. The Canadian field-naturalist. 50 The Canadian Field-Naturalist Vol. 97 O z >- UJ a. 150 100 50 0 PREY Rock Basses Pumpkinseed ? 281 Perch t 85 Basses* A 75 Golden Shiners O 71 Other Shiners X 47. 100 200 300 400 BASS LENGTH T L mm Figure 2. Relationships of individual prey species' lengths to length of predator, the Large- mouth Bass, Micropierus salmoides in Nogies Creek, 1977. *Includes; largemouth and smallmouth. and others. This coefficient varies from zero, when diets are completely distinct, to one, when the diets are similar in proportions of the prey groups or species. Thus, any
. The Canadian field-naturalist. 50 The Canadian Field-Naturalist Vol. 97 O z >- UJ a. 150 100 50 0 PREY Rock Basses Pumpkinseed ? 281 Perch t 85 Basses* A 75 Golden Shiners O 71 Other Shiners X 47. 100 200 300 400 BASS LENGTH T L mm Figure 2. Relationships of individual prey species' lengths to length of predator, the Large- mouth Bass, Micropierus salmoides in Nogies Creek, 1977. *Includes; largemouth and smallmouth. and others. This coefficient varies from zero, when diets are completely distinct, to one, when the diets are similar in proportions of the prey groups or species. Thus, any value greater than is accepted as indi- cating an overlap in diet. Table 3 revealed that 1- and 2-year olds, while feed- ing on similar food, ate substantially different propor- tions of prey from all of the other age groups. From age 3 onwards, however, Largemouth Bass fed on similar proportions of the 12 main food items. The younger Largemouth Bass were responsible for most of the predation on Ephemeroptera and Odonata, as well as Pumpkinseed and Yellow Perch (Table 2). One other major difference was that age 3 fish and older ate crayfish, while the I- and 2-year olds did not. In summary then, 0-age largemouth from Nogies Creek ate mainly small and varied invertebrates (Hamilton and Powles 1979); 1- year olds ate tad- poles, small fish and invertebrates, and from age 3 onwards, the diets overlapped, being characterized by intake of six species of "small-sized" fish prey, a high proportion of frogs and tadpoles, followed by crayfish (of low importance). Composition Through the Feeding Season With regard to the length of the feeding season, some food was present in the guts from April to October (Table 4). Before the end of October (and before freeze-up) less than 50% of the stomachs con- tained food (52% empty in 1976, 70% empty in 1977). At mid-April, only four stomachs (20%) contained food, which was mostly vegetation. The length of the feeding season was thus
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