Date of Award

Spring 1983

Document Type



Life & Environmental Sciences

First Advisor

Rev. Joseph Harrington

Second Advisor

Dr. John Christenson

Third Advisor

Dr. Joseph Ward


The relationships between preferred temperature and ontogeny in the guppy Lebistes reticulatus were investigated using a horizontal temperature gradient. The results suggest a preference for warmer temperatures in the juvenile fish. It appears there is a gradual shift in selection from warmer to cooler temperatures as the guppy matures to the adult stage. This higher temperature preference in the younger fish may be related to optimum growth rate and avoidance of predation especially from its own species. Predation experiments were also run in the gradient. No definite conclusions about the relationship between predation and temperature selection could be made from the data.