Features and Cultivation Process of Grass Carp

Grass cap is one of the Asian carp species. The southern part of China introduced them first to the world. Forty more countries, including the United States, imported these fish later. Although they were called trash fish then, the scenario is different now. People cultivate them in the hatchery for several reasons. It can be either for eating or controlling aquatic vegetation. Competitive anglers target the fisheries for setting new personal or worldwide records as well. If you are planning to farm grass carp, you should know the following details:

How Fast do Grass Carp Grow

how fast do grass carp grow
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Growth rate

The farm owners set their business plan based on the fish’s weight, growth, maturity, season, and motives. So, how fast do grass carp grow? A grass carp feeds up to three times of its weight per day. So, it grows up pretty quickly by staying in an environment full of desired plants. A juvenile of 8 inches can reach above 18.5 inches from spring to fall. According to the record, the highest length crossed 6.5 ft. However, they are usually 23.5 to 39.5 inches long and weigh 100 lbs. In many cases, their weight raises 2 pounds or more monthly. Such growth rate requires proper temperature, sufficient oxygen, and food supply. The rate starts to slow down as the carp ages.

Life expectancy

Studies show that the grass carp generally live between 5 to 9 years. Some fish can even live up to 11 years. Many commercial fisheries prefer sterilized ones over the regulars. The key difference is that sterilized species do not take part in reproduction. They survive ten years to 20 years under perfect circumstances.


It is common to confuse them with goldfish and silver carp due to similar coloration. The body color varies from deep brown to dark olive. It fades to brownish, golden, or yellowish shades on the sides. Their belly looks white or silvery-white, and scales are outlined in dark-brown.


Grass carp have an oblong-shaped frame along with a round abdomen and compressed rear. Their slightly flattened head includes a pair of non-fleshy and firm lips. There are no barbels at all. Moderately small eyes and large teeth are also part of the head. The eyes are situated on both sides of the head. 40 to 46 scales form the grass carp’s lateral line. Each of them has dark edging. These fish have a shorter dorsal fin compared to other look-alikes. It contains only 7 to 8 rays.

Food list

As we mentioned earlier, their diet mainly covers aquatic grass and other plants. Since they consume such quantities of plants, there can be food scarcity for the native species. In the absence of these items, they consume other foods. Larvae, insects, tiny fish, worms are their other favorites. They eat very clean and hate muddy water. That’s why they are less likely to take most grass carp baits. When it comes to artificial feed, you can provide grain-based meals, boilies with vegetable oil as well as pellets.


They like to swim in calm or slow-flowing water spots. Anglers generally find them in the medium to lower water depths. The majority of adults migrate to the upper layers in search of floating foods. When the spawning time arrives, they go to slightly faster-moving sections. The parents do not select super-fast streams as the high flow wash the egg away. Females lay numerous eggs every time, but the spawn-bed fails to accommodate all. They keep the eggs hidden to protect against enemies.

Ideal temperature

Almost all carp are capable of withstanding extreme weather. The same goes for grass carp. During the cold season, they lessen activities and food consumption. It helps to keep them alive in lean times. As a result, the growth gets slower than average. Grass carp keep continuing such inconsistent feeding until the warmth crosses 50 degrees. They consume the highest amount of foods within 70 and 86 degrees. It is the reason why summer gives the heaviest catches. Besides, the spawning period requires certain water conditions. 64-degree Fahrenheit is the perfect temperature for egg survival and further improvement of grass carp. In brief, a mature fish can endure from 32 to 100-degree Fahrenheit.

Production cycle in a hatchery

Owners have to buy a spring tank with a 7 to 10m diameter. It shZould have almost 2m of water. These carp are quite sensitive to LRH-A. Therefore, farmers release a few adult breeders into the container after injecting LRH-A or other hormones. They pay attention to constant water circulation throughout time.

Now, it’s time to transfer the eggs to round jars. Often, gravity does this job automatically; If not, we have to do it manually. Again, maintaining proper water circulation is a must.

The baby grass carp are moved in a clean pond as a nursery. It should be free from dirt and harmful organisms. If one can increase the number of algae and zooplankton, he won’t have to invest more in commercial foods. Applying organic fertilizers for eight to ten days will be helpful. Chinese farmers keep the grass carp there to grow around 30 mm in length. It takes 2 to 3 weeks.

The next phase is called fingerling rearing. A broader and larger pond is needed than the nursery one. Whether it yields only grass carp or mixed fish is up to the cultivator. He has to keep feeding the fish through the 4 to 6 months. Warmer climates can shorten the required period.

Lastly, they are shifted to a large and clean pond.

Harvesting techniques

Using either mono-culture or poly-culture strategies is possible in a large pond. The harvesting process can be selective and total. People go for ‘net’ harvesting methods for catching grass carp because they barely take baits. They collect only fish of marketable weight and release the rest. Only a few try selective harvesting. The best time of the day for maximum success is after dawn. Grass carp are available in the shallow water and easily fall prey to anglers. It is mainly effective for the late summer months.

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