FAMILY: Cyprinidae
|
NAME: Ctenopharyngodon idella - Grass carp |
|
Data provided courtesy of Aquaculture/Fisheries Center, University of Arkansas at Pine Bluff - (Dr. Peter Perschbacher) |
|
|
DISTRIBUTION: Ctenopharyngodon idella, or the grass carp, naturally occurs in eastern China and the former Soviet Union, latitude 50 degrees N to 23 degrees N. The grass carp can be found in lakes, ponds, and slow moving rivers below 1,000 m in this region. Northern rivers in which the grass carp naturally occurs in this region include the Amur, Sungari, and Ussuri. Southern rivers, almost all in China, include the Hwai, Yangtze, Pearl, East, and Min rivers. Grass carp is often found in the vegetative, stagnant, shallow areas of these water bodies. The grass carp has a high adaptability to different habitat types, which helps account for its successful introduction into other regions of the world. HABITS: The Grass Carp is wholly a freshwater fish, often found in the shallow, vegetative areas of streams, rivers, lakes and ponds. They are eurythermic, hardy, and migratory. The grass carp can withstand a variety of temperature ranges. The optimal temperature range for incubation is 21-25 degrees C, and this range expands as the fish matures. Ranges in water conditions include 125-215 ppm turbidity, 1-28 ppm for dissolved oxygen, and 7.5% and 12.0% salinity. With a lethal dissolved oxygen range spans from 0.3 to 0.4 ppm, the grass carp is tolerant of very poor water quality conditions. SPAWNING: Mating behavior consists of two to three males following a female. The female remains close to the surface in the river's center. The behavior is promiscuous, as the fish roll with one another and frequently break the surface. Direction of the current and water depth have not shown to be significant reproductive factors. Grass carp show external fertilization and polyspermy, i.e. multiple pronuclei in the egg. Fertilization occurs in the open water column. Spawning (pelagic) occurs during the spring, at temperatures ranging from 19-20 degrees C. The eggs are heavier than water, and will sink unless moving water keeps them afloat. Moving water stimulates a higher rate of egg production, facilitates fertilization. Males in the southern U.S. mature within 2 years, while females mature in 3 years. Triploid grass carp, which have been bred for weed control in the U.S., are generally smaller than their diploid counterparts, and have shorter life spans. GROWTH: Growth is rapid, with wild fish reaching a length of 6-12 in, by age 1. In culture and in different areas, growth varies greatly and is a function of density, feed, competition with other fish, and the suitability of environmental conditions. Grass carp may attain a weight of 100 lb. USES: Grass carp has been imported from Asia to many countries, including the United States; introduced for culture, experimentation, and weed control. The grass carp currently has little economic value, with two exceptions. The state of Hawaii is now advertising the fish as one of its products of aquaculture. Apparently, grass carp is eaten as seafood. Also, grass carp are raised as food in Boston's Chinatown (The Carp and Minnow Family). The grass carp are an inexpensive source of food because they can be caught without limit, and therefore are used extensively by poor populations. CULTURE: Grass carp were imported for biological control of noxious aquatic vegetation. Tests of their organoleptic and sportfishing qualities suggest that they have limited potential as a game (fighting) fish but are acceptable for table use. Juveniles and adults can be fed kitchen refuse, cereal brans, oilcakes, and silkworm pupae; night soil and dung are used in certain countries. To avoid competition with indigenous species, sterile (triploid) grass carp are used for weed control. Laws prohibit hatching of grass carp in Arizona, since the escape of nonsterile grass carp from a hatchery could damage the local ecology. REFERENCES:
|