Fish
Central Stoneroller
Campostoma anomalum · also called central stonerollers
Along the bottom of a clear, rocky stream, a central stoneroller scrapes algae off a submerged rock with the hard ridge of its lower jaw, while nearby a breeding male, its head crowned with sharp tubercles, holds off a rival competing for the same stretch of spawning gravel.
Overview
The central stoneroller, Campostoma anomalum, is a small, herbivorous fish native to clear, rocky streams across a broad range of the central and eastern United States. Its specialised algae-scraping jaw, dramatic male breeding tubercles, and status as one of the most widespread and locally abundant minnows in its range make it an ecologically important and behaviourally distinctive member of stream fish communities across much of the country.
A grazer with its own built-in scraper
Rather than relying on a typical fish mouth, the central stoneroller has evolved a hardened jaw edge purpose-built for scraping algae off rocks, turning stream-bottom stones into its primary dinner plate.
Status
Least Concern — widespread and abundant across suitable clear, rocky stream habitat throughout the central and eastern United States.
Central Stoneroller: common questions
How does the central stoneroller eat algae?
This species has a hard, cartilaginous ridge along its lower jaw, an adaptation specifically suited to scraping algae directly off rocks and other hard surfaces on the stream bottom, a feeding method quite different from the more typical mouth structure of many other minnow species.
Why do male central stonerollers develop bumps on their heads?
A breeding male of this species develops a crown of large, sharp tubercles across the top of the head, used to physically battle rival males for control of favourable spawning territory, a dramatic seasonal transformation that makes breeding males look quite different from females and non-breeding individuals.
Why is the central stoneroller ecologically important?
This species helps regulate algae growth on stream-bottom rocks through its grazing activity, while also serving as an important food source for larger predatory fish, giving it a meaningful ecological role both as a consumer of algae and as prey within the broader stream food web.
How common is the central stoneroller?
This species is one of the most widespread and locally abundant fish species found across many streams within its range, often numerically dominating the fish community in suitable clear, rocky stream habitat across the central and eastern United States.