Comparisons of Two Bluegill Populations by Means of the RNA-DNA Ratio and Liver-Somatic Index

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Abstract
Bluegills (Lepomis macrochirus Rafinesque) from two central Tennessee lakes revealed monthly and seasonal variations of liver RNA‐DNA ratios (liver RNA/DNA) and liver‐somatic indexes (LSIˈs) that were associated with gonad maturation, spawning, and temperature. Liver RNA/DNA indicated a longer summer growth depression in fish collected from the smaller, shallower lake. Although LSIˈs were consistently higher in the smaller, shallower lake, liver RNA/DNA and scale analyses showed faster growth rate in the larger, deeper lake. Thus the LSI may be a useful indicator of relative food intake‐energy storage levels within a single lake, but it does not necessarily reflect absolute growth rate of the fish. Liver RNA/DNA provided an indication of immediate or short‐term growth rates.