<br />36 Foreign Nonindigenous Carps and Minnows (Cyprinidae) in the U.S.-A Guide to their Identification
<br />
<br />Ecology
<br />
<br />The Grass Carp is a large species that can attain a
<br />weight of 45 kg (Robison and Buchanan, 1988; Etnier
<br />and Starnes, 1993) and a length of 1.5 m TL (Laird
<br />and Page, 1996). Typical longevity is about 5-11 years
<br />(Berg, 1964), but an individual in the Amur River was
<br />estimated to be 21 years, based on scale growth rings
<br />(Gorbach, 1961). Growth is relatively rapid, especially in
<br />the tropics where it can average 109 per day (Hickling,
<br />1967).
<br />Typical habitat includes quiet waters, such as lakes,
<br />ponds, pools, and backwaters of large rivers, and indi-
<br />viduals generally do not travel long distances except for
<br />the annual spawning migration (Mitzner, 1978; Nixon
<br />and Miller, 1978; Bain and others, 1990). Nevertheless,
<br />there are reports of juvenile Grass Carp traveling as
<br />far as 1,000 km from their original spawning grounds
<br />(Stanley and others, 1978). Shallow water is the gener-
<br />ally preferred habitat, although deeper waters are used
<br />when temperatures decrease (Nixon and Miller, 1978).
<br />A number of experimental studies have reported envi-
<br />ronmental tolerances for Grass Carp. Fry and fingerlings
<br />have been reported to tolerate water temperatures from
<br />0-40 oC (Stevenson, 1965; Vovk, 1979), and Stevenson
<br />(1965) reported that fingerlings in small ponds in
<br />Arkansas survived 5 months under heavy ice cover.
<br />Chilton and Muoneke (1992) reported an upper lethal
<br />temperature range for fry as 33-41 oC, and for yearlings
<br />as 35-36 oc. Bettoli and others (1985) documented a
<br />thermal maximum of 39.3 OC and a preferred tempera-
<br />ture of 25.3 oc. Collee and others (1978) reported that
<br />feeding declined sharply below 14 oc. Nico and others
<br />(2005) reviewed temperature tolerance of Grass Carp
<br />and the other Chinese carps.
<br />Oxygen consumption (per gram of body
<br />mass) increases with higher water temperature and
<br />decreases with fish age and mass (Chen and Shih,
<br />1955; Wozniewski and Opuszynski, 1988). The
<br />lethal low oxygen level for juveniles was <0.5 mg/L
<br />(Negonovskaya and Rudenko, 1974). The maximum
<br />pH for culture of Grass Carp was reported as 9.24
<br />(Liang and Wang, 1993). Egg hatching was delayed
<br />below pH 6.5 and increased mortality and deformation
<br />of larvae occurred below pH 6.0 (Li and Zhang, 1992).
<br />Sensitivity to low pH decreased with age (Li and Zhang,
<br />1992). Median lethal concentration of ammonia was
<br />determined to be 1.05 mg/L (Gulyas and Fleit, 1990).
<br />The Grass Carp appears to be tolerant of low levels
<br />of salinity, and may occasionally enter brackish-water
<br />areas. Fry (32-50 mm TL) survived transfer from fresh-
<br />
<br />water to a salinity of 12 ppt (Chervinski, 1977). Adults
<br />(2+ years) survived 10.5 ppt salinity for about 24 days
<br />and 17.5 ppt for 5 hours (Cross, 1970). However, Grass
<br />Carp acclimated to 3, 5, and 7 ppt had an upper tolerance
<br />of about 14 ppt (Kilambi and Zdinak, 1980). Maceina
<br />and Shireman (1980) showed that fingerlings reduce
<br />feeding at 9 ppt and stop feeding altogether at 12 ppt;
<br />thus, they predicted Grass Carp could inhabit brackish-
<br />water bodies up to 9 ppt. Maceina and Shireman (1979)
<br />reported that the species can tolerate 14 ppt for as long
<br />as 4 days, but that the upper long-term tolerance of
<br />fingerlings to saline waters was lower, about 10-14 ppt.
<br />Maceina and others (1980) noted that oxygen consump-
<br />tion decreased along a salinity gradient of 0-9 ppt.
<br />Movement of Grass Carp from one river to another
<br />through a brackish-water estuary (Pavlov and Nelovkin,
<br />1963, in Cross, 1970) is not surprising given the species'
<br />tolerance to low levels of salinity. Avault and Merowsky
<br />(1978) reported food preference and salinity tolerance of
<br />hybrid Common Carp X Grass Carp.
<br />The species is probably best known for its raven-
<br />ous appetite for plant matter (especially macrophytes);
<br />however, small Grass Carp feed on invertebrates before
<br />switching to plants. Watkins and others (1981) reported
<br />that Grass Carp larvae consumed benthic invertebrates
<br />(primarily chironomid larvae) and zooplankton until they
<br />reach about 55 mm TL. Edwards (1973) reported age-O
<br />Grass Carp consumed oligochaetes, mayflies, cadd-
<br />isflies, amphipods, and chironomids. Fry of Rainbow
<br />Trout (Oncorhynchus mykiss) and Common Carp were
<br />eaten by young Grass Carp (even in the presence of
<br />preferred plants), but Grass Carp would not eat the eggs
<br />of either species (Edwards, 1973; Singh and others,
<br />1976). Grass Carp larger than 25 em did not feed on
<br />fry in the laboratory (Singh and others, 1976). The size
<br />at which Grass Carp begins to feed on plants depends
<br />on temperature, with smaller fish switching to plants
<br />in warmer waters (Stanley and others, 1978). Adults
<br />feed on a variety of aquatic macrophytes, such as water
<br />hyacinth (Eichhornia crassipes), eelgrass (Vallisneria
<br />americana), cattails (Typha spp.), and Hydrilla spp.
<br />(Collee and others, 1978; reviewed in Opuszynski and
<br />Shireman, 1995; Cassani, 1996). In some cases, Grass
<br />Carp will consume animals when plant material is lack-
<br />ing (Nikol'skiy and Aliyev, 1974; Forester and Avault,
<br />1978). Alternatively, Grass Carp may consume terres-
<br />trial macrophytes in the absence of aquatic vegetation
<br />(Kilgen and Smitherman, 1971; Terrell and Fox, 1974).
<br />Kilgen and Smitherman (1971) reported that individuals
<br />raised their heads clear of the water to consume terres-
<br />trial macrophytes. The species is a voracious herbivore
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