Conference Papers

Acoustic surveys were conducted in late summer/early fall during the years 2004-2018 to estimate pelagic prey fish biomass in Lake Michigan. Midwater trawling during the surveys as well as acoustic target strength provided a measure of species and size composition of the fish community for use in scaling acoustic data and providing species-specific abundance estimates. The 2018 survey...

Ecological studies have been conducted on the Nevada National Security Site (NNSS) since the 1960s. Desert bighorn sheep (Ovis canadensis nelsoni) were considered rare visitors on the NNSS, with only 9 recorded observations between 1963 and 2009, all of which were males. Females and young were not documented definitively until winter 2011, when several were killed by a radiomarked female...

No abstract available.

Glen Canyon National Recreation Area (GCNRA) and Grand Canyon National Park (GCNP) offer unique recreational opportunities. An objective in the Long-Term Experimental and Management Plan Environmental Impact Statement (LTEMP EIS) is to maintain and improve the quality of recreational experiences (U.S. Department of the Interior, 2016). Some of the higher valued recreational activities...

The streamflow regime and sand supply of the Colorado River have been affected by the presence and operations of Glen Canyon Dam since filling of Lake Powell began in March 1963. Consequent changes in river morphology have included decreases in the size and abundance of sandbars used as campsites in Grand Canyon National Park (Dolan and others, 1974; Schmidt and Graf, 1990; Kearsley and...

Flood events have historically had a strong impact on riparian vegetation within Grand Canyon. Pre-dam sandbars were nearly devoid of perennial riparian vegetation due to the magnitude and frequency of periodic floods (Turner and Karpiscak, 1980). Vegetation has increased since dam closure (Waring, 1995), particularly since the early 1990s (Sankey and others, 2015). This increase in...

Forage fish are small, abundant, schooling planktivores that form a critical link in marine food webs by transferring energy from plankton up to birds, fishes, and marine mammals. Forage fishes in Puget Sound include the iconic Pacific herring as well as lesser known species such as surf smelt and the Pacific sand lance. There are significant knowledge gaps regarding the basic life...

Glen Canyon Dam has reduced downstream sediment supply to the Colorado River by about 95% in the reach upstream of the Little Colorado River confluence and by about 85% below the confluence (Topping and others, 2000). Operation of the dam for hydropower generation has additionally altered the flow regime of the river in Grand Canyon, largely eliminating pre-dam low flows (i.e., below 8...

Sediment-transport theory and field measurements indicate that the greatest or most efficient deposition of sand in eddies occurs during controlled floods (a.k.a. High-Flow Experiments or HFEs) when the greatest amount of the finest sand is available on the bed of the Colorado River (Topping and others, 2010). Conducting HFEs when the sand on the bed of the Colorado River is depleted and...

No abstract available.

The harsh environmental conditions and extreme flooding that created Grand Canyon also shaped the unique native fish that evolved in the Colorado River. Native fish have evolved their physiology, morphology and behavior to withstand high flood events. Flooding has been shown to benefit spawning, survival and recruitment of juvenile native fishes in many southwestern rivers. Annual pre...

Spring and fall high flow events released by Glen Canyon Dam appear to affect rainbow and brown trout in different ways that also very geographically, however other environmental factors are likely to play as important, or more important. Teasing apart impacts is made difficult by the lack of experimental design and limited replication of spring high flow events.