Research Highlights - Water Quality

Aquaculture/Fisheries Center Research Highlights

Water Quality

Reducing aquaculture losses caused by pesticide drift
Peter Perschbacher, Andrew Goodwin and Gerald Ludwig

Much of Arkansas aquaculture production occurs in ponds immediately adjacent to row crops that are sprayed with pesticides applied by aircraft. Farmers have long suspected that drift produced problems in ponds, but there is little data available to help farmers, applicators, and state regulators evaluate the real risks.

Studies have been conducted to determine the toxicity of common pesticides to crops produced in Arkansas including catfish, baitfish, ornamental fish, and shrimp. Additional studies have examined the potential of herbicide drift to kill planktonic algae in ponds. Loss of these algae would be expected to cause water quality problems and disrupt the food chains of some fish species.

Our studies have shown that herbicides have a very low toxicity to fish and that they are unlikely to kill pond algae at reasonable drift rates. Some pesticides were shown to be marginally detrimental to fish at high drift rates and extremely toxic to shrimp. The results of these studies are used by farmers to evaluate the likelihood of pesticide induced losses, by applicators to assist in decisions regarding safe chemicals and application conditions for treatments near ponds, and by the Arkansas State Plant Board when investigating fish kills.
Effects of aerial herbicides on phytoplankton and zooplankton, and water quality in fish ponds
Peter Perschbacher, Regina Edziyie and Gerald Ludwig

Propanil effects on plankton communities from five culture environments: goldfish, sunshine bass, L. vannamei shrimp, and two channel catfish blooms (Microcystis/Anabaena surface scum and bluegreens mixed in the water column). Propanil at double the high drift rate (20% of field rate) significantly decreased pH and morning oxygen levels in all culture environments compared to untreated controls. In the catfish pond with a Microcystis and Anabaena scum, propanil reduced Microcystis after the third day, and impacted water quality adversely.

Basis gold, a major aerial corn herbicide, tested on sunshine bass pond water. The three components were individually evaluated: nicosulfuron, rimsulfuron and atrazine. Atrazine was applied in early May and had no effect on morning oxygen levels, even though photosynthesis was reduced. Zooplankton were most impacted. Rotifers dropped to 57% and 36% at high drift rates (10% of field levels) 48 and 72 h after application, respectively.
Water quality in channel catfish ponds receiving varying protein levels and alternate day feeding patterns
Peter Perschbacher, Carole Engle and Carlos Leyva

On several sample dates, every day feeding of 32% protein feed compared to every other day feeding at 28, 32 and 36% protein feeds resulted in statistically lower water quality in the water quality parameters TAN, dissolved oxygen, and nitrite-nitrogen levels. However, chlorophyll a levels did not significant differ.
Effects of threadfin shad on channel catfish pond phytoplankton
Peter Perschbacher and Bart Green

Off-flavor cyanobacteria species were largely eliminated by threadfin shad. BG in general were severely reduced as well. Diatoms were stimulated. Total numbers of algae did not differ.
Effects of organic and inorganic fertilization on phytoplankton in sunshine bass fry ponds managed for pH control
Peter Perschbacher and Gerald Ludwig

Organic fertilization produced lower chlorophyll and algae numbers than inorganic, and thus desirable lower pH.