Sensitive and Poorly-known Fish Species in the Santa Cruz Mountains Bioregion
Pacific Lamprey Entosphenus tridentatus
Large (to 2 feet long) parasitic lamprey that migrates to the ocean to mature. The blind larvae rear in bottom mud for 2-4 years before transforming to adult body form (developing eyes and parasitic sucking disk) and migrating to the ocean. They return to freshwater in winter, apparently without homing to their natal stream, after 1-3 (mostly 2) years in the ocean. They are restricted to larger streams of the region (Pescadero, Soquel, Llagas, Uvas and Coyote creeks, San Lorenzo and Guadalupe rivers), and are relatively uncommon except in the San Lorenzo River. Lampreys have declined for some of the same reasons that steelhead and salmon have (water diversions, channelization, and dams that affect migration and rearing conditions). Lampreys are able to surmount some barriers that block steelhead (such as the spillway of Uvas Reservoir) and are sometimes able to complete their life cycle in freshwater if landlocked by dam construction.
Coho Salmon Oncorhynchus kisutch (SE, FE)
In the 1990s, Coho were found in cool coastal streams with flat reaches containing good woody pools (Pescadero, Gazos, Waddell, Scott and San Vicente creeks). Young-of-year coho have rarely reared in summer in local bar-built estuaries (lagoons), because of warmer water temperatures and competition with abundant juvenile steelhead. Coho were formerly more widespread, but still very rare compared to steelhead, which use a much wider variety of habitats. Coho are sensitive to nest destruction by winter storms because of early spawning (January and February) and to access problems due to early winter drought. Wild females almost always spawn and die as 3-year olds, so year classes are distinct and subject to loss from storms or drought. Even in streams where they are present, one or more year classes may have been lost (i.e. the 1994/1997/2000 year class was gone from all but Scott Creek, where it was scarce in 2000).
Accelerated growth in hatcheries (such as the Big Creek Restoration Hatchery in the Scott Creek watershed) can produce 2-year old spawning females to potentially fill in lost year classes. In addition, some coho juveniles may spend two years in freshwater; this may result in 4-year old fish to fill in weak or missing year classes. Coho were still present in Gazos, Waddell and Scott creek through 2005, with all three year classes present in Scott Creek. However, poor ocean conditions in 2005 and 2006 essentially eliminated wild coho south of San Francisco and severely reduced them elsewhere in California.
Captive brood stock raised at the restoration hatchery on Big Creek in the Scott Creek watershed, at the NOAA lab in Santa Cruz, and at Warms Spring Hatchery in the Russian River have prevented the extinction of the southern fish. These efforts have produced substantial numbers of one year old fish for release and also have out-planted captive-reared adults to spawn in the wild. Spawning in the wild by released adults produced wild juveniles in Scott and San Vicente creeks in 2012 and 2013. A ramped up hatchery effort to release more 1 year-old fish resulted in strong coho adult ocean returns in winter 2014-15, successful spawning, and abundant juveniles in Scott and San Vicente creeks. In addition, adult coho strayed to other streams on their return, and juvenile coho were found to be rearing in Waddell, Laguna, and Soquel creeks in summer 2015. In winter 2015-2016 fewer hatchery-reared coho apparently returned, possibly due to a warm-water “blob” of ocean water off the coast that reduced ocean survival. In addition, two major storms probably destroyed the redds (nests) of many coho (and steelhead). Coho juveniles in 2016 were apparently restricted to relatively small numbers in Scott and Waddell creeks. Juvenile abundance was as bad or worse in 2017-2019, apparently due to redd destruction by winter storms and possibly to altered ocean conditions. Hatchery-produced fry were introduced into Gazos Creek in June 2018 (the first coho there since 2005) and juveniles into Waddell Creek in fall 2018 and 2019. The hatchery effort will continue to be the essential component of restoration of southern coho for at least the next 10-15 years, with the goal of eventually reestablishing sustaining runs in San Gregorio, Pescadero, Gazos, Waddell, Scott, San Vicente, and Soquel creeks, and the San Lorenzo River.
Chinook Salmon Oncorhynchus tshawytscha (CSC)
Chinook are large salmon of larger north coast and Central Valley streams, with separate fall, late-fall, winter and spring spawning runs. Spring and winter runs are federally listed. Anecdotal records indicate that chinook were originally present in some south SF Bay streams, at least occasionally (such as during wet periods). The marginal original stocks were probably eliminated by diversions, dam building and severe pollution in south San Francisco Bay. However, runs of up to several hundred fall-run fish now often enter Coyote Creek and the Guadalupe River in Santa Clara County. The recent runs apparently originated as strays from Central Valley streams and hatcheries, and much of each run is probably still strays. However, some successful spawning and smolt production has occurred in both streams. In south bay streams they can attempt to enter as early as August, but water temperatures in late summer and early fall are too warm for successful spawning. Therefore, actions to aid migration, such as reservoir releases, only make sense once the cool, rainy season begins in mid-November or later. However, unlike steelhead, Chinook juveniles migrate to SF Bay during spring, at less than 6 months old, and avoid having to rear 1-2 summers in streams which are too warm or have water quality problems in summer and fall. On the coast, pen rearing operations (in Santa Cruz Harbor), using surplus central valley hatchery-spawned fish, have produced fall fishing for returning fish at the harbor and along the coast, and some fish have spawned in local coastal streams.
Steelhead Oncorhynchus mykiss (FT)
Steelhead are still present and common in most coastal watersheds, and are present in some southwest San Francisco Bay streams (San Francisquito and Stevens creeks and the tributaries of the Guadalupe River), although numbers in all watersheds have been significantly reduced by sedimentation, water diversion, dam construction, or urban development. They are able to use steeper, faster habitats than coho, and can also use warmer stream habitats, if fast-water riffles are present as feeding areas. Summer lagoons and some seasonal on-channel ponds can often provide important rearing habitat, if water temperatures are not too warm, water quality is good, and food is abundant. Poor access and reduced stream flows temporarily reduce abundance during short droughts, but populations generally rebound quickly because of flexible freshwater and ocean life history and the ability of a significantly number of fish to spawn in multiple years (the two salmons die after their single spawning attempt). Steelhead also spawn over a wider period (January – May), including later in winter and spring than coho, so they are less impacted by redd destruction by winter storms. The 2012-2015 drought and poor ocean conditions in 2005-2006 and 2015 had much less impact on steelhead on the coast than on coho. However, the severe 2012-2015 drought resulted in poor adult immigration from, and juvenile outmigration to, SF Bay and also to limited suitable summer rearing habitat. Steelhead have now been nearly eliminated from most south SF Bay streams. They commonly occur as resident (non-migratory) rainbow trout above natural and man-made barriers. Resident fish above complete natural barriers and most large reservoirs (except Uvas Reservoir) are not included in the federal listing.
Speckled Dace Rhinichthyes osculus
Speckled dace are widespread as several probable subspecies in California, but have been lost from most San Francisco Bay area sites (Alameda, Coyote and Llagas creeks and the Pajaro River). Dace are present only in the San Lorenzo River watershed, where they are reasonably common in riffles of the river and low gradient tributaries. Dace are small (to 4 inches) benthic-feeding insectivores found in warm (San Benito and Salinas rivers) or cool (San Lorenzo River) streams. They are usually rare or absent where sculpins, another benthic insectivore, are common.
Sacramento Perch Archoplites interruptus (CSC, possibly extirpated)
Originally present in the Pajaro River, Coyote Creek and other lowland streams historically connected to the Central Valley, this species has been extirpated from almost all of its native range due to the introduction of more competitive sunfishes from the eastern U.S. Sacramento perch have been introduced outside their native range in California (including Crowley Lake east of the Sierra and Clear Lake in Modoc County) and into other western and mid-western states (including Pyramid Lake in Nevada) because they often do relatively well in alkaline habitats stressful to other species. If reproducing populations of Sacramento perch are present in the bioregion (which is unlikely), they are probably in farm ponds.
Tule Perch Hysterocarpus traski
This freshwater member of the surf perch family was extirpated from Coyote Creek and the Pajaro River, but is still common in the Sacramento River delta and portions of the central valley (including San Luis Reservoir). Recently, tule perch have been captured in Coyote Creek and in the Guadalupe River system, apparently entering the streams from the San Felipe Pipeline (from San Luis Reservoir) and other water distribution pipelines. Their reappearance restores a species mostly lost from the bioregion (they persisted in Lake Merced near San Francisco), but also indicates that other fish and invertebrates, including exotic invaders, can enter Santa Clara Valley streams from the Central Valley via water transfers.
Tidewater Goby Eucyclogobius newberryi (FE)
This very small (<2 inch) fish is restricted to coastal lagoons, and apparently capable of only limited short-distance movements along the coast. Gobies avoid strong stream flow and tidal action, and heavily depend upon summer sandbar formation to produce calm water conditions for summer breeding (ecologically, it is a lagoon goby rather than a "tidewater" goby). When sandbars fail to form, the summer population explosions of this "annual" fish usually do not occur. Gobies are tolerant of a wide range of salinities (fresh to hypersaline), temperatures, and dissolved oxygen conditions, but have been lost from lagoons without backwater habitats to serve as winter high flow refuges. Some populations (Moran Lagoon and Soquel Creek) may be lost in flood years and be reestablished from closely adjacent more secure populations (Corcoran Lagoon). Eight populations easily came through recent flood and drought years, and are probably relatively secure (San Gregorio, Pescadero, Arroyo de los Frijoles, Waddell, Scott, Laguna, Baldwin, Wilder, Corcoran, and Aptos creeks). They are also present at 8+ other "at risk" sites that are more subject to severe flood or drought impacts (Pomponio, Laguna, Lombardi, Younger, Moores, San Lorenzo, Moran, Soquel, Pajaro).