Comparison of Minimally Invasive Monitoring Methods and Live Trapping in Mammals.

The conservation and management of wildlife requires the accurate assessment of wildlife population sizes. However, there is a lack of synthesis of research that compares methods used to estimate population size in the wild. Using a meta-analysis approach, we compared the number of detected individuals in a study made using live trapping and less invasive approaches, such as camera trapping and genetic identification. We scanned 668 papers related to these methods and identified data for 44 populations (all focused on mammals) wherein at least two methods (live trapping, camera trapping, genetic identification) were used. We used these data to quantify the difference in number of individuals detected using trapping and less invasive methods using a regression and used the residuals from each regression to evaluate potential drivers of these trends. We found that both trapping and less invasive methods (camera traps and genetic analyses) produced similar estimates overall, but less invasive methods tended to detect more individuals compared to trapping efforts (mean = 3.17 more individuals). We also found that the method by which camera data are analyzed can significantly alter estimates of population size, such that the inclusion of spatial information was related to larger population size estimates. Finally, we compared counts of individuals made using camera traps and genetic data and found that estimates were similar but that genetic approaches identified more individuals on average (mean = 9.07 individuals). Overall, our data suggest that all of the methods used in the studies we reviewed detected similar numbers of individuals. As live trapping can be more costly than less invasive methods and can pose more risk to animal well-fare, we suggest minimally invasive methods are preferable for population monitoring when less-invasive methods can be deployed efficiently.

Heuristics for the sustainable harvest of wildlife in stochastic social-ecological systems.

Sustainable wildlife harvest is challenging due to the complexity of uncertain social-ecological systems, and diverse stakeholder perspectives of sustainability. In these systems, semi-complex stochastic simulation models can provide heuristics that bridge the gap between highly simplified theoretical models and highly context-specific case-studies. Such heuristics allow for more nuanced recommendations in low-knowledge contexts, and an improved understanding of model sensitivity and transferability to novel contexts. We develop semi-complex Management Strategy Evaluation (MSE) models capturing dynamics and variability in ecological processes, monitoring, decision-making, and harvest implementation, under a diverse range of contexts. Results reveal the fundamental challenges of achieving sustainability in wildlife harvest. Environmental contexts were important in determining optimal harvest parameters, but overall, evaluation contexts more strongly influenced perceived outcomes, optimal harvest parameters and optimal harvest strategies. Importantly, simple composite metrics popular in the theoretical literature (e.g. focusing on maximizing yield and population persistence only) often diverged from more holistic composite metrics that include a wider range of population and harvest objectives, and better reflect the trade-offs in real world applied contexts. While adaptive harvest strategies were most frequently preferred, particularly for more complex environmental contexts (e.g. high uncertainty or variability), our simulations map out cases where these heuristics may not hold. Despite not always being the optimal solution, overall adaptive harvest strategies resulted in the least value forgone, and are likely to give the best outcomes under future climatic variability and uncertainty. This demonstrates the potential value of heuristics for guiding applied management.

Causes of admission, length of stay and outcomes for common kestrels in rehabilitation centres in the Czech Republic.

Rehabilitation centres help injured animals to recover and return back to the wild. This study aimed to analyse trends in intake and outcomes for the common kestrels (Falco tinnunculus) admitted into rehabilitation centres in the Czech Republic. From 2010 to 2019, a total of 12,923 kestrels were admitted to 34 rehabilitation centres with an increasing trend (rSp = 0.7697, P < 0.01) being found during the monitored period. Subadult kestrels (34.70%) and kestrels injured by power lines (26.57%) were most often admitted. Most kestrels in the rehabilitation centres died or had to be euthanized (81.66%), only 15.90% of the birds could be released back into the wild. The median length of stay in rehabilitation centres for kestrels that were subsequently released was 35 days. Considering survival rates, the most critical threat to kestrels was poisoning (100% of the cases resulted in death) but mortality of the kestrels admitted for most other reasons also exceeded 80%. Given the low success rate of the care of kestrels in rehabilitation centres and the relatively small proportion returned to the wild, it is essential to eliminate the causes leading to their admission, that is, to protect their natural habitats and to prevent unnecessary capture.

The successful reintroduction of African wild dogs (Lycaon pictus) to Gorongosa National Park, Mozambique.

Large carnivores have experienced widespread extirpation and species are now threatened globally. The ecological impact of the loss of large carnivores has been prominent in Gorongosa National Park, Mozambique, after most were extirpated during the 1977-92 civil war. To remedy this, reintroductions are now being implemented in Gorongosa, initiating with endangered African wild dogs (Lycaon pictus), hereafter 'wild dogs'. We describe the first transboundary translocation and reintroduction of founding packs of wild dogs to Gorongosa over a 28-month study period and evaluate the success of the reintroduction based on five key indicator categories. We also assess how wild dog space use and diet influenced their success. We found that pre-release, artificial pack formation in holding enclosures aided group cohesion and alpha pair establishment. Post-release, we also observed natural pack formations as a result of multiple dispersal events. Founder and naturally formed packs produced pups in two of the three breeding seasons and packs successfully recruited pups. Survival rate for all wild dogs was 73% and all mortality events were from natural causes. Consequently, the population grew significantly over the study period. All indicators of success were fully achieved and this study documents the first successful reintroduction of wild dogs into a large, unfenced landscape in Mozambique and only the second on the continent. Potential mechanisms underlying these early successes were the avoidance of habitats intensively used by lions, dietary partitioning with lion, avoidance of human settlements, and Gorongosa's management strategy. We predict further population expansion in Gorongosa given that 68% of the park is still unused by wild dogs. This expansion could be stimulated by continued reintroductions over the short- to medium-term. Recovery of wild dogs in Gorongosa could aid in the re-establishment of a larger, connected population across the greater Gorongosa-Marromeu landscape.

Short communication: Domesticated and wild fathead minnows differ in growth and thermal tolerance.

Many populations have evolved in response to laboratory environments (lack of predators, continual food availability, etc.). Another potential agent of selection in the lab is exposure to constant thermal environments. Here, we examined changes in growth, critical thermal maximum (CTmax), and food consumption under constant (25 °C) and fluctuating (22-28 °C and 19-31 °C) conditions in two populations of fathead minnows, Pimephales promelas: one that has been kept in a laboratory setting for over 120 generations (~40 years) and a corresponding wild one. We found that under thermal fluctuations, domesticated fathead minnows grew faster than their wild counterparts, but also exhibited lower thermal tolerance. Food consumption was significantly higher in the lab population under the constant and large fluctuation thermal treatments. Our results suggest that the lab population has adjusted to the stable conditions in the laboratory and that we should carefully apply lessons learned in the lab to wild populations.

Accelerated reproduction is not an adaptive response to early-life adversity in wild baboons.

In humans and other long-lived species, harsh conditions in early life often lead to profound differences in adult life expectancy. In response, natural selection is expected to accelerate the timing and pace of reproduction in individuals who experience some forms of early-life adversity. However, the adaptive benefits of reproductive acceleration following early adversity remain untested. Here, we test a recent version of this theory, the internal predictive adaptive response (iPAR) model, by assessing whether accelerating reproduction following early-life adversity leads to higher lifetime reproductive success. We do so by leveraging 48 y of continuous, individual-based data from wild female baboons in the Amboseli ecosystem in Kenya, including prospective, longitudinal data on multiple sources of nutritional and psychosocial adversity in early life; reproductive pace; and lifetime reproductive success. We find that while early-life adversity led to dramatically shorter lifespans, individuals who experienced early adversity did not accelerate their reproduction compared with those who did not experience early adversity. Further, while accelerated reproduction predicted increased lifetime reproductive success overall, these benefits were not specific to females who experienced early-life adversity. Instead, females only benefited from reproductive acceleration if they also led long lives. Our results call into question the theory that accelerated reproduction is an adaptive response to both nutritional and psychosocial sources of early-life adversity in baboons and other long-lived species.

Late lactation in small mammals is a critically sensitive window of vulnerability to elevated ambient temperature.

Predicted increases in global average temperature are physiologically trivial for most endotherms. However, heat waves will also increase in both frequency and severity, and these will be physiologically more important. Lactating small mammals are hypothesized to be limited by heat dissipation capacity, suggesting high temperatures may adversely impact lactation performance. We measured reproductive performance of mice and striped hamsters (Cricetulus barabensis), including milk energy output (MEO), at temperatures between 21 and 36 °C. In both species, there was a decline in MEO between 21 and 33 °C. In mice, milk production at 33 °C was only 18% of that at 21 °C. This led to reductions in pup growth by 20% but limited pup mortality (0.8%), because of a threefold increase in growth efficiency. In contrast, in hamsters, MEO at 33 °C was reduced to 78.1% of that at 21 °C, yet this led to significant pup mortality (possibly infanticide) and reduced pup growth by 12.7%. Hamster females were more able to sustain milk production as ambient temperature increased, but they and their pups were less capable of adjusting to the lower supply. In both species, exposure to 36 °C resulted in rapid catastrophic lactation failure and maternal mortality. Upper lethal temperature was lowered by 3 to 6 °C in late lactation, making it a critically sensitive window to high ambient temperatures. Our data suggest future heat wave events will impact breeding success of small rodents, but this is based on animals with a long history in captivity. More work should be performed on wild rodents to confirm these impacts.

Differences in the growth rate and immune strategies of farmed and wild mallard populations.

Individuals reared in captivity are exposed to distinct selection pressures and evolutionary processes causing genetic and phenotypic divergence from wild populations. Consequently, restocking with farmed individuals may represent a considerable risk for the fitness of free-living populations. Supportive breeding on a massive scale has been established in many European countries to increase hunting opportunities for the most common duck species, the mallard (Anas platyrhynchos). It has previously been shown that mallards from breeding facilities differ genetically from wild populations and there is some indication of morphological differences. Using a common-garden experiment, we tested for differences in growth parameters between free-living populations and individuals from breeding facilities during the first 20 days of post-hatching development, a critical phase for survival in free-living populations. In addition, we compared their immune function by assessing two haematological parameters, H/L ratio and immature erythrocyte frequency, and plasma complement activity. Our data show that farmed ducklings exhibit larger morphological parameters, a higher growth rates, and higher complement activity. In haematological parameters, we observed high dynamic changes in duckling ontogeny in relation to their morphological parameters. In conclusion, our data demonstrate pronounced phenotype divergence between farmed and wild mallard populations that can be genetically determined. We argue that this divergence can directly or indirectly affect fitness of farmed individuals introduced to the breeding population as well as fitness of farmed x wild hybrids.

Insulin-like growth factor 1 of wild vertebrates in a life-history context.

Broad variation in intra- and interspecific life-history traits is largely shaped by resource limitation and the ensuing allocation trade-offs that animals are forced to make. Insulin-like growth factor 1 (IGF-1), a growth-hormone-dependent peptide, may be a key player in the regulation of allocation processes. In laboratory animals, the effects of IGF-1 on growth- and development (positive), reproduction (positive), and longevity (negative) are well established. We here review the evidence on these effects in wild vertebrates, where animals are more likely to face resource limitation and other challenges. We point out the similarities and dissimilarities in patterns of IGF-1 functions obtained in these two different study settings and discuss the knowledge we need to develop a comprehensive picture of the role of IGF-1 in mediating life-history variation of wild vertebrates.

Direct evidence of poison-driven widespread population decline in a wild vertebrate.

Toxicants such as organochlorine insecticides, lead ammunition, and veterinary drugs have caused severe wildlife poisoning, pushing the populations of several apex species to the edge of extinction. These prime cases epitomize the serious threat that wildlife poisoning poses to biodiversity. Much of the evidence on population effects of wildlife poisoning rests on assessments conducted at an individual level, from which population-level effects are inferred. Contrastingly, we demonstrate a straightforward relationship between poison-induced individual mortality and population changes in the threatened red kite (Milvus milvus). By linking field data of 1,075 poisoned red kites to changes in occupancy and abundance across 274 sites (10 × 10-km squares) over a 20-y time frame, we show a clear relationship between red kite poisoning and the decline of its breeding population in Spain, including local extinctions. Our results further support the species listing as endangered, after a breeding population decline of 31% to 43% in two decades of this once-abundant raptor. Given that poisoning threatens the global populations of more than 2,600 animal species worldwide, a greater understanding of its population-level effects may aid biodiversity conservation through increased regulatory control of chemical substances. Our results illustrate the great potential of long-term and large-scale on-ground monitoring to assist in this task.

Monitoring glucocorticoid metabolite concentrations as a proxy of environmental stress across important life-history stages in captive African penguins.

Due to considerable global decline in wildlife population numbers and species diversity, because of various anthropogenic activities, conservationists increasingly rely on captive and managed populations as important reservoirs to ensure the survival of endangered and vulnerable species. However, very few of these facilities implement robust, non-invasive monitoring techniques to confirm the effectiveness of their management practices to address animal welfare challenges. This study assessed adrenocortical activity as an indication of environmental stress by investigating the effects of both natural (climate, life-history stages) and anthropogenic (visitor presence) factors on captive-housed African penguins. Seven male-female African penguin breeding pairs were housed in a large, naturalistic outside enclosure at the National Zoological Garden (NZG), South Africa. Weekly urofaecal samples were collected from all individuals over one-year to measure urofaecal glucocorticoid metabolite (ufGCM) concentrations. General linear mixed model analysis determined that visitor presence (for males) and rainfall (for females) were the two factors which best explained the variation in ufGCM concentrations of the study population; however, none of the environmental and anthropogenic factors monitored were found to be significant. A posthoc graphical analysis showed considerable individual variation in terms of ufGCM concentrations within and between sexes when comparing life-history stages. This study confirms that non-invasive steroid monitoring can be an effective tool set for defining and assessing environmental stressors for African penguins and potentially other captive seabirds. However, conservationists and wildlife managers should also consider that individual-, sex-, and population-specific differences in the response to environmental stressors can exist. As such, a generalized management protocol for a specific species may not be sufficient and should be customized according to the specific captive population and/or individual.

Long-term historical and projected herbivore population dynamics in Ngorongoro crater, Tanzania.

The Ngorongoro Crater is an intact caldera with an area of approximately 310 km2 located within the Ngorongoro Conservation Area (NCA) in northern Tanzania. It is known for the abundance and diversity of its wildlife and is a UNESCO World Heritage Site and an International Biosphere Reserve. Long term records (1963-2012) on herbivore populations, vegetation and rainfall made it possible to analyze historic and project future herbivore population dynamics. NCA was established as a multiple use area in 1959. In 1974 there was a perturbation in that resident Maasai and their livestock were removed from the Ngorongoro Crater. Thus, their pasture management that was a combination of livestock grazing and fire was also removed and 'burning' stopped being a regular occurrence until it was resumed in 2001 by NCA management. The Maasai pasture management would have selected for shorter grasses and more palatable species. Vegetation mapping in 1966-1967 recorded predominately short grasslands. Subsequent vegetation mapping in the crater in 1995 determined that the grassland structure had changed such that mid and tall grasses were dominant. After removal of the Maasai pastoralists from the Ngorongoro Crater in 1974, there were significant changes in population trends for some herbivore species. Buffalo, elephant and ostrich numbers increased significantly during 1974-2012. The zebra population was stable from 1963 to 2012 whereas population numbers of five species declined substantially between 1974 and 2012 relative to their peak numbers during 1974-1976. Grant's and Thomson's gazelles, eland, kongoni, and waterbuck (wet season only) declined significantly in the Crater in both seasons after 1974. In addition, some herbivore species were consistently more abundant inside the Crater during the wet than the dry season. This pattern was most evident for the large herbivore species requiring bulk forage, i.e., buffalo, eland, and elephant. Even with a change in grassland structure, total herbivore biomass remained relatively stable from 1963 to 2012, implying that the crater has a stable carrying capacity. Analyses of rainfall indicated that there was a persistent cycle of 4.83 years for the annual component. Herbivore population size was correlated with rainfall in both the wet and dry seasons. The relationships established between the time series of historic animal counts in the wet and dry seasons and lagged wet and dry season rainfall series were used to forecast the likely future trajectories of the wet and dry season population size for each species under three alternative climate change scenarios.

Modeling variation in the growth of wild and captive juvenile vervet monkeys in relation to diet and resource availability.

OBJECTIVES: To compare longitudinal weight gain in captive and wild juvenile vervet monkeys and conduct an empirical assessment of different mechanistic growth models. METHODS: Weights were collected from two groups of captive monkeys and two consecutive cohorts of wild monkeys until the end of the juvenile period (~800 days). The captive groups were each fed different diets, while the wild groups experienced different ecological conditions. Three different growth curve models were compared. RESULTS: By 800 days, the wild juveniles were lighter, with a slower maximum growth rate, and reached asymptote earlier than their captive counterparts. There were overall differences in weight and growth rate across the two wild cohorts. This corresponded to differences in resource availability. There was considerable overlap in growth rate and predicted adult weight of male and females in the first, but not the second, wild cohort. Maternal parity was not influential. While the von Bertalanffy curve provided the best fit to the data sets modeled together, the Logistic curve best described growth in the wild cohorts when considered separately. CONCLUSIONS: The growth curves of the two captive cohorts are likely to lie near the maximum attainable by juvenile vervets. It may be helpful to include deviations from these rates when assessing the performance of wild vervet monkeys. The comparison of wild and captive juveniles confirmed the value of comparing different growth curve models, and an appreciation that the best models may well differ for different populations. Choice of mechanistic growth model can, therefore, be empirically justified, rather than theoretically predetermined.

Mechanisms of Hantavirus Transmission in Oligoryzomys longicaudatus.

The cricetid rodent Oligoryzomys longicaudatus is the species host of Andes virus (ANDV) which causes hantavirus pulmonary syndrome in southern Argentina and Chile. Population density, behavioral interactions, and spacing patterns are factors that affect viral transmission among wild rodents. We predict that the highest prevalence of hantavirus antibody positive would be found among wounded, reproductive males and that, at high population densities, wounded, reproductive males would be dispersers rather than resident individuals. The study was conducted seasonally from October (spring) 2011 to October (spring) 2013 in a shrubland habitat of Cholila, Argentina. During each trapping session, we classified captured O. longicaudatus as resident or disperser individuals, estimated population density, and recorded wounds as an indicator of aggression among individuals. We obtained blood samples from each individual for serological testing. We used generalized linear models to test the statistical significance of association between antibody prevalence, and sex, resident/dispersal status, wounds and trapping session. The highest proportion of seropositive O. longicaudatus individuals was among wounded reproductive males during periods of the greatest population density, and the characteristics of seroconverted individuals support that transmission is horizontal through male intrasexual competition. A positive association between dispersing individuals and hantavirus antibody was detected at high population density. Our study design allowed us to obtain data on a large number of individuals that are seroconverted, enabling a better understanding of the ecology and epidemiology of the ANDV host system.

Local host-tick coextinction in neotropical forest fragments.

Ticks are obligatory parasites with complex life cycles that often depend on larger bodied vertebrates as final hosts. These traits make them particularly sensitive to local coextinction with their host. Loss of wildlife abundance and diversity should thus lead to loss of tick abundance and diversity to the point where only generalist tick species remain. However, direct empirical tests of these hypotheses are lacking, despite their relevance to our understanding of tick-borne disease emergence in disturbed environments. Here, we compare vertebrate and tick communities across 12 forest islands and peninsulas in the Panama Canal that ranged 1000-fold in size (2.6-2811.3 ha). We used drag sampling and camera trapping to directly assess the abundance and diversity of communities of questing ticks and vertebrate hosts. We found that the abundance and species richness of ticks were positively related to those of wildlife. Specialist tick species were only present in fragments where their final hosts were found. Further, less diverse tick communities had a higher relative abundance of the generalist tick species Amblyomma oblongoguttatum, a potential vector of spotted fever group rickettsiosis. These findings support the host-parasite coextinction hypothesis, and indicate that loss of wildlife can indeed have cascading effects on tick communities. Our results also imply that opportunities for pathogen transmission via generalist ticks may be higher in habitats with degraded tick communities. If these patterns are general, then tick identities and abundances serve as useful bioindicators of ecosystem health, with low tick diversity reflecting low wildlife diversity and a potentially elevated risk of interspecific disease transmission via remaining host species and generalist ticks.

Tracing individuals and populations of the tambaqui, Colossoma macropomum (Cuvier, 1818), from Brazilian hatcheries using microsatellite markers.

BACKGROUND: In recent years, tracing of alimentary produce of animal origin has become increasingly important, for economic, food safety and ecological reasons. The tambaqui, Colossoma macropomum, is the native fish most farmed in Brazil. The reliable identification of the origin of tambaquis (wild or farmed) offered for sale to the general public has become necessary to satisfy regulatory norms and uphold consumer confidence. Molecular methods based on the analysis of DNA sequences have often been used to evaluate the potential for tracing farmed fish, given their reliability and precision. RESULTS: Full likelihood and Bayesian approaches proved to be the most efficient for the identification, respectively, of individuals and populations for most of the fish sampled from seven hatcheries and one wild stock. The exclusion method and genetic distances were the least effective approaches for the identification of individuals and populations. The Bayesian method identified correctly more than 99% of the fry from most stocks, except those of the Santarém hatchery and River Amazon wild stock, which presented the best results for individual identification. CONCLUSIONS: The identification of populations was effective for most hatcheries, although the identification of individuals from most stocks was hampered by the reduced genetic variability. © 2018 Society of Chemical Industry.

Carcass and meat quality characteristics from Iberian wild red deer (Cervus elaphus) hunted at different ages.

BACKGROUND: Deer-meat consumption is increasing in several countries based on claims that it is a healthy red meat. This study assessed the effect of slaughter age (low - 26 months and younger; medium - from 27 months to younger than 42 months; and high - 42 months and older) on carcass characteristics and meat physicochemical properties of 150 Iberian wild red deer. RESULTS: Whole carcass yields of neck, backbone and flank increased (P < 0.001) with age, while yields of shoulder, tenderloin and leg decreased (P < 0.05) with age. The pH measured at 48 h post mortem at 9th rib level was not affected by age, while pH measured at 72 h post mortem at the longissimus thoracis et lumborum muscle decreased (P < 0.05) with age. Meat chemical composition was not affected by slaughter age, except for intramuscular fat (IMF), which increased (P < 0.05) with slaughter age. Finally, cooking loss and shear force were higher (P < 0.05) in meat from older deer. CONCLUSION: Most characteristics of meat from wild red deer depend on age at slaughter. The greater IMF of meat from older animals may render it more palatable. However, meat shear force also increased with age. Additional studies testing palatability seem to be necessary to evaluate the effects of slaughter age on the sensorial quality of meat from Iberian wild red deer. © 2018 Society of Chemical Industry.

Effect of age on nutritional properties of Iberian wild red deer meat.

BACKGROUND: This study assessed the effect of age (L, less than 27 months old; M, from 27 to 42 months old; H, 43 months and older) on the fatty acid profile, cholesterol content, amino acid composition and mineral content of 150 Iberian wild red deer meat samples. RESULTS: Intramuscular fat content increased (P < 0.05) with age (0.05 vs 0.12 vs 0.34% for L, M and H groups respectively), while cholesterol content decreased (P < 0.05) as the slaughter age increased (52.78 vs 48.72 vs 45.34 mg per 100 g meat for L, M and H groups respectively). The slaughter age showed differences among groups for saturated fatty acids, with the highest content in older animals (30.41 vs 34.55 vs 38.21% for L, M and H groups respectively), whereas younger deer displayed the highest polyunsaturated fatty acid levels (50.05 vs 45.24 vs 37.55% for L, M and H groups respectively). The n-6/n-3 ratio was more favorable (P < 0.05) for young and medium ages compared with that for older animals. In contrast, amino acid profile and mineral content were only slightly affected by age. CONCLUSION: As a general conclusion, wild red deer meat could be considered a good alternative to red meats for human consumption. © 2018 Society of Chemical Industry.

Avian Influenza Virus Surveillance in High Arctic Breeding Geese, Greenland.

The connectedness in Arctic regions between migratory waterbird populations originating from different continents and the potential for virus exchange at their shared Arctic breeding ground point to the need to explore the largely unstudied circumpolar circulation of avian influenza viruses (AIV). We here report the investigation of AIV in wild birds and lakes in a high Arctic area of Northeast Greenland. No AIV could be detected in the fecal, feather, and water samples collected from large flocks of pink-footed geese Anser brachyrhynchus and barnacle geese Branta leucopsis in and around refuge lakes, where they congregate at high density during their flightless molting period in summer.

Metal accumulation and expression of genes encoding for metallothionein and copper transporters in a chronically exposed wild population of the fish Hyphessobrycon luetkenii.

In the present study, metal (As, Cd, Cu, Fe, Mn, Pb and Zn) accumulation and expression of genes involved in metal metabolism (metallothioneins, ATP7A and CTR1) were evaluated in gills and muscle of the fish Hyphessobrycon luetkenii living in the João Dias creek, a site historically (~1870-1996) contaminated with a metal mixture associated with copper mining (Minas do Camaquã, southern Brazil). Fish were collected in a metal impacted site of the João Dias creek and kept in a cage at this site (PP fish) or translocated to a non-metal impacted reach of this creek (PC fish). Gill metal concentrations and metallothionein gene expression were lower in PC fish than in PP fish at any experimental time (24, 48 and 72 h). In muscle, no significant changes were observed. These findings indicate that metal accumulated in gills of wild fish chronically exposed to the metal mixture are more easily excreted than those accumulated in the muscle. In this case, expression of gene encoding for metallothionein is shown to play a key role in the regulation of metal accumulation in gills of H. luetkenii living in an area historically contaminated with a metal mixture associated with copper mining.