The Lahontan redside (''Richardsonius egregius'') is a

cyprinid Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest verte ...

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

of the

Great Basin The Great Basin is the largest area of contiguous endorheic basin, endorheic watersheds, those with no outlets, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja California ...

in eastern

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

and western

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

. Lahontan redsides are noted for their breeding colors, consisting of a bright red stripe with a yellow border on each side. At other times, the stripe is still visible, but the red is much reduced, leaving a gradual transition from the olive-colored back to silvery underside. Overall shape is slender, with a large eye and terminal mouth. The

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

has 7-8 rays, while the anal fin has 8-10 rays. The pectoral fins are somewhat long, the tips reaching nearly to the bases of the pelvic fins. The tail is deeply forked. Total length ranges up to 17 cm, but an 8 cm length is more typical of mature adults. They are found in a variety of habitats within their range, primarily feeding on small invertebrates. Stream populations shoal near the surface of quiet pools, where they catch drifting insects, while in lakes they form groups in the

littoral zone The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal areas ...

, generally preferring to stay over rocky bottoms, and eat a combination of surface insects, insect larvae, and planktonic crustacea. When the temperatures drop during winter, they move to deeper water and remain nearly motionless near the bottom. The spawning season lasts from late May to August, with the high point coming during the second half of June. They look for shallow water, either at lake margins, or in stream pools with sand and gravel bottoms, then form into swirling groups of 20-100 fish just above the bottom. The actual egglaying and fertilizing consists of subgroups swimming down and pressing themselves on the bottom, the eggs then adhering to the rocks and crevices. The range of these redsides is defined by the old

Lake Lahontan Lake Lahontan was a large endorheic Pleistocene lake of modern northwestern Nevada that extended into northeastern California and southern Oregon. The area of the former lake is a large portion of the Great Basin that borders the Sacramento Rive ...

basin. Rivers include the

Truckee River The Truckee River is a river in the U.S. states of California and Nevada. The river flows northeasterly and is long.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed October 20, 2012 Th ...

Carson River The Carson River is a northwestern List of Nevada rivers, Nevada river that empties into the Carson Sink, an endorheic basin. The main stem of the river is long although the addition of the East Fork makes the total length , traversing five co ...

, etc. They are also found in upper parts of the

Feather River The Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about long. Its length to its most distant headwater tributary is just over . The main stem Feather R ...

, probably as accidental introductions via the bait bucket. They are abundant across their range, and successful colonizers around its edges, so they are not considered threatened in any way. A variety of common names make reference to the breeding colors, including redside minnow, red-striped shiner, Lahontan redshiner, etc.

References

* * Peter B. Moyle, ''Inland Fishes of California'' (University of California Press, 2002), pp. 134–136 * {{Taxonbar, from=Q1103006 Richardsonius Fauna of the Great Basin Fish described in 1858