Hesperoleucus parvipinnis 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 : 236

Hesperoleucus parvipinnis Snyder, 1913

Gualala Roach

Holotype: USNM 74466 . Originally described from Gualala River, Sonoma Co., CA . Paratypes: CAS-SU 14903 .

Gualala Roach were first collected by Snyder (1908) who recognized them as Rutilus symmetricus but noted they bore “a distinctive local stamp by which they can be recognized without difficulty (p 175).” He later (1913) described them as H. parvipinnis . Murphy (1948) suggested these individuals constituted a subspecies not a species. Aguilar & Jones (2009) found them to be strongly genetically different from any other Roach along the California coast, suggesting they were more than a subspecies. Baumsteiger et al. (2017) found individuals within the Gualala system to be distinctive at the species level in all analyses, with pairwise F ST estimates between these individuals and Northern Roach to be the highest in the study (0.895). Thus the consensus reconfirms what Snyder (1913) proposed, that Gualala Roach are indeed a distinct species within Hesperoleucus .

Description. Adult Gualala Roach are small (typically 50–80 mm) and bronzy in color, similar in general appearance to California Roach ( H. symmetricus ). However, they differ from other Roach species by having smaller scales (54–65 along the lateral line), shorter, more rounded fins, a shorter snout (in relation to head length) and a more robust body ( Table 1). Gualala Roach have 7–8 dorsal rays (average 8) and 6–8 (average 7) anal rays ( Hopkirk 1973). Snyder (1913 p. 66) described Gualala Roach as having “a light lateral stripe two scales wide extending from upper edge of gill opening to base of caudal and entirely above the lateral line; below is a somewhat wider dark stripe, which in turn is followed by several narrower and very distinct dark stripes which grow lighter ventrally.”

Distribution. Gualala Roach are confined to the Gualala River and its tributaries in Sonoma Co. They are the most abundant fish species in the South and Wheatfield forks and in most headwater streams ( Entrix 1992; DeHaven 2008). Occurrence is greatly reduced in the colder North Fork ( Parker and Pool 1964; CDFG 1991) and in the mainstem below its confluence with the North Fork ( Kimsey 1953; DeHaven 2008).

Status. Historically, Gualala Roach were present throughout the Gualala River basin ( Higgins 1997). Agency salmonid surveys indicate Roach may have increased in abundance due to habitat alterations favorable to warm water-tolerant species ( Higgins 1997). Moyle et al. (2013) rate this species as “highly vulnerable” to extinction due to climate change. Statewide this is a species of Special Concern (IUCN status, Near-threatened) because of its limited distribution and increasing threats from vineyard and rural residential development, including introductions of non-native fishes ( Moyle et al. 2015).