A long-term study of larval chaoborus punctipennis (diptera: Insecta) vertical migration and the role of critical oxygen concentration

Abstract

The aquatic insect larvae of Chaoborus punctipennis exhibit diel vertical migration, remaining in deeper waters during the day and ascending at night. This behavior reduces visual predation on the larvae, but incurs costs. We attempted to determine if patterns existed in the vertical migration of C. punctipennis larvae related to changes in water oxygen concentration. For 13 of the past 19 years, data were collected over a 24-hour period in the fall in Poplar Tree Lake, Shelby County, Tennessee. We determined the mean depth at which larvae were found during the nighttime and daytime. There was no consistent change in either mean nighttime or daytime depth over time (P<0.22). We assumed that an oxygen concentration below 2.0 mg/l could not be tolerated by fish. Comparison of the depths at which this critical oxygen concentration occurred with mean larval depth showed a significant correlation (P>0.05), supporting the hypothesis that diel vertical migration affords protection from fish predation. © 2001, Copyright Taylor & Francis Group, LLC.