Adult Return Update

Russian River Coho Update: 1/10/20

Coho salmon and biologist measuring a redd.
Coho salmon (left) and biologist measuring a redd (right).

The total coho salmon adult estimate for the Russian River, as of January 9, is 325 fish; 106 age-3 adults and 219 age-2 adults (Table 1). In the tributaries, we have observed a total of 55 coho redds, 25 steelhead redds, 17 Chinook redds, and 11 unknown salmonid redds (Table 2). After a strong pulse of coho in early December, the number of new coho observed has declined over the past three weeks, but the steelhead run is beginning to pick up. Hopefully the rains coming later this week will bring in more fish.

As in previous years, we are seeing a lot of individual adults moving among multiple tributaries within the Russian River watershed. In the case of one fish that we tagged as a smolt in Green Valley, we detected it returning as an age-2 adult (jack) to four spawning tributaries as well as multiple Dry Creek backwaters (Figure 2, Table 3). Although this fish was detected in more streams than most returning adults, it is not uncommon to see individual fish moving back and forth among multiple tributaries throughout the spawning season.

For those of you interested in the Green Valley Creek watershed, you will be excited to note the return of our first adult coho from a 2017 fall release into Redwood Creek. This age-3 adult was first detected in Green Valley Creek in early December, milled around within the mainstem of Green Valley for a month, and was then detected on 12/31 at a pilot antenna we are testing out in Atascadero Creek, 1.24 km upstream of the confluence with Green Valley. Interestingly, we also had a few detections on the Atascadero antenna of both wild and hatchery juveniles tagged/released into upper Green Valley and Purrington creeks. Although we have long suspected that juvenile coho make their way up into Atascadero during the winter, this is the first time we have been able to document it.

Table 1. Number of unique adult hatchery coho salmon detections on Russian River PIT tag antenna arrays, and expanded counts through 1/9/20.
Table 1. Number of unique adult hatchery coho salmon detections on Russian River PIT tag antenna arrays, and expanded counts through 1/9/20.

Table 2. Number of redds observed in Russian River tributaries through 1/7/20.
Table 2. Number of redds observed in Russian River tributaries through 1/7/20.

Figure 2. Map of PIT antenna sites operated during winter 2019/20 in the Russian River watershed.
Figure 2. Map of PIT antenna sites operated during winter 2019/20 in the Russian River watershed.

Table 3. Detection history of a hatchery coho salmon tagged as a smolt in Green Valley Creek.
Table 3. Detection history of a hatchery coho salmon tagged as a smolt in Green Valley Creek.