The impacts of algal control in catfish and percid aquaculture ponds
A series of experiments in an Ohio state fish hatchery examined possible causes of variation in larval percid survival including: over-fertilization, pond age, copper sulfate treatment, phosphorus and copper residues in the pond sediment, fish density, and cannibalism. Also, addition of a blue dye and raising water level were evaluated as substitutes for CuSO4 use to control algal growth during catfish culture. First, I compared percids raised in the traditional 30 £gg P/l treated ponds to those raised in 20 £gg P/l treated ponds, while keeping the nitrogen level at 600 £gg N/l. Fish production was not significantly different between treatments, so over-fertilization was not responsible for percid survival fluctuation. Second, I compared the percid survival, growth, and yield between ponds that were only used to raise percids in the spring (SS ponds) with ponds that were double-cropped (DD ponds), with saugeye culture in the spring followed by channel catfish during the previous two summers. DD pond culture patterns had a negative impact on percid production, possibly due to the accumulation of copper in the sediment resulting from CuSO4 application during catfish culture, acting at least on zooplankton and perhaps on percids directly. Third, examination of the 12-year percid production data showed that the age of the ponds did not affect fish production. However, ponds that were treated most often with CuSO4 had a significantly lower percid production. Mean individual fish weight was unaffected between densities of 100,000 to 400,000 fish harvested/ha, suggesting that fish stocking density was not responsible for percid survival fluctuation. Stomach content analyses showed no cannibalism under current stocking density. Finally, I tested a blue dye and raising pond water level on the growth of benthic algae to substitute for CuSO4 application. Sediment chlorophyll a concentrations did not differ between 2 ml/m3 dye-treated and control ponds. Increasing dye concentration to 4 ml/m3 and/or raising pond water level by 20 cm still was not successful in restraining algal growth, but catfish survival and yield were similar among treatments and the control ponds.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:percid saugeye aquaculture algal control copper sulfate
Date of Publication:01/01/2003