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At least 775 records · Page 43Linked to original sources
USGS2018

Size, growth, and density data for shallow-water sea urchins from Mexico to the Aleutian Islands, Alaska, 1956–2016

Size, growth, and density have been studied for North American Pacific coast sea urchins Strongylocentrotus purpuratus , S. droebachiensis, S. polyacanthus , Mesocentrotus (Strongylocentrotus) franciscanus , Lytechinus pictus , Centrostephanus coronatus , and Arbacia stellata by various workers at diverse sites and for varying lengths of time from 1956 to present. Numerous peer-reviewed publications have used some of these data but some data have appeared only in graduate theses or the gray literature. There also are data that have never appeared outside original data sheets. Motivation for studies has included fisheries management and environmental monitoring of sewer and power plant outfalls as well as changes associated with disease epidemics. Studies also have focused on kelp restoration, community effects of sea otters, basic sea urchin biology, and monitoring. The data sets presented here are a historical record of size, density, and growth for a common group of marine invertebrates in intertidal and nearshore environments that can be used to test hypotheses concerning future changes associated with fisheries practices, shifts of predator distributions, climate and ecosystem changes, and ocean acidification along the Pacific Coast of North America and islands of the north Pacific.

Pacific Coast↗
USGS2018

Polychlorinated biphenyl tissue‐concentration thresholds for survival, growth, and reproduction in fish

Polychlorinated biphenyls (PCBs) have left a legacy of environmental contamination. Even though they were banned from production and active use in the 1970s, they persist in the environment and still have the potential to impact aquatic life. Our objective was to identify data from controlled laboratory studies of PCB‐related adverse effects in fish and to conduct a meta‐analysis on mortality, growth, and reproductive (MGR) threshold responses. For each endpoint type, we compiled data on the lowest‐observed‐adverse effect concentration (LOAEC) and the degree of effect at the LOAEC as a percentage of control. The LOAECs were expressed as tissue concentrations, so the term lowest‐observed‐adverse‐effect residue concentration (LOAER) was used to represent PCB exposures. The lower limit of applicability was set at 0.1 μg/g total PCB tissue concentration, below which adverse MGR effects in fish were not supported by the data. Sensitivity distributions identifying the probability of adverse effects in fish populations or communities predicted that 25% of fish species would be impacted between 0.1 and 7.5 μg/g. Concentration–response threshold regressions were developed from the MGR datasets. For example, a 1 μg/g total PCB tissue concentration would predict effects of 17% mortality, 15% growth, and 39% reproductive. The analysis determined the degree of adverse response, with uncertainty estimates, expected across a broad range of PCB tissue exposure concentrations in fish. Data generated from MGR endpoints were combined to determine an approach for overall effect thresholds for PCB‐related injury in fish. The MGR datasets included only laboratory data; however, responses were compared with field‐observed effects. The present review provides a comprehensive assessment of PCB‐induced injury in fish utilizing a data‐inclusive approach.

Environmental Toxicology and Chemistry↗
USGS1996

Effects of boron and selenium on mallard reproduction and duckling growth and survival

Boron (B) and selenium (Se) sometimes occur together in high concentrations in the environment and can accumulate in plants and invertebrates consumed by waterfowl. One hundred twenty-six pairs of breeding mallards (Anas platyrhynchos) were fed diets supplemented with B (as boric acid) at 0, 450, or 900 ppm, in combination with Se (as seleno-DL-methionine) at 0, 3.5, or 7 ppm, in a replicated factorial experiment. Ducklings produced received the same treatment combination as their parents. Boron and Se accumulated in adult liver, egg, and duckling liver. In adults, B and Se caused weight loss, and B decreased hemoglobin concentration, egg weight, and egg fertility. Both B and Se reduced hatching success and duckling weight, and B reduced duckling growth and duckling production, and caused several alterations in duckling liver biochemistry. Duckling survival was not reduced by B or Se, and neither B nor Se had histopathologic effects on adult or duckling liver, kidney, or spleen. There was little evidence of interaction between B and Se. This study demonstrated that B and Se, in the chemical forms and at the dietary levels administered in this study, can adversely affect mallard reproduction and duckling growth.

Environmental Toxicology and Chemistry↗
USGS2001

Mercury contamination and growth rate two piscivore populations

We found no relationship between fish growth rate and mercury concentration in a lake trout population and conditional support for an inverse relationship in a smallmouth bass population. A bioenergetics model indicated that mercury concentration was more responsive to dietary mercury intake than to growth rate. When biodilution is evident, it may bias contaminant versus fish size relationships.

Maine↗
USGS2024

Evaluation of chronic effects of potassium chloride and nickel on survival, growth, and reproduction of a unionid mussel (Lampsilis siliquoidea)

The ASTM International standard test method for freshwater mussels (E2455‐13) recommends 4‐week toxicity testing with juveniles to evaluate chronic effects on survival and growth. However, concerns remain that the method may not adequately address the sensitivity of mussels to longer term exposures (>4 weeks), particularly in relation to potential reproductive impairments. No standard method directly evaluates toxicant effects on mussel reproduction. The objectives of the present study were to (1) evaluate toxicity endpoints related to reproduction in fatmucket ( Lampsilis siliquoidea ) using two common reference toxicants, potassium chloride (KCl) and nickel (Ni); (2) evaluate the survival and growth of juvenile fatmucket in standard 4‐week and longer term (12‐week) KCl and Ni tests following a method refined from the standard method; and (3) compare the sensitivity of the reproductive endpoints with the endpoints obtained from the juvenile mussel tests. Reproductive toxicity tests were conducted by first exposing female fatmucket brooding mature larvae (glochidia) to five test concentrations of KCl and Ni for 6 weeks. Subsamples of the glochidia were then removed from the adults to determine three reproductive endpoints: (1) the viability of brooded glochidia; (2) the viability of free glochidia in a 24‐h exposure to the same toxicant concentrations as their mother; and (3) the success of glochidia parasitism on host fish. Mean viability of brooded glochidia was significantly reduced in the high KCl concentration (26 mg K/L) relative to the control, with a 20% effect concentration (EC20) of 14 mg K/L, but there were no significant differences between the control and any Ni treatment (EC20 > 95 µg Ni/L). The EC20s for viability of free glochidia after the additional 24‐h exposure and parasitism success were similar to the EC20s of brooded glochidia. The EC20s based on the most sensitive biomass endpoint in the 4‐week juvenile tests were 15 mg K/L and 91 µg Ni/L, similar to or greater than the EC20s from the reproductive KCl and Ni tests, respectively. When exposure duration in the juvenile tests was extended from 4 to 12 weeks, the EC20s decreased by more than 50% in the KCl test but by only 8% in the Ni test. Overall, these results indicate that a standard 4‐week test with juvenile mussels can prove effective for estimating effects in chronic exposures with different life stages although a longer term 12‐week exposure with juvenile mussels may reveal higher sensitivity of mussels to some toxicants, such as KCl.

Environmental Toxicology and Chemistry↗
USGS2020

Effect of an environmental flow on vegetation growth and health using ground and remote sensing metrics

Understanding the effectiveness of environmental flow deliveries along rivers requires monitoring vegetation. Monitoring data are often collected at multiple spatial scales. For riparian vegetation, optical remote sensing methods can estimate growth responses at the riparian corridor scale, and field‐based measures can quantify species composition; however, the extent to which these different measures are duplicative or complementary is important to understand when planning monitoring programmes with limited resources. In this study, we analysed riparian vegetation growth in the delta of the Colorado River in response to an experimental pulse flow. Our goal was to compare ground‐based measurements of vegetation structure and composition with satellite‐based Landsat radiometric variables, such as the normalized difference vegetation index (NDVI). We made this comparison in 21 transects following the delivery of 131.8 million cubic meters (mcm) of water in the stream channel during the spring of 2014 as a pulse flow and 38.4 mcm as base flows. Vegetation cover increased 14% and NDVI increased 0.02 (15%) by October 2015, and both variables returned to pre‐pulse flow values in October 2016. Observed changes in vegetation structure and composition did not persist after the second year. The highest increase in vegetation cover in October 2014 and October 2015 resulted from species that could respond rapidly to additional water such as reeds ( Arundo donax and Phragmites australis ), cattail ( Typha domingensis ), and herbaceous plants. Dominant shrubs, saltcedar ( Tamarix spp.) and arrowweed ( Pluchea sericea ), both indicative of nonrestored habitats showed variable increases in cover, and native trees ( Salicaceae family) presented low increases (1%). The strong NDVI–vegetation cover relationship indicates that NDVI is appropriate to detect changes at the riparian corridor scale but needs to be complemented with ground data to determine the contributions by different species to the observed trends.

Colorado River↗
USGS2023

Survival, cause-specific mortality, and population growth of white-tailed deer in western Virginia

Understanding the role of recruitment in population dynamics of white-tailed deer ( Odocoileus virginianus ) is important for management. In the central Appalachian Mountains, deer are part of a largely forested ecosystem that supports 3 carnivore species thought to be capable of influencing white-tailed deer recruitment: black bears ( Urus americanus ), coyotes ( Canis latrans ), and bobcats ( Lynx rufus ). Yet little is known about predation, how other environmental factors influence recruitment, or the importance of neonate survival to white-tailed deer population performance in the region. Our objectives were to identify causes of mortality for neonates, analyze effects of landscape attributes on survival of neonates, estimate survival rates for neonates and adult female white-tailed deer, and to model population growth trends based on current vital rates and hypothetical harvest and neonate survival scenarios. During 2019–2020, we captured 57 neonate deer in Bath County, Virginia, USA, by monitoring 38 pregnant females equipped with global positioning system collars and vaginal implant transmitters and by conducting transect searches for recently born neonates. We observed 37 neonate mortalities and identified cause of death using field and genetic evidence. Mortalities included 28 predation events and 9 deaths from other causes (e.g., abandonment, malnutrition, disease). Black bears accounted for 48.6% of neonate mortalities, and 64.2% of predation events ( n = 18), followed by bobcats ( n = 5) and coyotes ( n = 3). Annual survival for adult female deer was 0.871 and neonate survival to 12 weeks old was 0.310. Elevation was a significant predictor of neonate survival; mortality risk increased 20% for every 100-m increase in elevation. Models of annual population growth using observed vital rates predicted an increasing population (λ = 1.10). A 10% increase in female harvest would still result in a potential population increase of 2% (λ = 1.02), but a 20% increase in harvest rate would result in a potential 7% decline (λ = 0.93). Neonate survival was higher near fertile valley bottoms and lower along forested ridges characterized by shallow, infertile soils and limited edge or early successional forests. While predation, largely influenced by black bears, was the leading cause of neonate mortality and contributed to low neonate survival, we observed little evidence of population decline, and suggest there is opportunity for a modest increase in harvest of female deer.

Virginia↗
USGS2025

Spatially explicit capture-recapture using fecal DNA to estimate elk population abundance and growth in western North Carolina, USA

In an effort to restore extirpated elk to their historical range, 52 elk were reintroduced to Great Smoky Mountains National Park (GRSM) in North Carolina, USA, during 2001 and 2002. Since their reintroduction, elk numbers have increased, and elk have extended their range beyond GRSM boundaries. We used spatially explicit capture-recapture (SCR) methods based on fecal DNA to identify individual elk and estimate population abundance ( N ), apparent survival ( φ ), per capita recruitment ( f ), and population growth rate ( λ ) in western North Carolina. We walked a series of transects during 3 winter field seasons (2020–2022) and collected elk pellets encountered along those transects. We created spatially explicit capture histories and incorporated those data into both closed and open population SCR models. The top performing closed SCR models for males and females estimated density by year and as a function of the scaled distance to the nearest field, with densities decreasing as the distance increased. Combined male and female N were 179 elk (95% CI = 149–215) in 2020, 220 elk (95% CI = 188–256) in 2021, and 240 elk (95% CI = 207–279) in 2022. The top open population model estimated both φ and λ as functions of sex and year. The estimate of φ for males was 0.682 (95% CI = 0.317–0.908) during 2020–2021 and 0.339 (95% CI = 0.152–0.596) during 2021–2022 and for females was 0.953 (95% CI = 0.830–1.000) during 2020–2021 and 0.829 (95% CI = 0.601–1.000) during 2021–2022. The annual population growth rate ( λ ) for males was 1.127 (95% CI = 0.806–1.575) during 2020–2021 and 0.811 (95% CI = 0.566–1.163) during 2021–2022 and for females was 1.559 (95% CI = 1.162–2.091) during 2020–2021 and 1.122 (95% CI = 0.876–1.437) during 2021–2022. Our elk abundance estimates in areas >300 m from fields were negligible, and we suggest that sampling only the areas in and adjacent to fields in the future will result in reliable but more cost-efficient population estimates. Confidence intervals for vital rate parameters were wide for our 3-year dataset, but continued annual pellet sampling will increase sample sizes for vital rate estimation and thus improve precision. If elk herd expansion on public lands is desired, we suggest habitat modification to establish open grasslands adjacent to forests.

North Carolina↗
USGS2015

Rapid growth and genetic diversity retention in an isolated reintroduced black bear population in the central appalachians

Animal reintroductions are important tools of wildlife management to restore species to their historical range, and they can also create unique opportunities to study population dynamics and genetics from founder events. We used non-invasive hair sampling in a systematic, closed-population capture-mark-recapture (CMR) study design at the Big South Fork (BSF) area in Kentucky during 2010 and Tennessee during 2012 to estimate the demographic and genetic characteristics of the black bear ( Ursus americanus ) population that resulted from a reintroduced founding population of 18 bears in 1998. We estimated 38 (95% CI: 31–66) and 190 (95% CI: 170–219) bears on the Kentucky and Tennessee study areas, respectively. Based on the Tennessee abundance estimate alone, the mean annual growth rate was 18.3% (95% CI: 17.4–19.5%) from 1998 to 2012. We also compared the genetic characteristics of bears sampled during 2010–2012 to bears in the population during 2000–2002, 2–4 years following reintroduction, and to the source population. We found that the level of genetic diversity since reintroduction as indicated by expected heterozygosity ( H E ) remained relatively constant ( H E(source, 2004)  = 0.763, H E(BSF, 2000–2002)  = 0.729, H E(BSF, 2010–2012)  = 0.712) and the effective number of breeders ( N B ) remained low but had increased since reintroduction in the absence of sufficient immigration ( N B(BSF, 2000–2002)  = 12, N B(BSF, 2010–2012)   = 35). This bear population appears to be genetically isolated, but contrary to our expectations, we did not find evidence of genetic diversity loss or other deleterious genetic effects typically observed from small founder groups. We attribute that to high initial genetic diversity in the founder group combined with overlapping generations and rapid population growth. Although the population remains relatively small, the reintroduction using a small founder group appears to be demographically and genetically sustainable.

Kentucky, Tennessee↗
USGS2023

The effects of estradiol-17β on the sex reversal, survival, and growth of Red Shiner and its use in the development of YY individuals

Objective The Red Shiner Cyprinella lutrensis is one of the most prolific and ecologically destructive invasive fish species in the southwestern United States. The production and release of YY individuals as Trojan sex chromosome carriers can theoretically eradicate invasive fish populations by eventually eliminating phenotypic females. Methods The YY individuals are typically produced through hormonally induced sex reversals and selective breeding of subsequently feminized males. We tested three dosages of estradiol-17β (E2)-treated diets (50, 100, and 150 mg of E2 per kg of diet) administered to sexually immature Red Shiner for various durations to determine their effectiveness at feminizing Red Shiner cohorts. Survival, growth, and gonadal development were assessed for each treatment. Result All E2 treatments had minimal, if any, detrimental effects on the growth and gonadal development of Red Shiner. The 50-mg dosage lasting from 2 to 120 days posthatch achieved a 100% feminization rate while using the lowest amount of E2; therefore, this dosage and treatment interval are recommended when attempting Red Shiner feminization under these rearing conditions. Feminization of males allowed for the spawning of neofemales (F XY ) with wild-type males (M XY ), which resulted in the first putative YY Red Shiner. The YY verification crosses ( n = 20) resulted in predominately male offspring (189 males/191 offspring) except for (1) an intersex individual from an M YY × F XX cross with two previtellogenic oocytes in its testis and (2) a single female that may have resulted from an inbred cross between an XY male and a YY female or from an unknown autosomal or environmental effect on sexual phenotype. Conclusion More progeny tests with inbred and outbred crosses should be conducted to determine the prevalence of female offspring from YY individuals and how this may impact an eradication strategy featuring releases of YY Red Shiner.

North American Journal of Aquaculture↗
USGS2024

Survival and growth of larval Pallid Sturgeon are improved by a live diet

Objective Conservation propagation facilities in the upper basin of the Missouri River are currently experiencing inconsistent survival of first-feeding larval Pallid Sturgeon Scaphirhynchus albus among genetic families (i.e., distinct male–female pairings). The inconsistent survival can have unintended negative consequences for genetic representation of Pallid Sturgeon that are returned to the Missouri and Yellowstone rivers. We conducted a laboratory study designed to determine whether a live diet improves survival and growth of first-feeding larval Pallid Sturgeon. Methods First-feeding larval Pallid Sturgeon from three distinct genetic families were assigned to one of the following diets: live first instar brine shrimp ( Artemia franciscana ) nauplii, an Otohime dry diet, a 50–50% combination of Otohime and live first instar brine shrimp nauplii, or food restricted (no food). Mortality was evaluated at the end of each day and at the end of the trial (21 days after the onset of exogenous feeding), and individual weight (g) was measured at the end of the trial. Result Pallid Sturgeon larvae that received a live diet (either solely live first instar brine shrimp nauplii or the combined diet) experienced higher survival than larvae that were fed solely Otohime. Furthermore, there was statistical evidence that larvae receiving solely live first instar brine shrimp nauplii were heavier at 21 days postexogenous feeding than larvae that were fed either solely Otohime or the combined diet. Conclusion Our results suggest that a live diet can improve survival and growth of first-feeding larval Pallid Sturgeon at conservation propagation facilities.

North American Journal of Aquaculture↗
USGS2019

Age and growth of Freshwater Drum and Gizzard Shad occupying two reservoir-river complexes with different groundwater contributions

Restoring groundwater flow is a management option that improves water temperature regimes and benefits fishes. Although this strategy applies more readily to river systems, the thermal character of reservoirs is heavily influenced by inflowing rivers. We examined differences in age, structure, and growth of both Freshwater Drum Aplodinotus grunniens and Gizzard Shad Dorosoma cepedianum that occupy catchments with varying groundwater contributions in the south‐central United States. Seepage run data indicated that the Kiamichi River was losing surface water to groundwater in summer 2016, whereas groundwater inflows were apparent in the Elk River basin. Summer 2016 data showed that the Elk River had cooler water temperatures than the Kiamichi River and Grand Lake O’ the Cherokees water temperatures were similar to those in the incoming Elk River. We found higher densities of older Freshwater Drum and Gizzard Shad (maximums of 32 and 8 years old, respectively) in samples from the Grand basin than among fish that were sampled from the Kiamichi River basin (21 and 6 years old, respectively). Freshwater Drum grew at similar rates in both basins even though they reached larger maximum lengths in the Grand basin (649 mm TL) than in the Kiamichi River basin (600 mm). The average asymptotic length was greater for the Kiamichi population ( L ∞ = 613 mm) than for the Grand population ( L ∞ = 557 mm). Gizzard Shad from the Grand basin were larger than those from the Kiamichi River basin, though the latter population grew faster initially (Brody growth coefficient: K = 0.787 versus K = 0.179, respectively), but they had smaller asymptotic length ( L ∞ = 206 mm versus L ∞ = 343 mm). The role that groundwater plays in temperature regulation in these basins partially explains the observed differences. Our results suggest that the metabolic theory of ecology can be applied to fisheries management at a finer spatial scale.

Oklahoma↗
USGS2022

Redear Sunfish occurrence, abundance, growth, and size structure as related to abiotic and biotic factors in Florida lakes

Panfish support popular, socioeconomically valuable fisheries across the United States. Whereas Bluegill Lepomis macrochirus and Black Crappie Pomoxis nigromaculatus receive considerable research attention, Redear Sunfish L . microlophus are seldom studied despite their wide distribution, large size, socioeconomic contributions, and invasion potential in parts of their introduced range. We evaluated Redear Sunfish occurrence, density, relative abundance, growth, and size structure in 60 Florida lakes with varied surface area (2–12,412 ha), trophic state (oligotrophic to hypereutrophic), and macrophyte abundance (0.3–100% of lake volume inhabited), a range of environmental conditions over which Redear Sunfish populations have scarcely been investigated. Lake surface area, chlorophyll- a concentration, and macrophyte abundance explained 98% of variation in Redear Sunfish occurrence. Redear Sunfish density increased asymptotically with calcium concentration, whereas relative abundance (electrofishing fish/h) peaked at intermediate surface area (50–100 ha) and chlorophyll a (20 μg/L). Mean length at age 3 declined with increasing macrophyte abundance and was parabolically related to Redear Sunfish density, peaking at approximately 450 fish/ha. The proportional size distribution (PSD) and PSD of preferred-length fish were also negatively related to macrophyte abundance, and PSD declined with increasing Redear Sunfish density. Our results suggest that Redear Sunfish fisheries with abundant individuals of quality size (≥180 mm) require large (>100 ha), fertile (>20 μg/L chlorophyll a ) lakes with calcium concentrations >5 mg/L, moderate macrophyte abundance (0–25% of lake volume inhabited), and Redear Sunfish densities between 200 and 700 fish/ha. Our modeling approach can help managers predict Redear Sunfish occurrence, density, relative abundance, growth, and size structure based on a suite of abiotic and biotic variables.

Florida↗
USGS2019

Growth, condition, and trophic relations of stocked trout in southern Appalachian mountain streams

Stream trout fisheries are among the most popular and valuable in the United States, but many are dependent on hatcheries to sustain fishing and harvest. Thus, understanding the ecology of hatchery‐reared trout stocked in natural environments is fundamental to management. We evaluated the growth, condition, and trophic relations of Brook Trout Salvelinus fontinalis , Brown Trout Salmo trutta , and Rainbow Trout Oncorhynchus mykiss that were stocked in southern Appalachian Mountain streams in western North Carolina. Stocked and wild (naturalized) trout were sampled over time (monthly; September 2012–June 2013) to compare condition and diet composition and to evaluate temporal dynamics of trophic position with stable isotope analysis. Relative weights ( W r ) of stocked trout were inversely associated with their stream residence time but were consistently higher than those of wild trout. Weight loss of harvested stocked trout was similar among species and sizes, but fish stocked earlier lost more weight. Overall, 40% of 141 stomachs from stocked trout were empty compared to 15% of wild trout stomachs ( N = 26). We identified a much higher rate of piscivory in wild trout (18 times that of stocked trout), and wild trout were 4.3 times more likely to consume gastropods relative to stocked trout. Hatchery‐reared trout were isotopically similar to co‐occurring wild fish for both δ 13 C and δ 15 N values but were less variable than wild trout. Differences in sulfur isotope ratios (δ 34 S) between wild and hatchery‐reared trout indicated that the diets of wild fish were enriched in δ 34 S relative to the diets of hatchery‐reared fish. Although hatchery‐reared trout consumed prey items similar to those of wild fish, differences in consumption or behavior (e.g., reduced feeding) may have resulted in lower condition and negative growth. These findings provide critical insight on the trophic dynamics of stocked trout and may assist in developing and enhancing stream trout fisheries.

North Carolina↗
USGS2015

Growth rates and variances of unexploited wolf populations in dynamic equilibria

Several states have begun harvesting gray wolves ( Canis lupus ), and these states and various European countries are closely monitoring their wolf populations. To provide appropriate perspective for determining unusual or extreme fluctuations in their managed wolf populations, we analyzed natural, long-term, wolf-population-density trajectories totaling 130 years of data from 3 areas: Isle Royale National Park in Lake Superior, Michigan, USA; the east-central Superior National Forest in northeastern Minnesota, USA; and Denali National Park, Alaska, USA. Ratios between minimum and maximum annual sizes for 2 mainland populations ( n  = 28 and 46 yr) varied from 2.5–2.8, whereas for Isle Royale ( n  = 56 yr), the ratio was 6.3. The interquartile range (25th percentile, 75th percentile) for annual growth rates, N t +1 / N t , was (0.88, 1.14), (0.92, 1.11), and (0.86, 1.12) for Denali, Superior National Forest, and Isle Royale respectively. We fit a density-independent model and a Ricker model to each time series, and in both cases we considered the potential for observation error. Mean growth rates from the density-independent model were close to 0 for all 3 populations, with 95% credible intervals including 0. We view the estimated model parameters, including those describing annual variability or process variance, as providing useful summaries of the trajectories of these populations. The estimates of these natural wolf population parameters can serve as benchmarks for comparison with those of recovering wolf populations. Because our study populations were all from circumscribed areas, fluctuations in them represent fluctuations in densities (i.e., changes in numbers are not confounded by changes in occupied area as would be the case with populations expanding their range, as are wolf populations in many states).

Alaska, Michigan, Minnesota↗
USGS1995

Increases in gill cytosolic corticosteroid receptor abundance and saltwater tolerance in juvenile coho salmon (Oncorhynchus kisutch) treated with growth hormone and placental lactogen

Juvenile coho salmon ( Oncorhynchus kisutch ) were injected with one of two recombinant bovine hormones, growth hormone (bGH; 5.0 and 0.5 μg · g -1 body wt) or placental lactogen (bPL; 5.0, 0.5, μg · g -1 body wt) to determine the effect on growth, plasma cortisol concentration, cytosolic corticosteroid receptors (CR) in the gills, and the development of hypoosmoregulatory ability. One week following a single injection or six weekly injections of bGH or bPL, the first were measured and samplest for CR concentration and Na + , K + . ATPase activity in the gills. Fish were also challenged with salt water (salinity 25%) for 24 hr to determine saltwater tolerance at the end of the 6-week treatment. Treatment with bPL and bGH significantly increased weight and length of the fish. The 0.05-μg bPL dose significantly elevated plasma cortisol concentration, whereas all other hormone treatments did not affect cortisol levels. bPL and bGH also significantly increased CR concentration and Na + , K + -ATPase activity in the gills. The perturbation in plasma sodium concentration was least in animals receiving the highest dose bPL and the bGH-treated animals following transfer to seawater. An increase in cytosolic CR by bGH and bPL may increase responsiveness of the gills to cortisol and partially accout for the increase in Na + , K + -ATPase activity and greater ability to regulate plasma sodium in seawater as exhibited by the experimental groups.

General and Comparative Endocrinology↗
USGS1993

Osmoregulatory actions of growth hormone and its mode of action in salmonids: A review

Osmoregulatory actions of growth hormone (GH) and its mode of action in salmonids are reviewed. We present evidence suggesting that insulin-like growth factor I (IGF-I) mediates some of the actions of GH on seawater acclimation. Plasma concentration and turnover of GH rise following exposure to seawater. Exogenous GH ( in vivo ) increases gill Na + ,K + -ATPase activity and the number of gill chloride cells, and inhibits an increase in plasma osmolarity and ions following transfer of fish to seawater. A single class of high affinity GH receptors is present in the liver, gill, intestine, and kidney. The levels of IGF-I mRNA in the liver, gill and kidney increased after GH-injection. After transfer to seawater, IGF-I mRNA increased in the gill and kidney following the rise in plasma GH, although no significant change was seen in the liver. Injection of IGF-I improved the ability of the fish to maintain plasma sodium levels after transfer to seawater. GH treatment also sensitizes the interrenal to adrenocorticotropin (ACTH), increasing cortisol secretion. Both cortisol and IGF-I may be involved in mediating the action of GH in seawater adaptation, although studies on the effect of GH on osmoregulatory physiology of non-salmonid species are limited. An integrated model of the osmoregulatory actions of GH is presented, and areas in need of research are outlined.

Fish Physiology and Biochemistry↗
USGS1992

Interactive effects of selenium, methionine, and dietary protein on survival, growth, and physiology in mallard ducklings

Concentrations of over 100 ppm (100 mg/kg) selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Both quantity and composition of dietary protein for wild ducklings may vary in selenium-contaminated environments. Day-old mallard (Anas platyrhynchos) ducklings received one of the following diets containing 22% protein: unsupplemented (controls), 15 ppm Se (as selenomethionine), 60 ppm Se, methionine supplemented, 15 ppm Se with methionine supplement, or 60 ppm Se with methionine supplement. In a second concurrent experiment the above sequence was repeated with a protein-restricted (11%) but isocaloric diet. In a third concurrent experiment all ducklings received 44% protein with 0, 15, or 60 ppm Se added. After 4 weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and histopathological lesions of the liver occurred. Antagonistic interactive effects occurred between supplementary methionine and Se, including complete to partial alleviation of the following Se effects by methionine: mortality, hepatic lesions, and altered glutathione and thiol status. With 11% protein, growth of controls was less than that with 22% protein, Se (60 ppm) caused 100% mortality, and methionine supplementation, although protective afforded less protection than it did with 22% protein. With 44% protein, ducklings experienced physiological stress, and Se was more toxic than with methionine-supplemented 22% protein. These findings suggest the potential for antagonistic effects of Se, methionine, and protein on duckling survival and physiology.

Archives of Environmental Contamination and Toxico↗