Coho salmon are trapped in the Russian River and urgently need a boost from Mother Nature.
Cut off by lack of rain from most of the small streams where they habitually spawn, the endangered coho face a ticking biological clock that could decimate this year's reproduction.
“We know their time is running out,” said Nick Bauer, a biologist with UC Cooperative Extension's coho monitoring program.
Coho Salmon Struggling in Russian River
Bauer was one of seven fish specialists who donned wetsuits and drysuits Thursday to check on the condition of the coho forced to congregate in pools along the river where they are exposed to foraging harbor seals and sea lions as well as human anglers.
Upstream from Monte Rio, the divers spotted coho, steelhead and primarily chinook salmon — the river's three spawning species — all apparently waiting for more water.
Flow in the lower river was 100 cubic feet per second on Thursday, a trickle compared with the average January flow of 8,000 cubic feet a second. At this time in ultra-dry 1977, the flow was 96 cfs.
Access to the major coho spawning grounds, such as Green Valley, Mill and Dutch Bill creeks, is blocked by low or no flow of water in the tributaries.
Without significant rain — and none is forecast through the end of the month — the coho are likely to die without spawning or lay their eggs in the main stem of the river where the eggs survival rate would be low.
“We might lose a year's class of fish,” said Mariska Obedzinski, coordinator of the coho monitoring program.
Coho salmon have a three-year life cycle that begins in freshwater creeks, includes a year or two of growth in the Pacific Ocean and ends with a one-way spawning run to the creeks of their birth.
Adult coho exhaust their strength and die after spawning, with their carcasses adding ocean-based nutrients to an inland food web that sustains plants, animals and even insect larvae that are the young coho fry's primary food.