Mylopharodon conocephalus, known as the hardhead, is a freshwater ray-finned fish from the family Cyprinidae, the carps and minnows, which is endemic to California.

It shows to preference for deep, clear pools which have substrates consisting of sand, gravel or boulders and a slow current.

[1] Hardhead are mainly bottom feeders, foraging on invertebrates and aquatic plant material from the stream bed although they will also eat drifting insects and algae from higher in the water column.

Hardhead found in smaller streams rarely reach longer than 28 centimetres (11 in) while old records suggest that this species attained total lengths of up to 1 metre (3.3 ft).

[4] Hardhead reach sexual maturity after their second year and spawn in April and May when the adults migrate upstream into the smaller tributary streams.

It is thought that the fertilised eggs develop among the gravel and that the larval and post-larval fry probably prefer the edges of streams where they can find thick vegetation to provide cover.

Small juveniles of 2–5 centimetres (0.79–1.97 in) in standard length may form in large schools in shallow backwaters and among cobbles and boulders near stream banks.

[4] Adult hardhead normally occur in schools in the deepest part of pools, where the slowly cruise around during the day, becoming more active in early morning and evening when they feed.

They are predominantly bottom feeders, consuming invertebrates and aquatic plants from stream beds although they will also feed on insects and algae drifting higher in the water column.

In one stream which seems to be largely unaltered, the Cosumnes River, hardheads are absent with an invasion of redeye bass (Micropterus coosae) being seen as the probable cause of their extirpation.

They are also vulnerable to pollution from agricultural runoff and their presence in midden sites of native peoples in the Sacramento and San Joaquin basins show that they were previously much more abundant and widespread than they are currently.