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The Fishes of Putah Creek: Lower Putah Creek

Peter B. Moyle

Imagine Putah Creek in the days of the Patwin. From the Diversion Dam you see where the creek's rhythm used to break from the irregular beat of water flowing over rocky riffles to the steady quiet flow through valley flatland. Here it meandered between great pools, losing its summer channel in vast swamp lands. Following winter rains, water roared down the creek, turning Patwin villages into islands in a sea of flood water and bringing salmon, steelhead and lamprey up from the ocean to spawn in the upper watershed. The floods attracted other fish to spawn and feed on the floodplain: splittail, thicktail chub, hitch, sucker, blackfish, pikeminnow, Sacramento perch, perhaps even giant white sturgeon. When the water receded, the creek pools retained many fish, including those that were permanent residents. For the Patwin, the creek was a nearly inexhaustible source of food, well worth the trials of living through floods and mosquitoes.

With fog-chilled hands
I grab the squirming blackfish
Thinking of Patwin.

Today, the 22 miles of creek below the dam are very different. The creek is much shorter; the once-meandering channel has been straightened and confined to between levees. The flood waters, no longer allowed to leave the channel, expend their energy cutting downward, making a miniature canyon where there was once swamp. Not surprisingly, the fishes are also very different. Most of the floodplain fishes are gone; some, like thicktail chub, are extinct. A host of alien fishes have invaded, encouraged by Euro-American settlers who failed to adopt the Patwin appreciation of local fishes. Yet when the flows are right, many of the native fishes still thrive. In fact, the communities of fishes once associated with diverse habitats throughout the vast Putah watershed are artificially compressed by conditions of flow from the dam to the Yolo Bypass.

Right below the dam, where the water rushes over awkward new boulders, there is a brief section of rainbow trout and sculpins, fish normally found in cool tributaries high in the hills. They are maintained by water, cold from being stored in Berryessa. When released from the diversion dam it quickly warms up as it moves downstream. While trout and sculpin are mainly in the fastest water here, they are joined by other native fishes in the slower water: threespine stickleback, Pacific lamprey, Sacramento sucker, hitch, pikeminnow, and occasionally California roach. As the creek flows through Winters it becomes warmer, deeper, and slower; suckers and pikeminnow become the dominant fishes, joined by tule perch (a fish that gives birth to fully-formed young, with males that begin courting females a few weeks after birth). Some alien fishes also become common here: smallmouth and largemouth bass, green sunfish, bluegill, common carp.

Pikeminnows slide by
Pursuing their unknown young
While I watch, bemused.

The further downstream from the dam, the more common the alien fishes become, although their abundance does depend on flow. During wet years, the native fishes may dominate all the way down to Pedrick Road on the UCD campus. In dry years, the transition of dominance will likely be at Stevenson Road, or above. But usually the aliens are in charge from UCD down to the by-pass, replacing the now-extirpated native assemblage of warm-water fishes. The aliens are quite diverse and some are popular in fisheries: largemouth bass, bluegill, crappie, carp, goldfish, channel catfish, white catfish, black bullhead, logperch, inland silverside, red shiner, golden shiner. One new native joins them, Sacramento blackfish, which has defied the odds and manages to thrive in alien assemblages.

During the higher flows of winter and spring, anadromous fish pass through these assemblages on their way upstream to spawn, bringing the nutrients of the ocean far inland. Most spectacular are chinook salmon which used to spawn in the Berryessa Valley. Today, a few salmon manage to spawn (and then die) each year in the lower reaches of the creek, roughly between Pedrick Road and the diversion dam. Their young hatch in March and leave the creek in May, headed to the estuary after growing big and fat on the creek's abundant insects and larval fishes. Eel-like lampreys also make their way up the creek to spawn in April and May. Their young spend up to seven years living buried peacefully in the creek's muddy backwaters. During the highest and muddiest flows of winter, a few steelhead rainbow trout come up to spawn below the diversion dam, their young mixing with the young of resident trout. Historically, steelhead swam through the flood plain and canyons to spawn in swift headwaters that flowed into the Berryessa Valley.

Hey you old lamprey
Eeling up our backyard creek
Welcome home.

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