Anthropogenic change decouples a freshwater predator's density feedback.

Intraspecific interactions within predator populations can affect predator-prey dynamics and community structure, highlighting the need to better understand how these interactions respond to anthropogenic change. To this end, we used a half-century (1969-2018) of abundance and size-at-age data from Lake Erie's walleye (Sander vitreus) population to determine how anthropogenic alterations have influenced intraspecific interactions. Before the 1980s, the length-at-age of younger walleye (ages 1 and 2) negatively correlated with older (age 3 +) walleye abundance, signaling a 'density feedback' in which intraspecific competition limited growth. However, after the early 1980s this signal of intraspecific competition disappeared. This decoupling of the density feedback was related to multiple anthropogenic changes, including a larger walleye population resulting from better fisheries management, planned nutrient reductions to improve water quality and transparency, warmer water temperatures, and the proliferation of a non-native fish with novel traits (white perch, Morone americana). We argue that these changes may have reduced competitive interactions by reducing the spatial overlap between older and younger walleye and by introducing novel prey. Our findings illustrate the potential for anthropogenic change to diminish density dependent intraspecific interactions within top predator populations, which has important ramifications for predicting predator dynamics and managing natural resources.

Solid organ procurement from burned children.

BACKGROUND: Burns have constituted a traditional contraindication to solid organ procurement because of concerns that such organs may be damaged by burn shock associated splanchnic ischemia and contaminated by burn wound manipulation associated bacteremia. METHODS: Over a 5-year period, we attempted solid organ procurement from five burned children who had suffered concurrent anoxic brain injury. RESULTS: These four boys and one girl had an average age of 8.1 years (range, 2.5-12 years) and burn size of 29% (range, 4-70%). All were injured in house fires and four of five (80%) required prehospital external cardiac compressions. Brain death was declared an average of 35 hours (range, 2.75-77 hours) after injury. Solid organs procured and successfully transplanted from this group were 4 livers, 10 kidneys, and 2 hearts. Two of the livers and one heart were placed into pediatric recipients. Procured tissues included three sets of cardiac valves, and two corneas. All solid organs transplanted were functional at 6 months, although longer follow-up is not available. CONCLUSION: Early identification and diagnosis of brain death during resuscitation of burn patients with anoxic brain injury, combined with careful resuscitation and support of the brain dead potential organ donor, can result in the recovery of suitable solid organs and tissues for transplantation.