Distribution, abundance, and composition of fishes in Bright Angel and Kanab creeks, Grand Canyon National Park, Arizona

摘要

Brown and rainbow trout perennially dominated Bright Angel Creek; native species (flannelmouth and bluehead suckers) generally occurred only during spawning (March and April-May, respectively) and initial rearing of juveniles (bluehead sucker only). Flannelmouth suckers spawned at depths between 20-40 cm, currents between 0.4-0.8 m/sec, and over loosely compacted substrates (gravel, rock). Speckled dace abundance had markedly decreased since previous investigations, possibly due to brown trout becoming the dominant predator in the stream. Four native and 6 non-native species were taken in Kanab Creek; spawning was documented for bluehead sucker and speckled dace. Small bluehead suckers (160 mm) were perennial residents below a barrier 6.2 km above the mouth. Larger individuals (>200 mm) were absent in winter, but spawned in the lower 3.2 km of the stream in April and early May. Bluehead suckers spawned in shallow waters (25 cm), slow currents (0.25 m/sec), and over loosely compacted substrates (pebble, gravel).