Rock Bass

Rock Bass

Characteristics

olive colored with brassy reflections and dark mottlings along the sides, whitish breast and belly; 6 spines in anal fin and 12 in the dorsal; seldom exceed 10 inches

Distribution

Rock Bass Distribution

northeastern interior streams; rarely in the upper part of the Des Moines and Mississippi Rivers and large natural lakes

Foods

aquatic insects, minnows and other small fish

State Record

1 pounds, 8 ounces - Mississippi River, Dubuque County, June 1973 - Jim Driscoll, Dubuque, Iowa

Expert Tip

true to their name, the rock bass can be caught in streams by fishing close to the rocks near the current

Details

Occurrence of this species is limited in Iowa to the clearer, rocky habitats of the interior streams, particularly streams in the northeast part of the state. They are quite common in these reaches. Rock bass are rarely found in the upper parts of the Des Moines and Mississippi rivers. Occasionally it is found in the large, natural lakes.

The rock bass is a stout, heavy-bodied sunfish with a large mouth, which extends beyond mid-eye when the mouth is closed. The spiny dorsal fin and soft dorsal fin are broadly connected but without a notch. The dorsal fin is much longer and more pronounced than the anal fin. Six anal fin spines and 12 dorsal fin spines distinguish this fish from all other sunfishes. Body color is olive with brassy reflections and dark mottlings along the sides. The breast and belly are whitish, and the lower side has spots that form prominent horizontal lines. There is brown mottling and faint banding on the anal, dorsal and tail fins. The pectoral fins are rounded, set low and are amber in color.

This fish cohabits the same environment with smallmouth bass, and their food habits are quite similar, except smallmouth are far more piscivorous. Young rock bass consume zooplankton as their primary forage, but as they grow larger in size there is a selection of more aquatic insects in the diet which is supplemented with minnows and other small fish.

The rock bass is mainly a sedentary and secretive fish spending much of its activity passively hiding in the shadows of underwater structures.

Spawning coincides with that of smallmouth bass. Nest building by the male starts when the water temperature is 65 to 75 degrees F, usually in May and June. Nests are constructed by males over gravel and sand bottoms where the females lay several thousand eggs. Females contain an average of 5,000 eggs, but one or several fish may deposit part or all of their eggs in a single nest. After hatching, the young fish are found only in quiet water areas protected from waves and strong current. Rock bass grow 1 1/2 to 2 inches the first year and reach 5 to 7 inches in length after three years. Rock bass have lived 13 years in nature and weighed 1 1/2 pounds, but most rock bass in Iowa seldom exceed 10 inches. The Iowa record for rock bass is 1 pound, 8 ounces, and was caught in 1973.


Return
Present in these Iowa water bodies:
Lake/Stream County Location Acres/Length
Pool 16, Mississippi River Scott The amenities list are for Buffalo Shores campground in Buffalo, Iowa. Amenities at other locations in Pool 16 vary by location. 13000.00
Pool 17, Mississippi River Muscatine Amenities list for Muscatine City Ramp. This ramp is located in downtown Muscatine. Amenities vary by location in Pool 17. 7580.00
Turkey River (above Clermont) Fayette This section of river includes the headwaters in Howard county and flows through Winneshiek and Fayette Counties. A popular access is at Vernon Springs Park just 2.5 miles southwest of Cresco. 89.00
Volga River Clayton This stretch includes the headwaters in Fayette County and flows through Clayton County where it empties into the Turkey River just west of Garber. 81.00
Upper Iowa River (above Decorah) Winneshiek This stretch is found in Howard and Winneshiek County. A popular access is found in Kendallville Park and Campground off of Hwy 139 about 8 miles northeast of Cresco. 79.00
Maquoketa River (above Monticello) Delaware Access points begin below the dam at Backbone State Park. 68.00
Turkey River (below Clermont) Clayton This stretch is found in Fayette and Clayton County. A popular scenic and historical area is the Motor Mill Access about 8 miles southeast of Elkader on Galaxy Road. 65.00
Cedar River (above Nashua) Floyd This stretch is found in Chickasaw, Floyd, and Mitchell County. A popular multi-use location is the Charles City Whitewater Park in downtown Charles City on Hwy 14. 63.00
Upper Iowa River (below Decorah) Allamakee This stretch includes Winneshiek and Allamakee County. A popular access is at Lower Dam about 11 miles northeast of Decorah. 57.00
Wapsipinicon River (Troy Mills to Oxford Junction) Jones This stretch is located in Linn and Jones County. A popular access on this stretch is in Pinicon Ridge Park, just off Hwy 13 by Central City. 53.00
Lidtke Impoundment Howard This impoundment is adjacent to Lidtke Mill and located on the Upper Iowa River just north of Lime Springs. 43.40
Vernon Springs Impoundment Howard Located 2.5 miles southwest of Cresco. 39.40
Elkader Impoundment Clayton Elkader 30.40
Lake Oelwein Fayette Located on the south edge of Oelwein. 23.00
Otranto Impoundment Mitchell Located 0.25 miles east of Otranto, Iowa on the Cedar River. 19.00
Bear Creek Fayette Located 6 miles southeast of Fayette off of Kornhill Road or CR C24. Access from 128th Street. 1.20
Bohemian Creek Winneshiek Located about 1.5 miles east of Protivin. 0.30