Evaluation of a Stable Isotope Labeling Technique for Mass-Marking Fin Rays of Age-0 Lake Sturgeon

The effectiveness of marking age-0 lake sturgeon, Acipenser fulvescens Rafinesque, pectoral fin rays with a stable strontium isotope was evaluated. Age-0 lake sturgeon were reared in water spiked with 0 (control), 25, 50, or 100 μg L-1 86SrC03 for 10 and 24 d; fish from each treatment group were retained for up to 120 d post-labeling to assess mark retention. Enriched isotope marks imparted to fin rays were distinct from fin ray 88Sr/86Sr ratios of control fish immediately following marking, with the 100 μg L-1 86SrCO3 treatments consistently yielding the highest rate of marking success (83-92%). Lower marking success (25-69%) was observed with the 25 and 50 μg L-1 86SrCO3 treatments. Isotopic marks in fin rays were retained for 120 d post-labeling. Immersion marking of juvenile fish pectoral fin rays with distinct strontium isotope ratios is possible and does not require sacrificing fish to check for marks

Fin Ray Chemistry as a Potential Natural Tag for Smallmouth Bass in Northern Illinois Rivers

Natural chemical markers in otoliths and fin rays have proven useful for describing environmental history of fishes in a variety of environments. However, no studies have evaluated smallmouth bass (Micropterus dolomieu) pectoral fin ray chemistry as a non-lethal alternative to otolith chemistry. We evaluated the trace element composition of smallmouth bass fin rays collected from northern Illinois rivers and determined the accuracy with which fish could be classified to their environment of capture using pectoral fin ray strontium:calcium (Sr:Ca) and barium:calcium (Ba:Ca) ratios. Fish were collected from nine sites during summer 2008. Fin ray Sr:Ca differed among some sites, reflecting previously observed differences in water and otolith chemistry for other fish species. Fin ray Ba:Ca did not differ among sites. Classification accuracy for individual fish to location of capture based on fin ray Sr:Ca was relatively poor when data from all nine sites in different watersheds were included. However, individual fish captured from the upper Illinois River watershed were accurately assigned to the river in which they were collected when data were restricted to these sites. Natural chemical signatures in fin rays will likely be effective for reconstructing environmental history of smallmouth bass when spatial differences in water chemistry are present, enabling investigations of stock mixing and recruitment sources for this species

Trace element and Stable Isotopic Signatures in Otoliths and Pectoral spines as Potential Indicators of Catfish Environmental History

Natural chemical markers in otoliths and fin rays have proven useful for retrospectively describing environmental history of fishes in a variety of environments. However, no studies have applied this technique to catfishes or evaluated catfish pectoral spine chemistry as a nonlethal alternative to otolith chemistry. We characterized relationships between water, otolith, and pectoral spine (articulating process) chemistry for channel catfish Ictalurus punctatus, flathead catfish Pylodictis olivaris, and blue catfish I. furcatus and determined the accuracy with which fish could be classified to their environment of capture using otolith and pectoral spine chemical signatures. Fish and water samples were collected from nine sites during 2009. Otolith, spine, and water samples were analyzed for Sr:Ca and Ba:Ca; otolith δ18O and δ13C and water δ18O were also measured. Water, otolith, and spine Sr:Ca were highly correlated, as were water and otolith δ18O. Relationships between water, otolith, and spine chemistry did not differ among species. Otolith Sr:Ca, δ18O, and δ13C and spine Sr:Ca differed among sites, reflecting geographic differences in water chemistry. Neither otolith nor spine Ba:Ca differed among sites despite inter-site differences in water Ba:Ca. Both otolith Sr:Ca, δ18O, and δ13C and fin spine Sr:Ca classified fish to their environment of capture with a high degree of accuracy, except in the middle and lower Mississippi River where many recent immigrants appeared to be present. Natural chemical signatures in otoliths or pectoral spines will likely be effective for reconstructing environmental history of catfishes when spatial differences in water chemistry are present, enabling investigations of stock mixing and recruitment sources for these species

Identification of Stocked Muskellunge and Potential for Distinguishing Hatchery-Origin and Wild Fish Using Pelvic Fin Ray Microchemistry

The effectiveness of pelvic fin ray microchemistry of muskellunge Esox masquinongy Mitchill to identify stocked individuals along with the potential to identify naturally reproduced fish were evaluated. Fish and water samples were obtained from one hatchery and seven lakes with natural differences in water Sr:Ca to determine whether location-specific environmental signatures were recorded in sectioned muskellunge pelvic fin rays, including fish of known environmental history. Water and fin ray Sr:Ca were strongly correlated. Six lakes in Illinois possessed Sr:Ca signatures that were distinct from the hatchery where muskellunge were raised, resulting in pronounced shifts in Sr:Ca across sectioned fin rays of stocked fish. Hatchery and lake-specific Sr:Ca signatures were stable across years. Sixteen of 19 individual fish known to have been stocked based on PIT tags implanted at stocking were correctly identified as hatchery-origin fish using fin ray core Sr:Ca. Results also indicated that the hatchery Sr:Ca signal can be retained for at least seven years in fin rays of stocked fish. Fin ray microchemistry is a non-lethal approach for determining environmental history of muskellunge that could be used to assess movement patterns in lake and river systems and the degree to which muskellunge populations are supported by natural reproduction and stocking

Effects of Mowing and Tebuthiuron on the Nutritional Quality of Wyoming Big Sagebrush

Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) is the most abundant and widely distributed subspecies of big sagebrush and has been treated through chemical application, mechanical treatments, and prescribed burning in efforts thought to improve habitat conditions for species such as greater sage-grouse (Centrocercus urophasianus) and mule deer (Odocoileus hemionus). Although the response of structural attributes of sagebrush communities to treatments is well understood, there is a need to identify how treatments influence the quality of sagebrush as winter food for wildlife. Our purpose was to identify how mowing and tebuthiuron treatments influenced dietary quality of Wyoming big sagebrush in central Wyoming. Two study areas were mowed in January and February 2014 and tebuthiuron was applied in two study areas in May 2014. We constructed 6 exclosures in each of these four study areas (24 total), which encompassed 30 m x 30 m areas of treated and untreated sagebrush within each exclosure. Samples of current annual growth were collected from 18 sagebrush plants from treated and 12 plants from control portions of mowing exclosures during November 2013–2015 and tebuthiuron exclosures during November 2014–2015. Samples were analyzed for crude protein and plant secondary metabolites known to influence dietary selection of sagebrush by sage-grouse and other sagebrush occurring herbivores. Our results suggest mowing and tebuthiuron treatments may slightly increase crude protein concentrations directly after treatments without immediate changes in plant secondary metabolites. Slight increases in dietary quality of sagebrush following treatments coupled with potential trade-offs with loss of biomass associated with treatments corroborates previous research that treating Wyoming big sagebrush may have little benefit for sage-grouse and other sagebrush-dependent wildlife. Future work should evaluate not only how treatments influence sage-grouse habitat use and 2 reproductive success, but how treatments influence other wildlife species in fragile sagebrush ecosystems

A review of the impacts of invasive wild pigs on native vertebrates

The wild pig (Sus scrofa) is a successful invasive species that has become well established outside of its native range in Eurasia. The invasive wild pig is the result of released or escaped domesticated livestock becoming feral, or Eurasian boar introduced for hunting purposes. The global spread of wild pigs has recently been exacerbated in some areas, such as the USA, by anthropogenically assisted dispersal. Once established in novel ecosystems, wild pigs have the potential to have significant negative impacts on the ecosystem, and the scientific literature is replete with examples. It is generally accepted that wild pigs negatively impact native fauna where they have become established, yet the degree to which they impact faunal communities has not been well described. This paper serves as a review of the information to date on the implications of wild pig invasions and impacts they have on terrestrial vertebrates in their invasive range. In addition, the review highlights our need for more research in this area, particularly regarding declining species

Contrasting Population Characteristics of Yellow Bass (Morone mississippiensis) in Two Southern Illinois Reservoirs

We investigated two southern Illinois reservoirs with contrasting size structures of yellow bass (Morone mississippiensis) to compare growth, mortality and recruitment patterns. Yellow bass were collected from Crab Orchard and Little Grassy Lakes during April-May 2009 using AC electrofishing. Total length and weight were recorded and sagittal otoliths sectioned and aged by two readers. Increments between otolith annuli were measured and the Weisberg linear growth model was used to assess age and environmental (growth year) effects on individual growth for fish from the two lakes. Von Bertalanffy growth models indicated faster growth and a greater maximum total length for yellow bass in Little Grassy Lake. However, growth of fish in Little Grassy Lake nearly ceased after age 4. The Weisberg model indicated differences in individual growth rate between the two lakes that were consistent across years (age effects were significant but growth year effects and the age-growth year interaction were not). Inter-lake differences in fish growth were present up to age 3. Recruitment was relatively stable in Crab Orchard, with year classes up to age 7 observed. Recruitment was more erratic in Little Grassy, with age 5 being the dominant year class and fish up to age 11 present. Differences in growth and recruitment patterns for yellow bass in these two lakes may be attributed to substantial inter-lake differences in turbidity, morphoedaphic index, or yellow bass density. Maximum age of yellow bass (age 11) was higher than previously reported for this species, likely due to the use of otoliths to age fish rather than scales. This study provides baseline information on age and growth, mortality, recruitment, and size structure of yellow bass that can be compared to data from future studies to elucidate factors influencing population dynamics of this species

Reconciling opposing soil processes in row-crop agroecosystems via soil functional zone management

Sustaining soil productivity in agricultural systems presents a fundamental agroecological challenge: nutrient provisioning depends upon aggregate turnover and microbial decomposition of organic matter (SOM); yet to prevent soil depletion these processes must be balanced by those that restore nutrients and SOM (soil building processes). These nutrient provisioning and soil building processes are inherently in conflict; management practices that create spatial separation between them may enable each to occur effectively within a single growing season, thereby supporting high crop yield while avoiding soil depletion. Soil functional zone management (SFZM), an understudied but increasingly adopted strategy for annual row-crop production, may help meet this agroecological challenge by creating spatial heterogeneity in biophysical conditions between crop rows and inter-rows. However, the process-level effects of this spatial heterogeneity on nutrient provisioning and soil building processes have not been characterised. We assessed the magnitude and spatial distribution of nutrient provisioning and soil building processes in model SFZM (ridge tillage) and conventional tillage (chisel plough) systems in four US states encompassing a major global agricultural production region. For soil building we measured bulk density, aggregation and permanganate oxidisable carbon (POXC); for nutrient provisioning we measured microbial decomposition activity, nutrient mineralisation and plant-available nitrogen. After two years, POXC increased under ridge tillage (0–20 cm depth) compared with chisel plough. Ridge tillage also enhanced nutrient provisioning processes in crop rows, increasing plant-available nitrogen in synchrony with maize peak nitrogen demand. Structural equation modelling revealed that improvement in soil building processes under ridge tillage caused rapid enhancement of nutrient provisioning processes in SOM-poor soils. Increases in crop row POXC stimulated microbial decomposition activity, which was associated with increased plant-available nitrogen during the phase of maize peak nitrogen demand. The decimetre-scale spatial heterogeneity created by ridge tillage enables reconciliation of nutrient provisioning and soil building processes in row-crop agroecosystems. In doing so, ridge tillage promotes critical soil processes necessary for increasing the range of ecosystem services provided by intensive production systems. SFZM approaches may have particular value in regions with SOM-poor soils, which would benefit from rapid increases in surface organic carbon. Also, by concentrating and promoting nutrient provisioning processes around crop roots during crop peak nitrogen demand, ridge tillage may enhance nitrogen-use efficiency and reduce current fertiliser requirements

Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample

Physical dust models are presented for 65 galaxies in SINGS that are strongly detected in the four IRAC bands and three MIPS bands. For each galaxy we estimate (1) the total dust mass, (2) the fraction of the dust mass contributed by PAHs, and (3) the intensity of the starlight heating the dust grains. We find that spiral galaxies have dust properties resembling the dust in the local region of the Milky Way, with similar dust-to-gas ratio and similar PAH abundance. The observed SEDs, including galaxies with SCUBA photometry, can be reproduced by dust models that do not require "cold" (T ≾ 10 K) dust. The dust-to-gas ratio is observed to be dependent on metallicity. In the interstellar media of galaxies with A_O ≡ 12 + log_(10)(O/H) > 8.1, grains contain a substantial fraction of interstellar Mg, Si, and Fe. Galaxies with A_O 8.1 have a median q_(PAH) = 3.55%. The derived dust masses favor a value X_(CO) ≈ 4 × 10^(20) cm^(-2) (K km s^(-1))^(-1) for the CO-to-H_2 conversion factor. Except for some starbursting systems (Mrk 33, Tol 89, NGC 3049), dust in the diffuse ISM dominates the IR power