The grass carp, or Ctenopharyngodon idella, is a freshwater fish native to Asia, but it has been introduced in several regions around the world, including Quebec. This species is often used for biological control of aquatic plants due to its herbivorous diet. Although it is not a primary target for sport fishermen, it is of certain interest to those seeking a different challenge. Its impressive size and relative strength make it an interesting opponent, especially for big game fishing enthusiasts. In Quebec, it is mainly found in the southern part of the province, in water bodies where it has been introduced for aquatic vegetation management.

The grass carp has an elongated, cylindrical body covered with large, silvery scales that give it a smooth and shiny appearance. Its color varies from olive green to brown, with a lighter belly. Its mouth is terminal, devoid of barbels, and oriented forward, which is typical of herbivorous fish. The fins are generally clear, with shades of gray. The dorsal fin is long, while the caudal fin is forked, providing good propulsion. Young grass carp closely resemble adults but are more slender. During the spawning period, males may develop nuptial tubercles on their heads, a common characteristic among several cyprinids.

In Quebec, the grass carp is primarily found in the south, particularly in the watersheds of the Richelieu River and the St. Lawrence River. It has been introduced into these waters to manage the proliferation of aquatic plants. Its presence is still limited, as it does not reproduce naturally in Quebec waters. The species prefers calm, shallow waters, such as those found in bays and marshes. It is also found in certain lakes where it has been introduced for ecological management projects. However, its abundance remains moderate, and it is less common in colder or fast-flowing waters.

The grass carp prefers calm, vegetation-rich waters, such as shallow lakes, ponds, and slow-moving rivers. It is often associated with areas where aquatic vegetation is dense, as it primarily feeds on aquatic plants. The species tolerates temperature variations well but is more active in warm waters, between 68 and 82 °F. It generally avoids deep waters, preferring littoral zones where it can easily access its food. The best chances of encountering them are in areas with beds of submerged plants, such as water grasses and marshes.

The grass carp reaches sexual maturity between 4 and 5 years. Spawning typically occurs in the spring when water temperatures exceed 68 °F. Eggs are released into open water, where they float and hatch after a few days. Fry initially feed on zooplankton before switching to a herbivorous diet as they grow. Growth is rapid under ideal conditions, and young fish quickly reach a size that makes them less vulnerable to predators. The species can live up to 20 years, although most individuals live between 10 and 15 years.

Spring → Spawning → Summer → Rapid Growth → Autumn → Winter Preparation → Winter → Slowed Metabolism

The grass carp is generally social, forming groups, especially when feeding. It is not particularly territorial and can coexist with other fish species. Sensitive to changes in light and temperature, it is more active in warm, sunny weather but may reduce its activity in the face of environmental disturbances. Sudden changes in pressure or temperature can affect its feeding behavior, making it less active. The species is relatively tolerant of turbid waters, allowing it to adapt to various habitats.

The diet of the grass carp is primarily herbivorous. Young fry start by consuming zooplankton, but as soon as they reach a sufficient size, they switch to a diet mainly consisting of aquatic plants. Adults consume a wide variety of submerged and emergent vegetation, such as algae, grasses, and leaves. In winter, their feeding activity decreases significantly due to a slowdown in metabolism. In spring and summer, their appetite peaks, making them easier to locate in areas of dense vegetation.

In spring, the grass carp becomes active with rising temperatures, preparing for spawning. This is a good time to target them, especially in shallow areas with plenty of vegetation. In summer, they remain active, particularly early in the morning or late in the afternoon when temperatures are milder. Autumn sees a gradual decline in their activity as the water cools. In winter, they enter a semi-lethargic state, feeding very little, which makes them difficult to catch. The best conditions for fishing are during warm, stable weather with little wind.

For grass carp, lures are not as effective as natural baits, but if you want to experiment, choose lures that mimic aquatic plants or small invertebrates. In clear water, natural colors like green or brown work well. In murky water, opt for more visible lures like yellow or orange. Sunny conditions allow for the use of brighter lures, while overcast weather may favor more muted tones.

For grass carp, a sturdy fishing rod of 8 to 10 feet is recommended, with medium to heavy power and moderate action. A fixed spool reel with a line capacity of 15 to 20 lb is ideal. Use hooks size 2 to 4 for plant baits. A fluorocarbon leader can be useful for its invisibility and abrasion resistance.

Handle the grass carp carefully, supporting its body to avoid causing stress. If you wish to release it back into the water, do so quickly and ensure it is well oxygenated before letting it go. For a photo, hold it horizontally and avoid keeping it out of the water for too long.

Natural predators of the grass carp in Quebec include large carnivorous fish such as pike and muskellunge. Some species of water birds, such as herons and ospreys, may also prey on young carp.

In Quebec, the grass carp is not considered an indigenous species, but it is managed for its biological control capabilities. There are no specific regulations governing its fishing, but it is advisable to release it if caught accidentally, unless it poses a risk to the local ecosystem.