During the breeding season, red-orange patches appear on the chin, operculum, and at the bases of pectoral, pelvic, and anal fins.

[10] Don Loarie, some rights reserved (CC BY)[11] The steeply forked tail, narrow peduncle, large conical head, slightly subterminal mouth, and placement of the dorsal fin behind the pelvic fins shown in this image are the most characteristic universal features of the California roach.

Additionally this individual exhibits the orange patches on its chin, operculum, and base of its pectoral, pelvic, and anal fins that indicate this sample was photographed during its breeding season.

Because California roach primarily feed from the silty bottoms of streams their stomachs fill with detritus and debris.

Spawning occurs mainly from March through June but can vary depending on water temperature, which typically needs to exceed 16 °C.

They move into shallow, flowing water, over bottoms covered with small rocks 3-5 cm in diameter, and form up into schools.

[3] The modern distribution of the California roach excludes many streams they were historically found in due to invasive species and habitat changes.

[3] Invasive species are responsible for further absences in their historical range, such as the Redeye Bass which have caused California roach presence to disappear in the Consumnes River.

[14] Other habitat alterations have further decreased their abundance and range such as the 19th century hydraulic mining in the upper Yuba River in which California roach are almost completely absent.

[15] California roach have also had their distribution expanded beyond natural barriers to places such as Hetch-Hetchy Reservoir, which is 1,162 m in elevation and filled with predators, presumably through introduction by anglers as bait.

[16] More recent studies suggest reclassifying California roach as a Species of Special Concern and to change the IUCN listing as Near threatened.

[17] California roach are threatened by invasive species and anthropogenic causes of habitat change, such as mining and dam construction, as mentioned in the distribution section.

[18] If considered as one taxonomic species, the chances of California roach's immediate extinction would be relatively low due to their wide and varied habitat range.