Objective

• 1.) Determine seasonal fish communities and food habits of fishes in Bright Angel Creek.
• 2.) Determine if competition for food exists between native and non-native fishes.
• 3.) Estimated consumption of invertebrates and fish by non-native fishes.

Overview

Non-native trout removal is being conducted by the National Park Service and other stakeholders to restore and enhance native fish communities in Bright Angel Creek (BAC), Grand Canyon. To assess resource availability and evaluate the effects non-native brown (BNT) and rainbow (RBT) trout have on the food web in BAC, we sampled fish, benthic invertebrates, and drifting invertebrates seasonally from November 2010 to September 2011. Food habits of BNT and RBT were evaluated from stomach samples collected during invertebrate sampling periods, and annual resource consumption by trout was estimated using bioenergetics models. Invertebrate drift rates varied seasonally ranging from 95.3 g dry mass (DM) day-1 to 169.5 g DM day-1. Native fish (speckled dace and bluehead sucker) and Corydalus sp. were the dominant food types found in BNT stomachs, whereas Baetis mayflies and filamentous algae dominated RBT stomachs. Piscivory rates were 18% and 5% for BNT and RBT, respectively. Annual resource consumption was similar between BNT (186 g DM yr-1) and RBT (150.7 g DM yr-1), however this pattern varied between food types. Our results indicate BNT and RBT can affect native fishes through resource consumption and BNT are more likely to have an impact through predation.