Effects of Artificial Feeding and Copper Sulfate on Nutrients and Dissolved Oxygen in Fish Ponds
Creators:Reynolds, Curtis A.
Advisor:Culver, David A.
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. College of Biological Sciences Undergraduate Research Theses; 2011
Artificial feeding is commonly added to aquaculture ponds to enhance growth and survival of juvenile fish. Thus feed is applied to ponds for direct nutritional supplement effects; however it may have negative effects on water quality and prey items that lead to reduced growth and survival. This practice also introduces excessive nitrogen and phosphorus into ponds, and causes reduced oxygen conditions during aerobic decomposition of feed. Copper sulfate (used to control phytoplankton growth and treat parasitic infections) may also contribute to low dissolved oxygen by reducing algal primary production. Nitrogen and phosphorus content of artificial feed incubated in pond water for 0, 1, 2, 4, 8, 16, and 32 hours was measured to calculate the molar ratio (N:P) and the release of these nutrients over time. To calculate the consumption of oxygen we incubated pond water with known feed additions in BoD bottles, for 6 hours. Using winkler’s titrations the consumption of oxygen was calculated in each bottle. We assessed the effects of artificial feeding by measuring the spatial variation in morning (8 am) dissolved oxygen levels in ponds with a gradient of feeding treatments (0%, 1%, and 3%). Results showed that total nitrogen and phosphorus release are excessive compared to source water contributions. Phosphorus is released in excess to nitrogen at a molar ratio of 10:1, potentially supporting to growth of nuisance cyanobacteria. Oxygen consumption increases rapidly with feeding rate suggesting the negative impacts of high feeding rates on DO. Copper sulfate reduces the consumption of DO, at each feed increment, possibly owing to the reduction in bacterial biomass. Spatial heterogeneity was seen in all ponds with low dissolved oxygen localized near the site of feed addition. This poses a potential problem to hatchery managers because fish may have limited access to feed in anoxic zones. Higher DO in shallow areas of ponds may be habitat refuge for culture fish. Copper sulfate reduces DO likely owning to the reduction in algal primary production in ponds. Managers should consider reducing the amount of artificial feeding and try to avoid treatment with copper sulfate in order to improve water quality and growth and survival of fish.
Ohio Department of Natural Resources Division of Wildlife
Sport Fish Restoration
Sport Fish Restoration