. Bulletin. Natural history; Natural history. 46 Illinois Natural History Survey Bulletin Vol. 29, Art. 1 In the years of our investigation, only two dominant year-classes of bigmouth buffalo appeared in the adult fishery, those of 1948 and 1953. At Spirit Lake, Iowa, O. J. Koch noted that young buf- falo appeared in large numbers only about every 5 years (Sigler 1949a: 210). The presence of a large adult popula- tion of fish 6 years and older at Lake Chautauqua in 1951 and 1952 indicated that, with commercial fishing of light intensity (individual wing-net fishing), broods of small to moderat
. Bulletin. Natural history; Natural history. 46 Illinois Natural History Survey Bulletin Vol. 29, Art. 1 In the years of our investigation, only two dominant year-classes of bigmouth buffalo appeared in the adult fishery, those of 1948 and 1953. At Spirit Lake, Iowa, O. J. Koch noted that young buf- falo appeared in large numbers only about every 5 years (Sigler 1949a: 210). The presence of a large adult popula- tion of fish 6 years and older at Lake Chautauqua in 1951 and 1952 indicated that, with commercial fishing of light intensity (individual wing-net fishing), broods of small to moderate size, cou- pled with an occasional large brood, were sufficient to maintain a popula- tion of bigmouth buffalo of desirable sizes. The increased removal of bigmouth buffalo after 1951 (Table 5) changed the bufiFalo population of Lake Chau- tauqua in 4 years from one containing a high percentage of old, large fish to one of predominantly young, small fish (Fig. IS). The dominant 1953 brood appears in Fig. 18 to have been much stronger in 1956 than the 1948 brood was in 1951. Actually these broods as 4-year-old fish were of about equal strength; the comparatively smaller number of old fish in 1956 than in 1951 was responsible for the apparent differ- ence indicated by Fig. 18. Carp: Age Composition of Catch.— Age readings indicated that most of the carp taken commercially in the seine hauls at Lake Chautauqua in 1957 and 1958 were 4-, 5-, and 6-year-old fish. The carp taken commercially in the early years of our study were of larger sizes than those taken in 1957 and 1958 1951 1173 FISH) I I '\ M <0. 16 ZO 22 24 26 28 30 32 TOTAL LENGTH IN INCHES Fig. 20.—Length-frequency distribution of channel catfish in the commercial seine hauls at Lake Chautauqua, I 951-1 958. The graphs """I reveal the changes that occurred in the sizes ^ of catfish as a result of increased fishing pres- sure on the species. oo. 1955 (474 FISH). Please note that these images are
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