Relationships Between Diet and Growth of Age-0 Largemouth Bass in a Kentucky Lake Embayment

Diet and growth of the 1993 year-class of age-0 largemouth bass were determined in Ledbetter Embayment of Kentucky Lake. Diet was analyzed to determine the relationship between diet quality and the resulting size structure of the cohort. Length-weight and head capsule-weight regressions were used to estimate the dry weight of prey items in the diet. Largemouth bass were divided into 2 size classes (large and small) based on the mean length for each sampling date. Growth rates were calculated for both classes and compared with piecewise linear regression of total length on day of the year with the use of an additional dummy variable. There was a pivotal period in mid-July when there was a divergence in growth rates. The growth rate of small age-0 fish slowed dramatically, while the growth of large age-0 largemouth bass increased. During this period the large age-0 largemouth bass were consuming more prey fishes and fewer insects and zooplankton by weight than were small age-0 largemouth bass. After July, small age-0 largemouth bass consumed 2.5 times more prey items and prey of much smaller size than large fish. Early in life, the condition of small age-0 largemouth bass was significantly higher, resulting in the conclusion that small age-0 largemouth bass were possibly allocating more assimilated energy towards growth in weight, while large fish were assimilating more energy towards growth in length. The variation in growth observed within the cohort resulted in a multi-modal length-frequency distribution by the end of the summer.

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