Harvey B.C.,U.S. Department of Agriculture |
White J.L.,U.S. Department of Agriculture |
Nakamoto R.J.,U.S. Department of Agriculture |
North American Journal of Fisheries Management
Resource managers commonly face the need to evaluate the ecological consequences of specific water diversions of small streams. We addressed this need by conducting 4 years of biophysical monitoring of stream reaches above and below a diversion and applying two individual-based models of salmonid fish that simulated different levels of behavioral complexity. The diversion of interest captured about 24% of streamflow between June and October but had little or no effect over the remainder of the year. The change in biomass of Rainbow Trout Oncorhynchus mykiss and steelhead (anadromous Rainbow Trout) over the dry season (June-October) favored the upstream control over the downstream diversion reach over 4 years (2008-2011). Dry-season growth did not differ consistently between the two reaches but did exhibit substantial annual variation. Longer-term observations revealed that in both reaches most fish growth occurred outside the period of dry-season diversion. After calibration to the upstream control reach, both individual-based models predicted the observed difference in fish biomass between control and diversion reaches at the ends of the dry seasons. Both models suggested the difference was attributable in part to differences in habitat structure unrelated to streamflow that favored the upstream reach. The two models both also reproduced the large seasonal differences in growth, small differences between reaches in individual growth, and natural distributions of growth among individuals. Both the empirical data and simulation modeling suggested that the current level of diversion does not threaten the persistence of the salmonid population. In multiyear simulations using the two models, the model incorporating greater flexibility in fish behavior exhibited weaker population-level responses to more extreme reductions in dry-season streamflow. We believe the application of individual-based models in this case has placed resource managers in a relatively strong position to forecast the consequences of future environmental alterations at the study site.Received March 22, 2013; accepted October 17, 2013. © 2014 Copyright © Taylor & Francis Group, LLC. Source
Rosenberger A.E.,University of Idaho |
Rosenberger A.E.,University of Alaska Fairbanks |
Rosenberger A.E.,U.S. Geological Survey |
Dunham J.B.,U.S. Geological Survey |
And 2 more authors.
Management of aquatic resources in fire-prone areas requires understanding of fish species' responses to wildfire and of the intermediate- and long-term consequences of these disturbances. We examined Rainbow Trout populations in 9 headwater streams 10 y after a major wildfire: 3 with no history of severe wildfire in the watershed (unburned), 3 in severely burned watersheds (burned), and 3 in severely burned watersheds subjected to immediate events that scoured the stream channel and eliminated streamside vegetation (burned and reorganized). Results of a previous study of this system suggested the primary lasting effects of this wildfire history on headwater stream habitat were differences in canopy cover and solar radiation, which led to higher summer stream temperatures. Nevertheless, trout were present throughout streams in burned watersheds. Older age classes were least abundant in streams draining watersheds with a burned and reorganized history, and individuals >1 y old were most abundant in streams draining watersheds with an unburned history. Burned history corresponded with fast growth, low lipid content, and early maturity of Rainbow Trout. We used an individualbased model of Rainbow Trout growth and demographic patterns to determine if temperature interactions with bioenergetics and competition among individuals could lead to observed phenotypic and ecological differences among populations in the absence of other plausible mechanisms. Modeling suggested that moderate warming associated with wildfire and channel disturbance history leads to faster individual growth, which exacerbates competition for limited food, leading to decreases in population densities. The inferred mechanisms from this modeling exercise suggest the transferability of ecological patterns to a variety of temperature-warming scenarios. © 2015 by The Society for Freshwater Science. Source
Lang | Date: 2010-02-28
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Lang | Date: 2005-07-21
Mens womens and childrens clothing and fashion accesssories namely shirts, t-shirts,long sleeve t shirts, sweaters,pants,jeans,shorts,sports wear,namely jogging suits,athletic shoes,tank tops, jackets and jerseys.
Harvey B.C.,U.S. Department of Agriculture |
River Research and Applications
Habitat fragmentation is widely assumed to have negative effects on populations and communities, but some effects of fragmentation are subtle, difficult to measure and not always negative. For stream fish, barriers to upstream passage, such as waterfalls or culverts with perched outlets, are a common cause of fragmentation. We explored the effects of barriers on a virtual stream trout population occupying a network of reaches in the inSTREAM individual-based trout population model. The model includes daily habitat selection by individual fish, with barriers represented by assuming trout cannot move upstream past a barrier and move downstream over a barrier only if habitat above it offers low potential fitness. In 78-year simulations of a resident trout population occupying the stream network of a 25-km 2 catchment, we varied barrier density and observed effects on population stability properties and demographics. Increasing barrier density decreased subpopulation persistence in first-order tributaries but not larger streams. Barriers at tributary mouths reduced the population's resistance to extreme flows, but additional barriers caused no further loss of resistance. Barriers reduced overall abundance and biomass at intermediate and high densities and caused a small but surprising increase in biomass at low density. In comparison with fish in the remainder of the network, fish in isolated first-order tributaries had higher survival early in life, smaller sizes at age and reproduced as smaller, younger individuals. Fish that passed over barriers contributed relatively little to downstream populations but, had they not moved, would have increased persistence and abundance of the tributaries they moved from. Relationships such as these would be very difficult to elucidate without a model representing individual behaviour. © 2011 John Wiley & Sons, Ltd. Source