| A series of experiments was carried out to examine the possible causes of variation in larval percid survival in a state fish hatchery in Ohio. Possible causes include: over-fertilization, pond age, copper sulfate treatment, phosphorus and copper residues in the pond sediment, fish density, and cannibalism. I also evaluated the effects of a blue dye and raising water level on algal growth as a substitute for copper sulfate use during catfish culture.; First, I tested the hypothesis that fish ponds were over-fertilized by comparing fish raised in the traditional 30 μg P/l treated ponds, to those raised in a reduced 20 μg P/l treated ponds, while keeping the weekly nitrogen level at 600 μg N/l. Results show that neither harvested fish length, weight, survival, ind/ha, yield, nor fish growth was significantly different between treatments.; Second, I examined the percid survival, growth, and yield among ponds that were single-cropped with only percids in the spring (SS ponds) and ponds that were double-cropped with saugeye in the spring followed by channel catfish in the summer during the previous two consecutive years (DD ponds) to evaluate the effects of copper sulfate treatment and sediment residual copper and phosphorus on fish and its prey.; Third, examination of the 12-year (1991–002) percid production data showed that the age of the ponds did not affect fish production. However, ponds that were treated most often with copper sulfate during catfish production in the summer accumulated significantly more copper in the sediment.; Finally, I tested a light-attenuating dye (Crystal Blue-Ocean) and raising pond water level on the growth of benthic algae to substitute for copper sulfate applied during catfish culture since it could be the major cause of percid survival fluctuations at the hatchery. An eight-week experiment showed that chlorophyll a concentrations on sediment did not differ significantly between 2 ml/m3 dye-treated and control ponds at either shallow or deep areas of the ponds. (Abstract shortened by UMI.)... |
