The distinctive feature of the splittail is the larger upper lobe of its caudal fin, which is almost twice as long as the head.

The Sacramento splittail is a semi-anadromous fish, meaning it spends parts of its life both in the ocean and in freshwater.

They act as prey for other predatory fishes, such as striped bass (Morone saxatilis), as well as aquatic birds.

[6] Splittail are bottom feeders, consuming bottom-dwelling invertebrates and detritus, generally in areas of low to moderate current.

In Suisun Bay, opossum shrimp (mostly Neomysis mercedis), amphipods such as Corophium, and copepods are favorite foods, while in the Sacramento Delta they eat clams, crustaceans, and insect larvae.

The fish may rely on increasing water temperatures and day length to determine when to begin spawning.

Unfavorable environmental conditions, such as high salinity and low water levels, can greatly affect whether or not they spawn.

The spittail has two distinct populations separated genetically, one in the Central Valley and one in the San Pablo area.

[10] Agricultural pesticide use in the Central Valley, where the Sacramento-San Joaquin Delta is located, has been noted to lead to runoff contamination of water.

[13] The Central Valley's system of sloughs and backwaters maintained by annual flooding has greatly changed.