Publications by authors named "Brett M Johnson"

The successes of introduced populations in novel habitats often provide powerful examples of evolution and adaptation. In the 1950s, opossum shrimp () individuals from Clearwater Lake in Minnesota, USA were transported and introduced to Twin Lakes in Colorado, USA by fisheries managers to supplement food sources for trout. were subsequently introduced from Twin Lakes into numerous lakes throughout Colorado.

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Mercury (Hg) is a concerning contaminant due to its widespread distribution and tendency to accumulate to harmful concentrations in biota. We used a machine learning approach called random forest (RF) to test for different predictors of Hg concentrations in three species of Colorado reservoir sport fish. The RF approach indicated that the best predictors of 864 mm northern pike (Esox lucius) Hg concentrations were covariates related to salmonid stocking in each study system, while system-specific metrics related to productivity and forage base were the best predictors of Hg concentrations of 381 mm smallmouth bass (Micropterus dolomieu), and walleye (Sander vitreus).

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Background: Ablation is used for both rhythm control and improved quality of life (QoL) in atrial fibrillation (AF). It has been suggested that young adults may experience high recurrence rates after ablation and data remain lacking regarding QoL benefits. We aimed to investigate AF ablation outcomes and QoL benefits in young adults undergoing AF ablation using a large prospectively maintained registry and automated patient-reported outcomes (PRO).

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Epstein-Barr virus (EBV)-associated smooth muscle tumors (SMT) have been described in immunosuppressed states, including in post-transplant patients. Here, we discuss a heart-liver transplant recipient who was found to have multifocal hepatic EBV-SMT. His immunosuppression was initially transitioned from tacrolimus to sirolimus because of the proposed benefits of the mechanistic target of rapamycin inhibitors on EBV-SMT.

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Superior mesenteric artery (SMA) syndrome, or Wilkie syndrome, is a rare cause of small bowel obstruction due to compression of the duodenum between the SMA and aorta. Patients most at risk of SMA syndrome include those with rapid weight loss due to a variety of conditions including chronic illness, malignancy, trauma, HIV, eating disorders, substance abuse, or bariatric surgery. Characteristic radiologic findings include an aortomesenteric angle less than 25 degrees and an aortomesenteric distance of less than 8 mm.

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Partial decoupling of mercury (Hg) loading and observed Hg concentrations ([Hg]) in biotic and abiotic samples has been documented in aquatic systems. We studied two Colorado reservoirs to test whether shifts in prey for sport fish would lead to changes in [Hg] independent of external atmospheric Hg deposition. We compared sport fish total mercury concentrations ([T-Hg]) and macroinvertebrate (chironomids and crayfish) methylmercury concentrations ([MeHg]) before and after food web shifts occurred in both reservoirs.

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Kinetically controlled catalytic cross-metathesis reactions that generate (Z)-α,β-unsaturated esters selectively are disclosed. A key finding is that the presence of acetonitrile obviates the need for using excess amounts of a more valuable terminal alkene substrates. On the basis of X-ray structure and spectroscopic investigations a rationale for the positive impact of acetonitrile is provided.

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The spread of Mysis diluviana, a small glacial relict crustacean, outside its native range has led to unintended shifts in the composition of native fish communities throughout western North America. As a result, biologists seek accurate methods of determining the presence of M. diluviana, especially at low densities or during the initial stages of an invasion.

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Mercury (Hg) is a persistent global contaminant that biomagnifies, often reaching maximum levels in apex predators. Mercury contamination in piscivorous fish is a serious health risk for anglers and other fish consumers. We used data collected from a reservoir in Colorado to develop bioenergetics-based simulations of Hg bioaccumulation to estimate Hg concentrations in walleye (Sander vitreus), a popular sport fish.

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Mercury (Hg) contamination in sport fish is a global problem. In freshwater systems, food web structure, sport fish sex, size, diet and growth rates influence Hg bioaccumulation. Fish stocking is a common management practice worldwide that can introduce external energy and contaminants into freshwater systems.

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Article Synopsis
  • The study examined how the size of blue crabs affects their predation on marsh periwinkles in a salt marsh ecosystem.
  • Changes in the size distribution of periwinkles were linked to strong population cohorts and elevation above tidal levels rather than predation by crabs.
  • Laboratory experiments revealed that larger crabs are much more effective at preying on periwinkles, and an individual-based model predicted that predation rates decrease as crabs move away from their low-tide refuge.
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The success of any program for stocking walleye (Stizostedion vitreum vitreum) fingerlings is strongly dependent on growth of the stocked fish during the summer and early fall months immediately following their release into lakes, reservoirs, or rivers. An individual-based model (IBM) was developed to describe growth of young-of-the-year (YOY) walleyes in Lake Mendota (Wisconsin, USA). The IBM was used to evaluate stocking strategies for walleye fingerlings.

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