Biological Opinions - Bureau of Reclamation

action. Reclamation estimated that the proposed action would result in flows that could support
over 20,000 coho salmon in the mainstem Klamath River in the R Ranch and Trees of Heaven
reaches. Assuming 50 coho salmon redds in the mainstem Klamath River, Reclamation
estimated that 9,000 natural origin coho salmon juveniles resulting from mainstem spawning
may be present in the mainstem. Based on the available habitat, Reclamation concluded that the
proposed action will likely provide adequate habitat for natural-origin juvenile coho salmon
during the spring until the annual hatchery goal of 75,000 IGH coho salmon juveniles are
released into the mainstem Klamath River between March 15 and May 1 (CDFG 2012 in
Reclamation 2012). Although Reclamation (2012) did not analyze competition or predation by
hatchery-origin or natural-origin Chinook salmon and steelhead, Reclamation (2012)
acknowledged that coho salmon juveniles rearing in the mainstem will experience decreased
growth, increased or premature emigration, increased competition for food, decreased feeding
territory sizes, and increased mortalities following the release of approximately 75,000 hatcheryorigin
coho salmon.
NMFS concurs with Reclamation’s assessment that habitat availability for juveniles in the
mainstem Klamath River is most critical between March to June because of: (1) the spring
redistribution of coho salmon parr; (2) the presence of most, if not all, coho salmon smolts from
the Interior Klamath Diversity Stratum in the mainstem during this time; and (3) the presence of
other stressors, such as the addition of IGH salmonids, the onset of elevated water temperatures,
and disease prevalence. During the spring, natural origin coho salmon parr and, to a lesser
extent, smolts compete for habitat with natural origin and hatchery-released salmon and
steelhead in late March to June. Competition for habitat peaks during May and early June when
natural origin smolts co-occur with approximately five million Chinook salmon smolts from
IGH. Therefore, habitat availability during spring is the most essential for coho salmon
juveniles.
During the fall (i.e., October and November), coho salmon parr migrate through mainstem
habitat as they redistribute from thermally suitable, summer habitat into winter rearing habitat
characterized by complex habitat structure and low water velocities in tributaries (Lestelle 2007).
The presence of coho salmon juveniles in the mainstem Klamath River is likely low in the fall
and winter, and habitat availability in the mainstem Klamath River during the fall and winter is
not considered limited. During the summer, coho salmon juveniles in the mainstem are limited
to thermal refugia during the day, and habitat availability in the mainstem Klamath River during
the summer is not considered limited for the relatively fewer coho salmon parr rearing in the
mainstem during this period.
The amount of rearing habitat available in the mainstem Klamath River is correlated with flows,
especially at certain ranges where water velocity, depth, and cover provide suitable conditions
for fry and juvenile rearing (Figures 11.17 and 11.18). As discussed earlier in the Effects to
SONCC Coho Salmon ESU Critical Habitat section, the Trees of Heaven, Seiad Valley, and
Rogers Creek reaches all show reduced habitat availability as a result of the proposed action.
Further downstream at the Rogers Creek reach, the proposed action will reduce habitat
availability between March and June in average water years (≥50 percent exceedance; Table
11.12) and in above average water years for the latter spring months (Table 11.12).
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