An overview of current programs on drug development and regulation for aquaculture: US Fish and Wildlife Service perspective.
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Chemical contaminants in fish feeds used in federal salmonid hatcheries in the USA.
Recent studies have demonstrated that fish feeds contain significant concentrations of contaminants, many of which can bioaccumulate and bioconcentrate in fish. Organochlorine (OC) contaminants are present in the fish oils and fish meals used in feed manufacture, and some researchers speculate that all fish feeds contain measurable levels of some contaminants. To determine the concentration of contaminants in feeds used in US Fish and Wildlife Service's National Fish Hatcheries, we systematically collected samples of feed from 11 cold-water fish hatcheries. All samples (collected from October 2001 to October 2003) contained at least one polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), polychlorinated biphenyl (PCB) congener, or dichlorodiphenyltrichloroethane (DDT) metabolite. Of the 55 samples in which they were analyzed 39 contained PCDDs, 24 contained PCDFs and 24 contained DDT or its metabolites. There were 10- to 150-fold differences in concentrations of total PCBs, PCDDs, PCDFs and DDT. Although PCBs were the most commonly detected contaminant in our study, concentrations (range: 0.07-10.46 ng g(-1) wet weight) were low compared to those reported previously. In general, we also found lower levels of OCs than reported previously in fish feed. Perhaps most notable was the near absence of OC pesticides - except for DDT or its metabolites, and two samples containing hexachlorocyclohexane (HCH). While contaminant concentrations were generally low, the ecological impacts can not be determined without a measure of the bioaccumulation of these compounds in the fish and the fate of these compounds after the fish are released.
Animal Feed↗
Comparison of an enzyme-linked immunosorbent assay (ELISA) to gas chromatography (GC)--measurement of polychlorinated biphenyls (PCBs) in selected US fish extracts.
The analysis of PCBs in fish tissues by immunoassay methods was evaluated using fish collected from a US monitoring program, the National Contaminant Biomonitoring Program of the US Department of Interior, Fish and Wildlife Service. Selected composite whole fish samples, which represented widely varying concentrations and sources of PCBs, were extracted and subjected to congener PCB analysis by gas chromatography (GC) and total PCB analysis using an ELISA (ePCBs) calibrated against technical Aroclor 1248. PCB congener patterns in these fishes were different from the patterns found in commercial Aroclors or their combinations as demonstrated by principal component analysis of normalized GC congener data. The sum of the PCB congeners measured by GC (total-PCBs) ranged from 37 to 4600 ng/g (wet weight). Concentrations of PCBs as determined by the ELISA method were positively correlated with total-PCBs and the ePCBs/total-PCBs ratios for individual samples ranged from 1 to 6. Ratios of ePCBs/total-PCBs for dilutions of Aroclors 1242, 1254, and 1260 and for matrix spikes range from 0.6 for 1242 to 2.5 for 1254 and 1260. These results suggest that higher chlorinated PCB congeners have higher affinity for the anti-PCB antibodies. Partial least squares with latent variable analysis of GC and ELISA data of selected Aroclors and fish samples also support the conclusion that ELISA derived PCB concentrations are dependent on the degree of chlorination.
Animals↗
Organochlorine residues in fish: National Pesticide Monitoring Program, 1970-74.
As part of the National Pesticide Monitoring Program, the U.S. Fish and Wildlife Service analyzed organochlorine contaminant residues in fish samples collected from about 100 stations each year from 1970 to 1974. During this period, mean residues of DDT and its metabolites declined nationally but remained widespread, and high concentrations continued to be present in areas where DDT use was extensive. Results of interlaboratory crosscheck analyses supported these conclusions, despite interpretation problems posed by intercompound analytical interferences in 1970 and 1971. Temporal trends in PCB residues were less obvious. Highest PCB residues were found in the industrialized areas of the Northwest and Midwest, and traces were present at most stations. Dieldrin and endrin residues remained essentially unchanged during this period; dieldrin residues were widespread and were highest in Hawaii and in areas of the Midwest where aldrin was used extensively. Toxaphene occurrence increased; it was formerly found only in fish from streams draining cotton-farming regions, but residues were detected in 1974 samples from other areas. According to the recommendation of the National Academy of Sciences' Water Quality Criteria, organochlorine residues in freshwater fish may have represented a hazard to piscivorous fish and wildlife at 71 percent of the stations sampled in 1970 and 66 percent in 1974.
Animals↗
Transgenic arthropods for pest management programs: risks and realities.
The ability to genetically engineer arthropods using recombinant DNA methods opens new opportunities for improving pest management programs but also creates new responsibilities, including evaluation of the potential risks of releasing transgenic arthropods into the environment. It is now becoming easier to transform diverse species of arthropods by a variety of recombinant DNA methods. Useful genes and genetic regulatory elements are being identified for pest arthropods, but less effort is being expended to identify genes that could improve the efficacy of beneficial arthropods. A transgenic strain of the natural enemy Metaseiulus (= Typhlodromus or Galendromus) occidentalis (Acari: Phytoseiidae) was developed using a method termed maternal microinjection. This transgenic strain was released into an experimental site on the campus of the University of Florida in 1996 after extensive reviews by the University of Florida Biosafety Committee, Florida Department of Agriculture and Consumer Services, United States Department of Agriculture Animal and Plant Health Inspection Service, and the United States Fish and Wildlife Service. The short term releases established a precedent for releasing a transgenic arthropod but, at present, no guidelines are available that would allow transgenic arthropods to be released permanently into the environment. Several scientific, environmental, and policy issues must be resolved before transgenic pests or beneficial arthropods can be deployed in practical pest management programs.
Animals↗
Mercury, arsenic, lead, cadmium, and selenium residues in fish, 1971-73--National Pesticide Monitoring Program.
As part of the National Pesticide Monitoring Program, the Fish and Wildlife Service, U.S. Department of Interior, analyzed selected fish samples from 100 monitoring stations for residues of mercury, arsenic, lead, cadmium, or selenium in 1971-73. At most stations, detectable residues of all metals were present in more than 95 percent of the composite samples. Fishes with mercury residues exceeding 0.5 mg/kg wet weight in the whole fish were mainly predators. Fishes with residues of arsenic, lead, cadmium, and selenium exceeding 0.5 mg/kg included predatory and nonpredatory species. The number of composite samples in which residues of these elements exceeded 0.5 mg/kg decreased from 1971 to 1973, whereas the percentage of samples with detectable residues increased slightly. Only selected samples were analyzed in 1973; therefore, these figures should be used only cautiously as trend data. Species of fish collected varied considerably between geographic regions but were similar from year to year within each region.
Animals↗
Cadmium, lead, mercury, arsenic, and selenium concentrations in freshwater fish, 1976-77--National Pesticide Monitoring Program.
As part of the National Pesticide Monitoring Program, the Fish and Wildlife Service, U.S. Department of the Interior, collected freshwater fish during 1976--77 from 98 monitoring stations and analyzed them for residues of cadmium, lead, mercury, arsenic, and selenium. Range and geometric mean values in mg/kg wet weight follow: Cd, 0.01--1.04, 0.07; Pb, 0.10--4.92, 0.32; Hg, 0.01--0.84, 0.11; As. 0.05--2.92, 0.27; Se, 0.05--2.87, 0.56. An arbitrary 85th percentile was calculated for concentrations of each element in fish to identify monitoring stations having fish with higher-than-normal concentrations: Cd, 0.11 mg/kg; Pb, 0.44; Hg, 0.19: As, 0.38; Se, 0.82. Log-transformed mean concentrations in fish from 1976--77 monitoring stations are compared with means from the same stations in 1972 (Cd, Hg, Pb, As, Se) and 1973 (Se) to depict temporal trends in whole-body concentrations: Cd, significant decline; Pb, no significant difference; Hg, significant decline; As, significant increase; Se, no significant difference. Because of changes in laboratories and analytical procedures, these conclusions should be used cautiously as trend information. Production, consumption, and disposal of cadmium, lead, mercury, arsenic, and selenium are discussed as potential environmental sources of the elements to the aquatic environment. Specific environmental sources are suggested for monitoring stations having trace element levels exceeding calculated 85th percentiles.
Animals↗
Organochlorine residues and elemental contaminants in U.S. freshwater fish, 1976-1986: National Contaminant Biomonitoring Program.
As part of the National Contaminant Biomonitoring Program (NCBP, formerly a component of the National Pesticide Monitoring Program), the U.S. Fish and Wildlife Service periodically determined concentrations of organochlorine chemical residues and elemental contaminants in freshwater fish collected from a nationwide network of stations. In late 1986 and early 1987, the last time the network was sampled, a total of 319 composite fish samples were collected from 97 NCBP stations. The samples were analyzed for residues of organochlorine chemicals and the elements As, Cd, Cu, Hg, Pb, Se, and Zn. The mean concentration of total DDT and its homologs (p,p'-constituents) declined from 1984 to 1986, thus continuing a trend that began in 1970. The most persistent DDT homolog (p,p'-DDE) was detected at all stations sampled in 1986, and averaged 74% of total DDT residues, up from 70% in 1974-1979 but essentially unchanged from 1984. Collectively, these findings indicated a low rate of influx and continued weathering of DDT in the environment; nevertheless, DDT concentrations in fish from some stations in the South remained high enough to constitute a threat to piscivorous wildlife. Residues of polychlorinated biphenyls (PCBs) also remained widespread, but a significant downward trend in total PCB concentrations and incidence was evident, and PCB mixtures containing early eluting components were present at fewer stations than in the past. PCB concentrations were generally highest in fish from the industrialized rivers of the Northeast and Midwest and from the Great Lakes. Concentrations of toxaphene also declined, as did its incidence, from 88% of the stations sampled in 1980-1981 to 64% in 1986; however, analytical problems with the 1986 samples may have contributed to the latter. The risks represented by PCBs and toxaphene could not be evaluated on the basis of our data. Among cyclodiene insecticides, dieldrin and chlordane-related residues were the most widespread. Mean concentrations of dieldrin declined through 1986, but remained consistently highest in the Great Lakes. For chlordane-related residues, mean concentrations were lower that reported previously, and trans-nonachlor continued to replace cis-chlordane as the most abundant component. Collectively, these findings suggested a lower rate of chlordane influx to the aquatic environment; however, a point source of cyclodiene insecticides to the Mississippi R. near Memphis, TN, remained evident. Residues of mirex, PCA, BHC isomers, endrin, heptachlor, and HCB were either found at relatively few (< 25%) of the stations sampled in 1986 or were characterized by relatively low concentrations. Concentrations of the herbicide Dacthal (DCPA) were also low, but incidence increased from 46% of the stations sampled in 1984 to 61% in 1986. In general, organochlorine chemical concentrations were lower in 1986 than at any time reported previously. For elemental contaminants, the geometric mean, maximum, and 85th percentile concentrations (respectively, all in microgram/g wet weight) in 1986 samples were as follows: As, 0.083, 1.53, 0.24; Cd, 0.011, 0.32, 0.04; Cu, 0.794, 11.0, 1.7; Hg, 0.087, 0.44, 0.18; Pb, 0.058, 1.90, 0.21; Se, 0.417, 3.41, 0.66; and Zn, 21.191, 94.5, 31.7. Mean concentrations of Cu increased and concentrations of As decreased relative to the 1984 collection, but these changes may reflect subtle differences in the species composition of the 1986 collection relative to other collections; concentrations of both elements differ greatly among fishes. There were no other statistically significant changes from 1984 to 1986; however, mean concentrations of As, Cd, Pb, and Zn declined from 1976, when elemental contaminants in fish were first measured in the NCBP, and 1986. In contrast, mean concentrations of Hg and Se did not change appreciably. Moreover, and in contrast to the other elements measured in 1986, concentrations of Hg and Se were high enough to constitute a threat to pisc
Animals↗
A cluster of acoustic neuromas in fish hatchery workers.
The National Institute for Occupational Safety and Health (NIOSH) received a request from the United States Fish and Wildlife Service (FWS) to determine if there is a relationship between acoustic neuroma and fish hatchery work. The request was triggered by a report from an FWS employee who suspected the possibility of such an association. Investigators used data provided by the personnel office of the FWS to calculate the incidence of acoustic neuroma among fish hatchery workers, and then to compare it with national rates. Four confirmed cases of acoustic neuroma were found among former fish hatchery workers. The overall incidence was estimated to be 15.41 per 100,000 person-years. This rate is more than 15 times higher than the rate among the general population. Even so, the small number of cases, as well as other factors, preclude the NIOSH from concluding that there is a definite cause-and-effect relationship. Further study is warranted.
Adult↗
Comparison of individual and pooled sampling methods for detecting bacterial pathogens of fish.
Examination of finfish populations for viral and bacterial pathogens is an important component of fish disease control programs worldwide. Two methods are commonly used for collecting tissue samples for bacteriological culture, the currently accepted standards for detection of bacterial fish pathogens. The method specified in the Office International des Epizooties Manual of Diagnostic Tests for Aquatic Animals permits combining renal and splenic tissues from as many as 5 fish into pooled samples. The American Fisheries Society (AFS) Blue Book/US Fish and Wildlife Service (USFWS) Inspection Manual specifies the use of a bacteriological loop for collecting samples from the kidney of individual fish. An alternative would be to more fully utilize the pooled samples taken for virology. If implemented, this approach would provide substantial savings in labor and materials. To compare the relative performance of the AFS/USFWS method and this alternative approach, cultures of Yersinia ruckeri were used to establish low-level infections in groups of rainbow trout (Oncorhynchus mykiss) that were sampled by both methods. Yersinia ruckeri was cultured from 22 of 37 groups by at least 1 method. The loop method yielded 18 positive groups, with 1 group positive in the loop samples but negative in the pooled samples. The pooled samples produced 21 positive groups, with 4 groups positive in the pooled samples but negative in the loop samples. There was statistically significant agreement (Spearman coefficient 0.80, P < 0.001) in the relative ability of the 2 sampling methods to permit detection of low-level bacterial infections of rainbow trout.
Animals↗
Prediction of climate change effects of fish communities in the Mackinaw River watershed, Illinois, USA.
As part of an integrated assessment of multiple sector impacts produced by predicted changes in climate we have integrated a set of models, which provide predictions of fish populations under changing flow and temperature regimes. The core of the approach is the U. S. Fish and Wildlife Service Physical Habitat Simulation Model (PHABSIM). PHABSIM estimates habitat conditions based on flow, which are life stage specific. The output from PHABSIM is used to model fish populations, considering both flow and a temperature threshold, which affects spawning date. Water temperatures were modelled based on air temperature. The resulting assessment tool provides the means to evaluate the effect of multiple stressors produced by climate change scenarios. The model has been used to estimate smallmouth bass (Micropterus dolomieui) populations for representative reaches of the Mackinaw River, Illinois. The model has been used to illuminate population effects of changing flow and temperature under historical climate/weather conditions, as well as under climate change scenarios. The integrated models in the assessment tool have provided a useful addition to watershed management, improving our capacity to evaluate natural resources impact at temporal scales typical of climate change, and management response systems.
Animals↗
Avian mortality at oil pits in the United States: A review of the problem and efforts for its solution.
Oil production operations produce waste fluids that may be stored in pits, open tanks, and other sites accessible to wildlife. Birds visit these fluid-filled pits and tanks ("oil pits"), which often resemble water sources, and may become trapped and die. The US Fish and Wildlife Service (USFWS) has a program to reduce these impacts by locating problem pits, documenting mortality of protected wildlife species, and seeking cleanup or corrective action at problem pits with the help of state and federal agencies regulating the oil industry. Species identification and verification of protected status for birds recovered from oil pits are performed at the USFWS National Fish and Wildlife Forensics Laboratory. From 1992 to 2005, a minimum of 2060 individual birds were identified from remains recovered from oil pits, representing 172 species from 44 families. The taxonomic and ecological diversity of these birds indicates that oil pits pose a threat to virtually all species of birds that encounter them. Ninety-two percent of identified bird remains belonged to protected species. Most remains identified at the Forensics Laboratory were from passerines, particularly ground-foraging species. Based on Forensics Laboratory and USFWS field data, oil pits currently cause the deaths of 500,000-1 million birds per year. Although law enforcement and industry efforts have produced genuine progress on this issue, oil pits remain a significant source of mortality for birds in the United States.
Animals↗
Addressing global warming and biodiversity through forest restoration and coastal wetlands creation
The Climate Challenge is a partnership between the Department of Energy and the electric utility industry to reduce, avoid, and sequester greenhouse gases. A portion of the initiative, the sequestration of greenhouse gases, is the focus of this presentation. Over 4 million acres of bottomland hardwood forests were cleared for agriculture in the Mississippi River Valley in the 1970s. Reestablishing these forests would improve depleted wildlife habitats, serve as wildlife corridors, increase biodiversity, and decrease soil erosion. Louisiana is losing coastal wetlands at a rate of approximately 25 square miles/year. This coastal erosion is due to a number of factors and many efforts are currently underway to address the matter. One such effort is the use of material generated in the dredging of navigational canals; however, this material is low in nutrient value, making the regeneration of marsh grasses more difficult. In addition, bottomland hardwood forests and coastal wetland grasses are excellent 'carbon sinks' because they take carbon dioxide out of the atmosphere and store it in living plant tissue. Entergy Services, Inc. is an electric utility with a service territory that comprises portions of both the Lower Mississippi River Valley and the Gulf of Mexico coastline. This provides an opportunity to positively address both habitat losses noted above while at the same time addressing global warming, forest fragmentation, and biodiversity. Entergy, through its affiliation with the UtiliTree Carbon Company, is participating in projects that will investigate the feasibility of using bottomland hardwood reforestation on cleared marginal farmlands now managed by the Louisiana Department of Wildlife and Fisheries and the US Fish and Wildlife Service. Entergy has also begun a research project with the Environmental Protection Agency and the State of Louisiana. The research is a compost demonstration project that will utilize wood waste generated through our tree-trimming program as a compost material that will be mixed with low nutrient dredge material to create new coastal wetlands. Taken together, Entergy's initiatives will be able to address global warming through carbon sequestration, restore fragmented forest habitats, reduce coastal erosion and improve the quality of a vital coastal aquatic nursery habitat. Efforts will be made to manage the created habitats for biodiversity. Pulling all these ideas together creates an effect in which the whole is greater than the sum of the parts. In such a synergy of ideas, there are no losers and the winners are both industry participants and the environment.
Journal Article↗
ENVIRONMENTAL AUDITING: Patterns of Aquatic Species Imperilment in the Southern Appalachians: An Evaluation of Regional Databases.
/ For regional analyses of species imperilment patterns, data on species distributions are available from the U.S. Fish and Wildlife Service and from the state heritage programs. We compared these two different databases as sources of best available information for regional analyses of patterns of aquatic species imperilment for 132 counties in the southern Appalachians and examined patterns produced from the databases. The heritage program database contained information about a greater number of imperiled species because species need not be federally listed as threatened or endangered to be included in this database. In the southern Appalachians, about half of imperiled molluscs and about one-fourth of imperiled fish were listed as threatened or endangered; much smaller proportions of other taxonomic groups were federally listed. Most threatened and endangered species appeared on both lists, but for about 40% of the species inconsistencies exist, notably a lack of recent records in the heritage program dataset. Numbers of species in each county were significantly different between the two datasets for Georgia, Tennessee, and Virginia, where the largest number of threatened and endangered species reside. Nevertheless, some counties always appeared as centers of imperilment, and the general spatial patterns of imperilment were similar.
Journal Article↗
Scientific research, stakeholders, and policy: continuing dialogue during research on radionuclides on Amchitka Island, Alaska.
It is increasingly clear that a wide range of stakeholders should be included in the problem formulation phase of research aimed at solving environmental problems; indeed the inclusion of stakeholders at this stage has been formalized as an integral part of ecological risk assessment. In this paper, we advocate the additional inclusion of stakeholders in the refinement of research methods and protocols and in the execution of the research, rather than just at the final communication and reporting phase. We use a large study of potential radionuclide levels in marine biota around Amchitka Island as a case study. Amchitka Island, in the Aleutian Island Chain of Alaska, was the site of three underground nuclear tests (1965-1971). The overall objective of the biological component of the study was to collect a range of marine biota for radionuclide analysis that could provide data for assessing current food safety and provide a baseline for developing a plan to monitor human and ecosystem health in perpetuity. Stakeholders, including regulators (State of Alaska), resource trustees (US Fish and Wildlife Service, State of Alaska), representatives of the Aleut and Pribilof Island communities, the Department of Energy (DOE), and others, were essential for plan development. While these stakeholders were included in the initial problem formulation and approved science plan, we also included them in the refinement of protocols, selection of bioindicators, selection of a reference site, choice of methods of collection, and in the execution of the study itself. Meetings with stakeholders resulted in adding (or deleting) bioindicator species and tissues, prioritizing target species, refining sampling methods, and recruiting collection personnel. Some species were added because they were important subsistence foods for the Aleuts, and others were added because they were ecological equivalents to replace species deleted because of low population numbers. Two major refinements that changed the research thrust were (1) the inclusion of Aleut hunters and fishers on the biological expedition itself to ensure that subsistence foods and methods were represented, and (2) the addition of a fisheries biologist on a NOAA research trawler to allow sampling of commercial fishes. Although the original research design called for the collection of biota by Aleut subsistence fishermen, and by a commercial fishing boat, the research was modified with continued stakeholder input to actually include Aleuts and a fisheries biologist on the expeditions to ensure their representation. The inclusion of stakeholders during the development of protocols and the research itself improved the overall quality of the investigation, while making it more relevant to the interested and affected parties. Final responsibility for the design and execution of the research and radionuclide analysis rested with the researchers, but the process of stakeholder inclusion made the research more valuable as a source of credible information and for public policy decisions.
Alaska↗
Development of a murre (Uria spp.) egg control material.
The Seabird Tissue Archival and Monitoring Project (STAMP) is a collaborative Alaska-wide effort by the US Fish and Wildlife Service's Alaska Maritime National Wildlife Refuge (USFWS/AMNWR), the US Geological Survey's Biological Resources Division (USGS/BRD), the Bureau of Indian Affairs Alaska Region Subsistence Branch (BIA/ARSB), and the National Institute of Standards and Technology (NIST) to monitor long-term (decadal) trends in environmental contaminants using seabird eggs. To support this effort, a matrix- (seabird egg) and concentration-specific control material was needed to ensure quality during analytical work. Although a herring gull egg quality assurance (HGQA) material is available from Environment Canada (EC), contaminant concentrations in this material tended to be higher than those observed in Alaskan murre (Uria spp.) eggs. Therefore, to prepare a more appropriate control material, a total of 12 common murre (U. aalge) and thick-billed murre (U. lomvia) eggs from four Bering Sea and Gulf of Alaska nesting locations were cryohomogenized to create 190 aliquots each containing approximately 6 g. This new control material was analyzed by different methods at NIST and EC facilities for the determination of concentrations and value assignment of 63 polychlorinated biphenyl (PCB) congeners, 20 organochlorine pesticides, and 11 polybrominated diphenyl ether (PBDE) congeners. The total PCB concentration is approximately 58 ng g(-1) wet mass. Results obtained for analytes not listed on the certificates of analysis of the previously used control materials, HGQA and NIST's Standard Reference Material (SRM) 1946 Lake Superior Fish Tissue, are also presented.
Alaska↗
Tandem repeat sequence variation and length heteroplasmy in the mitochondrial DNA D-loop of the threatened Gulf of Mexico sturgeon, Acipenser oxyrhynchus desotoi.
Genetic variability within the Suwannee River, Florida, population of Gulf of Mexico sturgeon, Acipenser oxyrhynchus desotoi, was assessed by examining sequence and length variation within the control region, or D-loop, of the mitochondrial genome. Although once abundant throughout the Gulf of Mexico, Gulf sturgeon are now listed as a threatened species by the U.S. Fish and Wildlife Service. Mitochondrial DNA was analyzed for length variation from 168 individual Gulf sturgeon by PCR amplification and visualization of PCR products using ethidium bromide-stained agarose gels. Of the 168 individual Gulf sturgeon, 31 (18.5%) were heteroplasmic for one to four copies of an 81-base pair, tandemly repeated sequence in the D-loop region. However, no individuals homoplasmic for multiple copies of the repeat sequence were observed. The existence and nature of these tandem repeats in heteroplasmic individuals was confirmed by direct sequencing of the PCR products for a subset of 22 individuals. The results are consistent with the apparent nature and mechanism of heteroplasmy observed in a congeneric species, A. transmontanus. In addition, sequences for 187 base pairs outside of the tandem repeats were identical among all 16 individuals assayed for this region. Lack of variable sequences is concordant with earlier studies involving mtDNA restriction fragment length profiles of Gulf sturgeon found in the Suwannee River. The absence of sequence variation exclusive of the tandem repeats is consistent with the hypothesis that the subspecies has undergone a population or evolutionary bottleneck.
Animals↗
Dietary Exposure to Mercury in Nestling Wood Storks (Mycteria americana) in Georgia
The United States breeding population of the wood stork (Mycteria americana) was listed as endangered in 1984; the U.S. Fish and Wildlife Service has listed the determination of potential contaminant hazards as a task important to the recovery of the species. Storks nest in colonies and adult storks forage over wide areas and return with prey items to feed to nestlings. The most recently consumed prey items are usually regurgitated by nestlings when they are handled. In 1995, over 200 food items from four wood stork colonies were collected while banding nestlings between 20 and 40 days old, and total mercury determined in individual food items. Two colonies were located on the Atlantic coast and two in inland areas. Overall dietary mercury concentration for each colony was calculated based on the biomass of each type of food item within the diet. Freshwater prey items had higher mercury concentrations than saltwater items most frequently chosen by storks. Daily Hg doses were estimated for a range of nestling sizes and daily food consumption rates. Risk factors were calculated based on two lowest observable adverse effect concentrations (LOAECs) from previous avian mercury ingestion studies. Based on one LOAEC, all four colonies in this study were at risk of sublethal effects due to mercury in the diet of nestling wood storks. More extensive studies of sublethal effects in avian species from mercury contamination are necessary for more accurate risk assessment.
Journal Article↗