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Effects of Waterhyacinth Cover on Water Chemistry, Phytoplankton, and Fish in Ponds¹

ABSTRACT

Waterhyacinth [Eichhornia crassipes (Mort.) Solms] cover of 0, 5, 10, or 25% surface was established in fertilized ponds stocked with the fish, Tilapia aurea (Steindachner), at Auburn, Alabama. Measurements of water chemistry, phytoplankton density, and fish production were made during the 1973 growing season.

Phytoplankton production was less in ponds with 10 and 25% cover by waterhyacinth than in ponds with 0 and 5% cover. Competition of waterhyacinth with phytoplankton involved shading and removal of phosphorus from the water.

Concentrations of dissolved oxygen were lowest in ponds with 25% cover, but oxygen tensions in all ponds were adequate for survival and growth of fish.

Reduction in phytoplankton growth in ponds with 10 and 25% cover resulted in much lower fish production. The presence of 5% cover by waterhyacinth did not significantly affect fish production.

Key Words: aquatic weeds • plant competition

¹ Research supported by Hatch Project Alabama No. 287 and Project AID/csd 2780 to the International Center for Aquaculture, Auburn University.

² Graduate Student and Associate Professor, respectively, Department of Fisheries and Allied Aquacultures, Auburn University, Auburn, AL 36830.

³ Present address, National Marine Fisheries Service, Southeast Fisheries Center, Pascagoula Laboratory, P. O. Drawer 1207, Pascagoula, MS 39567.

Received for publication December 10, 1974.