Currently more than 31 species of fish inhabit the Umatilla subbasin. Seventeen species are native to the subbasin (Table 14). Spring chinook, fall chinook and coho salmon became extinct in the basin in the 1900s and were reintroduced with hatchery stock in the 1980s and have begun to reproduce naturally.
Table 14. Fish Species present in the Umatilla River Subbasin
Fish species abundance based on average number of fish per 100m2: A=abundant, R=rare, U=uncommon, C=common, and I=insufficient data
The species composition and distribution of fish in the Willow Creek subbasin is not well known. However, resident redband trout are known to persist in the more suitable reaches and headwater tributaries of Willow Creek and the more common non salmonid resident species are likely present in abundance. Sixteen Mile Canyon, Sand Hollow and Juniper Canyon are known to be intermittent streams in many locations; however extensive surveys have not been conducted and there may be some perennial reaches that support fish
The predominant anadromous salmonid in the Umatilla subbasin is summer steelhead, which is the anadromous form of inland redband rainbow trout (Oncorhynchus mykiss). Redband trout have the widest distribution and likely the greatest abundance of salmonids in the basin (T. Bailey, Oregon Department of Fish and Wildlife, personal communication, January 2001).
Anadromous salmonids that currently occur in the subbasin include summer steelhead (O. mykiss), coho (O. kisutch), and spring and fall chinook (O. tshawytscha). Coho and chinook have been reintroduced from Columbia River hatchery stock, while steelhead are currently supplemented by hatchery-reared fish using wild, endemic broodstock to prevent domestication. Resident salmonid species inhabiting the Umatilla subbasin include mountain whitefish (Prosopium williamsoni), redband trout (O. mykiss) and bull trout (Salvelinus confluentus).
Spring chinook, fall chinook and coho were absent from the subbasin for approximately 75 years. Irrigation and agricultural development in the early 1900’s is the primary cause of the decline of steelhead, and directly related to the extirpation of spring chinook salmon (Bureau of Reclamation 1988; Oregon Department of Environmental Quality 2000). Their reintroduction and supplementation occurred in conjunction with actions designed to reconstruct diversion structures and augment flows (Oregon Department of Environmental Quality 2000).