Date of Award

Spring 2012

Document Type

Legacy Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

James O. Luken

Second Advisor

Deborah Hutchinson

Third Advisor

Scott L. Parker

Abstract

Tilapia are one of the most widely farmed freshwater fish in the world because of their hardiness and rapid growth. Their opportunistic nature also makes them potential biological control agents for invasive aquatic plants. Two of the most invasive and economically and environmentally destructive aquatic plants are water hyacinth and alligator weed, both of which can be found in the South Carolina low country. This research was divided into two experiments. The first experiment was conducted in June 2011 to observe the effects of blue tilapia and alligator weed individually and combined on water quality, as well as how blue tilapia affect the growth of alligator weed roots and stems. The results showed that when tilapia and alligator weed were combined, they caused significant increases in dissolved oxygen, turbidity, and conductivity when compared to the control treatment. These findings suggest that alligator weed and tilapia can have a noticeable interactive effect on water quality. The second experiment was conducted in October to observe the effects of two different densities of blue tilapia on water quality and the growth of water hyacinth roots. The results showed that only turbidity was affected by tilapia density; turbidity increased significantly as fish density increased. Tilapia consumed the roots of both plant species, but they were unable to eat enough of the root systems to kill either species. If stocked in high enough concentrations and/or combined with other control methods, tilapia have the potential to control both plants; however, because tilapia can negatively affect water quality, their use as a biological control agent is questionable and should be studied further.

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