The Napa River watershed supports thirty native fish species, including several threatened and/or rare species such as steelhead/rainbow trout, fall-run Chinook salmon, Pacific and river lamprey, hardhead, hitch, tule perch, and Sacramento splittail. The Napa River is estimated to have historically supported a run of 6,000–8,000 steelhead trout, and as many 2,000–4,000 coho salmon (USFWS 1968). By the late 1960s, coho salmon had been extirpated, and steelhead trout had declined to an estimated run of less than 2,000 adults. The present-day run of steelhead trout is believed to be less than 200 adults.
Introductions of exotic fish species have impacted most freshwater ecosystems in California, including the Napa River. Habitat alterations can determine the species composition of a fish community by favoring certain species over another. Habitat alterations have occurred gradually, but constantly, during the past century. The Napa River system has changed from being dominated by pools and riffles to a morphology dominated by large, deep pools with increased water temperatures and slow-moving water. Much of the Napa River and its tributaries now provide the preferred habitat of predatory fish species, many of which are exotic, such as largemouth bass.
A watershed’s ecological health is directly reflected by the condition of its fish populations. Migratory fish, including steelhead and salmon, are indicator species, meaning they are sensitive to environmental disturbance such as habitat alteration and pollution and, therefore, provide an early warning of ecosystem deterioration. Their populations are controlled by ecological conditions throughout the watershed, bay, and ocean. A large, diverse population indicates a healthy watershed system while low numbers are indicative of overall habitat degradation.
The Napa River and many other streams throughout Napa County historically supported large numbers of steelhead, chinook salmon, and coho salmon. Unfortunately, their populations have declined sharply in the past several decades. Coho salmon became extinct in the Napa River Watershed in the 1960s and steelhead are now protected under the Endangered Species Act. Protecting steelhead and salmon poses several challenges due to the unique characteristics of their life cycles. Although they grow to adulthood in the ocean, inland waters must provide the complex habitat and essential conditions for spawning and rearing. Many factors combine to create suitable habitat including clean water, adequate streamflow, abundant food, and a well-functioning riparian zone to thrive. If any of these requirements are absent or limited, their populations decline.
Recognizing the need to protect and restore Napa County’s remaining steelhead and salmon populations, many groups and individuals are actively involved in efforts to ensure their survival. These efforts include monitoring their abundance, improving the condition of existing fish habitat, expanding habitat through stream restoration and barrier removal, and educating the public about the values of steelhead and salmon and the importance of protecting these vanishing species. For more information or to volunteer, call the Napa County RCD at (707) 252-4188 or visit www.naparcd.org.
Source: Napa County Resource Conservation District
Photo: Todd Adams
Steelhead is the term commonly used for the anadromous life history form of rainbow trout (Oncorhynchus mykiss). Steelhead exhibit highly variable life history patterns throughout their range, but are broadly categorized into winter and summer reproductive ecotypes. The relationship between anadromous and resident life history forms of O. mykiss is poorly understood, but evidence suggests that the two forms are capable of interbreeding and that, under some conditions, either life history form can produce offspring that exhibit the alternate form (i.e., resident rainbow trout can produce anadromous progeny and vice versa) (Shapovalov and Taft 1954, Burgner et al. 1992, Hallock 1989). The fact that little to no genetic differentiation has been found between resident and anadromous life history forms inhabiting the same basin supports this hypothesis (Busby et al. 1993, Nielsen 1994).
Steelhead found in the Napa River watershed belong to the Central California Coast evolutionarily significant unit (ESU) (NMFS 1997). This ESU extends from the Russian River to Aptos Creek, and includes tributaries to San Francisco and San Pablo bays eastward to the Napa River, excluding the Sacramento-San Joaquin River basin. Winter runs of steelhead occur in the Napa River mainstem and tributaries. Critical habitat is designated to include all river reaches and estuarine areas accessible to listed steelhead in coastal river basins from the Russian River to Aptos Creek, and the tributaries to San Francisco and San Pablo bays (NMFS 2000).
Source: Stillwater Sciences, Napa River Watershed Limiting Factors Analysis
Fall-run Chinook salmon have been observed in the Napa River in recent years (Jones 1999, as cited in NMFS 1999; Leidy and Sisco 1999), upstream to the base of the Kimball Canyon Dam north of Calistoga (Leidy and Sisco 1999). Fall Chinook returns to the Napa River are thought to be small and sporadic, with only occasional observations of spawning primarily between Zinfandel Lane, slightly downstream of St. Helena, and the City of Calistoga (Leidy and Sisco 1999; S. Anderson, pers. comm., 2000; Emig, pers. comm., 2000; Rugg, pers. comm., 2000). The National Marine Fisheries Service believes that these populations are not self-sustaining and likely consist of strays from other basins and are more likely present only on an intermittent basis during favorable periods (NMFS 1999).
Source: Stillwater Sciences - Napa River Watershed Limiting Factors Analysis
Thanks to a 2006 grant from the Napa County Wildlife Conservation Commission, the Napa County Resource Conservation District (RCD) was able to purchase a digital camcorder, video editing software, and an underwater housing unit to film local fishes for educational and monitoring purposes. In winter 2006, RCD Senior Biologist Jonathan Koehler tested the camera and captured spectacular underwater photos and video footage of several species of fish, including steelhead trout and Chinook salmon, in the Napa River and its tributaries
With funds provided by the Conservation Division of the Napa County Conservation, Development and Planning Department, RCD Education Coordinator Jenny McIlvaine edited the footage to create these two 4-minute films, Swimming with Salmon and Swimming with Steelhead.
Web-enabled video clips of the footage are provided at the top of this page.
|Common name||Scientific name||Family|
|White Sturgeon||Acipenser transmontanus||Acipenseridae|
|Sacramento Sucker||Catostomus occidentalis||Catostomidae|
|Pacific Herring||Clupea pallasii||Clupeidae|
|Northern Anchovy||Engraulis mordax||Clupeidae|
|Riffle Sculpin||Cottus gulosus||Cottidae|
|Coastrange Sculpin||Cottus aleuticus||Cottidae|
|Prickly Sculpin||Cottus asper||Cottidae|
|Pacific Staghorn Sculpin||Leptocottus armatus||Cottidae|
|Sacramento Pikeminnow||Ptychocheilus grandis||Cyprinidae|
|Sacramento Blackfish||Orthodon microlepidotus||Cyprinidae|
|California Roach||Hesperoleucus symmetricus||Cyprinidae|
|Sacramento Splittail||Pogonichthys macrolepidotus||Cyprinidae|
|Shiner Perch||Cymatogaster aggregata||Embiotocidae|
|Tule Perch||Hysterocarpus traski||Embiotocidae|
|Three-spine Stickleback||Gasterosteus aculeatus||Gasterosteidae|
|Bay Goby||Lepidogobius lepidus||Gobiidae|
|Longjaw Mudsucker||Gillichthys mirabili||Gobiidae|
|Arrow Goby||Clevelandia ios||Gobiidae|
|Delta Smelt||Hypomesus transpacificus||Osmeridae|
|Jack Smelt||Atherinopsis californiensis||Osmeridae|
|Longfin Smelt||Spirinchus thaleichthys||Osmeridae|
|Pacific Lamprey||Lampetra tridentata||Petromyzontidae|
|River Lamprey||Lampetra ayresi||Petromyzontidae|
|Western Brook Lamprey||Lampetra richardsoni||Petromyzontidae|
|Speckled Sanddab||Citharichthys stigmaeus||Pleuronectidae|
|Starry Flounder||Platichthys stellatus||Pleuronectidae|
|Steelhead / Rainbow Trout||Oncorhynchus mykiss||Salmonidae|
|Chinook Salmon||Oncorhynchus tshawytscha||Salmonidae|
Stillwater Sciences Limiting Factors Analysis, 2002 (based on information derived from Leidy 1997, CDFG surveys; see Appendix A2, and Moyle 2002.)