[3] The Yaqui topminnow has an elongated, slightly curved body with a rounded to squared tail fin.

Along with other species of topminnow, Yaqui topminnow exhibit several relatively unique reproductive characteristics among fish: eggs are fertilized internally; the female can store sperm from several males in a special structure called the spermatheca, and can fertilize eggs for a prolonged period after receiving the sperm; the female can simultaneously carry a number of different broods at different stages of development; and they bear live young rather than lay eggs.

The Yaqui topminnow can be distinguished by its superior mouth, longer snout, and the pattern of lateral banding on the body of the female, which rarely extends anterior to the bases of the pelvic fins.

[1] It faces the loss of its aquatic habitat types and competition with the western mosquitofish (Gambusia affinis).

[3] Much of its United States population occurs on the San Bernardino National Wildlife Refuge, where it is protected.