Hesperoleucus mitrulus Snyder 1913

Hesperoleucus mitrulus Snyder, 1913

Northern Roach

Holotype: USNM 74474. Originally described from Drew Creek, Lake Co., OR. Paratypes: CAS-SU 22491; UMMZ 139019.

Northern Roach were first collected in 1898 by C. Rutter as Rutilus symmetricus (Rutter 1908). Rutter (1908: 139) stated “We have but few small specimens of this form, the longest being but 3 inches long. They were taken in North Fork Pitt (sic) River near Alturas and at the mouth of Joseph Creek, several hundred miles from where any other specimens of symmetricus have been taken. The form may prove to not to be symmetricus, but we cannot identify it otherwise with the material at hand.” In 1913, Snyder described the Goose Lake drainage fish as Hesperoleucus mitrulus. The first inclusion of Roach from the Pit River as part of H. symmetricus was by Hubbs et al. (1979). Genetically, Aguilar & Jones (2009) found that individuals from these locations were distinct from all other CA Roach. Our genomic study (Baumsteiger et al. 2017) also found all individuals collected from these locations to be distinct at the species-level in every analysis.

Description. Northern Roach are small (adult size typically 50–100 mm TL) bronzy cyprinids, similar in appearance to the California Roach (Moyle 2002; Fig. 3). They have a robust body, deep caudal peduncle, short snout and short rounded fins. Northern Roach differ from CA Roach in having short rounded fins and “cup-like” scales (Snyder 1913; Table 1). Snyder (1908) examined 20 fish from Drew Creek, Oregon and all individuals had 8 dorsal rays and 7 anal rays. Snyder found that males had longer, larger fins than did females, especially pectoral fins; the sexes could be differentiated by the ratio of pectoral fin length to body length.

Distribution. The original collections by Rutter (1908) consisted of the North Fork of the Pit River and the mouth of Joseph Creek. Snyder (1908) collected widely in the upper Pit River, Goose Lake basin of California and Oregon, and in the Summer, Abert, Harney and Warner basins of Oregon but only found Roach in tributaries to Goose Lake, Lake Co., Oregon. The first inclusion of individuals from the Pit River as part of this species was by Hubbs et al. (1979). While no mention is made of a range extension for the taxon, it is assumed this change was precipitated by the 1934 collection of 19 roach in the North Fork Pit River near Alturas, Modoc County (unpublished field notes and collections of Carl Hubbs at the Univ. of Michigan as reported in Reid et al. 2003).

In the most comprehensive sampling of the Pit system in California to date, Moyle and Daniels (1982) found Roach at only 8% of 261 collection sites. Northern Roach were found in only three widely separated drainages: (1) Ash–Rush–Willow Creek drainage, Lassen/Modoc Co., (2) Bear Creek, tributary to the Fall River, Shasta Co. and (3) Beaver Creek, Lassen Co. All locations are above Pit River Falls (Shasta Co.) which divides the Pit River Basin into upper and lower drainages. The falls are a barrier to fish movement (Kinziger et al. 2016). Historically, the waterfall was the northern range limit for some Sacramento River fishes, such as Tule Perch, Hysterocarpus traskii (Moyle 2002). Roach below the falls had unimpeded access to the Sacramento River system and are assumed to be H. s. symmetricus. However, genetic and morphometric studies have not been conducted and relationships remain uncertain.

Status. Northern Roach have been uncommon in California ever since they were first collected in 1898, although by that time much of the Pit River drainage had been heavily altered by grazing, agriculture and logging (Moyle & Daniels 1982). Subsequently, alien fish species that compete with or prey on Northern Roach (e.g. Green Sunfish, Lepomis cyanellus) became widely introduced. Their absence from some streams, however, may be the result of specific habitat requirements. Northern Roach prefer spring pools and swampy stream reaches, unlike the intermittent stream habitats where other species of Roach are found (S. Reid, pers. comm.). Thus in Lassen/Modoc Co., Roach are found in small numbers, inhabiting the weedy margins of streams and, in one case, an isolated spring pond (Moyle & Daniels 1982; S. Reid, pers. comm.). However a fairly recent survey of fishes in the Oregon portion of the Goose Lake watershed found Northern Roach to be relatively abundant in six small creeks (Scheerer et al. 2010).

Moyle et al. (2015) rated the Northern Roach as a Species of Special Concern in California and the International Union for the Conservation of Nature (IUCN) lists their status as High Concern. Additionally, these Roach are highly vulnerable to extinction in the next century from climate change effects on their small streams (Moyle et al. 2013).