Research Highlights - Water Quality

Aquaculture/Fisheries Center Research Highlights

Water Quality

Effects of aerial herbicides on phytoplankton and zooplankton and water quality in fish ponds
Peter Perschbacher, R. Edziyie and Gerald Ludwig

Goldfish pond water with a surface scum of the bluegreen algae Microcystis and Anabaena was tested in mesocosms with propanil at drift rates of 1 and 10% of field rates. These rates have not resulted in significant reductions in water quality or plankton, but with a scum condition significant reduction in morning oxygen was noted. Recovery occurred in 2 days.

Fry pond water was tested with Basis Gold, which is composed primarily of atrazine, at rates that produced reduced zooplankton levels in hybrid striped bass production pond water. No effect was seen on zooplankton and results are being further studied.
Paddlefish effects on water quality
Peter Perschbacher

Fingerling paddlefish were stocked at 1360 kg/ha in a 1250-l tank. Water from 4 culture ponds was pumped into the tanks and compared to a control tank for 3 days, sequentially. Significant reductions in chlorophyll, zooplankton and phytoplankton numbers were noted. Nitrite-n was higher. Bluegreen algae, including off-flavor species, were reduced. The indiscriminant filtering mode of paddlefish was attributed to the changes in water quality.
Effect of increasing stocking rates of channel catfish on phytoplankton composition
Peter Perschbacher, Brent Southworth and Carole Engle

Phytoplankton samples taken at two-week intervals during a production experiment with varying stocking rates of channel catfish did not reveal differences in percentage composition or frequency of off-flavor species among treatments. Adequate nutrients for the typical bluegreen blooms that dominate, including off-flavor species, were judged present at all levels.
Effect of increasing levels of threadfin shad on channel catfish pond phytoplankton
Peter Perschbacher and Bart Green

Phytoplankton samples taken every two weeks revealed significant differences in phytoplankton composition due to threadfin shad filtering. Reduction in the relative abundance of bluegreen algae, including off-flavor species, and increased diatom and euglena abundance occurred. However, taste testing of catfish at the end of the production period did not produce improvement in taste scores with increasing stocking of shad.
Effect of aquashade on fall phytoplankton in commercial catfish ponds
Peter Perschbacher and Andrew Radomski

Weekly phytoplankton samples were taken from 3 commercial catfish ponds treated with aquashade at 1 ppm and from untreated control ponds. Significant differences were found, including reductions in bluegreen algae and off-flavor species, but trends are not clear and still being assessed. Spring sampling is continuing to obtain additional data.