The grass carp is native to the Pacific Far East region, with its natural habitat spanning from northern Vietnam to the Amur River on the Sino-Russian border. This particular carp species is the sole member of the Ctenopharyngodon genus, making it truly unique in its characteristics and behavior.
Grass carp possess distinctive features that set them apart from other fish species. They exhibit an elongated, chubby body shape with a torpedo-like form. The slightly oblique terminal mouth is equipped with firm, non-fleshy lips, devoid of any barbels. A notable characteristic is the presence of 40 to 42 scales along the complete lateral line. Their pharyngeal teeth are broad, ridged, and arranged according to the formula "2, 4-4, 2". The dorsal fin typically consists of eight to ten soft rays, while the anal fin is positioned closer to the tail compared to most cyprinids. The coloration of the grass carp's body ranges from dark olive on the upper side, transitioning to brownish-yellow on the sides, ultimately culminating in a white belly adorned with slightly outlined scales.
One of the most astounding attributes of grass carp is their exceptional growth rate. When stocked in the spring at a modest size of 20 cm (7.9 in), these fish can reach lengths exceeding 45 cm (18 in) by the time fall arrives. On average, they measure between 60 and 100 cm (23.5–39.5 in), with the potential to grow up to a maximum length of 2.0 m (6.6 ft) and weigh as much as 45 kg (99 lb). Such rapid growth and substantial size make the grass carp a truly captivating species to observe and study.
Grass carp thrive in various freshwater environments, including lakes, ponds, pools, and backwaters of large rivers. They exhibit a strong preference for water bodies that possess abundant vegetation and demonstrate either slow-flowing or standing water conditions. In their natural habitat, grass carp primarily inhabit large, slow-moving rivers, where they engage in spawning activities. Interestingly, the survival of their eggs and young offspring relies heavily on the presence of long rivers, as the eggs must remain suspended and drifting downstream to develop successfully.
As herbivores, adult grass carp feed predominantly on aquatic plants, encompassing both higher aquatic plants and submerged terrestrial vegetation. However, they also consume detritus, insects, and other invertebrates. Remarkably, grass carp can consume up to three times their own body weight daily, thriving in environments that provide an abundant supply of vegetation. These adaptable feeding habits enable them to flourish in small lakes and backwaters, making them an integral part of the aquatic ecosystem.
Grass carp have been introduced to numerous countries worldwide, exhibiting their ability to adapt and flourish in different regions. In the Northern Hemisphere, countries and territories that have witnessed grass carp introductions include Japan, the Philippines, Malaysia, India, Pakistan, Iran, Israel, the United States, and several European nations. However, despite their introduction to various rivers, grass carp have successfully established self-reproducing populations in only a limited number of Northern Hemisphere rivers, indicating their specific reproductive requirements.
In the United States, grass carp were initially imported from Taiwan and Malaysia in 1963, primarily for aquaculture purposes. However, accidental escapes and subsequent planned introductions resulted in the species spreading across the country. By the 1970s, grass carp had been introduced to 40 states, and they are now reported in 45 of the 50 states. In fact, grass carp populations have been observed reproducing in the Great Lakes Basin since 2013. The introduction of grass carp has also occurred in several Southern Hemisphere countries, including Argentina, Venezuela, Australia, New Zealand, Fiji, and South Africa.
One of the primary reasons for introducing grass carp to new environments is their remarkable ability to control aquatic weed growth. Countries like New Zealand and the Netherlands have harnessed the potential of grass carp to combat overabundant aquatic plants. In New Zealand, grass carp were introduced after thorough investigations into their impact and value in secure facilities. Today, the New Zealand government approves the use of grass carp for aquatic weed control, albeit with specific authorization requirements. Similarly, in the Netherlands, the Dutch Ministry of Agriculture, Nature, and Food Quality has regulated the introduction of grass carp since 1973, ensuring effective management of aquatic weed issues.
In addition to their ecological significance, grass carp hold immense culinary value, particularly in China. They are considered one of the Four Domestic Fish (四大家鱼) and have been cultivated as a food source for centuries. Grass carp meat is known for its tenderness and minimal bone content, making it a popular choice in various Chinese cuisines, including Cantonese cuisine. The delicate flavor and versatility of grass carp have cemented its position as a sought-after ingredient, delighting taste buds across the globe.
Grass carp present a thrilling challenge for anglers due to their large size and formidable strength when hooked. However, their vegetarian dietary preferences and inherent wariness make them relatively difficult to catch using traditional angling methods. The International Game Fish Association (IGFA) world record for a grass carp caught on a line and hook stands at an impressive 39.75 kg (87.6 lb), achieved in Bulgaria in 2009. Additionally, in areas where bowfishing is permitted, grass carp are a popular target species for recreational bowfishermen.
It is important to note that in regions where grass carp populations are maintained as a biocontrol for noxious weeds, catch-and-release practices are strongly encouraged to ensure the preservation of these valuable fish for future ecological balance.