The life history and feeding habits of the Topeka shiner, Notropis topeka (Gilbert), were studied in the headwaters of the South Fork Cottonwood River, Butler County, Kansas, and the West Branch of Mill Creek, Wabaunsee County, Kansas, from July 1979 through June 1981. A total of 1002 specimens was examined.
The habitat of Topeka shiners in the South Fork Cottonwood River consisted of the uppermost stream sections that maintained permanent pools because of the contribution of small springs and subterranean flow. Substrates varied from gravel to rubble, usually with a thin silt covering. In midsummer and fall, surface water was restricted to the larger and deeper pools in the study area. Heavy mortality in the fish populations was evident. Adult Topeka shiners occupied the lower half of the water column in pools, whereas young-of-the-year fish inhabited shallow pool margins until the end of their first summer.
Nineteen percent of age-1 males were sexually mature (in second summer of life); 80% of age-2 males and 100% of age-3 males were mature. The average numbers of mature (largest) ova in age-1 and age-2 females collected 23 May 1981 were 356 and 819, respectively. The number of mature ova increased with length, weight, and age of the female. Sixty-two percent of age-1 females and 100% of age-2 females were mature.
Topeka shiners ranged in age from 2 to 36 months. The mean lengths of fish at ages of 12, 24, and 36 months were 34.6 mm, 42.5 mm, and 53.2 mm SL, respectively. The growth rate of age group 0 and 0 fish was approximately 0.13 mm/day. The sex ratio did not differ significantly from 1:1 except in the age-2 group, in which males outnumbered females 3.3:1.
Topeka shiners were principally diurnal feeders and typically fed near the substrate, mostly on chironomids and ephemeropterans. Although algae and detritus were prevalent in gut contents, it was unclear whether Topeka shiners were intentionally consuming and digesting this material.