Resource use of crucian carp along a lake productivity gradient is related to body size, predation risk, and resource competition

Generalist fish species can feed on a wide resource spectrum and across trophic levels depending on resource availability and trophic interactions. Crucian carp (Carassius carassius) represents a good candidate species to investigate variation in the trophic ecology of generalist fish as it can be found in highly variable fish communities and its resource use is well documented. In this study, we explored the trophic ecology of crucian carp at the individual and population levels using stable isotope and gut content analysis. We tested if trophic resource use varied according to lake productivity, predation risk, intra- and interspecific competition, or individual fish size. We found that crucian carp resource preference was highly variable among and within lakes. In predator-free lakes, small crucian carp occurred in high densities, showed increased interindividual specialisation, and relied mainly on pelagic zooplankton. In presence of predators, large crucian carp occurred in low densities and included greater proportions of benthic macroinvertebrates in their diet. This shift in resource use was further favoured in productive, shallow lakes where littoral prey were probably abundant. Resource partitioning was an important factor determining crucian carp niche use, as fish had higher trophic position in absence of other cyprinids. Crucian carp showed highly dynamic resource use and food preferences in response to variable environmental conditions. Overlooking complex diet preferences of generalist fish may lead to an oversimplification of freshwater community dynamics.Peer reviewe

Resource use of crucian carp along a lake productivity gradient is related to body size, predation risk, and resource competition

Generalist fish species can feed on a wide resource spectrum and across trophic levels depending on resource availability and trophic interactions. Crucian carp (Carassius carassius) represents a good candidate species to investigate variation in the trophic ecology of generalist fish as it can be found in highly variable fish communities and its resource use is well documented. In this study, we explored the trophic ecology of crucian carp at the individual and population levels using stable isotope and gut content analysis. We tested if trophic resource use varied according to lake productivity, predation risk, intra- and interspecific competition, or individual fish size. We found that crucian carp resource preference was highly variable among and within lakes. In predator-free lakes, small crucian carp occurred in high densities, showed increased interindividual specialisation, and relied mainly on pelagic zooplankton. In presence of predators, large crucian carp occurred in low densities and included greater proportions of benthic macroinvertebrates in their diet. This shift in resource use was further favoured in productive, shallow lakes where littoral prey was probably abundant. Resource partitioning was an important factor determining crucian carp niche use, as fish had higher trophic position in absence of other cyprinids. Crucian carp showed highly dynamic resource use and food preferences in response to variable environmental conditions. Overlooking complex diet preferences of generalist fish may lead to an oversimplification of freshwater community dynamics.publishedVersio

Sykehusproduktivitet etter statlig overtakelse: En nordisk komparativ analyse

Ved hjelp av dataomhyllingsanalyse (DEA) beregnes utviklingen i produktivitet i de fire nordiske landene for perioden 1999 til 2004. Dernest analyseres effekten av sykehusreformen på produktiviteten i Norge ved hjelp av en regresjonsanalyse. Datamaterialet består av til sammen 729 sykehusobservasjoner. For sykehusene i Norge og Finland benyttes data for hele perioden 1999-2004, for sykehusene i Sverige for perioden 2001-2004, mens data for Danmark kun har vært tilgjengelig for 2002. Sykehusene aktivitet måles som tjenesteproduksjon i til sammen seks grupper pasienter, hvor inndelingen baseres på DRG systemet. Ressursbruken måles gjennom bruk av driftskostnader, men korrigeres for lønns- og prisforskjeller mellom de fire landene. I Norge analyseres årlig utvikling i produktivitet gjennom Samdata-rapportene. Analysene i dette prosjektet viser i grove trekk samme utvikling som resultatene i Samdata, til tross for at det er forskjeller både i operasjonalisering av aktivitet, ressursbruk og i korrigeringer for pris- og lønnsvekst. Resultatene viser at Norske sykehus, i gjennomsnitt, har et produktivitetsnivå i denne perioden som ligger lavere enn tilsvarende i Finland. Forskjellene blir imidlertid mindre mot slutten av perioden. Norske sykehus har i hele perioden et produktivitetsnivå som ligger over sykehusene i Sverige. Effekten av sykehusreformen analyseres gjennom å teste hvorvidt det i perioden etter reformen skjer et positivt eller negativt skift i produktivitetsnivået i Norge sammenholdt med endringene i de Sverige og Finland. Ulike modellspesifikasjoner benyttes. Resultatene er robuste ovenfor modellspesifikasjon, og tyder på at sykehusreformen har hatt en statistisk signifikant positiv effekt på produktiviteten i størrelsesorden 3 til 4 prosentpoeng.sykehusreformen i Norge; produktivitet; somatiske sykehus; dataomhyllingsanalyse; DEA

Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover

Several commercially available color standards exist, generated by a variety of manufacturers including LabSphere, Lucideon, and Avian Technologies. Previous work has characterized the photometric properties of LabSphere Spectralon targets. Here, we measure the visible and shortwave infrared (VSWIR; 0.4 to 2.5  μm) reflectance at multiple angles and determine the photometric properties of materials manufactured by Lucideon and Avian Technologies for potential use as calibration target materials for the Mars 2020 Mastcam-Z instrument. The Lucideon black, gray 33, green, and cyan samples are found to be significantly forward scattering. The yellow, red, and gray 70 samples are found to be weakly forward scattering. The Avian Technologies AluWhite98 sample was found to be weakly backward scattering. We characterize the absorptions observable and note the occurrence of wavelength-dependent photometric properties. The reflectance and photometric data collected and released here enable the use of these color standards for calibration of data from Mastcam-Z and other Mars-2020 rover instruments as well as provide key information for many other imaging and spectroscopy applications that require the calibration of data from multiple lighting or viewing geometries

An Instrument Anomaly in the Mars Exploration Rover Panoramic Camera (Pancam) 1009 nm Filter (R7): Characterisation, Simulation, Correction and Preliminary Verification

During pre‐flight calibration of the panoramic camera (Pancam) instrument on board the Mars Exploration Rovers MER A (Spirit) and MER B (Opportunity), a discrepancy was noted between 11‐band spectra extracted from Pancam images of the camera's radiometric calibration target and reflectance spectra obtained with a spectrometer. This discrepancy was observed in the longest‐wavelength filter of the camera (the longpass R7 filter with system λ_(eff) = 1,009 nm) and consisted of a reduction in contrast between bright and dark regions. Here we describe and characterize this effect. We propose that the effect arises because long‐wavelength photons close to the silicon band‐gap at 1,100 nm are allowed through the R7 filter, pass through the bulk charge‐coupled device, scatter from the backside, pass through the charge‐coupled device again, and are registered in a pixel other than the pixel through which they originally entered. Based on this hypothesis we develop a model capable of accurately simulating the effect, and correct for it. We present preliminary results from testing this correction on preflight, as well as in‐flight, images. The effect is small, but in some specific cases in small regions of high contrast, the effect is significant. In in‐flight images of Martian terrain we observed the signal in dark shadows to be artificially inflated by up to ∼ 33% and analysis of early‐mission calibration target images indicated that the reduced contrast due to the artifact is equivalent to >100 DN (full well = 4095 DN) for a hypothetical perfectly dark pixel

Photometric characterization of Lucideon and Avian Technologies color standards including application for calibration of the Mastcam-Z instrument on the Mars 2020 rover

Several commercially available color standards exist, generated by a variety of manufacturers including LabSphere, Lucideon, and Avian Technologies. Previous work has characterized the photometric properties of LabSphere Spectralon targets. Here, we measure the visible and shortwave infrared (VSWIR; 0.4 to 2.5  μm) reflectance at multiple angles and determine the photometric properties of materials manufactured by Lucideon and Avian Technologies for potential use as calibration target materials for the Mars 2020 Mastcam-Z instrument. The Lucideon black, gray 33, green, and cyan samples are found to be significantly forward scattering. The yellow, red, and gray 70 samples are found to be weakly forward scattering. The Avian Technologies AluWhite98 sample was found to be weakly backward scattering. We characterize the absorptions observable and note the occurrence of wavelength-dependent photometric properties. The reflectance and photometric data collected and released here enable the use of these color standards for calibration of data from Mastcam-Z and other Mars-2020 rover instruments as well as provide key information for many other imaging and spectroscopy applications that require the calibration of data from multiple lighting or viewing geometries

Visible to near-infrared MSL/Mastcam multispectral imaging: Initial results from select high-interest science targets within Gale Crater, Mars

The Mastcam CCD cameras on the Mars Science Laboratory Curiosity Rover each use an 8-position filter wheel in acquiring up to 1600 × 1200 pixel images. The filter set includes a broadband near-infrared cutoff filter for RGB Bayer imaging on each camera and 12 narrow-band geology filters distributed between the two cameras, spanning the wavelength range 445–1013 nm. This wavelength region includes the relatively broad charge-transfer and crystal-field absorption bands that are most commonly due to the presence of iron-bearing minerals. To identify such spectral features, sequences of images taken with identical pointings through different filters have been calibrated to relative reflectance using pre-flight calibration coefficients and in-flight measurements of an onboard calibration target. Within the first 1000 sols of the mission, Mastcam observed a spectrally diverse set of materials displaying absorption features consistent with the presence of iron-bearing silicate, iron oxide, and iron sulfate minerals. Dust-coated surfaces as well as soils possess a strong positive reflectance slope in the visible, consistent with the presence of nanophase iron oxides, which have long been considered the dominant visible-wavelength pigmenting agent in weathered martian surface materials. Fresh surfaces, such as tailings produced by the drill tool and the interiors of rocks broken by the rover wheels, are grayer in visible wavelengths than their reddish, dust-coated surfaces but possess reflectance spectra that vary considerably between sites. To understand the mineralogical basis of observed Mastcam reflectance spectra, we focus on a subset of the multispectral data set for which additional constraints on the composition of surface materials are available from other rover instruments, with an emphasis on sample sites for which detailed mineralogy is provided by the results of CheMin X-ray diffraction analyses. We also discuss the results of coordinated observations with the ChemCam instrument, whose passive mode of operation is capable of acquiring reflectance spectra over wavelengths that considerably overlap the range spanned by the Mastcam filter set (Johnson et al. 2016). Materials that show a distinct 430 nm band in ChemCam data also are observed to have a strong near-infrared absorption band in Mastcam spectral data, consistent with the presence of a ferric sulfate mineral. Long-distance Mastcam observations targeted toward the flanks of the Gale crater central mound are in agreement with both ChemCam spectra and orbital results, and in particular exhibit the spectral features of a crystalline hematite layer identified in MRO/CRISM data. Variations observed in Mastcam multi-filter images acquired to date have shown that multispectral observations can discriminate between compositionally different materials within Gale Crater and are in qualitative agreement with mineralogies from measured samples and orbital data