Largescale stoneroller

 

Characteristics

Elongate body that is nearly round in cross section. The snout slightly overhangs a sub-terminal mouth, which lacks a barbel. A cartilaginous and chisel-shaped lower jaw is a distinctive feature. Slightly hooked pharyngeal teeth are found in a 4-4 arrangement. Lateral line scale counts range from 41 to 49, and circumferential scale counts vary from 30 to 38 with total lateral and circumferential scale counts from 71 to 87. Dorsal, anal and pelvic fins have 8 rays, and the pectoral fins have 16 rays. The long intestine is completely coiled around the air bladder and is covered with a black peritoneum. Body color is dark olive on the back and sides with a marked difference to the white belly, and the sides have a mottled look because of the scattered dark scales. Breeding males develop dark colors and tubercles, but lack the dark bar across the anal fin and tubercles between the nostrils.

Distribution

 

Found in scattered locations throughout the Eastern Broadleaf Forest Aquatic Subregion in northeast Iowa. In the Central Plains Aquatic Subregion, it is only found in the upper Iowa River watershed. Nowhere is this species considered more than occasional throughout its range.

Foods

A bottom feeder, they use their lower jaw to scrape algae and ooze from rocks and logs.

State Record

State Records are not documented for non-game species.

Expert Tip

None

Details

The Largescale Stoneroller is found most often in pools next to riffles in large streams and rivers. Its habitat is similar to the Central Stoneroller, but it prefers faster waters and larger riffles in gravel areas, and is less tolerant of headwaters, turbidity and reduced flow. The Largescale Stoneroller is most abundant in medium to large-sized streams with moderate gradient and substrates of well-defined gravel, rubble or bedrock riffles where it is often the most abundant fish species present. 

Adults may grow to 7-inches long.

Recent stream sampling information is available from Iowa DNR's biological monitoring and assessment program.