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Our Native Fish
The Napa River watershed supports an assemblage of sixteen native fish species, including several threatened and/or rare species such as steelhead/rainbow trout, fall-run Chinook salmon, Pacific and river lamprey (Lampetra tridentata, L. ayresi), hardhead (Mylopharodon conocephalus), hitch (Lavinia exilicauda), tule perch (Hysterocarpus traski), and Sacramento splittail (Pogonichthys macrolepidotus). The Napa River is estimated to have historically supported a run of 6,000–8,000 steelhead, and as many 2,000–4,000 coho salmon (USFWS 1968). By the late 1960s, coho salmon had been extirpated, and steelhead had declined to an estimated run of less than 2,000 adults. The present-day run of steelhead is believed to be less than a few hundred 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. These changes have shifted the Napa River system away from a pool-riffle morphology 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 (Micropterus salmoides).
| Common Name | Scientific Name | Family Name |
|---|---|---|
| Steelhead/rainbow trout | Oncorhynchus mykiss | Salmonidae |
| Chinook salmon | Oncorhynchus tshawytscha | Salmonidae |
| Sacramento sucker | Catostomus occidentalis | Catostomidae |
| Prickly sculpin | Cottus asper | Cottidae |
| Riffle sculpin | Cottus gulosus | Cottidae |
| Pacific lamprey | Lampetra tridentata | Petromyzontidae |
| Hardhead | Mylopharodon conocephalus | Cyprinidae |
| Sacramento pikeminnow | Ptychocheilus grandis | Cyprinidae |
| Threespine stickleback | Gasterosteus aculeatus | Gasterosteidae |
| California roach | Hesperoleucus symmetricus | Cyprinidae |
| Tule perch | Hysterocarpus traski | Embiotocidae |
| Sacramento splittail | Pogonichthys macrolepidotus | Cyprinidae |
| White sturgeon | Acipenser transmontanus | Acipenseridae |
| Pacific staghorn sculpin | Leptocottus armatus | Cottidae |
Source: Napa County Resource Conservation District
Stillwater Sciences Limiting Factors Analysis, 2002 (based on information derived from Leidy 1997, CDFG surveys; see Appendix A2, and Moyle 2002.)
