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.
Rates of leaf litter processing at eight sites were used in conjunction with other methods to evaluate the impact of highway construction on aquatic habitats. Monthly processing of white oak leaves from four different mesh size bags at unimpacted reference sites indicated that the three larger mesh sizes were useful for comparing sites, as they did not restrict invertebrate colonization and provided similar rates of processing within sites. Small mesh size (0.12 mm) prevented leaf shredding macroinvertebrates from colonizing bags, and caused significantly slower leaf processing in a riffle.Leaf processing was fastest in a reference rime above an area of highway construction but was significantly slower in the reference pool due to low current velocity and the absence of shredders. Leaf processing in a rifile below the highway was slower than the reference rime, and the number of shredders was reduced. Removal of streamside vegetation during highway construction caused increased stream temperatures and reduced the amount of natural leaf accumulations, thereby reducing shredder habitat. At other sites highway construction caused less of an impact than preexisting environmental influences. Leaf processing in an rime of a lower pH stream was significantly slower than in the reference rime. Shredders were absent from the low pH stream, and rates of leaf processing in the acid impacted rime and pool were similar to those of the reference pool. Comparisons of the low pH stream with the reference stream indicated that physical processes were less important than biological processes of leaf decay. Leaf processing in ponds was similar to that of stream pools. Processing was faster in a small versus large pond, and a high density of invertebrates was associated with leaf bags in the small pond after one year.
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