Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2008
Publication Date: N/A
Interpretive Summary: The dye Aquashade is applied to ponds to reduce light transmission and thereby prevent the growth of rooted plants and filamentous algae in ponds. This is done in order to prevent the plants from fouling nets during the time fish are harvested. Fouled nets result in wasted time and injury and/or death to fish, particularly small fish that are to be stocked into other ponds. Producers of fingerling sunshine bass would like to use this dye. However, the producers are concerned that the dye might also inhibit growth of the microscopic phytoplankton that are food for zooplankton that in turn are food for sunshine bass fry during their first three weeks of growth. To determine the effects of dye, Aquashade (c) was applied to three ponds as they were being filled. Three weeks later, at the time fry are trained to eat manufactured feeds the dye was applied to three additional ponds. Three more ponds had no dye applied. The water quality, amount of phytoplankton, total dry weight of rooted plants, amount of zooplankton and fish production from the three sets of ponds was determined and compared. Almost no differences were found among all the ponds. Therefore, use of the dye did not inhibit fingerling production.
Technical Abstract: Rooted macrophytes make harvesting fingerling sunshine bass from ponds difficult because they can smother fish or tangle in the seines and increase fish stress by increasing time needed to retrieve the fingerlings from the net. Aquashade® is a dye that is used to reduce macrophyte growth by reducing light needed for photosynthesis. Fingerling culturists are reluctant to use the dye because it may reduce phytoplankton concentrations and consequently reduce zooplankton food supplies of the larval fish. In this study Aquashade® was applied at the rate of 4 mg/L (twice the recommended rate) to three ponds when they were filled and to three ponds at the time fry were started on prepared feed. An additional three ponds served as a control. All ponds were evenly stocked with sunshine bass larvae at 15,000/0.04 ha. Water quality and plankton were monitored daily for seven weeks until fingerlings were harvested. Almost no differences were found among treatment ponds for in water quality, chlorophyll a, primary productivity, phytoplankton and zooplankton concentrations or weight of rooted macrophytes. No differences were found in the number, total weight or per cent survival of fingerlings harvested from the ponds. Differences in average individual total length, total weight and coefficient of condition were found but were not thought to be related to use of the dye. Use of the dye was not detrimental to fingerling production at the concentration of dye used but it also was not effective for rooted macrophyte control.