The existence of these feeding Preferences suggests the possibility that
carp could allow nonpreferred plants to become abundant, particularly
understocking or fish escape occurs and only the most palatable species
are then consumed.
Fowler and
(1978) and Fowler (1985) report a shift
in dominance from Potcmogeton to
spicatwn in an understocked lake.
In Deer
Point Lake, Florida (Van Dyke, Leslie, and Nall 1984; Leslie et al. 1987; Van
a large reservoir stocked in 1976, M. spicatwn returned as a problem.
Carp have either escaped or have been removed by predation from this impound-
ment, and the remaining low density of animals has been unable to control the
milfoil.
This lake has been restocked with grass carp.
Grass carp exhibit a metabolic strategy unlike most fish (Wiley and Wike
Their aerobic metabolism rate is about half that of other fish, but
1986).
their average consumption rate (at 21" C or higher) is about 50 to 60 percent
of body weight per day, which is 2 to 3 times that of carnivorous fish.
These
two factors offset their very low assimilation efficiency, about one third
About 50 percent of ingestion, on the average, is
that of carnivorous fish.
Triploids have a growth rate of about 9 g day
(f or a l-kg carp fed
egested.
An energy budget for
is
420 g of Potcmogeton
per day).
iley and Wike 1986):
=
74E +
where
I = ingestion
M = metabolism
E = egestion
G = growth
Average daily growth rates from Florida lakes range from 10.0 to 10.4 g day
The largest grass carp
recorded (Lake Wales, Florida) in the
United States weighed 32.7 kg (72 lb).**
Personal Communication, 1987, J. M. Van Dyke, Florida Department of
Natural Resources, Tallahassee, FL.
Personal Communication, 1987, Harold Revels, Florida Fish and Game
Commission, Tallahassee, FL.
133
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