Proximal and distal factors associated with the decline in secondary invertebrate prey production in the Colorado River, Glen Canyon, Arizona.

Using a bioenergetic model, demographic data for the Rainbow Trout (Oncorhynchus mykiss) population were compiled and used to estimate total prey consumption in the Colorado River, Glen Canyon , AZ. Additionally, other data including invertebrate diet, drift, and benthic measurements were  used to make generalized estimates of daily production rates for the most common benthic invertebrate taxa. The primary objectives were to test a set of hypotheses regarding proximate and distal drivers that were  regualating secondary production of invertebrate prey in Glen Canyon. These production estimates represent an estimate of aggregate prey items that include Chironomidae and Simulium arcticum [complex]), as well as amphipods (Gammarus lacustris); and other miscellaneous oligochaetes (including Lumbricidae, Lumbriculidae, and Tubificidae). For the most supported proximate hypothesis, we also investigate the extent to which water chemistry or physical characteristics of the Lake Powell reservoir serves as more distal drivers of the ecosystem. Lastly, we estimate population scale foraging efficiency and test the hypothesis that this foraging efficiency varies through time, resulting in reduced foraging efficiency when prey production outstrips the predator population’s consumption potential. Most of the data used were from previously published findings that were collected or measured by other studies. Size stratified estimates of trout abundance, mass at length, and daily growth were derived from a previous analysis of rainbow trout using mark-recapture data collected during January, April, July, September, and October from 2012 to 2016 (U.S. Geological Survey 2021, unpublished Natal Origin Data). Other, supplementary data for benthos were compiled from Blinn and Shannon 2002, and other data sources that are described in Benenati et al. 2002, and Cross et al. 2013. Trout diet data were from Yackulic et al. (2021) and described in the associated journal article (Dodrill et al. 2021). Nutrient and water quality data were collected 2.4 km above Glen Canyon Dam in Lake Powell at depth of penstocks. Other hydrological data were acquired from U.S. Bureau of Reclamation (https://www.usbr.gov/rsvrWater/HistoricalApp.html, U.S. Bureau of Reclamation 2016) and U.S. Geological Survey (unpublished data). These data can be used to look at temporal patterns (daily, seasonal, and year-to-year) in the flux of invertebrate prey and associated covariates (proximal and distal drivers). These data can also be used to examine the metabolic costs of rainbow trout in relationship to an ecosystem that is prey limited.

Tags: abundance, arizona, benthic-ecosystems, bioenergetic-model, biological-and-physical-processes, biota, colorado-river, consumption, data-release, diet-data, field-sampling, fish, fish-size, food-web, foraging, glen-canyon, glen-canyon-dam, inlandwaters, interpolation, invertebrates, laboratory-experiments, lake-powell, lees-ferry, mark-recapture-data, metabolic-costs, modeling, northern-arizona, nutrient-limitations, phosphorous, prey, reservoir, seasonal, trophic-effects, usgs-61d4b0e2d34ed79293fe90ed, water-quality
Organization: Department of the Interior