. Bulletin. Natural history; Natural history. 94 ILLINOIS NATURAL HISTORY SURVEY BULLETIN Figure 10 presents graphically the lengths of 19 rock bass. These measurements fall into two well separated groups, each representing a year class. One group, probably two years old, varies from 4^^ to 514 inches with a mode at 5 inches, while the other group varies from 6 to 714 inches with a mode at 6I/2 inches and is made up presumably of three-year old fish. In Fig. 11, which summarizes the data for 88 channel cat, three fairly well defined groups appear, presumably representing fishes two, three and.
. Bulletin. Natural history; Natural history. 94 ILLINOIS NATURAL HISTORY SURVEY BULLETIN Figure 10 presents graphically the lengths of 19 rock bass. These measurements fall into two well separated groups, each representing a year class. One group, probably two years old, varies from 4^^ to 514 inches with a mode at 5 inches, while the other group varies from 6 to 714 inches with a mode at 6I/2 inches and is made up presumably of three-year old fish. In Fig. 11, which summarizes the data for 88 channel cat, three fairly well defined groups appear, presumably representing fishes two, three and. 19 ZO Tl H Z9 «4 ZS ZS Length in inche<s Fig. 12.—Age groups of mud cat. four years old. Fishes of the first group vary from 6 to 9 inches with a mode at 7 inches; the second group, from 9 to 13 inches with a mode at 11 inches. Those of the third group appear to vary around 15 inches as a mode. The data for mud cat are arranged graphically in Fig. 12, which shows modes at 8, 11, 14 and 17 inches. The three individuals 20, 23 and 26 inches in length may represent three additional year groups. A better method of age determination is by examination of scales, spines and bones, which show annulations indicating the age and past his- tory of individuals in much the same way as do the annual rings in the trunk of a tree. During the course of this study spines or scales were taken from most of the fishes caught, and an analysis of these data will form the subject matter of later reports. THE FISHES OF THE KASKASKIA In this section are presented some of the more obvious distinguishing characteristics of each of the larger fishes, a summary of known informa-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Illinois. Natural History Survey Division. Urbana, State of Illinois, Dept. of Registration and Education
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Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
