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USGS2021

Development of demographic models to analyze populations with multi-year data—Using Agassiz’s Desert Tortoise (Gopherus agassizii) as a case study

We developed a model for analyzing multi-year demographic data for long-lived animals and used data from a population of Agassiz’s desert tortoise ( Gopherus agassizii ) at the Desert Tortoise Research Natural Area in the western Mojave Desert of California as a case study. The study area was 7.77 square kilometers and included two locations: inside and outside the fenced boundary. The wildlife-permeable, protective fence was designed to prevent entry from vehicle users and sheep grazing. We collected mark-recapture data from 1,123 tortoises during seven annual surveys consisting of two censuses each over a 34-year period. Additional data were collected when marked tortoises were recovered dead and removed between survey years. We used a Bayesian modeling framework to develop a multistate Jolly-Seber model because of its ability to handle unobserved (latent) states and modified this model to incorporate the additional data from non-survey years. Three size-age states (juvenile, immature, adult), sex (female, male), two location states (inside and outside the fenced boundary), and three survival states (not-yet-entered, entered/alive, and dead/removed) were incorporated into the model. We calculated population densities and estimated probabilities of growth of the tortoises from one size-age state to a larger size-age state, survival after 1 year and 5 years, and detection. Our results show a declining population with low estimates for survival after 1 year and 5 years. The probability for tortoises to move from outside to inside the boundary fence was greater than for tortoises to move from inside the fence to outside. The probability for detecting tortoises differed by size-age state and was lowest for the smallest tortoises and highest for the adult tortoises. The framework for the model can be used to analyze other animal populations where vital rates are expected to vary depending on multiple individual states.

Open-File Report↗

USGS2022

Round Goby captured in a North American estuary: Status and implications in the Hudson River, New York

Round Goby Neogobius melanostomus , a nonnative fish species to North America, has been rapidly expanding through the connected waterways of the Laurentian Great Lakes. Herein, we document the eastward and southern expansion of Round Goby into the Hudson River, New York, an iconic coastal estuary that drains to Long Island Sound and the Atlantic seaboard. In summer and early fall 2021, routine fish monitoring conducted by the New York State Department of Environmental Conservation documented a population of Round Goby in the tidal portion of the Hudson River. Over the course of monitoring in 2021, personnel collected 112 Round Goby between Albany, New York, and Poughkeepsie, New York, with the southernmost collection occurring approximately 140 km downstream of invasion front as reported in 2020 within the New York State Canal System. Although Round Goby previously colonized large rivers and streams in the Great Lakes watershed, there is little information about the invasion success and ecological impacts of Round Goby in estuarine environments in North America. We discuss the distribution and biological characteristics of the Hudson River Round Goby population as well as the potential ecological implications and areas of future research and monitoring for this range expansion.

New York↗

USGS1981

Sampling strategies for radio-tracking coyotes

Ten coyotes radio-tracked for 24 h periods were most active at night and moved little during daylight hours. Home-range size determined from radio-locations of 3 adult coyotes increased with the number of locations until an asymptote was reached at about 35-40 independent day locations or 3 6 nights of hourly radio-locations. Activity of the coyote did not affect the asymptotic nature of the home-range calculations, but home-range sizes determined from more than 3 nights of hourly locations were considerably larger than home-range sizes determined from daylight locations. Coyote home-range sizes were calculated from daylight locations, full-night tracking periods, and half-night tracking periods. Full- and half-lnight sampling strategies involved obtaining hourly radio-locations during 12 and 6 h periods, respectively. The half-night sampling strategy was the best compromise for our needs, as it adequately indexed the home-range size, reduced time and energy spent, and standardized the area calculation without requiring the researcher to become completely nocturnal. Sight tracking also provided information about coyote activity and sociability.

Wildlife Society Bulletin↗

USGS2008

Birds of the US-Mexico borderlands: Distribution, ecology and conservation

The concept for this volume began as a scientifi c symposium at the North American Ornithological Conference (NAOC) in Veracruz, Mexico in October 2006. The symposium was entitled “Avian Distributional Change, Anthropogenic Challenges, and Recent Avian Research and Technological Advances within the US–Mexico Border Region,” and was cochaired by two of us (DJK and TB) along with Carol Beardmore (Sonoran Joint Venture) and Bill Howe (USDI Fish and Wildlife Service). In light of the importance of the borderland region for birds and bird conservation, and because of the great need for additional information about this poorly studied region, we have compiled this volume to present new information about bird distribution, ecology, and conservation.

Studies in Avian Biology↗

USGS2024

More than a decade of conservation biology and research in Sonora and Arizona: The endangered Sonoran Tiger Salamander and threatened Chiricahua Leopard Frog

Only two species of amphibians from Arizona are listed under the federal Endangered Species Act. The Sonoran Tiger Salamander was listed as an endangered species without critical habitat in 1997. The Chiricahua Leopard Frog was listed as a threatened species in 2002; critical habitat was designated in 2012. In this review, we summarize conservation and research conducted on these two species with a focus on work in the southeastern Arizona/northeastern Sonora borderlands, but we also touch upon seminal work on the Chiricahua Leopard Frog at Buenos Aires National Wildlife Refuge (BANWR).

Arizona, Sonora↗

USGS2008

Environmental contaminant hazards to wildlife at National Capital region and Mid-Atlantic National Park Service units

Pollutant data for air, water, soil and biota were compiled from databases and internet sources and by staff interviews at 23 National Park Service (NPS) units in 2005. A metric was derived describing the quality and quantity of data for each park, and in combination with known contaminant threats, the need for ecotoxicological study was identified and ranked. Over half of NP units were near Toxic Release Inventory sites discharging persistent pollutants, and fish consumption advisories were in effect at or near 22 of the units. Pesticide and herbicide use was found to be minimal, with the exception of those units with agricultural leases. Only 70 reports were found that describe terrestrial vertebrate environmental contaminant data at or near the units. Of the >75,000 compounds in commerce, empirical exposure data were limited to merely 58 halogenated compounds, insecticides, rodenticides, metals, and some contemporary compounds. Further ecotoxicological monitoring and research is warranted at several units including Shenandoah National Park, Richmond National Battlefield Park, Chesapeake & Ohio Canal National Historical Park, Valley Forge National Historical Park, Hopewell Furnace National Historic Site, Monocacy National Battlefield, and Harpers Ferry National Historical Park. The types of investigations vary according to the wildlife species present and potential contaminant threats, but should focus on contemporary use pesticides and herbicides, polychlorinated biphenyls, mercury, lead, and perhaps antibiotics, flame retardants, pharmaceuticals, and surfactants. Other management recommendations include inclusion of screening level contaminant risk assessments into the NPS Vital Signs Program, development of protocols for toxicological analysis of seemingly affected wildlife, alternative methods and compounds for pest management, and use of non-toxic fishing tackle by visitors.

Book chapter↗

USGS2008

Davis Pond freshwater prediversion biomonitoring study: freshwater fisheries and eagles

In January 2001, the construction of the Davis Pond freshwater diversion structure was completed by the U.S. Army Corps of Engineers. The diversion of freshwater from the Mississippi River is intended to mitigate saltwater intrusion from the Gulf of Mexico and to lessen the concomitant loss of wetland areas. In addition to the freshwater inflow, Barataria Bay basin would receive nutrients, increased flows of sediments, and water-borne and sediment-bound compounds. The purpose of this biomonitoring study was, therefore, to serve as a baseline for prediversion concentrations of selected contaminants in bald eagle ( Haliaeetus leucocephalus ) nestlings (hereafter referred to as eaglets), representative freshwater fish, and bivalves. Samples were collected from January through June 2001. Two similarly designed postdiversion studies, as described in the biological monitoring program, are planned. Active bald eagle nests targeted for sampling eaglet blood (n = 6) were generally located southwest and south of the diversion structure. The designated sites for aquatic animal sampling were at Lake Salvador, at Lake Cataouatche, at Bayou Couba, and along the Mississippi River. Aquatic animals representative of eagle prey were collected. Fish were from three different trophic levels and have varying feeding strategies and life histories. These included herbivorous striped mullet ( Mugil cephalus ), omnivorous blue catfish ( Ictalurus furcatus ), and carnivorous largemouth bass ( Micropterus salmoides ). Three individuals per species were collected at each of the four sampling sites. Freshwater Atlantic rangia clams ( Rangia cuneata ) were collected at the downstream marsh sites, and zebra mussels ( Dreissena spp.) were collected on the Mississippi River. The U.S. Geological Survey (USGS) Biomonitoring of Environmental Status and Trends (BEST) protocols served as guides for fish sampling and health assessments. Fish are useful for monitoring aquatic ecosystems because they accumulate pesticides and other contaminants. Biomarker data on individual fish, generated at the USGS National Wetlands Research Center (Lafayette, La.), included percent white blood cells in whole blood, spleen weight to body weight ratio, liver weight to body weight ratio, condition factor, splenic macrophage aggregates, and liver microsomal 7-ethoxyresorufin-o-deethylase (EROD) activity. Fish age was estimated by comparing total lengths with values from the same species in the Southeast United States as determined from the literature. Contaminant analyses were coordinated by the U.S. Fish and Wildlife Service (USFWS) Analytical Control Facility (Laurel, Md.), where residues of organochlorine (OC) pesticides, total polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (AHs), and trace elements were determined. The organic contaminant data were generated at the Mississippi State University Chemical Lab (Mississippi State, Miss.), and the inorganic contaminant data were generated by the Texas A&M University Geochemical and Environmental Research Group (College Station, Tex.). Statistical tests were performed to assess relationships among contaminants, fish age, fish species, and collection sites. Trends in interspecific differences among fish in concentrations of contaminants were noted. Striped mullet (hereafter mullet) frequently displayed the highest chemical concentrations. Levels of contaminants were generally higher in samples obtained from the Mississippi River than in those collected from the diversion area and were higher in mussels and clams (hereafter bivalves) than in fish. Because the Mississippi River sampling site for mullet and largemouth bass was downriver of the structure and south of New Orleans and the catfish site was upriver, the downriver data may not be directly reflective of the results from the receiving waters at the Davis Pond structure. Compared to the Caernarvon freshwater prediversion study in 1990 that assessed possible influx of contaminants with the freshwater diversion, contaminant levels in fishes and bivalves in this study were generally lower, yet three nontoxic inorganic elements in Davis Pond fish samples exhibited ranges of concentrations that were more than two times higher than did those from Caernarvon. Levels in bivalves were different between diversions but about equal in the numbers of trace elements showing high levels per location. Contaminant values were compared to those listed in various literature and agency sources, both regional and national, including the National Contaminant Biomonitoring Program (NCBP), in which the 85th percentile and above represents what is considered to be an elevated contaminant concentration and cause for concern. Generally, bivalves were at the high end of their ranges for both organic and inorganic contaminants. In this study, OCs were detectable in 67 percent of fish from the Mississippi River site, ranging from 0.15 to 1.09 μg/g wet weight (ww) or fresh weight (fw), and in 11 percent of the fish from the marsh sites, ranging from 0.06 to 0.612 μg/g ww. Bivalves from the Mississippi River had OC levels of 0.096 μg/g ww, whereas none were detectable in bivalves at the marsh sites. In this study, p,p ’-dichlorodiphenyldichloroethylene ( p,p’ -DDE) (a biodegradation product of DDT [dichlorodiphenyl trichloroethane]) and total PCBs were the most frequently detected OCs and were primarily from the Mississippi River. For total OC content, using adjusted least squares means, some significant interactions were noted between fish species and sites. PAHs were detected in aquatic animals at all sites (range of 0.017–17.534 μg/g ww), as were AHs (range of 0.423–4.549 μg/g ww); the highest levels of PAHs and AHs were found in bivalves from the Mississippi River. When analysis of variance (α = 0.05) was performed with data from aquatic animals, there were only two significant relationships between PAHs, AHs, and OCs between species, site, and age or the interaction among these variables. There was an interaction between fish species and n-decane (an AH) in that mullet and largemouth bass had significantly higher levels than did catfish ( P = 0.0175). When general linear means were used to investigate associations of inorganic contaminants among fish species, site, and age or any interactions among these variables, no significant results were noted for arsenic, cadmium, lead, beryllium, boron, molybdenum, or nickel. The range of mercury in fish in this study was 0.04–0.14 μg/g ww (0.14– 0.48 μg/g dry weight [dw]), with the most elevated levels detected in predatory largemouth bass at the sampling point farthest downstream from the structure and within the marsh area. Mercury was positively correlated with fish age ( P = 0.0152), where levels were estimated to increase 0.0253 parts per million (ppm) dw per year. In the Mississippi River, catfish showed significantly higher levels of mercury than did mullet or largemouth bass ( P = 0.00167). Among fish species, mullet displayed the highest levels in fish of aluminum, barium, manganese, and iron, all considered to have low toxicity in hydrologic systems. An interaction between fish and site was seen with aluminum ( P = 0.0031), where concentrations in mullet were significantly higher in the Mississippi River than at the other sites, as was also seen with barium ( P = 0.0009), chromium ( P = <0.0001), manganese ( P = 0.0004), strontium ( P = 0.0074), vanadium ( P = 0.0156), and zinc ( P = 0.0059). For iron ( P = 0.0.0001), mullet and largemouth bass at both the Mississippi River and Lake Salvador showed higher levels than did catfish, and these two species showed higher levels at two of the four sites. An interaction between fish and site was also seen with chromium ( P = <0.0001) in that concentrations in mullet were significantly higher in the Mississippi River than at the other sites, as was also seen with strontium ( P = 0.0074), vanadium ( P = 0.0156), and zinc ( P = 0.0059), metals for which deleterious effects have been demonstrated in other ecosystems. The NCBP program lists the 85th percentile for zinc at 34.2 μg/g fw (117.9 μg/g dw). In the Davis Pond prediversion biomonitoring study (hereafter the current study), one fish (MUL31RIVER, fish ID 8) showed values higher than that (125.4 μg/g dw or 37.54 μg/g ww), and the Mississippi River bivalve sample (MUSSRIVER) had a value of 140 μg/g dw (41.2 μg/g ww). In the current study, approximately 86 percent of the fish had measurable selenium levels, yet none reached the 85th percentile. The 85th percentile for selenium from the NCBP was 0.73 μg/g ww. Significantly higher levels of selenium were seen in mullet than in largemouth bass and catfish ( P = 0.0023). The NCBP 85th percentile for lead is 0.22 μg/g ww (0.76 μg/g dw). In the current study, the range of concentrations of lead was as much as 18.3 ppm dw (MUL31RIVER, fish ID 8), with the three most elevated values (range of 3.46–5.31 μg/g ww) coming from mullet from the Mississippi River. Biomarker data are measurable and directly reflect the condition of the animal, and measuring more than one biomarker in an individual increases confidence in health assessments. In the current study, biomarkers included macrophage aggregates (MAs), liver (hepatosomatic index [HSI]) and spleen (splenosomatic index [SSI]) weight to body weight ratios, percent white blood cells (WBCs) in whole blood, and condition factor. Few significant differences were noted with any of the biomarkers between sites, and there were no relationships between species and sites. For improved use of biomarker assessments, an increase in fish sample size would be useful for postdiversion sampling, as would comparisons of fish of the same sex and reproductive condition. During the current study, success for eagle nests in the diversion area and reference sites was similar as determined by numbers of nestlings fledged. When temperatures were below average during winter 2000, nests in both regions similarly failed. At each nest, the primary evidence of food items was small mammals. Eaglets (n = 6) generally appeared healthy, and whole blood concentrations of organic contaminants exceeded detection limits with three incidences of p,p’ -DDE (0.002–0.006 μg/L ww) and one incidence of oxychlordane (0.002 μg/L ww). The levels of p,p’ -DDE were well below those that have been inversely correlated with productivity and success rates of nesting bald eagles on a regional scale. The low values found in the whole blood samples for OC pesticides and PCBs were even lower when corrected for plasma volume. Aluminum values were 3.66 and 5.75 μg/L in two samples, zinc ranged from 5.21 to 6.77 μg/L ww in six samples, and silicon ranged from 1.7 to 4.6 μg/L in four samples. Selenium was detectable in each bird with the range at 0.332–0.566 μg/L ww, and strontium ranged from 0.0581 to 0.0975 μg/L ww. Mercury was detectable in blood samples from each bird and ranged from 0.0254 to 0.0845 μg/L ww, whereas lead was detectable in four samples and ranged from 0.0042 to 0.0136 μg/L ww. Although no detectable levels of total PCBs were found (also correlated with decreased reproductive productivity), 70 percent of the aquatic animals from the Mississippi River contained total PCBs (range 0.13–0.79 μg/L), whereas only about 7 percent of the aquatic animals sampled from the marsh area contained PCBs. Suggestions for postdiversion sampling include lowering the analytical detection limit for some metals, sampling aquatic animals over the course of a single season, obtaining a higher sample number of mature fish of one species (for example, blue catfish) within a range of total lengths for biomarker analyses, obtaining otoliths for estimating fish ages, assessing dioxins in eaglet blood, examining triazines in water, and obtaining all Mississippi River fish samples as close to the Davis Pond structure intake as possible. Because contaminants found in blood of eaglets reflect their prey species and because of the contaminant levels found in fish in the current study, eaglets may not be consuming primarily these species; therefore, obtaining juvenile nutria ( Myocastor coypus ) or turtle species for contaminant analyses might be considered, as well as collecting greater blood volume and using plasma to measure OCs and PCBs. Data obtained postdiversion will be compared with prediversion data to monitor changes.

Louisiana↗

USGS2000

Ecology and biology of paddlefish in North America: historical perspectives, management approaches, and research priorities

Paddlefish ( Polyodon spathula , Polyodontidae)are large, mostly-riverine fish that once were abundant in medium- to large-sized river systems throughout much of the central United States. Concern for paddlefish populations has grown from a regional fisheries issue to one of national importance for the United States. In 1989, the U.S. Fish and Wildlife Service (USFWS) was petitioned to list paddlefish as a federally threatened species under the Endangered Species Act. The petition was not granted, primarily because of a lack of empirical data on paddlefish population size, age structure, growth, or harvest rates across the present 22-state range. Nonetheless, concern for paddlefish populations prompted the USFWS to recommend that paddlefish be protected through the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The addition of paddlefish to Appendix II of CITES, which was approved in March 1992, provides a mechanism to curtail illegal trade in paddlefish and their parts and supports a variety of conservation plans. Paddlefish populations have been negatively affected by overharvest, river modifications, and pollution, but the paddlefish still occupies much of its historic range and most extant populations seem to be stable. Although many facets of paddlefish biology and ecology are well understood, the lack of information on larval and juvenile ecology, mechanisms that determine recruitment, population size and vital rates, interjurisdictional movements, and the effects of anthropogenic activities present significant obstacles for managing paddlefish populations. Questions about the size and structure of local populations, and how such populations are affected by navigation traffic, dams, and pollution are regarded as medium priority areas for future research. The availability of suitable spawning habitat and overall reproductive success in impounded rivers are unknown and represent critical areas for future research. Research on reproductive and recruitment success in impounded rivers have significant implications for managing paddlefish, as rivers are modified further for human use.

Reviews in Fish Biology and Fisheries↗

USGS2011

Evidence and implications of recent and projected climate change in Alaska's forest ecosystems

The structure and function of Alaska's forests have changed significantly in response to a changing climate, including alterations in species composition and climate feedbacks (e.g., carbon, radiation budgets) that have important regional societal consequences and human feedbacks to forest ecosystems. In this paper we present the first comprehensive synthesis of climate-change impacts on all forested ecosystems of Alaska, highlighting changes in the most critical biophysical factors of each region. We developed a conceptual framework describing climate drivers, biophysical factors and types of change to illustrate how the biophysical and social subsystems of Alaskan forests interact and respond directly and indirectly to a changing climate. We then identify the regional and global implications to the climate system and associated socio-economic impacts, as presented in the current literature. Projections of temperature and precipitation suggest wildfire will continue to be the dominant biophysical factor in the Interior-boreal forest, leading to shifts from conifer- to deciduous-dominated forests. Based on existing research, projected increases in temperature in the Southcentral- and Kenai-boreal forests will likely increase the frequency and severity of insect outbreaks and associated wildfires, and increase the probability of establishment by invasive plant species. In the Coastal-temperate forest region snow and ice is regarded as the dominant biophysical factor. With continued warming, hydrologic changes related to more rapidly melting glaciers and rising elevation of the winter snowline will alter discharge in many rivers, which will have important consequences for terrestrial and marine ecosystem productivity. These climate-related changes will affect plant species distribution and wildlife habitat, which have regional societal consequences, and trace-gas emissions and radiation budgets, which are globally important. Our conceptual framework facilitates assessment of current and future consequences of a changing climate, emphasizes regional differences in biophysical factors, and points to linkages that may exist but that currently lack supporting research. The framework also serves as a visual tool for resource managers and policy makers to develop regional and global management strategies and to inform policies related to climate mitigation and adaptation.

Alaska↗

USGS2024

Effects of harmful algal blooms on amphibians and reptiles are under-reported and under-represented

Harmful algal blooms (HABs) are a persistent and increasing problem globally, yet we still have limited knowledge about how they affect wildlife. Although semi-aquatic and aquatic amphibians and reptiles have experienced large declines and occupy environments where HABs are increasingly problematic, their vulnerability to HABs remains unclear. To inform monitoring, management, and future research, we conducted a literature review, synthesized the studies, and report on the mortality events describing effects of cyanotoxins from HABs on freshwater herpetofauna. Our review identified 37 unique studies and 71 endpoints (no-observed-effect and lowest-observed-effect concentrations) involving 11 amphibian and 3 reptile species worldwide. Responses varied widely among studies, species, and exposure concentrations used in experiments. Concentrations causing lethal and sublethal effects in laboratory experiments were generally 1 to 100 µg/L, which contains the mean value of reported HAB events but is 70 times less than the maximum cyanotoxin concentrations reported in the environment. However, one species of amphibian was tolerant to concentrations of 10,000 µg/L, demonstrating potentially immense differences in sensitivities. Most studies focused on microcystin-LR (MC-LR), which can increase systemic inflammation and harm the digestive system, reproductive organs, liver, kidneys, and development. The few studies on other cyanotoxins illustrated that effects resembled those of MC-LR at similar concentrations, but more research is needed to describe effects of other cyanotoxins and mixtures of cyanotoxins that commonly occur in the environment. All experimental studies were on larval and adult amphibians; there were no such studies on reptiles. Experimental work with reptiles and adult amphibians is needed to clarify thresholds of tolerance. Only nine mortality events were reported, mostly for reptiles. Given that amphibians likely decay faster than reptiles, which have tissues that resist decomposition, mass amphibian mortality events from HABs have likely been under-reported. We propose that future efforts should be focused on seven major areas, to enhance our understanding of effects and monitoring of HABs on herpetofauna that fill important roles in freshwater and terrestrial environments. Environ Toxicol Chem 2024;00:1–14. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Environmental Toxicology and Chemistry↗

USGS2021

SUAS and machine learning integration in waterfowl population surveys

The rapid technological development of small Unmanned Aircraft Systems (sUAS) has led to an increase in capabilities of aerial image collection and analysis for monitoring a variety of wildlife species including waterfowl. Biologists mainly rely on conducting ocular surveys from fixed-wing aircraft or helicopters to estimate waterfowl abundance. sUAS provide an alternative that is safer, less expensive, and more flexible. Researchers have attempted to estimate waterfowl abundance from aerial imagery, but this method has proven to be too time consuming. Machine learning provides the opportunity to more efficiently estimate waterfowl abundance from aerial imagery. In this paper, we present a new integrated system of sUAS and machine learning for waterfowl population surveys. This system provides a user-friendly process for sUAS survey design, deployment, and data post-processing using deep learning methods to automatically detect and count waterfowl. To develop this system, we conducted many sUAS flights to capture a diversity of imagery and assembled six datasets of imagery taken from both fix-winged aircraft and sUAS flights. We used these datasets to develop and evaluate state-of-the-art deep learning models for waterfowl detection. Our system of using a combination of sUAS and machine learning has proved to be an efficient and accurate approach for collecting, analyzing, and estimating waterfowl abundance.

Conference Paper↗

USGS2001

Estimation of population size using open capture-recapture models

One of the most important needs for wildlife managers is an accurate estimate of population size. Yet, for many species, including most marine species and large mammals, accurate and precise estimation of numbers is one of the most difficult of all research challenges. Open-population capture-recapture models have proven useful in many situations to estimate survival probabilities but typically have not been used to estimate population size. We show that open-population models can be used to estimate population size by developing a Horvitz-Thompson-type estimate of population size and an estimator of its variance. Our population size estimate keys on the probability of capture at each trap occasion and therefore is quite general and can be made a function of external covariates measured during the study. Here we define the estimator and investigate its bias, variance, and variance estimator via computer simulation. Computer simulations make extensive use of real data taken from a study of polar bears (Ursus maritimus) in the Beaufort Sea. The population size estimator is shown to be useful because it was negligibly biased in all situations studied. The variance estimator is shown to be useful in all situations, but caution is warranted in cases of extreme capture heterogeneity.

Journal of Agricultural, Biological, and Environme↗

USGS2003

Effects of hydrology on red mangrove recruits

Coastal wetlands along the Gulf of Mexico have been experiencing significant shifts in hydrology and salinity levels over the past century as a result of changes in sea level and freshwater drainage patterns. Local land management in coastal zones has also impacted the hydrologic regimes of salt marshes and mangrove areas. Parks and refuges in south Florida that contain mangrove forests have, in some cases, been ditched or impounded to control mosquito outbreaks and to foster wildlife use. And while mangroves dominate the subtropical coastlines of Florida and thrive in saltwater environments, little is known about how they respond to changes in hydrology under managed or variable tidal conditions. USGS researchers designed a study to evaluate the basic hydrological requirements of mangroves so that their health and survival may be more effectively managed in controlled impoundments and restored wetlands. Mangroves are commonly found in the intertidal zone (between low and high tides) in a rather broad spectrum of hydrologic settings. Because they thrive at the interface of land and sea, mangroves are subject to changes in freshwater flow (flow rate, nutrients, pollutants) and to marine influences (sea-level rise, salinity). Salinity has long been recognized as a controlling factor that determines the health and distribution of mangrove forests. Field and experimental observations indicate that most mangrove species achieve their highest growth potential under brackish conditions (modest salinity) between 10 and 20 parts per thousand (ppt). Yet, if provided with available propagules, successful regeneration, and limited competition from other plants, then mangroves can survive and thrive in freshwater systems as well. Because little is known about the growthand survival patterns of mangrove species relative to changing hydrology, USGS scientists conducted greenhouse and field experiments to determine how flooded or drained patterns of hydrology would influence growth of the red mangrove, Rhizophora mangle (fig. 1). Red mangrove propagules (recruits) of select sizes and genotypes (i.e., genetically similar groups) were planted both in greenhouses and in the field. Seedling growth was monitored in both studies on a quarterly basis for over a year; measurements included shoot growth, seedling height, and a final harvest of plant biomass.

Fact Sheet↗

USGS1983

[Book review] Waterfowl ecology and management: Selected readings

This book is a compilation of papers from the extensive and varied published literature on the ecology and management of waterfowl. The 125 technical papers reprinted in this book are arranged in eight major sections and are from 21 journals, government reports, several books, and proceedings of symposia and annual conferences. The most frequent sources of papers are The Journal of Wildlife Management, The Auk, Transactions North American Wildlife and Natural Resources Conference, and Wildfowl. These readings span the period from 1937 through 1981. A majority of the technical papers was published during the sixties and seventies, reflecting the expansion of waterfowl research during that period. The front cover and the introductory page of each section are illustrated with black-and-white drawings of North American waterfowl by D. R. Barrick.

The Auk↗

USGS2010

Mercury monitoring in fish using a non-lethal tissue biopsy method

The occurrence of mercury in fish is well-known and often occurs at levels that warrant restricted consumption by sensitive human populations. Because of this, local wildlife and health agencies have developed monitoring programs to identify the magnitude of fish contamination and changes through time. Monitoring mercury levels in fish typically requires killing fish for removal of a fillet. Recently, researchers have proposed the use of a non-lethal tissue biopsy plug method as a surrogate for analysis of the entire fillet. A non-lethal method is particularly desirable for sampling rare or endangered fish or highly valued fisheries. The Missouri Department of Conservation manages several fisheries where the public is sensitive to excessive fish removal, yet there is a desire for mercury information. One such example is the trophy smallmouth bass (Micropterus dolomieu) fishery in the Ozark’s Eleven Point River. Plug removal is not expected to affect fish survival in the shortterm. However, limited information is available on survival of fish for weeks or months after plug removal.

Missouri↗

USGS2013

Diablotin Pterodroma hasitata : a biography of the endangered Black-capped Petrel

The Black-capped Petrel Pterodroma hasitata was believed extinct throughout much of the 20th century. It is the only gadfly petrel currently known to breed in the Caribbean Basin. Now seriously endangered, the species is presumed extirpated from Martinique, Dominica, and Guadeloupe, and breeding populations currently occur only on Hispaniola and perhaps Cuba. A related form (now considered a full species) once bred, but is now apparently extinct, on Jamaica. The Black-capped Petrel breeding population may number as few as 500 breeding pairs. Remaining populations suffer from multiple threats to terrestrial and pelagic habitats, including harvest by humans and predation by introduced mammals. The exact sizes, locations, and detailed chronologies of all Black-capped Petrel breeding sites remain poorly studied, although major colonies are today apparently restricted to steep sea and inland cliffs along the La Selle Ridge in Hispaniola. The largest known breeding population occurs in Haiti, although there is continued discussion about a possible breeding site in Cuba in the Sierra Maestra mountain range. Accounts from Cuba are based on the unverified assumption that birds observed at sea just offshore of that island are breeding locally. All evidence at present indicates that waters in or adjacent to the Florida Current and the Gulf Stream between north Florida and southern Virginia provide the primary foraging range of Black-capped Petrels. A small foraging area just off of southeast Cuba has also been reported, but the extent and seasonal use of this area are unknown. Concentrations of birds can be found along the Gulf Stream in southeastern US waters throughout the year, but are particularly common in May, August, and late December through early January. Concentrations of adult birds during winter, when peak breeding activity is underway, suggest that breeding birds forage along the Gulf Stream while commuting to and from breeding colonies. Such long-distance foraging is certainly possible for Pterodroma species. Potential threats to Black-capped Petrels include introduced predators, human encroachment on breeding and foraging habitats, and offshore oil, gas, and wind energy development. Increased mercury levels associated with petroleum production also pose a potential threat, as the Black-capped Petrel seems to be highly susceptible to mercury bioaccumulation compared with other pelagic species. In addition, fires and other bright light sources are known to attract Black-capped Petrels, making collisions with wires and other structures on lighted ships and platforms a potential concern. Haitian social-economic instability and increasing habitat loss suggest the likelihood of further population declines and increasing vulnerability of the species to extinction. Our findings are in accord with the recent decision by the US Fish and Wildlife Service (USFWS) to evaluate the need for additional protection of the species and the primary foraging habitat off the southeastern United States under the Endangered Species Act (USFWS 2012). Additional conservation measures and research strategies that warrant further consideration include (1) protection, monitoring, and management of known breeding populations and nesting habitat in the Dominican Republic and Haiti through controlling predators, installing artificial nest burrows in appropriate sites and hiring local wardens at breeding sites during the nesting season; (2) local and regional training, education and public awareness (e.g. Blanchard & Nettleship 1992); (3) restoration of the original common name Diablotin to common usage to promote the historical and cultural importance of this species; (4) studies to determine the distribution and genetic variability in the remaining populations; and (5) studies of satellite-tagged birds to assess their seasonal and geographic use of pelagic habitats.

Marine Ornithology: Journal of Seabird Research an↗

USGS2022

Condition of resident fish communities in the Eighteenmile Creek Area of Concern, New York

The lower 3.5 km of Eighteenmile Creek, a tributary to Lake Ontario in New York, was designated as an Area of Concern (AOC) in 1985 under the Great Lakes Water Quality Agreement due to extensive contamination of bed sediments by polychlorinated biphenyls (PCBs) and other toxicants. Five beneficial use impairments (BUIs) have been identified in this AOC, including degraded fish and wildlife populations. We surveyed fish communities in the Eighteenmile Creek AOC and in a comparable section of a nearby reference stream (Oak Orchard Creek) during June 2019 to infer whether legacy contaminants are currently impairing fish communities in the AOC to an extent that they differ from the regional reference condition. Estimates of community abundance, biomass, diversity, and fish condition from each system were compared using a noninferiority testing framework. Biomass, diversity, and fish condition in the Eighteenmile Creek AOC were similar or superior to that in Oak Orchard Creek, while abundance was 20% lower in the AOC. These findings and those of a 2007 sampling effort suggest that fish communities in the Eighteenmile Creek AOC are not impaired despite recent studies indicating that PCBs are bioaccumulating in fish tissues at 1–2 orders of magnitude above background levels. Future assessments in the Eighteenmile Creek AOC might focus on the condition of benthic macroinvertebrate communities and potential toxicity of local contaminants to piscivorous wildlife in order to fully address the remaining aspects of the fish and wildlife populations beneficial use impairment.

New York↗

USGS2004

Movement behavior, dispersal, and the potential for localized management of deer in a suburban environment

We examined the potential for localized management of white-tailed deer ( Odocoileus virginianus ) to be successful by measuring movements, testing site fidelity, and modeling the effects of dispersal. Fifty-nine females were radiomarked and tracked during 1997 through 2000 in Irondequoit, New York, USA, a suburb of Rochester. We constructed home ranges for those deer with A greater than or equal to 18 reclocations/season. Fifty percent minimum convex polygons (MCP) averaged 3.9 (SE = 0.53) ha in the summer and 5.3 (SE = 0.80) ha in the winter. Deer showed strong fidelity to both summer and winter home ranges, and 30 of 31 females showed overlap of summer and winter home ranges. Annual survival was 64%; the major cause of mortality was deer-automobile collisions. Average annual dispersal rates were <15% for yearlings and adults. Using matrix population modeling, we explored the role of female dispersal in sustaining different management objectives in adjacent locales of approximately 1,000 ha. Modeling showed that if female dispersal was 8%, culling would have to reduce annual survival to 58% to maintain a population just under ecological carrying capacity and reduce survival to 42% to keel) the population at one-half carrying capacity. With the same dispersal, contraception Would need to be effective in 32% of females if the population is near carrying capacity and 68% if the population is at one-half of carrying capacity. Movement behavior data and modeling results lend support to the use of a localized approach to management of females that emphasizes neighborhood-scale manipulation of deer populations, but our research suggests that dispersal rates in females could be critical to long-term success.

New York↗