ANADROMOUS SALMONID RECOVERY IN THE UMATILLA RWER BASIN, OREGON: A CASE STUDY¹

Abstract

The Umatilla River Basin Fisheries Restoration Plan was initiated in the early 1980s to mitigate salmonid losses caused by hydroelectric development and habitat degradation. The objectives are to enhance the abundance of endemic steelhead and reintroduce extirpated chinook and coho salmon. The project prompted collaborative effort among federal, state, and tribal agencies, and local water users. It has incorporated habitat restoration, flow enhancement, fish passage improvements, and population supplementation through artificial production. Water exchanges have successfully increased minimum flows during spring and fall migration. While flows remain depressed compared to historic conditions, there is potential for improved habitat, passage, and homing. The mean adult‐to‐adult return rate of hatchery‐reared steelhead exceeded replacement and that of the naturally‐spawning population. Although the smolt‐to‐adult survival rates of hatchery‐reared fish fluctuate, salmonid escapement has increased in recent years, permitting steelhead and spring chinook harvest. Enumeration of potential spawners and observed redds reveals an increase in natural production of all supplemented species. Comparison of hatchery‐reared and naturally‐spawning steelhead populations revealed differences in life history characteristics (in age composition and sex ratios) though run timing and genetic stock compositions of the two components of the populations have not differed. Sustained monitoring is needed to determine benefits of integrating habitat restoration and artificial production in restoring salmonid populations.

Fish community changes after minimum flow increase: testing quantitative predictions in the Rhône River at Pierre‐Bénite, France

“…The case‐study of Pierre‐Bénite supports the idea that fish community responses to hydraulics are partly predictable in large rivers. It expands the scope of the few studies indicating an impact of minimum flow increase on fish populations in smaller streams (Phillips et al. , 2000; Jowett & Biggs, 2004).…”

“…‘Before–after’ tests of the impacts of minimum flow restoration have generally focused on target populations (often salmonids) and yielded contrasting results (e.g. Harris, Hubert & Wesche, 1991; Phillips, Ory & Talbot, 2000; Jowett & Biggs, 2004; Souchon & Capra, 2004). We are not aware of such ‘before–after’ tests for fish communities in large rivers.…”

Testing predictions of changes in fish abundance and community structure after flow restoration in four reaches of a large river (French Rhône)

“…The few existing long-term studies that addressed the effects of minimum flow restoration on fish populations and communities produced equivocal results. Likewise, the few studies reporting increased fish abundance changes after flow restoration typically assessed restored flows that contrasted strongly with the previous flows, that is, the restored minimum flow was much increased compared with low previous values (Travnichek, Bain & Maceina, 1995;Phillips, Ory & Talbot, 2000;Jowett & Biggs, 2006). Based on a 13-year experiment on the effects of increased flow releases on salmon populations, Bradford et al (2011) reported an increase in salmon abundance in a previously dry reach but reported only weak abundance changes in previously flowing reaches.…”

Integrated modeling of flood flows and tidal hydrodynamics over a coastal floodplain

“…Hydro-modifications, such as constructing levees and armoring riverbanks as well as diverting water for agriculture along the river systems, also limit the usage of floodplain habitat by juvenile fish. Reconnection to the floodplain habitat is an important step in establishing and maintaining Pacific Northwest salmon populations [7][8][9][10][11].…”