Factors Affecting White Bass Abundance in Two Missouri River Reservoirs

Annual angler harvest of white bass (Morone chrysops) increased from 1985–2005 in Lake Oahe and Lake Sharpe, two mainstem Missouri River reservoirs in South Dakota. In 2006, harvest rates dropped appreciably in both reservoirs and remained low through 2015. It is hypothesized that a confirmed 2005 columnaris disease outbreak led to reduced annual angler harvest of white bass from both reservoirs. Mean annual angler harvest prior to the outbreak (1985–2005) in Lake Oahe decreased 65% and in Lake Sharpe decreased 57% post outbreak (2006–2015). To assess potential causes of sustained decreased adult white bass abundance in the reservoirs, we examined relationships among environmental (i.e., temperature, precipitation, water elevation, inflow) and biological factors (i.e., prey abundance, potential competitor abundance) with both age-0 and adult (\u3e100 mm total length) white bass relative abundance before and after the columnaris disease outbreak. Prior to the outbreak, age-0 and adult white bass abundance was related to biological variables (i.e., age-0 fish abundance, adult walleye abundance and adult predator abundance) on Lake Oahe and Lake Sharpe. Following the outbreak, age-0 and adult white bass abundance was related to environmental variables (i.e., January gauge height, precipitation and temperature, April and July gauge height and precipitation) in both reservoirs. We hypothesize that since the columnaris disease outbreak reduced white bass abundance, environmental and biological factors have changed roles in affecting age-0 and adult white bass abundance (and angler harvest) in both reservoirs. Although these relationships are not necessarily causes of reduced abundance, we believe they can aid in management of white bass populations by allowing prioritization of biological and environmental factors related to age-0 and adult white bass abundance after columnaris disease-related die-offs

Factors affecting the catch and harvest rates of paddlefish downstream of Gavins Point Dam, South Dakota, 2000–2020

Paddlefish, Polyodon spathula (Walbaum), provide an important snagging and bowfishing fishery below Gavins Point Dam in South Dakota. During 2009–2020, snagging catch rates of paddlefish decreased below Gavins Point Dam to presumed “normal” lower pre-2004 levels, while bowfishing catch (harvest) rates significantly increased during 2000–2020. Because Paddlefish are highly migratory, both local (i.e., monthly gauge height, precipitation, and air temperature near Gavins Point Dam) and remote (difference in Mississippi and Missouri River discharge near their confluence) environmental conditions were used to explain variation in snagging catch rates and bowfishing harvest rates. Snagging catch rates were related to October gauge height, whereby deeper water in October led to decreased catch rates below Gavins Point Dam. Bowfishing harvest rates increased significantly after a 2016 regulation change moved the season from July 1 to July 31, and from June 1 to June 30, likely because water clarity was greater in June than in July. Mean annual air temperature and precipitation explained variation in bowfishing harvest rates prior to the 2016 regulation change. Our findings, the first to examine both snagging and bowfishing fisheries below Gavins Point Dam, suggest that local abiotic factors are likely more important than remote discharge for explaining variation in snagging catch rates and bowfishing harvest rates in the channelised Missouri River

A Search for Variability in Exoplanet Analogues and Low-Gravity Brown Dwarfs

We report the results of a $J$-band survey for photometric variability in a sample of young, low-gravity objects using the New Technology Telescope (NTT) and the United Kingdom InfraRed Telescope (UKIRT). Surface gravity is a key parameter in the atmospheric properties of brown dwarfs and this is the first large survey that aims to test the gravity dependence of variability properties. We do a full analysis of the spectral signatures of youth and assess the group membership probability of each target using membership tools from the literature. This results in a 30 object sample of young low-gravity brown dwarfs. Since we are lacking in objects with spectral types later than L9, we focus our statistical analysis on the L0-L8.5 objects. We find that the variability occurrence rate of L0-L8.5 low-gravity brown dwarfs in this survey is $30^{+16}_{-8}\%$. We reanalyse the results of Radigan 2014 and find that the field dwarfs with spectral types L0-L8.5 have a variability occurrence rate of $11^{+13}_{-4}\%$. We determine a probability of $98\%$ that the samples are drawn from different distributions. This is the first quantitative indication that the low-gravity objects are more likely to be variable than the field dwarf population. Furthermore, we present follow-up $J_S$ and $K_S$ observations of the young, planetary-mass variable object PSO 318.5-22 over three consecutive nights. We find no evidence of phase shifts between the $J_S$ and $K_S$ bands and find higher $J_S$ amplitudes. We use the $J_S$ lightcurves to measure a rotational period of $8.45\pm0.05~$hr for PSO 318.5-22.Comment: accepted for publication in MNRA

The Hawaii Infrared Parallax Program. III. 2MASS J0249-0557 c:A Wide Planetary-mass Companion to a Low-mass Binary in the β Pic Moving Group

We have discovered a wide planetary-mass companion to the $\beta$ Pic moving group member 2MASSJ02495639-0557352 (M6 VL-G) using CFHT/WIRCam astrometry from the Hawaii Infrared Parallax Program. In addition, Keck laser guide star adaptive optics aperture-masking interferometry shows that the host is itself a tight binary. Altogether, 2MASSJ0249-0557ABc is a bound triple system with an $11.6^{+1.0}_{-1.3}$ $M_{\rm Jup}$ object separated by $1950\pm200$ AU (40") from a relatively close ($2.17\pm0.22$ AU, 0.04") pair of $48^{+12}_{-13}$ $M_{\rm Jup}$ and $44^{+11}_{-14}$ $M_{\rm Jup}$ objects. 2MASSJ0249-0557AB is one of the few ultracool binaries to be discovered in a young moving group and the first confirmed in the $\beta$ Pic moving group ($22\pm6$ Myr). The mass, absolute magnitudes, and spectral type of 2MASSJ0249-0557 c (L2 VL-G) are remarkably similar to those of the planet $\beta$ Pic b (L2, $13.0^{+0.4}_{-0.3}$ $M_{\rm Jup}$). We also find that the free-floating object 2MASSJ2208+2921 (L3 VL-G) is another possible $\beta$ Pic moving group member with colors and absolute magnitudes similar to $\beta$ Pic b and 2MASSJ0249-0557 c. $\beta$ Pic b is the first directly imaged planet to have a "twin," namely an object of comparable properties in the same stellar association. Such directly imaged objects provide a unique opportunity to measure atmospheric composition, variability, and rotation across different pathways of assembling planetary-mass objects from the same natal material.Comment: Accepted to AJ, only change is color scheme of figure

Factors Affecting White Bass Abundance in Two Missouri River Reservoirs

Annual angler harvest of white bass (Morone chrysops) increased from 1985–2005 in Lake Oahe and Lake Sharpe, two mainstem Missouri River reservoirs in South Dakota. In 2006, harvest rates dropped appreciably in both reservoirs and remained low through 2015. It is hypothesized that a confirmed 2005 columnaris disease outbreak led to reduced annual angler harvest of white bass from both reservoirs. Mean annual angler harvest prior to the outbreak (1985–2005) in Lake Oahe decreased 65% and in Lake Sharpe decreased 57% post outbreak (2006–2015). To assess potential causes of sustained decreased adult white bass abundance in the reservoirs, we examined relationships among environmental (i.e., temperature, precipitation, water elevation, inflow) and biological factors (i.e., prey abundance, potential competitor abundance) with both age-0 and adult (\u3e100 mm total length) white bass relative abundance before and after the columnaris disease outbreak. Prior to the outbreak, age-0 and adult white bass abundance was related to biological variables (i.e., age-0 fish abundance, adult walleye abundance and adult predator abundance) on Lake Oahe and Lake Sharpe. Following the outbreak, age-0 and adult white bass abundance was related to environmental variables (i.e., January gauge height, precipitation and temperature, April and July gauge height and precipitation) in both reservoirs. We hypothesize that since the columnaris disease outbreak reduced white bass abundance, environmental and biological factors have changed roles in affecting age-0 and adult white bass abundance (and angler harvest) in both reservoirs. Although these relationships are not necessarily causes of reduced abundance, we believe they can aid in management of white bass populations by allowing prioritization of biological and environmental factors related to age-0 and adult white bass abundance after columnaris disease-related die-offs

Effects of the 2011 Missouri River flood on walleye natal recruitment and habitat use in Lake Sharpe, South Dakota

Floods affect fish populations in the short term (e.g. entrainment, mortality) and long term (e.g. recruitment, habitat availability), but oftentimes long-term effects are overlooked. In 2011, a catastrophic flood with record peak flows (4,200 m3/s) occurred in Lake Sharpe, a mainstem Missouri River reservoir. The flood’s immediate impacts on the Lake Sharpe walleye (Sander vitreus) population have been documented, but long-term effects on natal recruitment and habitat use have not been assessed. We used otolith chemistry to evaluate spatial patterns in walleye natal recruitment and late-summer (i.e. July − September) habitat use in years before, during, and after the flood to gain insight into long-term flood impacts on the Lake Sharpe walleye population. From 2004 to 2013, all walleye hatched in embayments and main channel habitats as opposed to stilling basins or tributaries, and the majority of age ≥ 1 fish (i.e. age-1 or older) used the former habitats in late summer. During the flood year, natal recruitment remained stable relative to pre-flood levels in embayments (26% pre-flood, 20% during flood) and main channels (74% pre-flood, 80% during flood). Habitat use of age ≥ 1 walleye was generally unaltered by the flood as it remained consistent in embayments and main channel habitats before, during, and after the disturbance. Hence, the Lake Sharpe walleye population was largely unaffected by the flood in terms of natal recruitment and habitat use. Our results highlight the resilience of the Lake Sharpe walleye population to a catastrophic flood, providing fisheries professionals with an otolith chemistry approach for quantifying flood effects on natal recruitment and habitat use and developing spatially informed management approaches (e.g. habitat protection/rehabilitation, harvest regulations)

Positron emission tomography of tau in Iraq and Afghanistan Veterans with blast neurotrauma

Military personnel are often exposed to multiple instances of various types of head trauma. As a result, there has been increasing concern recently over identifying when head trauma has resulted in a brain injury and what, if any, long-term consequences those brain injuries may have. Efforts to develop equipment to protect soldiers from these long-term consequences will first require understanding the types of head trauma that are likely responsible. In this study, we sought to identify the types of head trauma most likely to lead to the deposition of tau, a protein identified as a likely indicator of long-term negative consequences of brain injury. To define the types of head trauma in a military population, we applied a factor analysis to interviews from a larger cohort of 428 Veterans enrolled in the Translational Research Center for Traumatic Brain Injury and Stress Disorders. Three factors were identified: Blast Exposure, Symptom Duration, and Blunt Concussion. Sixteen male Veterans from this study and one additional male civilian (aged 25–69, mean 35.2 years) underwent simultaneous positron emission tomography/magnetic resonance imaging using a tracer that binds to tau protein, the ligand T807/AV-1451 (Flortaucipir). Standard uptake value ratios to the isthmus of the cingulate were calculated from a 20-minute time frame 70 min post-injection. We found that tracer uptake throughout the brain was associated with Blast Exposure factor beta weights, but not with either Symptom Duration or Blunt Concussion. Associations with uptake were located primarily in the cerebellar, occipital, inferior temporal and frontal regions. The data suggest that in this small, relatively young cohort of Veterans, elevated T807/AV-1451 uptake is associated with exposure to blast neurotrauma. These findings are unanticipated, as they do not match histopathological descriptions of tau pathology associated with head trauma. Continued work will be necessary to understand the nature of the regional T807/AV-1451 uptake and any associations with clinical symptoms. Keywords: Blast, Positron emission tomography, Tau, Traumatic brain injury, Vetera