Abstract |
The drift of stream organisms in the Kaskaskia River was investigated over a 2-year period and associated with the time of day, season of the year, turbidity, temperature, water level, and several other environmental factors. The amount of composition of drift showed definite diel and annual patterns. The diel cycle was characterized by a drastic increase in abundance of drifting organisms with the evening reduction of light intensity and a decline in abundance with an increase in light in the very early morning. The annual pattern shows an increase during the spring and into the summer with a gradual decline in the late fall to very low numbers of drift organisms during the winter months. The occurrence of terrestrial organisms in the drift was influenced strongly by heavy rain and strong winds and showed an increase during the autumn when leaves were falling into the water. A mainstream impoundment changed the composition and abundance of drift and contributed great amounts of fish food to the river. (Author) |