The hybrid grass carp, a cross between the male bighead carp (Hypothalmichthys nobilis) and the female grass carp (Ctenopharyngodonidella), was first produced in the United States in 1979 for biocontrol purposes. Unlike the fish produced in 1979 and 1980, the hybrid grass carp spawned in 1981 were assumed to be uniform, triploid, and to have growth and feeding rates comparable to those of grass carp. A comparison study to determine differences in the morphology of the 1979, 1980, and 1981 hybrid grass carp revealed that the hybrid grass carp spawned in 1981 have a longer relative gut length, fewer deformities of the gill rakers, and fewer diploid fish than the previous spawns. In feeding trials, the growth rate of the 1981 hybrid grass carp (2.5 to 3.9 g fish-1 day-1) were similar to that of the 1979 and 1980 fish (2.8 and 3.9 g fish-1 day-1, respectively). In field tests, their mortality rate ranged from 20.8 to 97.4% and was similar to that of other hybrid grass carp. Due to the increased gut length, low feeding rate, and high mortality, the 1981 hybrid grass carp were unable to control (eliminate) the growth of aquatic vegetation in field trials in Blue Lake and in a detention pond which had been treated with herbicide prior to stocking. The 1981 hybrid grass carp has proven to be less effective than previous hybrid grass carp spawns as a biocontrol agent.
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Osborne, John A.
Master of Science (M.S.)
College of Arts and Sciences
Length of Campus-only Access
Masters Thesis (Open Access)
Callahan, Janine L., "Comparison of Hybrid Grass Carp and Grass Carp" (1983). Retrospective Theses and Dissertations. 672.
Contributor (Linked data)