Hesperoleucus venustus navarroensis Snyder, 1913

Baumsteiger, Jason & Moyle, Peter B., 2019, A reappraisal of the California Roach / Hitch (Cypriniformes, Cyprinidae, Hesperoleucus / Lavinia) species complex, Zootaxa 4543 (2), pp. 221-240 : 231-232

Hesperoleucus venustus navarroensis Snyder, 1913

Northern Coastal Roach

Holotype: USNM 74477 . Originally described as Hesperoleucus navarroensis from Navarro River , near Philo, Mendocino Co., CA . Paratype: CAS-SU 22488 .

Snyder (1913) described two species as occurring within the range of this subspecies: H. navarroensis from the Navarro River basin, and H. venustus , from a mixture of Russian River, Tomales Bay, and San Francisco Bay regions. Hopkirk (1973) disagreed with Snyder, placing Russian River individuals within the subspecies H. s. navarroensis and downgrading Tomales and San Francisco Bay individuals to population status. Aguilar & Jones (2009) found genetic distinctiveness for a Navarro/Russian grouping and a Tomales/SF Bay grouping within their microsatellite analyses. They also found some mtDNA distinctiveness for each location proposed (Navarro, Russian, and Tomales/SF Bay). Baumsteiger et al. (2017) found clear genomic distinctions between Navarro/ Russian and Tomales/SF Bay individuals, consistent with other studies, supporting our assertion of two subspecies within the Coastal Roach species.

Description. Like other Coastal Roach, members of this subspecies are relatively trim, with a slender caudal peduncle, short, pointed snout, and variable length fins (dependent on which region is sampled). Individuals are typically 80-120 mm total length, with a large, conical head. Eyes are large and the mouth is sub-terminal. The dorsal fin has 7–9 rays (average 8) and the anal fin has 6–9 rays (average 8). Most pharyngeal teeth (0,5—4,0) have curved tips which overhang slightly. Scales are small, numbering 47–63 (average 54) along the lateral line. Fish appear darker on the upper half while the lower half is much lighter. Northern Coastal Roach differ from Gualala Roach in having fewer anal rays ( Hopkirk 1973) and one less row of scales above the lateral line ( Snyder 1913).

Distribution. Northern Coastal Roach are generally restricted to the Navarro River and Russian River basins. There are no records of Roach being found in watersheds between these basins. The exact distribution within the two watersheds is poorly documented but they appear to be present wherever water quality is suitable and alien predators are absent. The introduced population in the Eel River constitutes a major range expansion north.

Status. Because this subspecies is restricted to just two watersheds in its native range, it is highly subject to localized effects of farming, ranching, water diversions, dams, and other perturbations. However there are no reports of dwindling numbers in these systems, suggesting that, for now, populations of this subspecies are relatively robust.

Russian River Roach. The Russian River Roach was originally described as a population of H. venustus by Snyder (1913), along with populations in streams flowing intoTomales and San Francisco bays. Following the downgrading of this group to subspecies status, Russian River Roach were later lumped with Navarro Roach as H. s. navarroensis by Hopkirk (1973). This move was confirmed genetically by Aguilar & Jones (2009). The recent analysis by Baumsteiger et al. (2017) found them to be part of the Northern subspecies of Coastal Roach but as a distinct population segment (DPS). Hierarchical genomic analyses revealed Eel River individuals cluster (are synonymous) with Russian River individuals in all analyses. An analysis using only fish from the two watersheds showed population structure at each of three sampling locations within the Russian River whereas within the Eel River there was no population structure among the four locations sampled. This means that the Eel River population is derived from a very recent introduction from the Russian River.

Description. Russian River Roach have a trim, slender body, a somewhat pointed snout, a slender caudal peduncle. The fins are somewhat longer than those of other Coastal Roach. They have 8–9 dorsal rays (average 9) and 7–9 anal rays (average 8); there are 8–11 gill rakers (average 10) and 47–60 scales in the lateral line (average 53) ( Hopkirk 1973). Individuals rarely exceed 120 mm total length. Minor morphological differences were observed between Russian River and Navarro Roach by Snyder (1913) and Murphy (1948). Differences included a higher prevalence of individuals with 9 dorsal rays in the Russian rather than the 8 generally seen in Navarro (see Table 1).

Distribution. Russian River Roach are restricted to the Russian River and its tributaries in Sonoma Co. as well as to the Eel River watershed. They are common in the middle sections of many tributary creeks, including Mark West, Santa Rosa, Maacama, Austin, and Big Sulphur and Pieta ( Moyle et al. 2015). Individuals are also present in the main stem Russian River ( Pintler & Johnson 1958; Cook 2005). They become increasingly rare in the lower sections of the main river, where their downstream limit appears to be Duncan’s Mill, just above the main estuary ( Moyle et al. 2015). However, Goodwin et al. (1993) found that Roach seemed to move down into the estuary during the summer and return upstream in the fall. Within the Eel River watershed, fish are widespread and abundant, with Brown & Moyle (1997) finding individuals at 230 of 412 (56%) sampling locations in the watershed.

Status. Little is known of Russian River Roach abundance trends in their native habitat because few recent, systematic surveys have been conducted in tributary streams where they are most abundant. In the Russian River, gradual loss of tributary populations through dewatering and other factors, combined with mainstem river changes that reduce connectivity among tributaries may limit distribution and reduce abundance. The DPS is currently listed as a state Species of Special Concern (IUCN, Near-threatened) because of a limited distribution, the presence of dams and diversions in the Russian River watershed, and a poorly understood status ( Moyle et al. 2015). Eel River fish were not included in the designation. The increasingly stressful conditions in the Russian River and its tributaries led Moyle et al. (2013) to rate the Russian River Roach as “highly vulnerable” to extinction in its native range as the result habitat loss due to climate change, if present trends continue.

Navarro Roach. Hopkirk (1973) was the first to suggest that the original species/subspecies described by Snyder (1913) should include Russian River individuals. Aguilar & Jones (2009) and Baumsteiger et al. (2017) later found genetic distinctiveness between individuals from the Navarro and Russian rivers, prompting their recognition as distinct population segments of Northern Coastal Roach.

Description. Like other Coastal Roach, Navarro Roach are small, stout-bodied cyprinids with a narrow caudal peduncle, deeply forked tail, short snout, and small, rounded paired fins. They are typically less than 100 mm total length. The head is large and conical, the eyes large and the mouth is sub-terminal and slants downward. The dorsal fin is short (7–9 rays; average 8) and is positioned behind the insertion point of the pelvic fin. The anal fin has between 6–9 rays. Pharyngeal teeth (0,5–4,0) have curved tips which overhang grinding surfaces of moderate size. Scales are small, numbering 47–63 along the lateral line and 32–38 before the dorsal fin. Individuals are usually dark on the upper half of their bodies, ranging from a shadowy gray to a steel blue, while the lower half is much lighter, usually a dull white/silver color. Snyder (1913) described them as having a light lateral stripe approximately two scales wide extending from upper edge of the gill opening to the base of tail and entirely above the lateral line. Below this line is a somewhat wider dark stripe and then several narrower and very distinct dark stripes which grow lighter ventrally. As mentioned previously, small morphological differences are found between Russian and Navarro populations ( Table 1).

Distribution. Navarro Roach are confined to the Navarro River and its tributaries within Mendocino Co. (including Greenwood Creek) but are widely distributed within the watershed, from the mouth throughout the river and its tributaries ( Feliciano 2004).

Status. The Navarro Roach, through its original lumping with CA Roach, was a state Species of Special Concern with an IUCN status of Near-threatened ( Moyle et al. 2015). However with its new taxonomic status, a reevaluation will eventually be necessary, despite being widespread and abundant within its limited range. Most of the Navarro River watershed was logged and converted to orchards and vineyards in the 20 th century. While removal of big trees created more of the warm-water habitat preferred by Navarro Roach, diversion of water has greatly reduced flows, presumably countering the effects of tree removal. Because of these factors, Moyle et al. (2013, 2015) considered it highly vulnerable to extinction in the next century from climate change and other factors.