The effect of chronic exposure to ethanol on learning and memory was assessed in rats. Adult rats were fed a liquid diet containing ethanol (Et) ad libitum, pair-fed an isocaloric/isonutritious control diet (Ct), or fed lab chow and water (Ch) ad libitum. These diets were provided for as long as 28 weeks prior to testing and during the period of behavioral testing. Rats were required to learn a radial arm maze task that depended upon extramaze cues (visual and spatial) or intramaze cues (various odors). Each rat was tested twice daily for 26 days. The number of reference and working memory errors and the time required to successfully navigate the maze (latency) were recorded. Et-fed rats consistently performed the same or better than the Ct-fed or Ch-fed rats. The enhanced behavior was task-specific and transient. The enhancement was observed in rats after 14 or 20 weeks of ethanol exposure, but not in rats exposed to ethanol for 28 weeks. Et-fed rats performed significantly better on the reference memory task in the odor condition of the maze task, whereas their performance in the spatial task was similar to that for the two control groups. Thus, after an extended period of exposure (e.g., 28 weeks), ethanol had no effect on learning and memory. On the other hand, under certain conditions (14 or 20 weeks), ethanol transiently enhanced memory.

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Tiger trout (Salmo trutta × Salvelinus fontinalis) are sterile hybrids often stocked as a biocontrol agent for undesirable fishes and to enhance recreational angling. Yet, how different ecological processes affect their post-stocking performance remain poorly understood. Rapid growth early in life can foster rapid transitions to piscivory, and improve survival. Identifying factors that benefit early growth can help managers optimize tiger trout stocking for meeting multiple fisheries management objectives. Here, we characterized the trophic ecology and growth of tiger trout stocked at varying densities into seven lentic subalpine systems in Colorado, USA. Study systems supported different species of undesirable fish (e.g., minnows or suckers). We used stable isotopes of carbon and nitrogen to quantify trophic relationships among tiger trout and other fishes in each system. We then evaluated several system-specific attributes as predictors for the size of tiger trout at age-1 using a Random Forest model. Stable isotopes demonstrated the potential for resource competition among tiger trout and other fishes, but potential varied by system. Indices of resource competition ranked highest in the Random Forest model, but the stocking density of tiger trout was most important, suggesting that intraspecific competition outweighed interspecific competition in driving early growth. These processes were mediated by system productivity. Thus, stocking density in combination with the realized carrying capacities of systems should be considered when making management decisions for tiger trout.

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