Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract only
Publication Acceptance Date: 10/6/2004
Publication Date: 9/18/2004
Citation: Ludwig, G.M., Hobbs, M.S., Perschbacher, P. 2004. Control of pH in sunshine bass fingerling production ponds [abstract]. Book of Abstracts, Aquaculture America. p. 253. Interpretive Summary:
Technical Abstract: When sunshine bass fingerling production ponds are filled and fertilized according to recommended practices, high pH often develops just at the time recommended for stocking 5-day-old fry. The pH levels often exceed those found to be lethal to striped bass and its hybrids during laboratory studies. Unionized ammonia levels resulting from fertilizer and high pH may also reach unhealthy concentrations. Anecdotal evidence suggests that using only organic fertilizers results in lower pH levels in their ponds. Similar evidence from bait-fish farmers suggests that sodium bicarbonate will reduce the effect of pH spikes. An experiment was performed that compared the effect of using sodium bicarbonate at 56 kg/ha or eliminating the use of inorganic fertilizers on pH and other water chemistry variables and on concentrations of chlorophyll a, phytoplankton, primary productivity, and zooplankton during 12 days after ponds were filled and fertilized. Fry are usually stocked within that time period. Control ponds were fertilized with organic and inorganic fertilizers at published amounts. Ponds were 0.04 hectares. Sodium bicarbonate use resulted in a nominally lower pH on all days of the experiment; however ponds that only received organic fertilizer had pH values significantly lower than the other treatments 75% of the days. Chlorophyll a, TAN and un-ionized ammonia concentrations were also significantly lower in organic-only fertilized ponds than in the other two treatments on most days and well below sunshine bass fry tolerance limits. For most water chemistry variables tested, use of sodium bicarbonate resulted in a slight but not statistically significant (at p=0.05) improvement while use of only organic fertilizer significantly improved water quality. Although total nutrient input was lowest in the organic-only fertilized ponds, rotifers, copepod nauplii, copepods and cladocerans, the food base for sunshine bass fry were not significantly reduced. The experimental ponds had been used for sunshine bass fingerling culture for many years. That suggests using lower amounts of fertilizer in older ponds would be safer for sunshine bass fingerling culture.