Hesperoleucus venustus subsp. subditus Snyder 1913

Hesperoleucus venustus subditus Snyder, 1913

Southern Coastal Roach

Holotype: USNM 74475. Originally described as Hesperoleucus subditus from Pajaro Basin, San Benito and Santa Clara Cos., CA. Paratypes: BMNH 1900.9.29.176; CAS-SU 22489; USNM 49579, 75338–40, 75342–43, 75345– 50.

Unlike previous listings by Snyder (1913), Tomales Bay (H. venustus) and Monterey Bay (H. subditus) species are genomically part of a southern subspecies of Coastal Roach (Baumsteiger et al. 2017). Previous works have recognized these individuals as distinct lineages both morphologically and genetically (Murphy 1948; Hopkirk 1973; Aguilar & Jones 2009). So while their distinctiveness seems consistent, their taxonomic level has not been properly defined till now.

Description. Adult total length is typically 55–100 mm, up to 125 mm. Roach typically have 7–10 dorsal rays (average 9), 6–8 anal rays (average 7), and 47–62 lateral line scales (average 54) (Hopkirk 1973). The remaining characters vary between different DPSs proposed within this subspecies (see below), including thickness of caudal peduncle, fin length, body size, and snout shape (Snyder 1913; Murphy 1948; Hopkirk 1973).

Distribution. Southern Coastal Roach are restricted to the drainages of Tomales Bay/northern SF Bay in the north and Monterey Bay in the south. There are no records of Roach being present in watersheds between these two systems but thorough sampling is needed to be sure of their absence.

Status. Although both DPSs within this subspecies are considered to be Near-threatened (see below), the subspecies as a whole seems fairly abundant in their native ranges (Moyle et al. 2015). However, this is still probably a small subset of the original range of this subspecies, given the current geographic divide between the two DPSs within the subspecies. Both are found in areas where freshwater sources are limited and human use is high, making them candidates for decline through water manipulation. Additionally, most locations with this subspecies are relatively small, isolated creeks, making climate change an increasing problem for their persistence.

Tomales Roach. Snyder (1913) described Hesperoleucus venustus from the Russian River, Tomales Bay tributaries, and San Francisco Bay tributaries. Hopkirk (1973) recognized that Roach from these three regions were different from each other but similar enough to California Roach that he declared H. venustus to be a synonym of H. s. symmetricus. He did suggest, however, that individuals in Tomales Bay tributaries were distinct enough to be recognized as a subspecies. The genetic studies of Jones (2001), Aguilar & Jones (2009) and Baumsteiger et al. (2017) indicated that populations from Tomales Bay tributaries are distinct, which we recognize here. Jones (2001) found populations of Tomales Roach from Lagunitas and Walker creeks shared nuclear DNA allele frequencies but were reciprocally monophyletic for mitochondrial DNA haplotypes. Aguilar & Jones (2009) determined from the mtDNA analysis of fish from Lagunitas and Walker Creeks that they were clearly a distinct lineage from CA Roach. Microsatellites, however, were not as definitive, with one analysis finding weak support for Tomales Roach as a distinct lineage, while another analysis found that, although distinguishable, individuals from Lagunitas and Walker Creeks clustered with Monterey Roach. Our genomic analysis (Baumsteiger et al. 2017) provided further clarity, showing that Tomales Bay locations are clearly definable within the Southern Coastal Roach subspecies, as a distinct population segment.

Description. Tomales Roach look similar to other members of the CA Roach complex but are most similar to Russian River Roach (Table 1). Adult total length is typically 55–100 mm, up to 125 mm. Like Russian River Roach, Tomales Roach differ from CA Roach in having a more trim, slender body, a more pointed snout, a more slender caudal peduncle, and longer fins. Tomales Roach have 8–10 dorsal rays (average 9), 6–7 anal rays (average 7), and 47–62 lateral line scales (average 54) (Hopkirk 1973).

In tributaries to San Francisco Bay, Snyder (1905, 1908) demonstrated that sex could be established by using the ratio of pectoral fin length to body length. Males exhibited a ratio of> 0.21 while females bore pectoral fins between 0.16 and 0.20 the length of their body. Both sexes exhibit bright orange and red breeding coloration on the operculum, chin and the base of the paired fins. Males may also develop numerous small breeding tubercles (pearl organs) on the head (Murphy 1943).

Distribution. Tomales Roach are restricted to the Lagunitas Creek and Walker Creek drainages of western Marin County. Roach of uncertain taxonomic affinity have also been reported from Pine Gulch Creek, tributary to Bolinas Lagoon (Murphy 1948) and Salmon Creek, Marin Co. (Moyle 2002). However, a 1997 survey of Pine Gulch Creek recorded no Roach present (Fong 1999).

Status. There is no indication that Tomales Roach in Walker and Lagunitas Creeks are in decline, but no regular surveys exist. Dams and diversions, however, have altered flows and habitat. They are currently listed as a state Species of Special Concern (IUCN Status, Near-threatened) but do not appear to be in immediate danger of extinction as a DPS. Fragmentation of populations, along with habitat alterations, may be limiting distribution and abundance (Moyle et al. 2015). Increasing urban water demands, coupled with predicted climate change impacts, are likely to lead to more widespread drying of stream segments and elimination of Roach populations. As a result, Moyle et al. (2013) considered Tomales Roach as “highly vulnerable” to extinction by 2100 from the effects of climate change. Moyle et al. (2015) considered it to be a species of “moderate concern”, not facing immediate extinction threats.

Monterey Roach. The Monterey Roach has been of interest because of its frequent hybridization with Monterey Hitch (L. e. harengus) (Miller 1945; Avise et al. 1975) but it retains its identity as a distinct taxon (Baumsteiger et al. 2017). Its isolation from other populations within the subspecies is of note, indicating that should be managed as a distinct population segment.

Description. Monterey Roach are similar in appearance to CA Roach (see description) but can be distinguished by having fewer dorsal (7–9; average 8) and anal fins rays (6–8; average 7), fewer scales in the lateral line, slightly shorter fins, a slightly more robust body and a thicker caudal peduncle (Snyder 1913; Murphy 1948; Hopkirk 1973).

Distribution. Monterey Roach are widely distributed in the Pajaro, Salinas, and San Lorenzo River systems as well as Soquel Creek, all tributaries to Monterey Bay on the central coast of California. Pescadaro Creek, just north of Monterey Bay, also contains Monterey Roach. Within the Pajaro watershed, Monterey Roach no longer occur in the mainstem but are present in Uvas Creek, Llagas Creek upstream of Chesbro Reservoir, the North Fork of Pacheco Creek upstream of Pacheco Reservoir, Arroyo Dos Picachos and in the San Benito River and its tributaries, including Tres Pinos, Laguna, and Clear Creeks (Smith 2007). In the Salinas River system, Roach also have been extirpated from the mainstem and now occur primarily in tributaries such as Arroyo Seco (J.J. Smith, pers. comm. 2009) and Gabilan Creek, although recent survey information is lacking.

Status. Monterey Roach are apparently still numerous and widely distributed in smaller streams in much of their native range, but the DPS has been largely extirpated from the mainstem Pajaro and Salinas River systems due to habitat alteration, degraded water quality and quantity and alien species (Smith 1982, 2007). Long-term trends are not known but populations are likely fewer and more fragmented than historically. Moyle et al. (2015) listed them as a state Species of Special Concern (IUCN status of Near-threatened) and noted they were “highly vulnerable” to climate change due to potential reductions in stream flow throughout the watersheds (Moyle et al. 2013).