling survival declined throughout our study; this decline was likely driven by intrinsic, cohort-specific processes and was not explainable by post-fledging wind and climate conditions. Independent resightings at other colonies suggest the apparent decline may have been at least partially influenced by permanent emigration (natal dispersal) that occurred more frequently when the colony size was large. Recruitment was primarily age-dependent, with no detectable effect of early life experience or annual changes in colony size, colony productivity, climate, or average weather conditions. We estimated an average recruitment age of seven years, which is older than typically reported for Atlantic kittiwake populations, and supports a more conservative life history strategy for kittiwakes in the Pacific. Variation in apparent survival of recruits was cohort-specific and did not correlate with age or annual changes in the factors listed above. Instead, apparent survival of recruits was best explained by colony size during a cohort’s second year, suggesting a degree of negative density dependence in post-recruitment survival or fidelity. This information could prove useful to managers deciding how to allocate resources among small, growing colonies and large, well-established colonies.

Alaska↗

Ecological and management implications of climate change induced shifts in phenology of coastal fish and wildlife species in the Northeast CASC region

Climate change is causing species to shift their phenology, or the timing of recurring life events such as migration and reproduction, in variable and complex ways. This can potentially result in mismatches or asynchronies in food and habitat resources that negatively impact individual fitness, population dynamics, and ecosystem function. Numerous studies have evaluated phenological shifts in terrestrial species, particularly birds and plants, yet far fewer evaluations have been conducted for marine animals. This project seeks to improve our understanding of shifts in the timing of seasonal migration, spawning or breeding, and biological development (i.e. life stages present, dominant) of coastal fishes, marine mammals,and migratory shore and seabirds along the U.S Atlantic coast. Ideally the suite of species selected will allow us to compare whether fish, marine mammals, shore and seabird predators are shifting their phenology at different rates than their primary prey and optimal habitat conditions, thus influencing trophic interactions and population dynamics. A comprehensive literature review will be conducted simultaneous to data collection and synthesis to determine what is known, and what knowledge/information/data gaps exist regarding regional phenological responses of coastal species to climate change. Project results will help managers assess the vulnerability of coastal species to climate change by providing information on how they are responding to impacts in the region.

Conference Paper↗

Bug flows: Don’t count your midges until they hatch

Usually when people hear about a “bug problem” it’s due to an undesirable overabundance of insects (think plague of locusts). In the Colorado River in Grand Canyon, however, we are faced with the opposite predicament: the river is essentially devoid of bugs. Aquatic insects are a fundamental component of a healthy river ecosystem. Most aquatic insects spend their juvenile life stages (egg, larva, pupa) in the river and their winged adult life stage flying along the riparian corridor. Throughout these metamorphoses one thing is for certain: aquatic insects are prey for fish, birds, bats, lizards, and even other invertebrates. In Grand Canyon, food web studies conducted by the US Geological Survey (USGS) have demonstrated that populations of both native and sport fish are food limited (Cross et al. 2013, Kennedy et al. 2013). In other words, fish in Grand Canyon are consistently facing a calorie deficit. Indeed, the US Fish and Wildlife Service has cited the inadequate and unreliable food supply as the single greatest problem facing endangered Humpback Chub populations in the Grand Canyon (USFWS 2019).

Boatman's Quarterly Review↗

Global status of trout and char: Conservation challenges in the twenty-first century

Freshwater ecosystems are among the most threatened ecosystems in the world (Richter et al. 1997; Strayer and Dudgeon 2010), and freshwater fishes may now be the most threatened group of vertebrates (Ricciardi and Rasmussen 1999; Vorosmarty et al. 2010; Darwall and Freyhof 2016). Of the 7,300 freshwater fish species globally assessed by the International Union for Conservation of Nature (IUCN, www.iucnredlist.org) in 2013, nearly one of every three species was threatened with extinction (Darwall and Freyhof 2016). Growing pressures from a multitude of direct and indirect human stressors (e.g., habitat loss and degradation, pollution, invasive species, overexploitation, diversion or alteration of biological flows, climate change, and others) threaten the persistence of many freshwater fish species and entire aquatic communities around the globe (Limburg et al. 2011). This pattern is particularly true for salmonid fishes (family Salmonidae, subfamily Salmoninae, belonging to the genera Oncorhynchus, Salvelinus, Salmo, Hucho, Parahucho, Brachymystax, and Salvethymus). Salmonids are globally-distributed, coldwater taxa with life-cycles restricted entirely to freshwater ecosystems (typically referred to as trout and char), but also Atlantic and Pacific salmon with more complex anadromous life-histories.

Book chapter↗

How and why is the timing and occurrence of seasonal migrants in the Gulf of Maine changing due to climate?

Plants and animals undergo certain recurring life-cycle events, such as migrations between summer and winter habitats or the annual blooming of plants. Known as phenology, the timing of these events is very sensitive to changes in climate (and changes in one species’ phenology can impact entire food webs and ecosystems). Shifts in phenology have been described as a “fingerprint” of the temporal and spatial responses of wildlife to climate change impacts. Thus, phenology provides one of the strongest indicators of the adaptive capacity of organisms (or the ability of organisms to cope with future environmental conditions). In this study, researchers are exploring how the timing and occurrence of a number of highly migratory marine animals is changing due to a series of climatic and ecological shifts. First, using existing long-term historical data series, they will determine the direction and magnitude of how migration, abundance, or other phenological factors have changed for marine mammals, sea turtles, and fishes that migrate into the Gulf of Maine on a seasonal basis. Because marine animals are inherently difficult to detect, the team will apply dynamic occupancy models to evaluate seasonal migration patterns and habitat use across multiple habitats in the Gulf of Maine region. The project team will also synthesize regional information on a key, ecologically-important prey fish, sandlance, whose timing and abundance is a strong predictor of the occurrence and behavior of predator species targeted in this study as well as a range of other regional fish and wildlife of conservation and management concern. Results from this component of the project will identify coastal fish and wildlife species that are relatively more or less able to adapt and thus potentially vulnerable to climate change; determine the likely primary drivers of those changes; and identify data gaps and future monitoring needs. Ultimately, this information will be available and useful for regional coastal management and adaptation decisions that will allow managers to effectively plan for the future. In a second component of the project, researchers will focus specifically on changes in migration patterns of the endangered North Atlantic right whale. While shifts in the distribution and time of recurring life events are adaptive responses that may help species cope with climate impacts, they can also lead to changes in how species interact with humans. The North Atlantic right whale is one of the most endangered whale species on the planet. In the North Atlantic Ocean, ship strikes and entanglements with commercial fishing gear represent fatal threats to right whales. Recent reports suggest that North Atlantic right whale migration patterns have changed. Many researchers posit that shifts in migration are responsible for recent increases in the overlap between right whales and human activities, especially fishing. To help understand how changes in right whale movements and behaviors may overlap with ship traffic, and thus put the animals at risk of encountering vessels, we will combine right whale habitat models with ship traffic maps. The end result will be a set of maps identifying risk levels.

Gulf of Maine↗

Benefits and limitations of installing driving surface aggregate at two federal lands sites

The worldwide network of unpaved roads is estimated to include at least 14 million km (8.7 million miles; 1). Although they are vital for local communities, these roads are expensive to maintain and may cause environmental damage through sediment and dust pollution (e.g., 2). Among aggregate-surfaced roads, locally available materials are often used as a surface wearing course, with little or no testing and sometimes no formal specification. The materials vary widely in quality and may deteriorate quickly. As a result, road managers may be forced to increase the frequency of maintenance grading and aggregate replacement to compensate for the poor performance. Improving the quality of surface aggregate on unpaved roads is one strategy for increasing road performance while also reducing environmental impacts. Although higher-quality aggregates require greater up-front investment, they can result in lower overall life-cycle costs by extending road life and reducing maintenance costs. Driving Surface Aggregate (DSA) is an aggregate specification developed by the Pennsylvania State University Center for Dirt and Gravel Road Studies that is designed to achieve maximum compaction and resist erosion. The gradation of DSA, coupled with recommended optimum moisture and placement guidelines, results in a smoother, more tightly bound surface that preserves fine material rather than allowing it to escape as sediment or dust. In previous studies, DSA has been shown to reduce sediment runoff by 80-90% (3) and dust production by up to 90% (4) compared to existing road surface gradations. Although DSA has been used extensively in the state of Pennsylvania, USA, the specification is almost unknown elsewhere. The objective of this study was to demonstrate the benefits and limitations of DSA when deployed across a wider geographic area. We installed road sections of DSA at two federal lands sites in the eastern United States. Sediment runoff, dust production, and road surface condition on these sections were measured approximately 12 months post-construction. At both sites, DSA reduced sediment runoff by up to 91%, relative to traditional aggregates. At one site in Indiana, DSA also reduced dust production and aggregate loss. At the other site in Vermont, DSA and traditional aggregate sections performed similarly in dust production and road condition. Overall, this study 1) demonstrates that DSA can be an effective and environmentally responsible aggregate choice for unpaved roads, and 2) provides information on site conditions (e.g., roads near headwater streams) under which DSA is likely to be particularly beneficial.

Indiana, Vermont↗