Submersed weed management with triploid grass carp in waterlily production ponds
No Thumbnail Available
Files
Date
1990
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Weed control by triploid grass carp (Ctenopharyngodon idella Val.) in waterlily (Nymphaea cultivars) production ponds was investigated and simulated. The 4 x 2 factorial experiment involved eight duplicated treatments consisting of four levels of weed control and two waterlily cultivars. Treatments included a no-weeding control, 2 manual weeding, 1 and 2 grass carp per 52.5-m^2 experimental pen. Initial and monthly densities of aquatic weed biomass, species composition, number of hydrilla (Hydrilla verticillata Royle) turions in soil core samples, and upper surface leaf areas and total number of flowers produced per waterlily plant were measured in each pen until complete weed control occurred in both grass-carp treatments. Generally, biomass of aquatic weeds differed significantly among weed-control treatments. Weed biomass in the manual-weeding treatment was lower than in all others soon after initiation of the experiment; in both grass-carp treatments, weed reduction was evident only after winter. Diversity of weed types was very low during the experiment, and succession occurred with changing seasons. Hydrilla was dominant at the beginning of the experiment and watermilfoil (Myriophyllum spicatum L.) near termination. Hydrilla turions in soil increased in fall, and decreased in spring and summer. The competitive effect of weeds on the growth of waterlilies was clearly seen in the latter part of the experiment, with significantly greater leaf areas in the manual-weeding, 1-carp pen^-1 and 2-carp pen^-1 treatments over the control. Following weed elimination, some grass carp ate waterlilies; whereas, others did not. A systems model was developed to simulate the effect of grazing by grass carp on the dynamics of weed biomass in a shallow water body in south Texas. Fish growth was a function of assimilation and metabolism. The model was parameterized using available information from the literature and results of the field experiment. It predicted that a stocking density of 110[plus or minus]7 grass carp ha^-1 (vegetated) would be required to reduce vegetation to 40% of its maximum biomass in the second summer. Two selected management schemes were simulated to estimate the grass carp density necessary to achieve continuous vegetation control at the 40% level.
Description
Typescript (photocopy)
Vita
Major subject: Wildlife and fisheries sciences
Vita
Major subject: Wildlife and fisheries sciences
Keywords
Major wildlife and fisheries sciences